Alyson Ford

Interests

No activities entered.

Courses

Scholarly Contributions

Journals/Publications

• Collaboration, E., Akiyama, K., Algaba, J. C., Alberdi, A., Alef, W., Anantua, R., Asada, K., Azulay, R., Baczko, A., Ball, D., Balokovi{\'c}, M., Barrett, J., Benson, B. A., Bintley, D., Blackburn, L., Blundell, R., Boland, W., Bouman, K. L., Bower, G. C., , Boyce, H., et al. (2021). First M87 Event Horizon Telescope Results. VII. Polarization of the Ring. \apjl, 910(1), L12.
• Collaboration, E., Akiyama, K., Algaba, J. C., Alberdi, A., Alef, W., Anantua, R., Asada, K., Azulay, R., Baczko, A., Ball, D., Balokovi{\'c}, M., Barrett, J., Benson, B. A., Bintley, D., Blackburn, L., Blundell, R., Boland, W., Bouman, K. L., Bower, G. C., , Boyce, H., et al. (2021). First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon. \apjl, 910(1), L13.
• Goddi, C., Mart{\'\i-Vidal}, I., Messias, H., Bower, G. C., Broderick, A. E., Dexter, J., Marrone, D. P., Moscibrodzka, M., Nagai, H., Algaba, J. C., Asada, K., Crew, G. B., G{\'omez}, J. L., Impellizzeri, C. V., Janssen, M., Kadler, M., Krichbaum, T. P., Lico, R., Matthews, L. D., , Nathanail, A., et al. (2021). Polarimetric Properties of Event Horizon Telescope Targets from ALMA. \apjl, 910(1), L14.
• Group, E., Algaba, J., Anczarski, J., Asada, K., Balokovi{\'c}, M., Chandra, S., Cui, Y. -., Falcone, A., Giroletti, M., Goddi, C., Hada, K., Haggard, D., Jorstad, S., Kaur, A., Kawashima, T., Keating, G., Kim, J. -., Kino, M., Komossa, S., , Kravchenko, E., et al. (2021). Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign. \apjl, 911(1), L11.
• Janssen, M., Falcke, H., Kadler, M., Ros, E., Wielgus, M., Akiyama, K., Balokovi{\'c}, M., Blackburn, L., Bouman, K. L., Chael, A., Chan, C., Chatterjee, K., Davelaar, J., Edwards, P. G., Fromm, C. M., G{\'omez}, J. L., Goddi, C., Issaoun, S., Johnson, M. D., , Kim, J., et al. (2021). Event Horizon Telescope observations of the jet launching and collimation in Centaurus A. Nature Astronomy, 5, 1017-1028.
• Kocherlakota}, P., Rezzolla, L., Falcke, H., Fromm, C. M., Kramer, M., Mizuno, Y., Nathanail, A., Olivares, H., Younsi, Z., Akiyama, K., Alberdi, A., Alef, W., Algaba, J. C., Anantua, R., Asada, K., Azulay, R., Baczko, A., Ball, D., Balokovi{\'c}, M., , Barrett, J., et al. (2021). Constraints on black-hole charges with the 2017 EHT observations of M87*. \prd, 103(10), 104047.
• Narayan, R., Palumbo, D. C., Johnson, M. D., Gelles, Z., Himwich, E., Chang, D. O., Ricarte, A., Dexter, J., Gammie, C. F., Chael, A. A., Collaboration, E., Akiyama, K., Alberdi, A., Alef, W., Algaba, J. C., Anantua, R., Asada, K., Azulay, R., Baczko, A., , Ball, D., et al. (2021). The Polarized Image of a Synchrotron-emitting Ring of Gas Orbiting a Black Hole. \apj, 912(1), 35.
• Bailin, J., Cannon, J. M., Ford, H. A., Hunt, L., Johnson, M. C., Kamphuis, P., Martinkus, C. P., Mcquinn, K. B., Skillman, E. D., Westmeier, T., & Wong, O. I. (2018). The Hi Neighborhoods Around STARBIRDS. Proceedings of the International Astronomical Union, 344(S344), 280-282. doi:10.1017/s1743921318005811
  More info

  AbstractStarbursts are finite periods of intense star formation (SF) that can dramatically impact the evolutionary state of a galaxy. Recent results suggest that starbursts in dwarf galaxies last longer and are distributed over more of the galaxy than previously thought, with star formation efficiencies (SFEs) comparable to spiral galaxies, much higher than those typical of non-bursting dwarfs. This difference might be explainable if the starburst mode is externally triggered by gravitational interactions with other nearby systems. We present new, sensitive neutral hydrogen observations of 18 starburst dwarf galaxies, which are part of the STARburst IRregular Dwarf Survey (STARBIRDS) and each were mapped with the Green Bank Telescope (GBT) and/or Parkes Telescope in order to study the low surface brightness gas distributions, a common tracer for tidal interactions.
• Di Teodoro, E. M., McClure-Griffiths, N. M., Lockman, F. J., Denbo, S. R., Endsley, R., Ford, H. A., & Harrington, K. (2018). Blowing in the Milky Way wind: neutral hydrogen clouds tracing the Galactic nuclear outflow. ApJ.
  More info

