John H Bieging

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• Bieging, J., Patel, S., Hofmann, R., Peters, W., Kainulainen, J., Zhang, M., & Stutz, A. (2018). The Arizona Radio Observatory CO Mapping Survey of Galactic Molecular Clouds. VI. The Cep OB3 Cloud (Cepheus B and C) in CO J\nbsp=\nbsp2\ndash1, $^13$CO J\nbsp=\nbsp2\ndash1, and CO J\nbsp=\nbsp3\ndash2. \apjs, 238, 20.
• Imara, N., Lada, C., Lewis, J., Bieging, J., Kong, S., Lombardi, M., & Alves, J. (2017). X Marks the Spot: Nexus of Filaments, Cores, and Outflows in a Young Star-forming Region. \apj, 840, 119.
• Rho, J., Hewitt, J., Bieging, J., Reach, W., Andersen, M., & G{\"usten}, R. (2017). Discovery of Broad Molecular Lines and of Shocked Molecular Hydrogen from the Supernova Remnant G357.7+0.3: HHSMT, APEX, Spitzer, and SOFIA Observations. \apj, 834, 12.
• Bieging, J., Patel, S., Peters, W., Toth, L., Marton, G., & Zahorecz, S. (2016). The Arizona Radio Observatory CO Mapping Survey of Galactic Molecular Clouds. V. The Sh2-235 Cloud in CO J=2-1, $^13$CO J=2-1, and CO J=3-2. \apjs, 226, 13.
• Jose, J., Kim, J., Herczeg, G., Samal, M., Bieging, J., Meyer, M., & Sherry, W. (2016). Star Formation in W3\mdashAFGL 333: Young Stellar Content, Properties, and Roles of External Feedback. \apj, 822, 49.
• Kilpatrick, C., Bieging, J., & Rieke, G. (2016). A Systematic Survey for Broadened CO Emission toward Galactic Supernova Remnants. \apj, 816, 1.
• Bieging, J. H., Kong, S., Lada, C., Lada, E., Román-Zúñiga, C., Lombardi, M., Forbrich, J., & Alves, J. (2015). The Relationship between the Dust and Gas-Phase CO across the California Molecular Cloud. The Astrophysical Journal, 805, 19.
• Bieging, J. H., Ladeyschikov, D., Sobolev, A., Parfenov, S., & Alexeeva,, S. (2015). Star formation in the S233 region. Monthly Notices of the Royal Astronomical Society, 452, 2306-2317.
• Bieging, J. H., Kilpatrick, C. D., & Rieke, G. H. (2014). Interaction between Cassiopeia A and Nearby Molecular Clouds. The Astrophysical Journal, 796(144), 16.
• Bieging, J. H., Revelle, M., & Peters, W. L. (2014). The Arizona Radio Observatory CO Mapping Survey of Galactic Molecular Clouds: IV. The NGC 1333 Cloud in Perseus in CO J=2 - 1 and ¹³COJ=2 - 1. The Astrophysical Journal Supplement, 214(7), 17.
• Burleigh, K. J., Bieging, J. H., Chromey, A., Kulesa, C., & Peters, W. L. (2014). CO survey of molecular clouds. III. Serpens (Burleigh+, 2013). VizieR Online Data Catalog, 220, 90039.
• Bieging, J. H. (2013). Gas-phase CO depletion and N₂H⁺ abundances in starless cores. Astronomy & Astrophysics, 560(41), 24.
• Burleigh, K. J., Bieging, J. H., Chromey, A., Kulesa, C., & Peters, W. L. (2013). The Arizona Radio Observatory CO mapping survey of galactic molecular clouds. III. the serpens cloud in CO J = 2-1 and ¹³CO J = 2-1 emission. Astrophysical Journal, Supplement Series, 209(2).
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  Abstract: We mapped 12CO and 13CO J = 2-1 emission over 1.04 deg2 of the Serpens molecular cloud with 38″ spatial and 0.3 km s-1 spectral resolution using the Arizona Radio Observatory Heinrich Hertz Submillimeter Telescope. Our maps resolve kinematic properties for the entire Serpens cloud. We also compare our velocity moment maps with known positions of young stellar objects (YSOs) and 1.1 mm continuum emission. We find that 12CO is self-absorbed and 13CO is optically thick in the Serpens core. Outside of the Serpens core, gas appears in filamentary structures having LSR velocities which are blueshifted by up to 2 km s -1 relative to the 8 km s-1 systemic velocity of the Serpens cloud. We show that the known Class I, flat, and Class II YSOs in the Serpens core most likely formed at the same spatial location and have since drifted apart. The spatial and velocity structure of the 12CO line ratios implies that a detailed three-dimensional radiative transfer model of the cloud will be necessary for full interpretation of our spectral data. The "starless cores" region of the cloud is likely to be the next site of star formation in Serpens. © 2013. The American Astronomical Society. All rights reserved.
• Rosero, V., Hofner, P., Kurtz, S., Bieging, J., & Araya, E. D. (2013). Methyl cyanide observations toward massive protostars. Astrophysical Journal, Supplement Series, 207(1).
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  Abstract: We report the results of a survey in the CH3CN J = 12 → 11 transition toward a sample of massive proto-stellar candidates. The observations were carried out with the 10 m Submillimeter Telescope on Mount Graham, AZ. We detected this molecular line in 9 out of 21 observed sources. In six cases this is the first detection of this transition. We also obtained full beam sampled cross-scans for five sources which show that the lower K-components can be extended on the arcminute angular scale. The higher K-components, however, are always found to be compact with respect to our 36″ beam. A Boltzmann population diagram analysis of the central spectra indicates CH3CN column densities of about 1014 cm-2, and rotational temperatures above 50 K, which confirms these sources as hot molecular cores. Independent fits to line velocity and width for the individual K-components resulted in the detection of an increasing blueshift with increasing line excitation for four sources. Comparison with mid-infrared (mid-IR) images from the SPITZER GLIMPSE/IRAC archive for six sources show that the CH3CN emission is generally coincident with a bright mid-IR source. Our data clearly show that the CH3CN J = 12 → 11 transition is a good probe of the hot molecular gas near massive protostars, and provide the basis for future interferometric studies. © 2013. The American Astronomical Society. All rights reserved..
• Schöier, F., Ramstedt, S., Olofsson, H., Lindqvist, M., Bieging, J. H., & Marvel, K. B. (2013). The abundance of HCN in circumstellar envelopes of AGB stars of different chemical type. Astronomy and Astrophysics, 550.
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  Abstract: Aims. A multi-transition survey of HCN (sub-) millimeter line emission from a large sample of asymptotic giant branch (AGB) stars of different chemical type is presented. The data are analysed and circumstellar HCN abundances are estimated. The sample stars span a large range of properties such as mass-loss rate and photospheric C/O-ratio. The analysis of the new data allows for more accurate estimates of the circumstellar HCN abundances and puts new constraints on chemical models. Methods. In order to constrain the circumstellar HCN abundance distribution a detailed non-local thermodynamic equilibrium (LTE) excitation analysis, based on the Monte Carlo method, is performed. Effects of line overlaps and radiative excitation from dust grains are included. Results. The median values for the derived abundances of HCN (with respect to H 2) are 3 × 10-5, 7 × 10-7 and 10-7 for carbon stars (25 stars), S-type AGB stars (19 stars) and M-type AGB stars (25 stars), respectively. The estimated sizes of the HCN envelopes are similar to those obtained in the case of SiO for the same sample of sources and agree well with previous results from interferometric observations, when these are available. Conclusions. We find that there is a clear dependence of the derived circumstellar HCN abundance on the C/O-ratio of the star, in that carbon stars have about two orders of magnitude higher abundances than M-type AGB stars, on average. The derived HCN abundances of the S-type AGB stars have a larger spread and typically fall in between those of the two other types, however, slightly closer to the values for the M-type AGB stars. For the M-type stars, the estimated abundances are much higher than what would be expected if HCN is formed in thermal equilibrium. However, the results are also in contrast to predictions from recent non-LTE chemical models, where very little difference is expected in the HCN abundances between the various types of AGB stars. © ESO, 2013.
• Strelnitski, V., Bieging, J. H., Hora, J., Smith, H. A., Armstrong, P., Lagergren, K., & Walker, G. (2013). The Parsec-scale Environment and the Evolutionary Status of MWC 349A. The Astrophysical Journal, 777, 89.
• Strelnitski, V., Bieging, J. H., Hora, J., Smith, H. A., Armstrong, P., Lagergren, K., & Walker, G. (2013). The parsec-scale environment and the evolutionary status of MWC 349A. Astrophysical Journal, 777(2).
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  Abstract: We report on a study of the ∼10′ (∼5 pc in projection) environs of the peculiar, high-luminosity emission-line star MWC 349A in the IR, radio, and visible domains. Besides the recently discovered X-shaped, arcmin-scale IR nebula centered on MWC 349A ("X nebula"), with the kinematic age of ∼104 yr, we identify several young objects pointing toward an ongoing process of active star formation in this region and estimate some physical parameters of the newly discovered objects. The radiation of the X nebula is due to a geometrically and optically thin dust front heated to Td ≈ 60-70 K by the radiation of the central star. The bipolar dust front probably results from the interaction of a powerful stellar wind with the circumstellar disk. One of the related objects is an elongated, cold molecular cloud, ∼1 pc in size, adjacent to MWC 349A in projection and having the same radial velocity (V LSR ≈ +9 km s-1). The proximity of the molecular cloud may indicate that MWC 349A was born locally rather than being a runaway object ejected from the core of Cyg OB2 several Myr ago. If it is still associated with its natal cloud, MWC 349A may be a rare example of the observable pre-main-sequence stage of a ∼30 M ⊙star. If the association with the molecular cloud is an effect of projection, however, MWC 349A may already be an evolved star, even if it was born locally. We discuss future observations that may shed more light on the evolutionary status of this unique object. © 2013. The American Astronomical Society. All rights reserved..
• Bieging, J. H., & Peters, W. L. (2011). The arizona radio observatory CO mapping survey of galactic molecular clouds. II. the W3 region in CO J = 2-1, ¹³CO J = 2-1, and CO J = 3-2 emission. Astrophysical Journal, Supplement Series, 196(2).
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  Abstract: We present fully sampled 38″ resolution maps of the CO and 13CO J = 2-1 lines in the molecular clouds toward the H II region complex W3. The maps cover a 2°0 × 1°67 section of the galactic plane and span -70 to -20kms-1 (LSR) in velocity with a resolution of 1.3kms-1. The velocity range of the images includes all the gas in the Perseus spiral arm. We also present maps of CO J = 3-2 emission for a 0°5 × 0°33 area containing the H II regions W3 Main and W3(OH). The J = 3-2 maps have velocity resolution of 0.87kms-1 and 24″ angular resolution. Color figures display the peak line brightness temperature, the velocity-integrated intensity, and velocity channel maps for all three lines, and also the (CO/13CO) J = 2-1 line intensity ratios as a function of velocity. The line intensity image cubes are made available in standard FITS format as electronically readable files. We compare our molecular line maps with the 1.1mm continuum image from the BOLOCAM Galactic Plane Survey (BGPS). From our 13CO image cube, we derive kinematic information for the 65 BGPS sources in the mapped field, in the form of Gaussian component fits. © 2011. The American Astronomical Society. All rights reserved.
