• Neutral Hydrogen Observations of Low Surface Brightness Galaxies around M101 and NGC 5485

      Karunakaran, A.; Spekkens, K.; Bennet, P.; Sand, D. J.; Crnojević, D.; Zaritsky, D.; Univ Arizona, Steward Observ (IOP PUBLISHING LTD, 2020-01-03)
      We present atomic hydrogen (H i) observations using the Robert C. Byrd Green Bank Telescope along the lines of sight to 27 low surface brightness (LSB) dwarf galaxy candidates discovered in optical searches around M101. We detect H i reservoirs in five targets and place stringent upper limits on the remaining 22, implying that they are gas-poor. The distances to our H i detections range from 7 to 150 Mpc, demonstrating the utility of wide-bandpass H i observations as a follow-up tool. The systemic velocities of three detections are consistent with that of the NGC 5485 group behind M101, and we suggest that our 15 nondetections with lower distance limits from the optical are associated with and have been stripped by that group. We find that the gas richness of confirmed M101 satellites are broadly consistent with those of the Milky Way satellites, as well as with those of satellites around other hosts of comparable mass, when survey completeness is taken into account. This suggests that satellite quenching and gas stripping proceed similarly around halos of similar mass, in line with theoretical expectations.
    • Systematically Measuring Ultradiffuse Galaxies in H i: Results from the Pilot Survey

      Karunakaran, Ananthan; Spekkens, Kristine; Zaritsky, Dennis; Donnerstein, Richard L.; Kadowaki, Jennifer; Dey, Arjun; Univ Arizona, Steward Observ (IOP PUBLISHING LTD, 2020-10-09)
      We present neutral hydrogen (Hi) observations using the Robert C. Byrd Green Bank Telescope (GBT) of 70 optically detected UDG candidates in the Coma region from the Systematically Measuring Ultra-Diffuse Galaxies survey (SMUDGes). We detect Hiin 18 targets, confirming nine to be gas-rich UDGs and the remainder to be foreground dwarfs. None of our Hi-detected UDGs are Coma Cluster members and all but one are in low-density environments. The Hi-detected UDGs are bluer and have more irregular morphologies than the redder, smoother candidates not detected in Hi, with the combination of optical color and morphology being a better predictor of gas richness than either parameter alone. There is little visual difference between the gas-rich UDGs and the foreground dwarfs in the SMUDGes imaging, and distances are needed to distinguish between them. We find that the gas richnesses of our Hi-confirmed UDGs and those from other samples scale with their effective radii in two stellar mass bins, possibly providing clues to their formation. We attempt to place our UDGs on the baryonic Tully-Fisher relation (BTFR) using optical ellipticities and turbulence-corrected Hiline widths to estimate rotation velocities, but the potential systematics associated with fitting smooth Sersic profiles to clumpy, low-inclination disks of low surface brightness precludes a meaningful analysis of potential BTFR offsets. These observations are a pilot for a large campaign now under way at the GBT to use the Hiproperties of gas-rich UDGs to quantitatively constrain how these galaxies form and evolve.