  We present the results of a new sensitive survey of neutral hydrogen aboveand below the Galactic Center with the Green Bank Telescope. The observationsextend up to Galactic latitude | b | < 10 deg with an effective angularresolution of 9.5' and an average rms brightness temperature noise of 40 mK ina 1 km/s channel. The survey reveals the existence of a population of anomaloushigh-velocity clouds extending up to heights of about 1.5 kpc from the GalacticPlane and showing no signature of Galactic rotation. These clouds have localstandard of rest velocities | Vlsr | < 360 km/s and, assuming a Galactic Centerorigin, they have sizes of a few tens of parsecs and neutral hydrogen massesspanning $10-10^5 \, M_\odot$. Accounting for selection effects, the cloudpopulation is symmetric in longitude, latitude, and Vlsr. We model the cloudkinematics in terms of an outflow expanding from the Galactic Center and findthe population consistent with being material moving with radial velocity Vw ~330 km/s distributed throughout a bi-cone with opening angle $\alpha>140$ deg.This simple model implies an outflow luminosity $Lw > 3 \times 10^{40}$ erg/sover the past 10 Myr, consistent with star formation feedback in the innerregion of the Milky Way, with a cold gas mass-loss rate $\lesssim 0.1 \,M_\odot$/yr. These clouds may represent the cold gas component accelerated inthe nuclear wind driven by our Galaxy, although some of the derived propertieschallenge current theoretical models of the entrainment process.[Journal_ref: ]
• HI4PI Collaboration, ., & Ford, H. A. (2016). HI4PI: A full-sky H I survey based on EBHIS and GASS. Astronomy & Astrophysics, 594. doi:10.1051/0004-6361/201629178
• Alfvin, E. D., Bailin, J., Cannon, J. M., Dolphin, A. E., Elson, E. C., Ford, H. A., Girardi, L., Hirschauer, A. S., Janowiecki, S., Johnson, M., Koribalski, B., Marigo, P., Mcquinn, K. B., Rosenberg, J. L., Rosenfield, P., Salzer, J. J., Sistine, A. V., Skillman, E. D., Venkatesan, A., & Warren, S. R. (2014). DISCOVERY OF A GAS-RICH COMPANION TO THE EXTREMELY METAL-POOR GALAXY DDO 68. The Astrophysical Journal, 787(1), L1. doi:10.1088/2041-8205/787/1/l1
  More info

  We present H I spectral-line imaging of the extremely metal-poor galaxy DDO 68. This system has a nebular oxygen abundance of only ~3% Z ☉, making it one of the most metal-deficient galaxies known in the local volume. Surprisingly, DDO 68 is a relatively massive and luminous galaxy for its metal content, making it a significant outlier in the mass-metallicity and luminosity-metallicity relationships. The origin of such a low oxygen abundance in DDO 68 presents a challenge for models of the chemical evolution of galaxies. One possible solution to this problem is the infall of pristine neutral gas, potentially initiated during a gravitational interaction. Using archival H I spectral-line imaging obtained with the Karl G. Jansky Very Large Array, we have discovered a previously unknown companion of DDO 68. This low-mass ( = 2.8 × 107 M ☉), recently star-forming (SFRFUV = 1.4 × 10–3 M ☉ yr–1, SFRHα < 7 × 10–5 M ☉ yr–1) companion has the same systemic velocity as DDO 68 (V sys = 506 km s–1; D = 12.74 ± 0.27 Mpc) and is located at a projected distance of ~42 kpc. New H I maps obtained with the 100 m Robert C. Byrd Green Bank Telescope provide evidence that DDO 68 and this companion are gravitationally interacting at the present time. Low surface brightness H I gas forms a bridge between these objects.
• Monachesi, A., Bell, E. F., Radburn-Smith, D. J., De Jong, R. S., Bailin, J., Dalcanton, J. J., Holwerda, B. W., Alyson Ford, H., Streich, D., Vlajić, M., & Zucker, D. B. (2013). Ghosts I: a new faint very isolated dwarf galaxy at D = 12 ± 2 Mpc. The Astrophysical Journal, 780(2), 179. doi:10.1088/0004-637x/780/2/179
  More info