• Kang, M., Choi, M., Bieging, J. H., Rho, J., Lee, J., & Tsai, C. (2011). Submillimeter observations of dense clumps in the infrared dark cloud G049.40-00.01. Astrophysical Journal, 743(2).
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  Abstract: We obtained 350 and 850 μm continuum maps of the infrared dark cloud G049.40-00.01. Twenty-one dense clumps were identified within G049.40-00.01 based on the 350 μm continuum map with an angular resolution of about 96. We present submillimeter continuum maps and report physical properties of the clumps. The masses of clumps range from 50 to 600 M. About 70% of the clumps are associated with bright 24 μm emission sources, and they may contain protostars. The two most massive clumps show extended, enhanced 4.5 μm emission indicating vigorous star-forming activity. The clump-size-mass distribution suggests that many of them are forming high-mass stars. G049.40-00.01 contains numerous objects in various evolutionary stages of star formation, from pre-protostellar clumps to H II regions. © 2011. The American Astronomical Society. All rights reserved.
• Shirley, Y. L., Huard, T. L., Pontoppidan, K. M., Wilner, D. J., Stutz, A. M., Bieging, J. H., & J., N. (2011). Observational constraints on submillimeter dust opacity. Astrophysical Journal, 728(2).
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  Abstract: Infrared extinction maps and submillimeter dust continuum maps are powerful probes of the density structure in the envelope of star-forming cores. We make a direct comparison between infrared and submillimeter dust continuum observations of the low-mass Class 0 core, B335, to constrain the ratio of submillimeter to infrared opacity (κsmm/κir) and the submillimeter opacity power-law index (κ α λ-β). Using the average value of theoretical dust opacity models at 2.2 μm, we constrain the dust opacity at 850 and 450 μm. Using new dust continuum models based upon the broken power-law density structure derived from interferometric observations of B335 and the infall model derived from molecular line observations of B335, we find that the opacity ratios are κ850/κ2.2 = (3.21-4.80)+0.44-0.30 × 10-4 and κ450/ κ2.2 = (12.8-24.8)+2.4-1.3 × 10-4 with a submillimeter opacity power-law index of βsmm = (2.18-2.58)+0.30-0.30. The range of quoted values is determined from the uncertainty in the physical model for B335. For an average 2.2 μm opacity of 3800 ± 700 cm2 g-1, we find a dust opacity at 850 and 450 μm of κ850 = (1.18-1.77)+0.36-0.24 and κ450 =(4.72-9.13)+1.9-0.98 cm2 g-1 of dust. These opacities are from (0.65-0.97) κOH5850 of the widely used theoretical opacities of Ossenkopf and Henning for coagulated ice grains with thin mantles at 850 μm. © 2011. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
• Bieging, J. H., Peters, W. L., & Kang, M. (2010). The arizona radio observatory CO mapping survey of galactic molecular clouds. I. the W51 region in CO and ¹³CO J = 2-1 emission. Astrophysical Journal, Supplement Series, 191(2), 232-246.
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  Abstract: We present 38'' resolution maps of the CO and 13CO J = 2-1 lines in the molecular clouds toward the HII region complex W51. The maps cover a 1.°25 × 1° section of the galactic plane and span +30 to +85 km s-1 (LSR) in velocity. The spectral resolution is ̃1.3 km s -1. The velocity range of the images includes all the gas in the Sagittarius spiral arm. Color figures display the peak line brightness temperature, the velocity-integrated intensity, and 2 km s-1 channel-averaged maps for both isotopologs, and also the CO/13CO J = 2-1 line intensity ratio as a function of velocity. The CO and 13CO line intensity image cubes are made available in standard FITS format as electronically readable tables. We compare our molecular line maps with the 1.1 mm continuum image from the BOLOCAM Galactic Plane Survey. From our 13CO image cube, we derive kinematic information for the 99 BGPS sources in the mapped field in the form of Gaussian component fits. The integrated 13CO line intensity and the 1.1 mm source flux density show only a modest degree of correlation for the 99 sources, likely due to a range of dust and gas physical conditions within the sources. However, the 1.1 mm continuum surface brightness and the integrated 13CO line intensity for small regions containing single BGPS sources and molecular clouds show very good correlations in many cases. Differences in the shapes of these correlations from one spatial region to another probably result from different physical conditions or structure in the clouds. © 2010.
• Kang, M., Bieging, J. H., Kulesa, C. A., Lee, Y., Choi, M., & Peters, W. L. (2010). A co line and infrared continuum study of the active star-forming complex W51. Astrophysical Journal, Supplement Series, 190(1), 58-76.
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  Abstract: We present the results of an extensive observational study of the active star-forming complex W51 that was observed in the J = 2 - 1 transition of the 12CO and 13CO molecules over a 1. ° 25 × 1. ° 00 region with the University of Arizona Heinrich Hertz Submillimeter Telescope. We use a statistical equilibrium code to estimate physical properties of the molecular gas. We compare the molecular cloud morphology with the distribution of infrared (IR) and radio continuum sources and find associations between molecular clouds and young stellar objects (YSOs) listed in Spitzer IR catalogs. The ratios of CO lines associated with Hii regions are different from the ratios outside the active star-forming regions. We present evidence of star formation triggered by the expansion of the Hii regions and by cloud-cloud collisions. We estimate that about 1% of the cloud mass is currently in YSOs.
• Strelnitski, V., Schwarz, K., Bieging, J., Fuchs, J. T., & Walker, G. (2010). Uniqueness and evolutionary status of MWC349A. Proceedings of the International Astronomical Union, 6(S272), 632-633.
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  Abstract: MWC349A, which had remained an ordinary member of the MWC catalog for a few decades, is now known as: (1) the brightest stellar source of radio continuum; (2) the only known high-gain natural maser in hydrogen recombination lines; and (3) the only strictly proven natural high-gain laser (in IR hydrogen recombination lines). These phenomena seem to occur in the circumstellar disk seen almost edge-on. They help us understand the structure and kinematics of the disk. The evolutionary status of MWC 349A is still debated: a young HAeBe star with a preplanetary disk or an old B[e] star or even a protoplanetary nebula? We discuss new observational data obtained at the Maria Mitchell Observatory and elsewhere which may cast light on this issue. © International Astronomical Union 2011.
• Kang, M., Bieging, J. H., Kulesa, C. A., & Lee, Y. (2009). Triggered star formation in a double shell near W51A. Astrophysical Journal Letters, 701(1), 454-463.
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  Abstract: We present Heinrich Hertz Telescope CO observations of the shell structure near the active star-forming complex W51A to investigate the process of star formation triggered by the expansion of an H II region. The CO observations confirm that dense molecular material has been collected along the shell detected in Spitzer IRAC images. The CO distribution shows that the shell is blown out toward a lower density region to the northwest. Total hydrogen column density around the shell is high enough to form new stars. We find two CO condensations with the same central velocity of 59 km s-1 to the east and north along the edge of the IRAC shell. We identify two young stellar objects in early evolutionary stages (Stage 0/I) within the densest molecular condensation. From the CO kinematics, we find that the H II region is currently expanding with a velocity of 3.4 km s-1, implying that the shell's expansion age is ∼ 1 Myr. This timescale is in good agreement with numerical simulations of the expansion of the H II region (Hosokawa & Inutsuka). We conclude that the star formation on the border of the shell is triggered by the expansion of the H II region. © 2009. The American Astronomical Society. All rights reserved.
• Kang, M., Bieging, J. H., Povich, M. S., & Lee, Y. (2009). Embedded young stellar object candidates in the active star-forming complex w51: Mass function and spatial distribution. Astrophysical Journal Letters, 706(1), 83-93.
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  Abstract: We present 737 candidate young stellar objects (YSOs) near the W51 giant molecular cloud over an area of 1.°25 × 1.°00 selected from Spitzer Space Telescope data. We use spectral energy distribution fits to identify YSOs and distinguish them from main-sequence (MS) or red giant stars, asymptotic giant branch stars, and background galaxies. Based on extinction of each YSO, we separate a total of 437 YSOs associated with the W51 region from the possible foreground sources. We identify 69 highly embedded Stage 0/I candidate YSOs in our field with masses >5 M Ȯ (corresponding to mid- to early-B MS spectral types), 46 of which are located in the central active star-forming regions of W51A and W51B. From the YSOs associated with W51, we find evidence for mass segregation showing that the most massive YSOs are concentrated on the W51 H II region complex. We find a variation in the spatial distribution of the mass function (MF) of YSOs in the mass range between 5 M Ȯ and 18 M Ȯ. The derived slopes of the MF are -1.26 and -2.36 in the active star-forming region and the outer region, respectively. The variation of the MF for YSOs embedded in the molecular cloud implies that the distribution of stellar masses in clusters depends on the local conditions in the parent molecular cloud. © 2009. The American Astronomical Society. All rights reserved.
• Povich, M. S., Churchwell, E., Bieging, J. H., Kang, M., Whitney, B. A., Brogan, C. L., Kulesa, C. A., Cohen, M., Babler, B. L., Indebetouw, R., Meade, M. R., & Robitaille, T. P. (2009). The extended environment of M17: A star formation history. Astrophysical Journal, 696(2), 1278-1306.
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  Abstract: M17 is one of the youngest and most massive nearby star-formation regions in the Galaxy. It features a bright H II region erupting as a blister from the side of a giant molecular cloud (GMC). Combining photometry from the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) with complementary infrared (IR) surveys, we identify candidate young stellar objects (YSOs) throughout a 15 × 1° field that includes the M17 complex. The long sightline through the Galaxy behind M17 creates significant contamination in our YSO sample from unassociated sources with similar IR colors. Removing contaminants, we produce a highly reliable catalog of 96 candidate YSOs with a high probability of association with the M17 complex. We fit model spectral energy distributions to these sources and constrain their physical properties. Extrapolating the mass function of 62 intermediate-mass YSOs (M ⊙ > 3M ⊙), we estimate that >1000 stars are in the process of forming in the extended outer regions of M17. The remaining 34 candidate YSOs are found in a 0.17deg 2 field containing the well-studied M17 H II region and photodissociation region (PDR), where bright diffuse mid-IR emission drastically reduces the sensitivity of the GLIMPSE point-source detections. By inspecting IR survey images from IRAS and GLIMPSE, we find that M17 lies on the rim of a large shell structure 05 in diameter (∼20 pc at 2.1kpc). We present maps of 12CO and 13CO (J = 2 → 1) emission observed with the Heinrich Hertz Telescope. The CO emission shows that the shell is a coherent, kinematic structure associated with M17, centered at v = 19km s -1. The shell is an extended bubble outlining the PDR of a faint, diffuse H II region several Myr old. We identify a group of candidate ionizing stars within the bubble. YSOs in our catalog are concentrated around the bubble rim, providing evidence that massive star formation has been triggered by the expansion of the bubble. The formation of the massive cluster ionizing the M17 H II region itself may have been similarly triggered. We conclude that the star formation history in the extended environment of M17 has been punctuated by successive waves of massive star formation propagating through a GMC complex. © 2009. The American Astronomical Society. All rights reserved.
