A Search for Gas-Rich Dwarf Galaxies in the Local Universe with ALFALFA and the WIYN One Degree Imager

Abstract

We present results from an optical search for Local Group dwarf galaxy candidates associated with the Ultra-Compact High Velocity Clouds (UCHVCs) discovered by the ALFALFA neutral hydrogen survey. The ALFALFA UCHVCs are isolated, compact HI clouds with projected sizes, velocities, and estimated HI masses that suggest they may be nearby dwarf galaxies, but that have no clear counterpart in existing optical survey data. We observed 26 UCHVCs with the WIYN 3.5-m telescope and One Degree Imager (ODI) in two broadband filters and searched the images for resolved stars with properties that match those of stars in typical dwarf galaxies at distances <2.5 Mpc. We identify one promising dwarf galaxy candidate at a distance of ~570 kpc associated with the UCHVC AGC 268071, and five other candidates that may deserve additional follow-up. We carry out a detailed analysis of ODI imaging of a UCHVC that is close in both projected distance and radial velocity to the outer-halo Milky Way globular cluster Pal 3. We also use our improved detection methods to reanalyze images of five UCHVCs that were found to have possible optical counterparts during the first phase of the project, and confirm the detection of a possible stellar counterpart to the UCHVC AGC 249525 at an estimated distance of ~2 Mpc. We compare the optical and HI properties of the dwarf galaxy candidates to the results from recent theoretical simulations that model satellite galaxy populations in group environments, as well as to the observed properties of galaxies in and around the Local Group.

33 pages, 10 figures, 5 tables. Published in the September 2023 issue of The Astronomical Journal

References in corpus (18)

• The Gaia mission
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Invisibles: A Detection Algorithm to Trace the Faintest Milky Way Satellites
• Ultra-faint dwarfs in a Milky Way context: Introducing the Mint Condition DC Justice League Simulations
• The velocity dispersion and mass profile of the Milky Way
• The Local Group dwarf Leo T: HI on the brink of star formation
• A Catalog of Ultra-compact High Velocity Clouds from the ALFALFA Survey: Local Group Galaxy Candidates?
• A Comprehensive Archival Search for Counterparts to Ultra-Compact High Velocity Clouds: Five Local Volume Dwarf Galaxies
• Two Local Volume Dwarf Galaxies Discovered in 21 cm Emission: Pisces A and B
• First stellar spectroscopy in Leo P
• The StEllar Counterparts of COmpact high velocity clouds (SECCO) survey. I. Photos of ghosts
• A peculiar HI cloud near the distant globular cluster Pal 4
• HST Imaging of the Local Volume Dwarf Galaxies Pisces A&B: Prototypes for Local Group Dwarfs
• Identifying galaxy candidates in WSRT HI imaging of ultra-compact high velocity clouds
• Detection of an Optical Counterpart to the ALFALFA Ultra-compact High Velocity Cloud AGC 249525
• Hubble Space Telescope Imaging of Isolated Local Volume Dwarfs GALFA-Dw3 and Dw4
• The Stellar Population and Orbit of the Galactic Globular Cluster Palomar 3
• A Correlated Search for Local Dwarf Galaxies in GALFA-HI and Pan-STARRS