Detection of an Optical Counterpart to the ALFALFA Ultra-compact High Velocity Cloud AGC 249525

Abstract

We report on the detection at $>$98% confidence of an optical counterpart to AGC 249525, an Ultra-Compact High Velocity Cloud (UCHVC) discovered by the ALFALFA blind neutral hydrogen survey. UCHVCs are compact, isolated HI clouds with properties consistent with their being nearby low-mass galaxies, but without identified counterparts in extant optical surveys. Analysis of the resolved stellar sources in deep $g$- and $i$-band imaging from the WIYN pODI camera reveals a clustering of possible Red Giant Branch stars associated with AGC 249525 at a distance of 1.64$\pm$0.45 Mpc. Matching our optical detection with the HI synthesis map of AGC 249525 from Adams et al. (2016) shows that the stellar overdensity is exactly coincident with the highest-density HI contour from that study. Combining our optical photometry and the HI properties of this object yields an absolute magnitude of $-7.1\le M_V\le -4.5$, a stellar mass between $2.2\pm 0.6\times 10^4{M}_{\odot }$ and $3.6\pm 1.0\times 10^5{M}_{\odot }$, and an HI to stellar mass ratio between 9 and 144. This object has stellar properties within the observed range of gas-poor Ultra-Faint Dwarfs in the Local Group, but is gas-dominated.

arXiv comment9 pages, 4 figures; accepted to ApJL

References in corpus (32)

• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• Dark Matter Substructure in Galactic Halos
• Where are the missing galactic satellites?
• The Optical and Near-Infrared Properties of Galaxies: I. Luminosity and Stellar Mass Functions
• SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems
• The observed properties of dwarf galaxies in and around the Local Group
• The Arecibo Legacy Fast ALFA Survey: I. Science Goals, Survey Design and Strategy
• Cosmicflows-2: The Data
• The Arecibo Legacy Fast ALFA Survey: The alpha.40 HI Source Catalog, its Characteristics and their Impact on the Derivation of the HI Mass Function
• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• The Baryonic Tully-Fisher Relation of Gas Rich Galaxies as a Test of LCDM and MOND
• High Velocity Clouds: Building Blocks of the Local Group
• Forged in FIRE: cusps, cores, and baryons in low-mass dwarf galaxies
• Discovery of an Unusual Dwarf Galaxy in the Outskirts of the Milky Way
• A Keck/DEIMOS spectroscopic survey of faint Galactic satellites: searching for the least massive dwarf galaxies
• Theoretical isochrones in several photometric systems II. The Sloan Digital Sky Survey ugriz system
• ALFALFA Discovery of the Nearby Gas-Rich Dwarf Galaxy Leo~P. III. An Extremely Metal Deficient Galaxy
• ALFALFA Discovery of the Nearby Gas-Rich Dwarf Galaxy Leo P. I. HI Observations
• Atomic Hydrogen Gas in Dark-Matter Minihalos and the Compact High Velocity Clouds
• Leo P: An Unquenched Very Low-Mass Galaxy
• Where are the Fossils of the First Galaxies? II. True Fossils, Ghost Halos, and the Missing Bright Satellites
• ALFALFA Discovery of the Most Metal-Poor Gas-Rich Galaxy Known: AGC 198691
• A Catalog of Ultra-compact High Velocity Clouds from the ALFALFA Survey: Local Group Galaxy Candidates?
• ALFALFA Discovery of the Nearby Gas-Rich Dwarf Galaxy Leo~P. II. Optical Imaging Observations
• Are Newly Discovered HI High Velocity Clouds Minihalos in the Local Group?
• Environmental dependence of the HI mass function in the ALFALFA 70% catalogue
• A Comprehensive Archival Search for Counterparts to Ultra-Compact High Velocity Clouds: Five Local Volume Dwarf Galaxies
• AGC198606: A gas-bearing dark matter minihalo?
• The StEllar Counterparts of COmpact high velocity clouds (SECCO) survey. I. Photos of ghosts
• Identifying galaxy candidates in WSRT HI imaging of ultra-compact high velocity clouds
• Searching for Optical Counterparts to Ultra-compact High Velocity Clouds: Possible Detection of a Counterpart to AGC 198606
• The StEllar Counterparts of COmpact high velocity clouds (SECCO) survey. II. Sensitivity of the survey and an Atlas of Synthetic Dwarf Galaxies

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