• Schöier, F. L., Fong, D., Bieging, J. H., Wilner, D. J., Young, K., & Hunter, T. R. (2007). The distribution of H¹³CN in the circumstellar envelope around IRC+10216. Astrophysical Journal, 670(1), 766-773.
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  Abstract: H13CN J = 8 → 7 submillimeter line emission produced in the circumstellar envelope around the extreme carbon star IRC+10216 has been imaged at subarcsecond angular resolution using the SMA. Supplemented by a detailed excitation analysis, the average fractional abundance of H13CN in the inner wind (≲ 5 × 1015 cm) is estimated to be about 4 × 10-7, translating into a total HCN fractional abundance of 2 × 10-5 using the isotopic ratio 12C/13C = 50. Multitransitional single-dish observations further require the H 13CN fractional abundance to remain more or less constant in the envelope out to a radius of ≈4 × 1016 cm, where the HCN molecules are effectively destroyed, most probably, by photodissociation. The large amount of HCN present in the inner wind provides effective line cooling that can dominate over that generated from CO line emission. It is also shown that great care needs to be taken in the radiative transfer modeling where nonlocal, and non-LTE, effects are important and where the radiation field from thermal dust grains plays a major role in exciting the HCN molecules. The amount of HCN present in the circumstellar envelope around IRC+10216 is consistent with predicted photospheric values based on equilibrium chemical models and indicates that any nonequilibrium chemistry occurring in the extended pulsating atmosphere has no drastic net effect on the fractional abundance of HCN molecules that enters the outer envelope. It further suggests that few HCN molecules are incorporated into dust grains. © 2007. The American Astronomical Society. All rights reserved.
• Bieging, J. H., Peters, W. L., Vilaro, B. V., Schlottman, K., & Kulesa, C. (2006). Sequential star formation in the Sh 254-258 molecular cloud: HHT maps of CO J=3-2 and 2-1 emission. Proceedings of the International Astronomical Union, 2(S237), 396-.
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  Abstract: The molecular cloud associated with the Sh 254-258 group of 5 small H II regions appears to be forming a (late)-OB association. We have mapped the associated molecular cloud in the J=2-1 line of the CO molecule over 0.75 o 1 o, and the CO J=3-2 line toward the 2 main peaks, with the University of Arizona Heinrich Hertz Submm Telescope (HHT). We propose a scenario for sequential formation of the stars exciting the H II regions, triggered by the compression/heating of the molecular gas. © 2007 International Astronomical Union.
• Bieging, J. H., Schmidt, G. D., Smith, P. S., & Oppenheimer, B. D. (2006). Optical spectropolarimetry of asymptotic giant branch and post-asymptotic giant branch stars. Astrophysical Journal Letters, 639(2 I), 1053-1068.
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  Abstract: Spectropolarimetric observations are presented for 21 AGB stars, 13 proto-planetary nebulae (PPNs), and two R CrB-type stars. The spectra cover the wavelength range from ∼4200 to 8400 Å with 16 A resolution. Among the AGB stars, 8 of 14 M giants, five of six carbon stars, and zero of one S star showed intrinsic polarization. At least 9 of 13 PPNs exhibited intrinsic polarization, while the R CrB-type stars show intrinsic polarization during fading episodes. There is a statistical correlation between mean polarization, (P), and IR color, K - [12], among the AGB stars such that redder stars tend to be more polarized. The PPN sample is significantly redder and more polarized, on average, than the AGB stars. This increase in 〈P〉 with increased reddening is consistent with an evolutionary sequence in which AGB stars undergo increasing mass loss, with growing asymmetries in the dust distribution as they evolve up and then off the AGB into the short-lived PPN phase. A related trend is found between polarization and mass-loss rate in gas, Mgas. The detectability of polarization increases with mass-loss rate, and probably all AGB stars losing mass at >10-6 M⊙ yr-1 have detectable polarization. Multiple observations of three polarized AGB stars show that in some cases 〈P〉 increases with mv, and in others it decreases. If polarization arises from scattering of starlight off an aysmmetric distribution of grains, then the distribution varies with time. Polarized features are detected in the TiO bands of three M-type Mira variables, in the CN bands of the carbon stars R Lep and V384 Per, and in the Swan bands of C2 in R CrB and two PPNs. Polarization effects in the molecular bands appear to be more common and the effects are larger in O-rich than C-rich objects. © 2006. The American Astronomical Society. All rights reserved.
• Biller, B. A., Close, L. M., Aigen, L. i., Marengo, M., Bieging, J. H., Hinz, P. M., Hoffmann, W. F., Brusa, G., & Miller, D. (2006). Resolving the dusty circumstellar structure of the enigmatic symbiotic star CH Cygni with the MMT adaptive optics system. Astrophysical Journal Letters, 647(1 I), 464-470.
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  Abstract: We imaged the symbiotic star CH Cyg and two PSF calibration stars using the unique 6.5 m MMT deformable secondary adaptive optics system. Our high-resolution (FWHM = 0″.3), very high Strehl (98% ± 2%), mid-infrared (9.8 and 11.7 μm) images of CH Cyg allow us to probe finer length scales than ever before for this object. CH Cyg is significantly extended compared to our unresolved PSF calibration stars (μ UMa and α Her) at 9.8 and 11.7 μm. We estimated the size of the extension by convolving a number of simple Gaussian models with the μ UMa PSF and determining which model provided the best fit to the data. Adopting the Hipparcos distance for this object of 270 pc, we found a nearly Gaussian extension with a FWHM at 9.8 μm of ∼40.5 ± 2.7 AU (0″.15 ± 0″.01) and a FWHM at 11.7 μm of 45.9 ± 2.7 AU (0″.17 ± 0″.01). After subtracting out the Gaussian component of the emission (convolved with our PSF), we found a faint ∼ 0″.7 asymmetric extension, which peaks in flux ∼0″.5 north of the stars. This extension is roughly coincident with the northern knotlike feature seen in HST WFPC2 images obtained in 1999. © 2006. The American Astronomical Society. All rights reserved.
• Peters, W. L., Bieging, J. H., Groppi, C. E., Kulesa, C. A., Walker, C. K., Hedden, A. S., & Puetz, P. S. (2006). Degree scale high resolution mapping of CO J=2-1 and 3-2 in giant molecular clouds. Proceedings of the International Astronomical Union, 2(S237), 463-.
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  Abstract: We present the first results from a project to map Giant Molecular Clouds (GMCs) in the 12CO J=2-1, 13CO J=2-1, and 12CO J=3-2 lines using the Heinrich Hertz Submillimeter Telescope (HHT) at the University of Arizona. We mapped nearly 2.5 sq. deg of W3 and 1.0 sq. deg of W51 in the J=2-1 lines. We have begun mapping in the J=3-2 line. We achieve angular resolutions of 33 and 24 in the J=2-1 and J=3-2 lines with 1.3 and 0.9 km s1 resolution. © 2007 International Astronomical Union.
• Biller, B. A., Close, L. M., Li, A., Bieging, J. H., Hoffmann, W. F., Hinz, P. M., Miller, D., Brusa, G., Lloyd-Hart, M., Wildi, F., Potter, D., & Oppenheimer, B. D. (2005). High-resolution mid-infrared imaging of the asymptotic giant branch star RV bootis with the steward observatory adaptive optics system. Astrophysical Journal Letters, 620(1 I), 450-458.
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  Abstract: We present high-resolution (∼0.″1), very high Strehl ratio (0.97±0.03) mid-IR adaptive optics (AO) images of the asymptotic giant branch (AGB) star RV Boo utilizing the MMT adaptive secondary AO system. RV Boo was observed at a number of wavelengths over two epochs (9.8 μm in 2003 May and 8.8, 9.8, and 11.7 μm in 2004 February) and appeared slightly extended at all wavelengths. While the extension is very slight at 8.8 and 11.7 μm, the extension is somewhat more pronounced at 9.8 μm. With such high Strehl ratios, we can achieve superresolutions of 0″.1 by deconvolving RV Boo with a point-spread function (PSF) derived from an unresolved star. We tentatively resolve RV Boo into a 0′.16 FWHM extension at a position angle of 120°. At a distance of 390+-100+250 PC, this corresponds to a FWHM of 60-15+40 AU. We measure a total flux at 9.8 μm of 145 ± 24 Jy for the disk and star. Based on a dust thermal emission model for the observed IR spectral energy distribution and the 9.8 μm AO image, we derive a disk dust mass of 1.6 × 10-6 M⊙ and an inclination of 30°-45° from edge-on. We discuss whether the dust disk observed around RV Boo is an example of the early stages in the formation of asymmetric structure in planetary nebulae. © 2005. The American Astronomical Society, All rights reserved.
• Hrivnak, B. J., & Bieging, J. H. (2005). CO J = 2-1 and 4-3 observations of proto-planetary nebulae: Time-variable mass loss. Astrophysical Journal Letters, 624(1 I), 331-351.
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  Abstract: Observations made with the Heinrich Hertz Telescope of CO millimeter and submillimeter emission toward a sample of 22 proto-planetary nebula (PPN) candidates resulted in detections of 12 sources in the COJ = 2-1 line. Of these 12, seven sources were also detected in the J = 4-3 line. These 4-3 transitions are the highest yet observed in all but one of these PPNs. Statistical equilibrium/radiative transfer models were calculated for the CO emission in the circumstellar envelopes (CSEs), assuming various power-law density distributions. These models were compared with the intensity and profile shape of the observed spectra. For the region of the CSE probed by CO emission, the density laws must be steeper than inverse squared and are consistent with power laws between ρ ∝ r-3 and r-4. These radial density distributions imply that the mass loss was not constant but increased during the last part of the asymptotic giant branch (AGB) phase. Mass-loss rates at the end of the AGB for the three best-constrained sources are found to be 7.7 × 10-5 M⊙ yr-1 (IRAS 22272+5435), 2.3 × 10-5 M⊙ yr-1 (IRAS 07134+ 1005), and 1.3 × 10-5 M⊙ yr-1 (IRAS 17436+5003) for the case of ρ ∝ r-3. These time-varying mass-loss rates can be integrated to calculate the enclosed envelope masses ejected in the past ∼ 10,000 yr. The ejected envelope masses close to the star lie in the range 0.02-0.30 M⊙; these values are consistent with theoretical models, which indicate that
• Oppenheimer, B. D., Bieging, J. H., Schmidt, G. D., Gordon, K. D., Misselt, K. A., & Smith, P. S. (2005). Spectropolarimetry and radiative transfer modeling of three proto-planetary nebulae. Astrophysical Journal Letters, 624(2 I), 957-972.
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  Abstract: We measured the spectrum of polarization for three proto-planetary nebulae (PPNs), IRAS 17411-2411, IRAS 08005-2356, and IRAS 04296+3429, and made model calculations with the dust-scattering Monte Carlo code DIRTY and the dust emission code 2Dust. We show that high levels of polarization in these PPNs correlate with extreme asymptotic giant branch (AGB) superwind mass-loss rates in excess of 10-4 M⊙ yr-1. All three objects show evidence for evacuated lobes cleared by collimated fast winds, and two indicate a significant equatorial mass enhancement. Our best-fit models require sharply peaked grain size distributions, suggesting that most of the light is being scattered by grains of a characteristic size in IRAS 17441-2411 and IRAS 08005-2356. IRAS 17441-2411 and IRAS 08005-2356 have lobes with wide opening angles, perhaps produced by deflection of a polar jet from an accreting companion by the AGB superwind. Modeling the spectropolarimetry of IRAS 04296+3429 indicates a point-symmetric, multipolar morphology in the PPN phase. The modeling of spectropolarimetry and other observations of PPNs provides a powerful way to constrain circumstellar morphology and dust parameters.