  We report the discovery of a new faint dwarf galaxy, GHOSTS?I, using HST/ACS data from one of our GHOSTS?(Galaxy Halos, Outer disks, Substructure, Thick disk, and Star clusters) fields. Its detected individual stars populate an approximately 1?mag range of its luminosity function (LF). Using synthetic color-magnitude diagrams (CMDs) to compare with the galaxy's CMD, we find that the colors and magnitudes of GHOSTS?I's individual stars are most consistent with being young helium-burning and asymptotic giant branch stars at a distance of ~12 ? 2?Mpc. Morphologically, GHOSTS?I appears to be actively forming stars, so we tentatively classify it as a dwarf irregular (dIrr) galaxy, although future Hubble Space Telescope (HST) observations deep enough to resolve a larger magnitude range in its LF are required to make a more secure classification. GHOSTS?I's absolute magnitude is , making it one of the least luminous dIrr galaxies known, and its metallicity is lower than [Fe/H] = ?1.5?dex. The half-light radius of GHOSTS?I is 226 ? 38?pc and its ellipticity is 0.47 ? 0.07, similar to Milky Way and M31 dwarf satellites at comparable luminosity. There are no luminous massive galaxies or galaxy clusters within ~4?Mpc from GHOSTS?I that could be considered as its host, making it a very isolated dwarf galaxy in the local universe.
• Calabretta, M. R., Ford, H. A., Kalberla, P. M., Kerp, J., Lockman, F. J., Mcclure-griffiths, N. M., Murphy, T., Newton-mcgee, K., Pisano, D. J., Staveley-smith, L., & Winkel, B. (2010). GASS: The Parkes Galactic All-Sky Survey. II. Stray-Radiation Correction and Second Data Release. Astronomy and Astrophysics, 521(2), A17. doi:10.1051/0004-6361/200913979
  More info

  Context. The Parkes Galactic all-sky survey (GASS) is a survey of Galactic atomic hydrogen (H i) emission in the southern sky observed with the Parkes 64-m Radio Telescope. The first data release was published by McClure-Griffiths et al. (2009). Aims. We remove instrumental effects that affect the GASS and present the second data release. Methods. We calculate the stray-radiation by convolving the all-sky response of the Parkes antenna with the brightness temperature distribution from the Leiden/Argentine/Bonn (LAB) all sky 21-cm line survey, with major contributions from the 30-m dish of the Instituto Argentino de Radioastronomia (IAR) in the southern sky. Remaining instrumental baselines are corrected using the LAB data for a first guess of emission-free baseline regions. Radio frequency interference is removed by median filtering. Results. After applying these corrections to the GASS we find an excellent agreement with the Leiden/Argentine/Bonn (LAB) survey. The GASS is the highest spatial resolution, most sensitive, and is currently the most accurate H i survey of the Galactic H i emission in the southern sky. We provide a web interface for generation and download of FITS cubes.
• Bailin, J., Calabretta, M. R., Dedes, L., Ford, H. A., Gibson, B. K., Janowiecki, S., Kalberla, P. M., Lockman, F. J., Mcclure-griffiths, N. M., Murphy, T., Nakanishi, H., Newton-mcgee, K., Pisano, D. J., & Staveley-smith, L. (2009). Gass: The Parkes Galactic All-Sky Survey. I. Survey Description, Goals and Initial Data Release. Astrophysical Journal Supplement Series, 181(2), 398-412. doi:10.1088/0067-0049/181/2/398
• Calabretta, M. R., Ford, H. A., Kalberla, P. M., Lockman, F. J., Mcclure-griffiths, N. M., Murphy, T., Nakanishi, H., Pisano, D. J., & Staveley-smith, L. (2008). An Interaction of a Magellanic Leading Arm High-Velocity Cloud with the Milky Way Disk. The Astrophysical Journal, 673(2), L143-L146. doi:10.1086/528683
  More info

  The Leading Arm of the Magellanic system is a tidally formed H I feature extending ~60° from the Magellanic Clouds ahead of their direction of motion. Using atomic hydrogen (H I) data from the Galactic All-Sky Survey (GASS), supplemented with data from the Australia Telescope Compact Array, we have found evidence for an interaction between a cloud in the Leading Arm and the Galactic disk where the Leading Arm crosses the Galactic plane. The interaction occurs at velocities permitted by Galactic rotation, which allows us to derive a kinematic distance to the cloud of 21 kpc, suggesting that the Leading Arm crosses the Galactic plane at a Galactic radius of -->R ≈ 17 kpc.

