Outer Disk Star Formation in HI selected Galaxies
arXiv:1608.05935 · doi:10.1017/S174392131601139X
Abstract
The HI in galaxies often extends past their conventionally defined optical extent. I report results from our team which has been probing low intensity star formation in outer disks using imaging in H-alpha and ultraviolet. Using a sample of hundreds of HI selected galaxies, we confirm that outer disk HII regions and extended UV disks are common. Hence outer disks are not dormant but are dimly forming stars. Although the ultraviolet light in galaxies is more centrally concentrated than the HI, the UV/HI ratio (the Star Formation Efficiency) is nearly constant, with a slight dependency on surface brightness. This result is well accounted for in a model where disks maintain a constant stability parameter Q. This model also accounts for how the ISM and star formation are distributed in the bright parts of galaxies, and how HI appears to trace the distribution of dark matter in galaxy outskirts.
arXiv commentProceedings of IAU Symposium 321, "Formation and Evolution of Galaxy Outskirts", Eds. A. Gil de Paz, J. C. Lee & J. H. Knapen, Cambridge University Press, Cambridge
References in corpus (37)
- The Formation of Galactic Disks
- The Star Formation Efficiency in Nearby Galaxies: Measuring Where Gas Forms Stars Effectively
- The Star Formation Law in Nearby Galaxies on Sub-Kpc Scales
- The GALEX Ultraviolet Atlas of Nearby Galaxies
- Modified Newtonian Dynamics as an Alternative to Dark Matter
- The HIPASS Catalogue - I. Data Presentation
- Comparison of H-alpha and UV Star Formation Rates in the Local Volume: Systematic Discrepancies for Dwarf Galaxies
- The 1000 Brightest HIPASS Galaxies: HI Properties
- Star Formation Thresholds in Galactic Disks
- The UV-optical Galaxy Color-Magnitude Diagram I: Basic Properties
- Extremely Inefficient Star Formation in the Outer Disks of Nearby Galaxies
- A Search for Extended Ultraviolet Disk (XUV-disk) Galaxies in the Local Universe
- The Arecibo Legacy Fast ALFA Survey: The Galaxy Population Detected by ALFALFA
- Recent Star Formation in the Extreme Outer Disk of M83
- Evidence for a Non-Uniform Initial Mass Function in the Local Universe
- Discovery of Recent Star Formation in the Extreme Outer Regions of Disk Galaxies
- The Survey for Ionization in Neutral Gas Galaxies: I. Description and Initial Results
- Discovery of an extended ultraviolet disk in the nearby galaxy NGC4625
- The Northern HIPASS catalogue - Data presentation, completeness and reliability measures
- NGC 2915. II. A Dark Spiral Galaxy With A Blue Compact Dwarf Core
- The GALEX Arecibo SDSS Survey II: The Star Formation Efficiency of Massive Galaxies
- Metal Transport to the Gaseous Outskirts of Galaxies
- Intergalactic HII Regions Discovered in SINGG
- Tightly Correlated HI and FUV Emission in the Outskirts of M83
- On the apparent coupling of neutral hydrogen and dark matter in spiral galaxies
- Gas, Dust, and Young Stars in the Outer Disk of M 31
- Outlying HII Regions in HI-Selected Galaxies
- The Survey for Ionization in Neutral Gas Galaxies- II. The Star Formation Rate Density of the Local Universe
- The Universal Initial Mass Function In The XUV Disk of M83
- The Metal-Enriched Outer Disk of NGC 2915
- Young Stars in the Outer HI Disc of NGC 6822
- Isolated OB Associations in Stripped HI Gas Clouds
- Characterising uniform star formation efficiencies with marginally-stable galactic disks
- The initial mass function and star formation law in the outer disc of NGC 2915
- Disk Stability and Neutral Hydrogen as a Tracer of Dark Matter
- Equilibrium Star Formation In A Constant Q Disk: Model Optimisation and Initial Tests
- A Gaseous Group with Unusual Remote Star Formation