• Bieging, J. H. (2003). Observations of small-scale structure in AGB star winds: Precursors of neutral globules in PNE?. Revista Mexicana de Astronomia y Astrofisica: Serie de Conferencias, 15, 68-.
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  Abstract: Millimeter-interferometric mapping of thermal emission from molecules which trace dense gas reveals much clumpy structure in the envelopes of two AGB stars. Observations were made with the Caltech OVRO mm-array. The signal-to-noise ratio of the data allowed use of self-calibration to achieve high dynamic range images (∼ 100:1) in individual spectral channel maps of 0.7 km s-1 width. The angular resolution is ∼ 2″. © Copyright 2003: Instituto de Astronomía, Universidad Nacional Autónoma de México.
• Meakin, C. A., Bieging, J. H., Latter, W. B., Hora, J. L., & Tielens, A. G. (2003). Hubble space telescope/NICMOS near-infrared imaging of the proto-planetary nebula OH 231.8+4.2. Astrophysical Journal Letters, 585(1 I), 482-493.
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  Abstract: We present observations of the bipolar nebula OH 231.8+4.2, made with the Hubble Space Telescope (HST) NICMOS camera, in three wide filter bands (F205W, F160W, and F110W). The images have excellent dynamic range after removal of low-level instrumental artifacts. In the F205W filter (λ ≈ 2.04 μm), we achieve a peak/rms of greater than 8000 with an angular resolution of 0″.20 (FWHM). The combination of high dynamic range and angular resolution confirms previous observations but also reveals new features in the near-IR morphology of the nebula, which at these wavelengths is dominated by scattered light. The northern (approaching) lobe shows well-defined, limb-brightened edges. The central jet splits into two filaments and exhibits some curvature between the center of the nebula and the end of the northern lobe. The southern (receding) lobe has a diffuse, flocculent appearance without a sharply defined central jet, in contrast to the northern lobe. A sharpened version of the F205W image shows indications of turbulent structures both in the northern lobe and jet and in the southern lobe. A faint cylindrical halo of scattered light shows a sharp increase in surface brightness inside a radius of ∼4″ from the center, possibly resulting from a transition from a spherical wind to a disk- or torus-like mass ejection, on the same timescale as the formation of the collimated fast wind seen in CO and HCO+ images. We calculate the extinction through the nebula from the measured near-IR colors and a silicate grain model. For a simple geometric model of a dense central disk, we estimate a disk mass (gas and dust) in the range 0.03-0.06 M⊙, relatively insensitive to grain size. The circumstance of an asymptotic giant branch (AGB) star with a massive, highly collimated, high-velocity bipolar flow may be understood in terms of the model of Soker & Rappaport if the central star underwent a change in mass-loss properties from a (roughly) spherical AGB wind to equatorially enhanced mass loss beginning ∼(1-3) × 103 yr ago. Supposing the presence of a dwarf companion in a suitable orbit, the bipolar nebula then is a consequence of a strong increase in mass loss as the central star evolves close to the tip of the AGB and will soon evolve to higher Teff and appear as a more typical proto-planetary nebula.
• Highberger, J. L., Savage, C., Bieging, J. H., & Ziurys, L. M. (2002). Erratum: Heavy-metal chemistry in proto-planetary nebulae: Detection of MgNC, NaCN, and A1F toward CRL 2688 (Astrophysical Journal (2001) 562 (790)). Astrophysical Journal Letters, 571(2 I), 1022-1023.
• Watson, C., Churchwell, E., Pankonin, V., & Bieging, J. H. (2002). Arcsecond images of CH₃CN toward W75N. Astrophysical Journal Letters, 577(1 I), 260-264.
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  Abstract: CH3CN (J = 6-5) was observed with a resolution of 2″ toward W75N using the BIMA interferometer. Two continuum sources were detected at 3 mm and designated MM1 and MM2 in previous studies. Alignment of the two continuum sources with the outflow axis from MM1 suggests that these continuum sources may be the result of the outflow interacting with the interstellar medium. MM1 is coincident with compact CH3CN emission. CH 3CN was not detected toward MM2. The distribution of optical depth (τL) is derived. An excitation analysis was not done because of large-line optical depths.
• Bieging, J. H. (2001). Discovery of two new HCN maser lines in five carbon stars. Astrophysical Journal Letters, 549(1 PART 2), L125-L129.
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  Abstract: A survey with the Heinrich Hertz Submillimeter Telescope of HCN emission from mass-losing carbon stars has revealed masers in the J = 3-2 and 4-3 transitions of the (011c0) vibrational bending mode. These lines have not previously been known to show maser action. Five stars - R Scl, V384 Per, R Lep, Y CVn, and V Cyg - out of 12 observed were detected as masers. Allowing for evidence of variability, this detection rate suggests that these HCN lines are masers at least some of the time in the majority of mass-losing carbon stars. The line widths and velocities imply that the maser action occurs in gas close to the star, where the circumstellar envelope is just being accelerated outward.
• Bieging, J. H., & Wilson, C. D. (2001). High-resolution images of CO J = 2-1 emission from the carbon star V cygni. Astronomical Journal, 122(2), 979-990.
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  Abstract: This paper presents observations of the CO J = 2-1 emission from the circumstellar envelope of the mass-losing carbon star V Cyg. The observations were made with the Caltech Millimeter Array. A previously published single-dish map was used to construct short-spacing visibilities not sampled by the interferometer data, thereby recovering missing flux in extended low brightness emission. The images have an angular resolution of ∼1″.2 with a velocity resolution of 1 MHz (1.3 km s-1). The channel maps are consistent with an expanding envelope that is roughly spherical, but they also show evidence for asymmetric structure, as well as small-scale clumping. We compare these observations, as well as other published spectra, with statistical equilibrium models for CO in a circumstellar envelope. Models that fit the spherically averaged data must invoke a mass-loss rate, Ṁ, that has decreased with time by a factor of ∼2-3 over the past several hundred years. The model kinetic temperature structure in radius, TK(r), decreases as r-0.8 out to r ≈ 6 × 1015 cm and levels off to a constant value at TK = 23 K beyond. The secular change in Ṁ may be related to changes in the stellar luminosity or temperature, as predicted by recent numerical hydrodynamic models for mass loss. The inferred kinetic temperature structure suggests that heating by the photoelectric effect on dust grains is important in the outer envelope.
• Highberger, J. L., Savage, C., Bieging, J. H., & Ziurys, L. M. (2001). Heavy-metal chemistry in proto-planetary nebulae: Detection of MgNC, NaCN, and AlF toward CRL 2688. Astrophysical Journal Letters, 562(2 PART II), 790-798.
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  Abstract: The metal-containing molecules AlF, MgNC, and NaCN have been detected toward CRL 2688, a circumstellar envelope in the proto-planetary nebula (PPN) phase. These measurements are the first detections of such species in a source other than the carbon star IRC +10216. Three transitions of MgNC were observed, each of which consists of two spin-rotation components, and five lines of NaCN were measured; both detections were made in the 2 mm wavelength region using the NRAO 12 m telescope. Three transitions of AlF were observed as well at 2 and 1.2 mm with the IRAM 30 m antenna. All three species appear to trace the AGB wind, not the high-velocity outflows characteristic of post-AGB mass loss. Rotational temperature analysis suggests that MgNC emission is from cooler gas than AlF and NaCN, indicating an outer shell distribution for this molecule, as is found in IRC +10216. AlF and NaCN appear to be confined to the inner envelope of CRL 2688. The column density obtained for MgNC in this source assuming a shell-like distribution is Ntot ∼ 4 × 1012 cm-2, corresponding to a fractional abundance, relative to H2, of f ∼ 4 × 10-9. This abundance is about a factor of 10 less than that in IRC +10216. For NaCN, the column density and fractional abundance in CRL 2688 are Ntot ∼ 0.7-3 × 1014 cm-2 and f ∼ 3-5 × 10-8, comparable to what has been measured for IRC +10216. In the case of AlF, the column density toward CRL 2688 was determined to be Ntot ∼ 0.9-3 × 1013 cm-2, resulting in f ∼ 4-5 × 10-9. In IRC + 10216, f(AlF) is 1-2 × 10-7. These data suggest that the chemistry in the outer envelope of CRL 2688 has altered abundances for species like MgNC, but inner shell molecules like NaCN may remain intact over a longer timescale. While the abundance of AlF in CRL 2688 is less than that of 19F in the solar system, in IRC +10216, the AlF abundance exceeds the fluorine solar value. Hence, observations of this molecule suggest that 19F is produced in thermal pulses in the AGB phase. © 2001. The American Astronomical Society. All rights reserved.
• Pankonin, V., Churchwell, E., Watson, C., & Bieging, J. H. (2001). A methyl cyanide search for the earliest stages of massive protostars. Astrophysical Journal Letters, 558(1 PART 1), 194-203.
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  Abstract: Forty-eight candidate massive protostar regions were surveyed for methyl cyanide (CH3CN) emission using the Heinrich Hertz Telescope (HHT) on Mount Graham, AZ. CH3CN J = 12-11 emission at 220 GHz was detected toward 25 regions. Thirteen of these are new detections, yielding a substantial number of new candidates for massive protostars. The CH133CN (J = 12-11) isotopomer was included in the bandpass of all observed sources and was detected toward eight sources in our sample. These sources are probably optically thick in some of the CH3CN lines. CH3CN J = 25-24 emission at 460 GHz was detected in at least one K-component toward five of 11 sources observed in this transition. Using a rotational equilibrium temperature analysis we estimate the CH3CN rotation temperatures and beam-averaged column densities for 20 of the sources.
• Saucedo-Morales, J., & Bieging, J. (2001). An empirical picture for the evolution of galaxies outside of clusters. Astrophysics and Space Science, 277(SUPPL.), 449-452.
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  Abstract: The main goal of this work is to study the properties of isolated elliptical galaxies with the hope of learning about their formation and evolution. A sample that contains ∼ 25% of the galaxies classified as ellipticals in the Karachentseva Catalog of Isolated Galaxies is investigated. Approximately one halt of these galaxies appear to be misclassified, a result which may imply a reduction of the percentage of ellipticals in the Karachentseva catalog to (6 ± 2)% of the total population of isolated galaxies. A significant number of merger candidates has also been found among the isolated galaxies. It is argued that the fraction of merger candidates to isolated ellipticals can be used to constrain models for the evolution of compact groups into isolated galaxies.
• Bieging, J. H., Shaked, S., & Gensheimer, P. D. (2000). Submillimeter- and millimeter-wavelength observations of SiO and HCN in circumstellar envelopes of AGB stars. Astrophysical Journal Letters, 543(2 PART 1), 897-921.
