Journal article
The Enigmatic (Almost) Dark Galaxy Coma P: The Atomic Interstellar Medium
The Astronomical journal, Vol.155(2), p.65
02/01/2018
DOI: 10.3847/1538-3881/aaa156
Abstract
We present new high-resolution H I spectral line imaging of Coma P, the brightest H I source in the system HI 1232 +20. This galaxy with extremely low surface brightness was first identified in the ALFALFA survey as an "(Almost) Dark" object: a clearly extragalactic H I source with no obvious optical counterpart in existing optical survey data (although faint ultraviolet emission was detected in archival GALEX imaging). Using a combination of data from the Westerbork Synthesis Radio Telescope and the Karl G. Jansky Very Large Array, we investigate the H I morphology and kinematics at a variety of physical scales. The H I morphology is irregular, reaching only moderate maxima in mass surface density (peak (sigma H I) similar to 10 M-circle dot pc(-2)). Gas of lower surface brightness extends to large radial distances, with the H I diameter measured at 4.0 +/- 0.2 kpc inside the 1 M-circle dot pc(-2) level. We quantify the relationships between mass surface density of H I gas and star formation on timescales of similar to 100-200 Myr as traced by GALEX far-ultraviolet emission. While Coma P has regions of dense H I gas reaching the N-H I = 10(21) cm(-2) level typically associated with ongoing star formation, it lacks massive star formation as traced by Ha emission. The H I kinematics are extremely complex: a simple model of a rotating disk cannot describe the H I gas in Coma P. Using spatially resolved position-velocity analysis we identify two nearly perpendicular axes of projected rotation that we interpret as either the collision of two H I disks or a significant infall event. Similarly, three-dimensional modeling of the H I dynamics provides a best fit with two H I components. Coma P is just consistent (within 3 sigma) with the known M-H I-D-H I scaling relation. It is either too large for its H I mass, has too low an H I mass for its H I size, or the two H I components artificially extend its H I size. Coma P lies within the empirical scatter at the faint end of the baryonic Tully-Fisher relation, although the complexity of the H I dynamics complicates the interpretation. Along with its large ratio of H I to stellar mass, the collective H I characteristics of Coma P make it unusual among known galaxies in the nearby universe.
Details
- Title: Subtitle
- The Enigmatic (Almost) Dark Galaxy Coma P: The Atomic Interstellar Medium
- Creators
- Catherine Ball - Macalester CollegeJohn M. Cannon - Macalester CollegeLukas Leisman - Valparaiso UniversityElizabeth A. K. Adams - University of GroningenMartha P. Haynes - Cornell UniversityGyula I. G. Jozsa - Rhodes UniversityKristen B. W. McQuinn - The University of Texas at AustinJohn J. Salzer - Indiana University BloomingtonSamantha Brunker - Indiana University BloomingtonRiccardo Giovanelli - Cornell UniversityGregory Hallenbeck - Washington and Jefferson CollegeWilliam Janesh - Indiana University BloomingtonSteven Janowiecki - International Centre for Radio Astronomy ResearchMichael G. Jones - Instituto de Astrofísica de AndalucíaKatherine L. Rhode - Indiana University Bloomington
- Resource Type
- Journal article
- Publication Details
- The Astronomical journal, Vol.155(2), p.65
- Publisher
- Iop Publishing Ltd
- DOI
- 10.3847/1538-3881/aaa156
- ISSN
- 0004-6256
- eISSN
- 1538-3881
- Number of pages
- 22
- Grant note
- Macalester College AST-0607007; AST-1107390; AST-1615483; AST-1211683 / NSF; National Science Foundation (NSF) DP150101734 / Australian Research Council's Discovery Project funding scheme; Australian Research Council Brinson Foundation AYA2015-65973-C3-1-R / MINECO/FEDER, UE
- Language
- English
- Date published
- 02/01/2018
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984627210702771
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