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1. ALFALFA Harvest: HI Imaging of Candidate Local Group Dwarf Galaxies

   Paine, S. ; Bralts-Kelly, L. ; Adams, E. ; Cannon, J. ; Giovanelli, R. ; Haynes, M. ; Janesh, W. ; Janowiecki, S. ; Oosterloo, T. ; Rhode, K. ; et al ( January 2020 , American Astronomical Society meeting)

   The ALFALFA blind extragalactic survey has populated the faint end of the neutral hydrogen (HI) mass function with statistical confidence for the first time. Of particular interest is a subset of the ALFALFA detections, termed "ultra-compact high-velocity clouds" (UCHVCs). These systems, if located within ~1 Mpc, would populate the lowest-mass end of the HI mass function. Subsequent optical imaging has revealed that some of these UCHVCs harbor associated (though sparse) stellar populations, revealing that they may be some of the most extreme galaxies known in the Local Volume, with optical properties akin to ultra-faint dwarf galaxies but with significant neutralmore »gas reservoirs. In this campaign, we investigate the neutral hydrogen properties of six UCHVC candidate galaxies using deep VLA HI spectral line imaging. A companion poster (Bralts-Kelly et al.) presents 3D kinematic modeling of selected sources. Here, we show the imaging products and discuss the morphological and kinematic properties of the six chosen sources: AGC 198606, AGC 215417, AGC219656, AGC 249525, AGC 258237, and AGC 268069.« less
2. SHIELD: Observations of Three Candidate Interacting Systems

   Ruvolo, Elizabeth ; Miazzo, Masao ; Cannon, John M. ; McNichols, Andrew ; Teich, Yaron ; Adams, Elizabeth A. ; Giovanelli, Riccardo ; Haynes, Martha P. ; McQuinn, Kristen B. ; Salzer, John Joseph ; et al ( January 2017 , American Astronomical Society ... meeting)

   The “Survey of HI in Extremely Low-mass Dwarfs” (SHIELD) is a multiwavelength study of local volume low-mass galaxies. Using the now-complete Arecibo Legacy Fast ALFA (ALFALFA) source catalog, 82 systems are identified that meet distance, line width, and HI flux criteria for being gas-rich, low-mass galaxies. These systems harbor neutral gas reservoirs smaller than 3x10^7 M_sun, thus populating the faint end of the HI mass function with statistical confidence for the first time. In a companion poster, we present new Karl G. Jansky Very Large Array D-configuration HI spectral line observations of 32 previously unobserved galaxies. Three galaxies in thatmore »study have been discovered to lie in close angular proximity to more massive galaxies. Here we present VLA HI imaging of these candidate interacting systems. We compare the neutral gas morphology and kinematics with optical images from SDSS. We discuss the frequency of low-mass galaxies undergoing tidal interaction in the complete SHIELD sample.Support for this work was provided by NSF grant 1211683 to JMC at Macalester College.« less
3. Using Very Large Array Data to Image the Ultra-Diffuse Galaxy AGC 749251

   Reiter, Kameron ; Leisman, Lukas ( January 2019 , American Astronomical Society, AAS Meeting)

   Ultra-diffuse galaxies (UDGs) have generated significant interest in recent years, as their stars appear too spread out relative to typical galaxies, and because some UDGs appear to have more than typical amounts of dark matter. The ALFALFA Survey has detected a number of UDGs in the field that are rich with neutral hydrogen (HI). We use the Karl G. Jansky Very Large Array (VLA) to image one of these HI-rich UDG, AGC 749251. We manually remove radio frequency interference, and reduce it using standard procedures in CASA. From the resulting data cubes we created 2D maps (moment 0 maps) andmore »maps of the radial velocities of the HI gas. We find that the HI in AGC 749251 shows reasonably ordered morphology and rotation, and extends beyond the already extended optical emission. We estimate the source's inclination and rotation velocity, constraining the source's dark matter content. We also compare our results to other, non-ultra diffuse galaxies, and suggest that the rotation velocity seems low compared with other sources of similar mass. This work has been supported by NSF grant AST-1637339.« less
4. SHIELD: EVLA HI Spectral Line Observations of Low-mass Dwarfs

   Miazzo, Masao ; Ruvolo, Elizabeth ; Cannon, John M. ; McNichols, Andrew ; Teich, Yaron ; Adams, Elizabeth A. ; Giovanelli, Riccardo ; Haynes, Martha P. ; McQuinn, Kristen B. ; Salzer, John Joseph ; et al ( January 2017 , American Astronomical Society ... meeting)

   The “Survey of HI in Extremely Low-mass Dwarfs” (SHIELD) is a multiwavelength study of local volume low-mass galaxies. Using the now-complete Arecibo Legacy Fast ALFA (ALFALFA) source catalog, 82 systems are identified that meet distance, line width, and HI flux criteria for being gas-rich, low-mass galaxies. These systems harbor neutral gas reservoirs smaller than 3x10^7 M_sun, thus populating the faint end of the HI mass function with statistical confidence for the first time. Here we present new Karl G. Jansky Very Large Array D-configuration HI spectral line observations of 32 previously unobserved galaxies. These low angular resolution (~40" beam) imagesmore »localize the HI gas; with a few exceptions, the HI gas is co-spatial with the optical centers of the galaxies. These images provide the first glimpse of the neutral interstellar medium in these systems.Support for this work was provided by NSF grant 1211683 to JMC at Macalester College.« less
5. HI-Bearing Ultra-Diffuse Galaxies: VLA Imaging of AGC 749290 and AGC 238764

   Gault, Lexi ; Leisman, Lukas ( January 2019 , American Astronomical Society, AAS Meeting)

   Ultra-diffuse galaxies (UDGs) are galaxies with a very low optical surface brightness; they have very few stars for their given radius. Since UDGs are thus difficult to study in visible light, we observe radio emission from neutral hydrogen gas (HI) in these galaxies. Here we present observations of the HI gas in the UDGs AGC 749290 and AGC 238764. Initially selected from a sample of Ultra-Diffuse Galaxies detected in the ALFALFA survey, these sources were imaged as a part of a follow up program using the Jansky Very Large Array (VLA) in both C and D configurations. We reduce themore »data using the CASA software suite, removing radio interference, applying calibration, and creating images. From these data we obtain spectra and maps of the galaxies' HI distribution and radial velocities. We find that both sources show ordered gas distributions and rotation, and that the HI gas extends well beyond the already extended optical emission. Further, we estimate inclinations and plot these sources on the Baryonic Tully-Fisher relation, providing tentative evidence that these sources are rotating too slowly for their given mass. This work has been supported by NSF grant AST-1637339.« less