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  Abstract: We report molecular line observations with the Heinrich Hertz Submillimeter Telescope of a sample of 30 asymptotic giant branch stars with spectral types M, S, and C. Measured lines include SiO J = 5-4, 8-7, 10-9, and HCN J = 3-2 and 4-3 transitions, which arise from energy levels ranging from 26 to 115 K above ground. The observed transitions were detected in almost all stars observed, regardless of spectral type. The HCN J = 3-2 and 4-3 lines in the M stars are bright compared with previous observations of the J = 1-0 line. We calculated emergent spectra for model circumstellar envelopes and compare these with the observed line intensity ratios. We conclude that (1) the HCN line intensity ratios for the M stars are inconsistent with chemical models in which HCN is produced via photochemistry in the outer circumstellar envelope. HCN must be formed by a nonequilibrium chemical process in the inner envelope or extended stellar atmosphere. (2) The HCN/SiO intensity ratios of lines with similar excitation energies clearly separate the carbon stars from the M and S stars. The M and S stars show a trend of increasing HCN/SiO intensity ratios with increasing mass-loss rate. (3) These data support the idea that pulsationdriven shocks result in the formation of organic molecules like HCN in the envelopes of M stars. Observations of these molecules could give useful constraints on hydrodynamic models for stellar mass loss driven by pulsational shocks in the stellar atmosphere. We detected emission from vibrationally excited HCN in the v = (0, 11c, 0), J = 3-2 and 4-3 transitions toward four carbon stars. In one star, V Cyg, the lines are strong and narrow, and are most likely a result of maser amplification.
• Highberger, J. L., Apponi, A. J., Bieging, J. H., Ziurys, L. M., & Mangum, J. G. (2000). Millimeter observations of vibrationally excited cs toward irc +10216: A new circumstellar maser?. Astrophysical Journal Letters, 544(2 PART 1), 881-888.
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  Abstract: New observations of vibrationally excited CS in its v = 1 state have been conducted toward the circumstellar shell of IRC +10216 using the NRAO 12 m telescope and the CSO. The J = 3 → 2, 6 → 5, and 7 → 6 transitions in the v = 1 level at 146, 292, and 340 GHz have been detected toward this object, and the J = 2 → 1 and 5 → 4 lines were also reobserved. After accounting for contamination from other species, these CS transitions all exhibit line profiles that are narrower (△V1/2 ∼ 10 km s-1) than those displayed by most molecules in IRC +10216, indicating an origin in the inner stellar envelope. The J = 3 → 2 line is particularly narrow (△V1/2 ∼ 10 1-2 km s-1), and consists of two separate velocity components at VLSR ∼ -26 and -22 km s-1. These characteristics are suggestive of weak maser action in this transition. The narrow line widths observed in the other transitions indicate a source size ≲ 0″.5, which implies a CS column density in the v = 1 state of ∼ 2-6 × 1016 cm-2. The ground-state (v = 0) column density is therefore on the order of 0.8-2 × 1018 cm-2 for Tvib = 500 K. The fractional abundance of CS relative to H2 is consequently f ∼ 3-7 × 10-5 at ∼ 14 R *. Such a high abundance close to the stellar photosphere is strong evidence that CS is a "parent" molecule in IRC +10216, as suggested by infrared studies of the v = 0 → 1 vibrational transition and interferometric observations.
• Latter, W. B., Dayal, A., Bieging, J. H., Meakin, C., Hora, J. L., Kelly, D. M., & Tielens, A. G. (2000). Revealing the photodissociation region: HST/NICMOS imaging of NGC 7027. Astrophysical Journal Letters, 539(2 PART 1), 783-797.
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  Abstract: We report results from a Hubble Space Telescope (HST) and Near-Infrared Camera and Multiobject Spectrometer (NICMOS) program to study the distribution of hot neutral (molecular hydrogen) and ionized circumstellar material in the young planetary nebulae NGC 7027. HST/NICMOS provided very high spatial resolution imaging in line and continuum emission, and the stability and large dynamic range needed for investigating detailed structures in the circumstellar material. We present dramatic new images of NGC 7027 that have led to a new understanding of the structure in this important planetary nebula. The central star is clearly revealed, providing near-infrared fluxes that are used to directly determine the stellar temperature very accurately (T(black star sing) = 198,000 K). It is found that the photodissociation layer as revealed by near-infrared molecular hydrogen emission is very thin (ΔR ∼ 6 × 1015 cm) and is biconical in shape. The interface region is structured and filamentary, suggesting the existence of hydrodynamic instabilities. We discuss evidence for the presence of one or more highly collimated, off-axis jets that might be present in NGC 7027. The NICMOS data are combined with earlier Hubble Space Telescope data to provide a complete picture of NGC 7027 using the highest spatial resolution data to date. The evolutionary future of NGC 7027 is discussed.
• d'Aubigny, C. Y., Walker, C. K., Groppi, C. E., Hill, J. M., Bieging, J. H., & Pompea, S. M. (2000). Submillimeter-wave receiver system for the large binocular telescope. Proceedings of SPIE - The International Society for Optical Engineering, 4015, 268-277.
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  Abstract: The Large Binocular Telescope (LBT) will consist of two, 8.417 m, spin-cast, optical quality primary mirrors on a common azimuth-elevation mount. The center-to-center distance between the primaries is 14.417 m. The LBT is being constructed on a site known to have relatively low atmospheric opacity at submillimeter wavelengths. In this paper we describe a unique 350 μm heterodyne receiver system designed for use on the LBT. The optical quality of the primaries and their size will give the LBT a light gathering power more than twice that of existing submillimeter-wave telescopes.
• Altenhoff, W. J., Bieging, J. H., Butler, B., Butner, H. M., Chini, R., Haslam, C. G., Kreysa, E., Martin, R. N., Mauersberger, R., McMullin, J., Muders, D., Peters, W. L., Schmidt, J., Schraml, J. B., Sievers, A., Stumpff, P., Thum, C., Kap-herr, A. V., Wiesemeyer, H., , Wink, J. E., et al. (1999). Coordinated radio continuum observations of comets Hyakutake and Hale-Bopp from 22 to 860 GHz. Astronomy and Astrophysics, 348(3), 1020-1034.
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  Abstract: We have observed both Comets Hyakutake and Hale-Bopp close to perigee with several telescopes at frequencies between 30 and 860 GHz for an extended period of time. The observed "light" curves can be described as a simple function of heliocentric and geocentric distances without any outburst or noticeable variability with time. Our most sensitive diameter estimate for C/Hyakutake resulted in an upper limit of 2.1 km. The nuclear diameter of C/Hale-Bopp was determined to 44.2 km after separation from the halo emission. The central part of both halos can be represented by a Gaussian with a linear size at half power points of 1870 and 11080 km for Hyakutake and Hale-Bopp, respectively. The spectral index for both comets is α = 2.8, indicating a similar particle size distributions in the halo of these comets. For Hale-Bopp the extended emission could be traced to more than 105 km from its nucleus. The derived masses, contained in the halo depend strongly on the assumed physical properties of the halo particles. With κ(1mm) = 75 cm2/g. possibly more appropriate for comets, a halo mass of 6 1010 g is derived for Hyakutake and of 8 1012 g for Hale-Bopp.
• Wilson, T. L., Mauersberger, R., Gensheimer, P. D., Muders, D., & Bieging, J. H. (1999). Dense cores in the Orion molecular cloud. Astrophysical Journal Letters, 525(1 PART 1), 343-356.
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  Abstract: We have used the Heinrich Hertz submillimeter telescope to measure the J = 3-2 and J = 2-1 lines of 12C16O and 12C18O, and the J = 3-2 line of 13C16O toward 125 high-density cores in the prominent S-shaped feature in L1640. We have also measured the (J, K)=(1,1) and (2,2) inversion transitions of NH3 from these sources. These results have been used to determine kinetic temperatures, H2 densities, and column densities. Estimates of the stability of these cores are made. Comparisons are also made with other nearby star formation regions such as the Taurus clouds. Sources in the northern part of the region surveyed have larger line widths, kinetic temperatures, Tk, and higher ratios of the J = 3-2 to J = 2-1 lines of C18O. It is likely that these sources are heated externally. Except for cores in the southern part of this cloud, Tk exceeds; 10 K, the value found for dark dust clouds. The average density for all cores is ∼3 × 104 cm-3. Orion KL is an extraordinary source, with much larger Tk, local density, and column density than any other source in our sample.
• Bieging, J. H., Knee, L. B., Latter, W. B., & Olofsson, H. (1998). Molecular line observations of southern S stars. Astronomy and Astrophysics, 339(3), 811-821.
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  Abstract: We observed a sample of southern S stars with the SEST telescope, in the SiO (v=0, J=3-2) transition at 130.3 GHz, and the HCN (J=1-0) transition at 88.6 GHz. SiO emission was detected in all seven stars observed, while HCN was detected in two. We employed a statistical equilibrium/radiative transfer model to estimate the SiO abundance for an assumed molecular distribution. The inferred SiO abundances are consistent with formation of the molecule under thermodynamic equilibrium (TE) conditions near the stellar photosphere, for reasonable physical conditions. We also model the HCN emission by a similar analysis, and find that if HCN is produced near the stellar photosphere, our model abundances are much higher than predicted by TE chemistry, unless the gas temperature is
• Dayal, A., Hoffmann, W. F., Bieging, J. H., Hora, J. L., Deutsch, L. K., & Fazio, G. G. (1998). Mid-infrared (8-21 micron) imaging of proto-planetary nebulae. Astrophysical Journal Letters, 492(2 PART I), 603-616.
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  Abstract: We present mid-infrared (8-21 μm) images of thermal dust emission from two proto-planetary nebulae (PPNs), IRAS 07134 + 1005 and IRAS 22272 + 5435, which show a strong 21 μm emission feature. Both of the sources are well resolved and show evidence for axial symmetry. From our images, we calculate temperature and optical depth maps and estimate the abundance of the 11 μm and 21 μm feature carriers. In both sources, the dust temperatures range from ∼160-200 K. The optical depths in IRAS 07134 are about a factor of 3 lower than those in IRAS 22272, but the emission is optically thin in both sources. Our analyses of the feature-to-continuum ratios suggests that 0.5%-5% of the carbon in these objects may be in the form of large PAH molecules. We construct optically thin, axially symmetric cylindrical shell models to simulate the observed mid-IR morphologies and spectra, and calculate nebular masses of 0.26 M0 for IRAS 07134 and 0.42 M⊙ for IRAS 22272. Although the mid-IR emission primarily comes from warm (T ≈ 190 K) dust, our models require a significant cooler dust (T ≈ 80 K) component to fit the observed mid- and far-IR spectral energy distributions. © 1998. The American Astronomical Society. All rights reserved.
• Olofsson, H., Bergman, P., Lucas, R., Eriksson, K., Gustafsson, B., & Bieging, J. H. (1998). A thin molecular shell around the carbon star TT Cyg. Astronomy and Astrophysics, 330(1), L1-L4.
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  Abstract: Interferometric CO(J=1→0 and 2→1) observations reveal a remarkably thin shell of molecular gas around the carbon star TT Cyg, width/radius ≲ 1.″3/34″ ≈ 0.04. It expands at ≈ 13 km s-1, and contains ∼0.02 M⊙ of gas provided the CO abundance with respect to H2 is 10-3 and the distance is 1 kpc. Only about a quarter of the shell has been mapped, but we infer an overall spherical shell with only small, but clear, deviations ai the per cent level. The radial structure of the shell is barely resolved at the arc second level, but there exists weak emission extending a few arc seconds inwards from the peak. A drastic change in mass loss properties, possibly combined with the effects of interacting winds, provides the most likely explanation to the origin of the shell.