Proceedings Publications

• Johnson, M. C., McQuinn, K. B., Cannon, J., Martinkus, C., Skillman, E., Bailin, J., Ford, H. A., Hunt, L., Westmeier, T., Wong, O. I., & Kamphuis, P. (2019, oct). The Hi Neighborhoods Around STARBIRDS. In Dwarf Galaxies: From the Deep Universe to the Present, 344.
• Pearce, E. C., Ford, H. A., Reddy Kanupuru, V. V., Schildknecht, T., & Block, A. (2017, September). Rapid Characterization of Geosynchronous Space Debris with 5-color Near-IR Photometry. In Advanced Maui Optical and Space Surveillance Technologies (AMOS) Conference 2017.
  More info

  The characterization of deep space debris has posed a significant challenge in SSA. To be most operationally effective, characterization must be performed quickly and under non-ideal operational conditions, generally using non-imaging techniques. The use of multi-color photometry and the resultant color indices in the near and short wave IR offer the potential to rapidly discriminate between debris and intact space objects such as rocket bodies and satellites. Specifically, the color indices surrounding the near IR Z band (0.83-0.925 µm) show promise to differentiate materials while providing a more efficient data collection when compared to spectroscopic techniques. Similar techniques have been demonstrated in the astronomical community to discriminate between different classes of near Earth asteroids. The diagnostic attributes of the Z band are particularly compelling as similar diagnostic color indices can be measured using visible telescopes and the corresponding Sloan z’ band. Initial results of an extensive survey of cataloged debris, high area-to-mass ratio (HAMR) debris, rocket bodies, and intact satellites with the UKIRT WFCAM are presented to assess the efficacy of these techniques.

Presentations

• Ford, H. A. (2020, 03-11-2020). Steward Observatory’s Radio Telescopes: Recent Advancements and Future Developments (Invited Talk). 31st IEEE International Symposium on Space Terahertz Technology.
  More info

  Invited talk at the 31st IEEE International Symposium on Space Terahertz Technology.
• Ford, H. A. (2018, Fall). An Overview of the Arizona Radio Observatory. Department of Astronomy/Steward Observatory Internal Symposium.
• Ford, H. A., Bregman, J., Hodges-Kluck, E., & Bailin, J. (2017, March). The Search for Extended HI Disks around Nearby Spirals. On the Origin (and Evolution) of Baryonic Galaxy Halos.
• Pearce, E. C., & Ford, H. A. (2017, 2017-04-12). Rapid Photometric Classification and Characterization of Space Objects. Non-Imaging Space Object Identification (NISOI) Workshop 2017. University of Arizona/LPL: Air Force Research Laboratory.
  More info

  An overview of the Steward Observatory satellite photometry program (led by Pearce) is presented along with preliminary results from the UKIRT near IR survey. Initial results focus on rapid discrimination of SL-12 rocket bodies with 5-color near-IR spectrophotometry. The NISOI Workshops are a series of working level meetings organized by AFRL/DE and held twice a year. Participation in the workshop is by invitation only and the presentation and discussion of preliminary results and in process work is strongly encouraged. This year is the first year that a University is hosting the Workshop on behalf of AFRL.
• Pearce, E. C., Ford, H. A., Reddy Kanupuru, V. V., Schildknecht, T., & Block, A. (2017, September). Rapid Characterization of Geosynchronous Space Debris with 5-color Near-IR Photometry. Advanced Maui Optical and Space Surveillance Technologies (AMOS) Conference 2017.
  More info

  The characterization of deep space debris has posed a significant challenge in SSA. To be most operationally effective, characterization must be performed quickly and under non-ideal operational conditions, generally using non-imaging techniques. The use of multi-color photometry and the resultant color indices in the near and short wave IR offer the potential to rapidly discriminate between debris and intact space objects such as rocket bodies and satellites. Specifically, the color indices surrounding the near IR Z band (0.83-0.925 µm) show promise to differentiate materials while providing a more efficient data collection when compared to spectroscopic techniques. Similar techniques have been demonstrated in the astronomical community to discriminate between different classes of near Earth asteroids. The diagnostic attributes of the Z band are particularly compelling as similar diagnostic color indices can be measured using visible telescopes and the corresponding Sloan z’ band. Initial results of an extensive survey of cataloged debris, high area-to-mass ratio (HAMR) debris, rocket bodies, and intact satellites with the UKIRT WFCAM are presented to assess the efficacy of these techniques.
• Ford, H. A. (2016, September). The Search for Highly Extended HI Disks around Spiral Galaxies. Department of Astronomy/Steward Observatory Internal Symposium.

Poster Presentations

• Johnson, M., McQuinn, K., Cannon, J., Martinkus, C., Skillman, E., Bailin, J., Ford, H. A., Hunt, L., Westmeier, T., Wong, O. I., & Kamphuis, P. (2018, August). The HI Neighborhoods Around STARBIRDS. IAU Symposium #344 (Dwarf Galaxies: From the Deep Universe to the Present).