• Ferrario, L., Wickramasinghe, D. T., Liebert, J., Schmidt, G. D., & Bieging, J. H. (1997). The magnetic field and emission-line spectrum of the remarkable white dwarf GD 356. Monthly Notices of the Royal Astronomical Society, 289(1), 105-116.
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  Abstract: New spectropolarimetric observations of the unique white dwarf GD 356 are presented. These observations show resolved Zeeman triplets of Hα and Hβ in emission with distinctive circular polarization properties. A detailed modelling of the spectropolarimetric observations points to the existence of a latitudinally extended spherical sector/strip covering approximately 0.1 of the stellar surface over which the stellar atmosphere has an inverted temperature distribution at low optical depths. Magneto-optical effects from regions producing photospheric absorption appear to be responsible for narrow circular polarization features which are observed near the π component of the emission lines. Radio observations of GD 356 were obtained at the Very Large Array at 8439.9 and 4860.1 MHz, to gain clues on the origin of the emission lines, but the failure to detect the star in either frequency band does not provide a useful test for the presence of a corona. Also, new infrared (IR) observations to search for a low-mass stellar companion as a possible source of matter for accretion yielded null results. We have investigated the possibility that the temperature inversion is caused by Bondi-Hoyle accretion from the interstellar medium. The absence of additional components of radiation in the X-ray, ultraviolet, optical and near-IR wavelengths implies that the accretion luminosity must be significantly less than the white dwarf luminosity. The implied low value for the specific accretion rate (ℳ < 10-6 g cm-2 s-1) indicates that a shock would not form, but that the atmosphere will be particle heated by direct bombardment by the infalling protons. A detailed model of the bombardment solution in the very low-accretion regime is required before the viability of such a model can be fully evaluated. © 1997 RAS.
• Glenn, J., Walker, C. K., Bieging, J. H., & Jewell, P. R. (1997). Millimeter-wave spectropolarimetry of evolved stars: Evidence for polarized molecular line emission. Astrophysical Journal Letters, 487(1 PART II), L89-L92.
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  Abstract: We present spectropolarimetry of CSJ = 2-1 emission from the evolved stars IRC +10216 and CRL 2688 and spectropolarimetry of the HCN J = 1-0 transition from CRL 2688. We detected a line-averaged linear polarization of ∼1% toward IRC +10216 on three separate occasions. We found no evidence for velocity dependence of the polarization within the emission line. A deviation from spherical symmetry in the radiative transfer of the envelope is implied because polarization was detected toward the central star. The polarization position angle of about -70° is orthogonal to the envelope elongation apparent in previous observations. Polarizations of 5.1% ± 1.5% (1 σ) and less than 0.9% (3 σ), respectively, were derived for CS and HCN from CRL 2688. © 1997. The American Astronomical Society. All rights reserved.
• Wink, J. E., Altenhoff, W. J., Bieging, J., Butler, B., Butner, H., Haslam, C. G., Kreysa, E., Martin, R., Mauersberger, R., McMullin, J., Muders, D., Peters, W., Schmidt, J., Schraml, J. B., Sievers, A., Stumpff, P., Kapp-Herr, A. V., Thum, C., & Zylka, R. (1997). Coordinated observations of Comet Hale-Bopp between 32 and 860 GHz. Earth, Moon and Planets, 77(3), 165-.
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  Abstract: The concept of simultaneous multifrequency continuum observations, successfully tested on Comet Hyakutake, was applied to Comet Hale-Bopp, using the Heinrich Hertz Submillimeter Telescope (HHT) with the four color bolometer between 250 and 870 GHz, the IRAM 30m telescope at 240 GHz, the MPIfR 100-m telescope at 32 GHz, and the IRAM interferometer near 90 and 240 GHz. Near-simultaneous measurements were done between February 15 and April 26, 1997, mainly concentrated in mid March shortly before perigee of the comet. The measurements gave the following preliminary results: 1. Interferometer detection of the nuclear thermal emission. If the signal at the longest interferometer spacing of 170 m is due to thermal emission from the nucleus only, its equivalent diameter is ~49 km. If, however, this signal contains a contribution from a strongly centrally peaked halo distribution (e.g., r-2 density variation) the diameter may be as low as 35 km. 2. The emission found interferometrically was always 5″ north and 0.1 sec east from the position predicted by Yeoman's solution 55. 3. The comparison of the interferometric continuum emission with the simultaneously obtained molecular line observations (reported on this conference) shows the origin of the strongest line emission concentrated on the nucleus. 4. The 30-m observations show a radio halo with a gaussian FWHP of ~11, corresponding to a diameter of 11000 km at geocentric distance of 1.2 a.u. 5. A spectral index of ~3.0 for the total signal, which may indicate a smaller mean particle size than for Hyakutake. Assuming an average cometary density of 0.5 gcm-3, the mass contained in the nucleus is ~1-3 1019 g and 1012 g in the particle halo.
• Bieging, J. H., & Rieu, N. (1996). Kinematics of molecular gas in the proto-planetary nebula CRL 2688 (the "egg"). Astronomical Journal, 112(2), 706-716.
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  Abstract: We present aperture synthesis images of the HCN J = 1 - 0 emission line toward the proto-planetary nebula CRL 2688 (the "Egg Nebula"). The images were obtained with the BIMA mm interferometer, and have angular and velocity resolutions of 3″ and 1.3 km s-1. The emission is well resolved spatially and is extended mainly in the east-west direction, coincident with the optical dark lane. There are also extensions of the HCN emission to the north and south, along the symmetry axis of the optical bipolar nebula. The north-south extensions are not consistent with predictions of photodissociation models for HCN. The morphology of the HCN maps shows a striking correspondence with the four bright lobes of the S(1) line of H2, which lie at the ends of the extended HCN emission. The velocity centroid of the HCN J = 1-0 line shows a significant gradient across the nebula. The magnitude of the gradient is larger than was found in previous work, attributable to improved angular resolution. The most blueshifted emission is to the north and east of the central star, while the most redshifted emission is to the south and west. The steepest gradient lies along a line intermediate between the bipolar axis (at P.A. 15°) and the dark equatorial lane (P.A. 105°). The gradients along each of these two axes are nearly equal, with a value of 0.9 km s-1arcsec-1. We suggest that the observed velocity gradient may be attributed to two kinematic components: (1) a radial outflow in which the velocity along or near the bipolar axis exceeds the flow velocity in the equatorial plane by at least a factor of 1.5; and (2) a rotational component in the equatorial plane. The implied specific angular momentum in the rotational component to the gas motion could be supplied from the orbital angular momentum of a binary companion. We discuss some possible mechanisms for transferring angular momentum, and argue that gravitational torques are unlikely to be effective enough to produce the observed velocity gradient, but that magnetic fields, acting through Alfvén waves, could do so if the stellar surface field is sufficiently high (of order several kilogauss). © 1996 American Astronomical Society.
• Dayal, A., & Bieging, J. H. (1996). Millimeter-wave observations of CO in planetary nebulae. Astrophysical Journal Letters, 472(2 PART I), 703-710.
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  Abstract: We present NRAO 12 m observations of CO (J = 1-0 and J = 2-1) in six planetary nebulae, including the first confirmed detection of a molecular outflow in K3-35 and the first observations of J = 1-0 emission from NGC 2440. The J = 2-1 spectrum toward K3-35 shows a strong peak at ∼10 km s-1 (V1sr) and a ∼40 km s-1 wide, lower excitation, high-velocity component. The strong peak is narrow (
• Bieging, J., & Bieging, J. H. (1995). Circumstellar chemistry from microwave and mm-wave spectroscopy. Advances in space research : the official journal of the Committee on Space Research (COSPAR), 15(3).
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  Stars in their late stages of evolution often shed matter in the form of a cool wind which is molecular in composition. These winds are a major source of replenishment of the interstellar gas and dust, so they furnish a large part of the raw materials for new generations of stars and planets. The chemistry of the circumstellar envelope depends strongly on the photospheric abundances of the elements, especially C and O. If C/O > 1, a rich organic chemistry is observable in the microwave and mm-wavelength emission lines of the reactions products. This paper reviews the observational evidence for the presence of organic molecules and their formation pathways in circumstellar envelopes, with special emphasis on rotational spectra at microwave and millimeter wavelengths.
• Dayal, A., & Bieging, J. H. (1995). The distribution of HCN, H¹³CN, and CN in IRC +10216. Astrophysical Journal Letters, 439(2), 996-1010.
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  Abstract: We present aperture synthesis images of millimeter-wavelength molecular emission lines of HCN (J = 1-0 at 88.6 GHz), H13CN (J = 1-0 at 86.3 GHz), and CN (N = 1-0, J = 3/2-1/2 at 113.5 GHz) toward the carbon star IRC +10216. The HCN and H13CN images were made with the BIMA interferometer, while the CN images were from a combination of interferometer and single-dish data. The HCN and H13CN images have an angular resolution of 8″ and a velocity resolution of ∼1.3 km s-1; the CN images have an angular resolution of 11″ and a velocity resolution of ∼0.9 km s-1. The images show that HCN and H13CN are found concentrated toward the center of the envelope, while CN is found in the shell surrounding the central star. The data for HCN and H13CN are compared with the output of a statistical equilibrium code, which takes into account the excitation by IR photons and collisions with H2, and calculates the radial brightness profiles and spectra. The models are used to determine the abundance distribution of H13CN. HCN is too optically thick for accurate modeling; we infer the HCN abundance by scaling H13CN up by a factor of 40. For CN, a simple LTE calculation is used to derive the abundance of the molecule as a function of distance from the star. The distributions of HCN and CN are qualitatively consistent with chemical models for AGB star envelopes. Our best estimate of the peak CN/HCN abundance ratio is about 0.12, and the radius of the peak CN abundance is 19″ from the star. Both of these values are significantly less than recent photochemical model predictions. We suggest that CN photodissociates or reacts with other radicals or ions more rapidly than these models assume.
• Bieging, J. H., & Latter, W. B. (1994). A millimeter-wavelength survey of S stars for mass loss and chemistry. Astrophysical Journal Letters, 422(2), 765-782.
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  Abstract: We report the results of a survey of 27 S stars within 1 kpc of the Sun for emission from the J = 1-0 and 2-1 lines of CO. For those stars with strong detections in CO, we also searched for emission from the J = 1-0 line of HCN and the J = 2-1, v = 0 emission lines of SiO. In addition, we searched for SiO J = 2-1, v = 1 maser emission in a total of 14 stars in our sample. We derive mass-loss rates for the S stars detected in CO and compare with other estimates. Our mass loss rates from the CO J = 1-0 line are well correlated with the rates derived by Jura (1988) from IR flux densities and a dust model, but our values are systematically higher than Jura's by about a factor of 2. The derived gas mass-loss rates for our sample are very similar to those found for carbon stars. We find, however, that the average dust/gas ratio of our sample of S stars is lower than that for carbon stars, suggesting that S stars are less efficient at producing grains, per unit of ejected mass, than are carbon stars. Four of eight stars surveyed show definite detections of HCN in their circumstellar envelopes. Five of seven stars have thermal (v = 0) SiO emission, while eight of 14 surveyed show maser (v = 1) SiO emission. We use our results to estimate HCN and SiO abundances and compare these with the results of thermodynamic equilibrium models for the formation of these species under photospheric conditions with C/O nearly equal to unity. The HCN and SiO abundances indicate that the formation of these species must occur at temperatures low enough for grain formation to be important, which may serve to enhance production of HCN. Our results show no evidence that S stars experience a cessation of mass loss, contrary to recent suggestions.
• Bieging, J. H., & Tafalla, M. (1993). The distribution of molecules in the circumstellar envelope of IRC +10216: HC₃N, C₃N, and SiS. Astronomical Journal, 105(2), 576-594.
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  Abstract: We present aperture synthesis images made with the BIMA mm interferometer of molecular emission lines of HC3N, C3N, and SiS at ∼109 GHz toward the carbon star IRC +10216. The images have angular resolutions of 5″-7″ and velocity resolution of ∼1 km/s. The data are compared with model calculations using a newly-developed statistical equilibrium code which predicts the brightness distribution and spectrum for linear molecules in a spherical expanding circumstellar envelope. Excitation by IR photons and collisions is included. The model calculations are used to derive the abundance of HC3N and SiS as a function of distance from the star. For C3N, an LTE calculation is used to derive the abundance distribution. The data clearly show that HC3N and C3N are distributed in concentric shells, with little or no emission from the inner envelope. The abundances derived from our model calculations are much larger than published ion-molecule chemical reaction networks predict, but are in reasonably good agreement with chemical models which include neutral molecule-radical reactions. Statistical equilibrium models for SiS indicate that the gas phase abundance of SiS must decrease substantially as the gas flows from the photosphere to a distance of ∼2×1015 cm, probably as a result of grain adsorption processes. Photodissociation appears to cut off the SiS distribution between 2-3×1016 cm. We find that IR line overlaps of SiS with HCN or C2H2 are probably not important in the excitation of SiS, but that the excitation temperatures of some rotational transitions of SiS are very sensitive to the IR flux from the central star and dust shell. This strong dependence of excitation on IR flux may account for observed spectral variability of SiS lines.
• Dayal, A., & Bieging, J. H. (1993). The abundance distribution of C₄H in IRC + 10216. Astrophysical Journal Letters, 407(1 PART 2), L37-L40.
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  Abstract: We have observed the N = 9-8 spin doublet emission line of C4H at 85.6 GHz in the carbon star IRC + 10216 with the BIMA millimeter interferometer. The aperture synthesis images have an angular resolution of ∼10″ and a velocity resolution of ∼1.3 km s-1. The data clearly show that C4H is distributed in a shell surrounding the central star, with little emission from the inner envelope. The peak of the average radial brightness profile in a map centered at the systemic velocity and with a width of 10 km s-1 is ∼0.88 K at a projected radius of 15″. From the brightness temperature profile we infer that the thickness of the shell at half-peak intensity is ∼15″. We derive the abundance of the molecule as a function of distance from the star using an LTE model. The peak abundance is calculated to be 1.8 ×10-6 (with respect to the H2 number density) at a radius of 16″.7 or 2.5 × 1016 cm assuming a distance of 100 pc, a mass-loss rate of 2 × 10-5 M⊙ yr-1, and an outflow velocity of 13.8 km s-1. We compare our derived C4H distribution with the predictions of a photochemical model and find that the model underestimates the observed abundance of C4H by a factor of 5.
• Sahai, R., & Bieging, J. H. (1993). Interferometric observations of non-maser SiO emission from circumstellar envelopes of AGB stars: Acceleration regions and SiO depletion. Astronomical Journal, 105(2), 595-607.
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  Abstract: We have obtained high (3″-4″) and medium (7″-9″) resolution images of the SiO J = 2-1 (V=0) emission from the circumstellar envelopes (CSEs) of three oxygen-rich Mira variables, χ Cyg, RX Boo, and IK Tau. The SiO images are roughly circular, implying that the CSEs are largely spherically symmetric on angular-size scales of ≈3″-9″. The emission is strongly centrally peaked, but shows a non-negligible amount of extended, low surface-brightness emission. The intrinsic SiO brightness distribution, as a function of radius, is best approximated by a power-law, rather than a Gaussian or exponential function, for our sources. The observed angular half-maximum intensity source radius is nearly independent of LSR velocity for all three CSEs. This behavior is a characteristic feature of power-law distributions, which are scale-free, rather than Gaussian or exponential ones, which have well-defined scale sizes. Detailed radiative transfer/excitation calculations, coupled with a kinematic model of gas acceleration by radiation pressure on dust grains have been used to successfully reproduce the characteristic properties of the observed SiO emission. We find that the emission can be understood using normal radial acceleration models, i.e., those in which the outflow velocity reaches half its terminal value within about 10 stellar radii. Very large-scale acceleration (up to ≈100 stellar radii) is not required, contrary to a recent model proposed by Lucas et al. [A&A, 262, 491 (1992)]. In χ Cyg and RX Boo, the line-profiles are rounded, typical of optically-thick emission from a spherical envelope expanding with a constant velocity. The presence of an additional (kinematically) narrower central component in the line profiles observed toward IK Tau (both with high and medium resolution observations), implies the existence of an inner circumstellar shell with a significantly smaller expansion velocity than the extended envelope. The radial distribution of the SiO abundance, from small (1015 cm) to large radii (> 1016 cm), is constrained by the observed half-maximum intensity source sizes, and ratios of the source fluxes in small and large beams. We find that a rapid depletion of SiO from the gas phase must occur at radii larger than about (1-2) 1015 cm, initially by the process of adhesion onto dust grains, followed by photodissociation by the interstellar UV. IK Tau has a higher average fraction (by a factor 2.7) of SiO left over in the extended envelope, as compared to χ Cyg and RX Boo, which are similar in this respect. Depending on the stellar mass-loss rates and distances, the initial SiO abundance in the circumstellar envelopes of IK Tau, χ Cyg, and RX Boo, is about (1-few) 10-5.
• Walker, C. K., Carlstrom, J. E., & Bieging, J. H. (1993). The IRAS 16293 - 2422 cloud core: A study of a young binary system. Astrophysical Journal Letters, 402(2), 655-666.
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  Abstract: We present submillimeter-wave single dish and millimeter-wave interferometric observations of the central core region of the far-infrared source IRAS 16293 - 2422. High-resolution millimeter continuum and CS images of IRAS 16293 reveal it to be a young binary system surrounded by a slowly rotating circumbinary shell of material. We use single dish CS observations in conjunction with the interferometric CS observations to probe the dynamics and physical properties of the gas associated with the system.
• Churchwell, E., Bieging, J. H., Van, K., Williams, P. M., Spoelstra, T., & Abbott, D. C. (1992). The wolf-rayet system WR 147: A binary radio source with thermal and nonthermal components. Astrophysical Journal Letters, 393(1), 329-340.
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  Abstract: A revised distance of 630 pc is derived for the Wolf-Rayet star WR 147(WN8) from newly obtained near-infrared photometry. This distance is almost free of reddening corrections, and it indicates that WR 147 is not associated with the Cyg OB2 association (which lies at a distance of 2 kpc), as previously thought. A terminal wind speed of 900 km s-1 is found for WR 147 from the P Cygni profile of the He I (21 S-21P) line at 2.058 μm. High-resolution VLA images were obtained at three different epochs at wavelengths 20, 6, 2, and 1.3 cm (although not all wavelength bands were imaged at each epoch) with angular resolutions of 1″.60, 0″.46, 0″.14, and 0″.11, respectively. These images show two radio components separated by 0″.58 (∼ 364 AU) in an approximately N-S direction. The optical astrometry of Moran et al. shows that the Wolf-Rayet star WR 147 coincides with the southern radio component WR 147S whose spectrum and visibility function are consistent with a thermal wind. The northern radio component WR 147N is clearly nonthermal. The radio emission from WR 147S can be accurately modeled by a spherical wind whose density decreases with distance as r-2. We find an average mass-loss rate of 4.2 ± 0.2 × 10-5 M⊙ yr-1 and a mean wind temperature of 9400 ± 1000 K. Several mechanisms were investigated to determine if the observed X-ray luminosity could be produced by interaction of the wind from WR 147S with another star at the position of WR 147N. The only mechanism we found that could produce adequate X-ray luminosity is gravitational capture by a neutron star orbiting in a dense, slow, equatorial wind from WR 147S. This result lends support to the magnetic rotator model of Poe, Friend, & Cassinelli for W-R stars. We caution, however that the X-ray emission could be produced by shocks in the wind of WR 147S or perhaps by colliding winds from WR 147S and WR 147N. The flux density of the WR 147 system varies by as much as 50% at 21 cm over a period of a week or two and as much as 20% at 6 cm over a period of several weeks. The variations are probably associated with WR 147N.
• White, S. M., Kundu, M. R., Bastian, T. S., Gray, D. E., Hurford, G. J., Kucera, T., & Bieging, J. H. (1992). Multifrequency observations of a remarkable solar radio burst. Astrophysical Journal Letters, 384(2), 656-664.
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  Abstract: Observations of an impulsive solar radio burst from three observatories are presented. The striking observational aspects of this flare are that the time profile was identical throughout at 8.6, 15, and 86 GHz, that the spectrum was apparently flat from 15 to 86 GHz, and that there was a sharp cutoff in the spectrum between 5.0 and 8.6 GHz. The simplest interpretation of the cutoff, namely as a plasma frequency effect, leads to the conclusion that there was exceptionally high-density material in the solar corona (∼ 5 × 1011 cm-3). Very Large Array images at 15 GHz show a single loop structure which brightened uniformly and showed little change in size during the whole impulsive phase. The flat spectrum is consistent with optically thin thermal bremsstrahlung emission, but the lack of observed soft X-ray emission and other properties of the flare cannot easily be accommodated by this mechanism. We also explore the possibility that the emission is optically thick due to thermal absorption of nonthermal gyrosynchrotron emission, or optically thin gyrosynchrotron emission absorbed by high-density material intervening along the line of sight. Both of these explanations also face difficulties.
• Bieging, J. H., Goss, W. M., & Wilcots, E. M. (1991). VLA observations of 21 centimeter H I absorption toward cassiopeia A. Astrophysical Journal, Supplement Series, 75(4), 999-1010.
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  Abstract: We have used the Very Large Array to map the 21 cm neutral hydrogen absorption in the Perseus spiral arm feature toward the supernova remnant Cassiopeia A. The velocity resolution of the data is 0.6 km s-1, and the final angular resolution displayed is 7″ (HPBW), which corresponds to a linear size of 0.10 pc at the adopted distance of Cas A (3 kpc). We present optical depth images as gray scale with contours superposed, for 41 spectral channels showing H I absorption. We also show representative optical depth spectra as a function of position over Cas A. The images represent a factor of 11 improvement in angular resolution over the earlier aperture synthesis work of Greisen, and a factor of 4 over the H I results reported by Goss, Kalberia, and Dickel. Our H I images show a great deal of structure in the absorbing gas, with the morphology dominated by elongated structures, appearing as loops, arcs, and filaments. We briefly discuss the implications of our results in terms of the structure of the interstellar medium, and of the relationship between the atomic and molecular gas in the Perseus arm features toward Cas A.
• Bieging, J. H., Wilner, D., & Thronson Jr., H. A. (1991). The molecular envelope of NGC 7027. Astrophysical Journal Letters, 379(1), 271-279.
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  Abstract: We present maps of the J = 1-0 emission line of CO toward the planetary nebula NGC 7027. The images were made by combining interferometer observations from the Berkeley-Illinois-Maryland Array (BIMA) with single-dish observations from the NRAO 12 m telescope. The maps have an angular resolution of 5″ and contain all the flux in the CO J = 1-0 line. The integrated intensity map shows that the circumstellar molecular envelope has a diameter to zero intensity of ∼70″, corresponding to a linear size of 0.30 pc at distance of 900 pc. The envelope has an axisymmetric, clumpy appearance, with unresolved clumps having a size of
• Jaminet, P. A., Danchi, W. C., Sutton, E. C., Russell, A. P., Sandell, G., Bieging, J. H., & Wilner, D. (1991). CO J = 3-2 and J = 2-1 observations of NGC 7027. Astrophysical Journal Letters, 380(2), 461-475.
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  Abstract: Using the 15 m James Clerk Maxwell Telescope, we have mapped the molecular envelope surrounding the planetary nebula NGC 7027 in the J = 3-2 line of 12CO and have observed the central position in the J = 3-2 line of 13CO and the J = 2-1 lines of 12CO and 13CO. The J = 3-2 12CO map shows substantial deviations from spherical symmetry. The mass-loss rate along the nebula's polar axis appears to be about half that in the equatorial directions. Bright line wings are caused by a bipolar flow of molecular gas along the low-density axis. This gas has an outflow velocity of 23 km s-1, larger than the 15 km s-1 expansion velocity of the bulk of the envelope. This flow is apparently driven by the pressure of the ionized region. A marked asymmetry in the J = 3-2 line profile toward the central position is probably due to a radiative transfer effect, which is more important in NGC 7027 than in other circumstellar envelopes due to the large velocity dispersion of neutral gas near the ionized region. We have compared the data with CO J = 1-0 observations and derive new estimates for envelope parameters from a detailed model. The kinetic temperature is 30 ± 3 K at a radius of r = 8″ and varies with radius approximately like r-0.85. The total mass-loss rate is 1-2 × 10-4 M⊙ yr-1, but the mass loss is aspherical. The CO:H2 abundance ratio is 2-1+2 × 10-4, and the 12COr:13CO abundance ratio is 90 ± 25. The radial extent of the CO emission is smaller than is consistent with the assumption of constant mass-loss rate and constant CO:H2 ratio. This may be due to dissociation of the CO by the interstellar radiation field at characteristic radii of about 35″ in equatorial directions and about 25″ in polar directions. Alternatively, the mass-loss rate and/or the CO:H2 ratio may have been smaller 8000 yr ago than they were in the more recent past.
• Kundu, M. R., White, S. M., Welch, W. J., & Bieging, J. H. (1991). High spatial resolution observations of solar flares at 3.3 mm wavelength. Advances in Space Research, 11(5), 91-94.
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  Abstract: We present the first high-spatial-resolution interferometric observations of solar flares at millimeter wavelengths, carried out with the Berkeley-Illinois-Maryland Array (BIMA). The observations represent an improvement of an order of magnitude in both sensitivity and spatial resolution compared with previous solar observations at these wavelengths. Most of the flares occurring within the field of view during the observations were detected by BIMA, including both very impulsive and longer-duration events. It appears that millimeter burst sources are not much smaller than microwave sources. If the emission in the flash phase is predominantly due to gyrosynchrotron emission, we can rule out thermal gyrosynchrotron models for the radio emission because the flux at millimeter wavelengths is too high. During the Flares 22 campaign we will collect both imaging data as well as dedicated patrol observations of flare time profiles at millimeter wavelengths. © 1991.
• Bieging, J. H. (1990). Aperture synthesis observations of molecules in CRL 2688. Astrophysical Journal, 359(1), 131-137.
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  Abstract: We have used the BIMA-Hat Creek interferometer to map the line emission of H13CN, HC3N, HNC, and SiS at 3 mm toward the bipolar object CRL 2688 (the " Egg nebula "). The molecular emission distributions show a slight departure from spherical geometry and have a major axis (∼10″) almost aligned with the direction of the dust lane of the Egg nebula. The SiS emission is less extended than that of the organic molecules and is confined to the central region of the envelope. A pedestal emission at both redshifted (∼ -15 to ∼ -5 km s-1) and blueshifted (∼ -65 to ∼ -45 km s-1) wings detected in the H13CN, and HC3N spectra may arise from a bipolar outflow or a time-variable wind corresponding to a high-speed wind phase. The abundances of H13CN, HC3N, and HNC in CRL 2688 are comparable to those observed in IRC + 10216. SiS is depleted in CRL 2688 by an order of magnitude with respect to the average SiS abundance observed in IRC +10216. It is shown that the determination of the abundances of HCN and H13CN is strongly affected by the self-absorption of the optically thick blended hyperfine components in the expanding envelope. If self-absorption is ignored, the HCN and H13CN abundances could be underestimated by a factor of ∼3.
• Kundu, M. R., White, S. M., Gopalswamy, N., Bieging, J. H., & Hurford, G. J. (1990). First high spatial resolution interferometric observations of solar flares at millimeter wavelengths. Astrophysical Journal, 358(2 PART 2), L69-L73.
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  Abstract: We present the first high spatial resolution interferometric observations of solar flares at millimeter wavelengths, carried out with the Berkeley-Illinois-Maryland Array (BIMA). The observations were made at 3.3 mm wavelength during the very active period of 1989 March, using one or three baselines with fringe spacings of 2″5″. The observations represent an improvement of an order of magnitude in both sensitivity and spatial resolution compared with previous solar observations at these wavelengths. Most of the flares occurring within the field of view during the observations were detected by BIMA, including both very impulsive and longer duration events. The longer flares generally seem to have been larger in size than the fringe spacings available, whereas some of the impulsive events may have had sizes comparable to our resolution. However, it appears that millimeter burst sources are not much smaller than microwave sources. The most intense bursts imply brightness temperatures of over 106 K and are due to nonthermal gyrosynchrotron emission or possibly thermal free-free emission. If the emission in the flash phase is predominantly due to gyrosynchrotron emission, we can rule out thermal gyrosynchrotron models for the radio emission because the flux at millimeter wavelengths is too high.
• Loushin, R., Crutcher, R. M., & Bieging, J. H. (1990). Observations of an expanding molecular ring in S106. Astrophysical Journal, 362(2 PART 2), L67-L69.
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  Abstract: We have mapped the 3 mm rotational transition of HCO+ toward S106 with the Berkeley-Illinois-Maryland Array and the NRAO 12 m telescope. The maps show evidence for an expanding molecular ring around IRS 4, the exciting star in S106. The radius of the ring is about 2 × 1017 cm, and its mass is ≤ 10 M⊙. The ring is expanding with a velocity of about 2 km s-1. The ring cannot be supported by rotation; magnetic fields and gas pressure may be important in determining the kinematics of the region. We also observe clumps of high-velocity material which may have been ablated from the ring and entrained in the ionized bipolar outflow.
• Walker, C. K., Carlstrom, J. E., Bieging, J. H., Lada, C. J., & Young, E. T. (1990). Observations of the dense gas in the IRAS 16293-2422 outflow system. Astrophysical Journal, 364(1), 173-177.
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  Abstract: We present millimeter-wave interferometric and single-dish observations of IRAS 16293-2422 in the CS J = 2 → 1 line. The images reveal clumpy, shell-like structures which appear to be limb-brightened emission from dense gas at the perimeter of the molecular outflow observed in CO. These structures may be ambient cloud material swept up by a stellar wind into dense shells. At all velocities where CS is detected, features related to the outflow are observed. Most of the mass of the outflow system is contained in low-velocity shells.
• Welch, W. J., Vogel, S. N., Plambeck, R. L., Wright, M. C., & Bieging, J. H. (1985). Gas jets associated with star formation. Science, 228(4706), 1389-1395.
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  Abstract: Young stellar objects of both high and low luminosity emit energetic jets or winds of material that are often highly collimated and often bipolar. Near the stars, turbulent swept-up gas is observed in the emission of interstellar molecules such as carbon monoxide, and small, bright regions of water maser emission and the nebulous bright patches known as Herbig-Haro objects appear to be participating in the outflows. There are striking changes in chemical abundances associated with the attendant shocks. Probably every star goes through this phase, which may mark the end of its period of accretion.
• Bieging, J. H., Morgan, J., Welch, W. J., Vogel, S. N., & Wright, M. C. (1984). INTERFEROMETER MEASUREMENTS OF ATMOSPHERIC PHASE NOISE AT 86 GHz.. Radio Science, 19(6), 1505-1509.
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  Abstract: The authors report measurements of the atmospheric phase noise at 86 GHz, made by using the Hat Creek millimeter wavelength interferometer. The measurements used a dual-frequency technique to estimate the receiver noise contribution to the phase. The data, which cover projected baselines between 2000 and 4000 wavelengths, are used to derive median root mean squared (rms) phase noise as a function of baseline length. The implications of these results for the resolution limit to millimeter wavelength interferometry are discussed. We also discuss the time domain spectrum of atmospheric phase noise and consider an observing strategy that can mitigate the effects of adverse atmospheric conditions.
• Bieging, J., & Downes, D. (1975). Improved declination for transient X ray source A0620-00. Nature, 258(5533), 307-308.

Proceedings Publications

• Kilpatrick, C., Bieging, J., & Rieke, G. (2016, jan). A Survey For Broadened CO Lines Toward Galactic Supernova Remnants. In American Astronomical Society Meeting Abstracts, 227.
• Kilpatrick, C., Rieke, G., & Bieging, J. (2016, jun). A survey for Galactic supernova remnant/molecular cloud interactions ssing carbon monoxide. In Supernova Remnants: An Odyssey in Space after Stellar Death.
• Rho, J., Hewitt, J., Reach, W., Bieging, J., Andersen, M., & G{\"usten}, R. (2016, jan). Shocked Gas from the supernova remnant G357.7+0.3. In American Astronomical Society Meeting Abstracts, 227.
• Kilpatrick, C., Bieging, J. H., & Rieke, G. (2014, jan). Analysis of Shock Interactions and Supernova Morphology from Molecular Emission Around Young Supernova Remnants. In American Astronomical Society Meeting Abstracts, 223, #353.21.
• Rudolph, A. L., Impey, C. D., Bieging, J. H., Phillips, C. B., Tieu, J., & Povich, M. S. (2014, jan). The CAMPARE Program:A New Model Promoting Minority Participation in Astronomy Research and Education. In American Astronomical Society Meeting Abstracts, 223, #445.03.
• Rudolph, A. L., Impey, C. D., Bieging, J. H., Phillips, C. B., Tieu, J., Prather, E. E., & Povich, M. S. (2013, jan). The California-Arizona Minority Partnership for Astronomy Research and Education (CAMPARE): A New Model for Promoting Minority Participation in Astronomy Research and Education. In American Astronomical Society Meeting Abstracts, 221, #115.03.
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