Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...20916705h&link_type=abstract
2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #167.05; Bulletin of the American Astronomical Society,
Astronomy and Astrophysics
Astronomy
Scientific paper
We compare deep optical images and HI interferometric maps of two dwarf irregular galaxies in order to explore the relationship between stars and gas in their outer disks. The V-band surface photometry extends to 29 mag/arcsec2. Between R25 and RH the stellar exponential profiles in both galaxies sharply change slopes, becoming steeper in the outer parts. This change in the stellar density suggests a change in the star formation process at that radius. We explore the reasons for that change by comparing the optical profiles with those of the HI, the material from which star-forming clouds develop. From the HI maps we measure azimuthally-averaged gas surface densities and gas velocity dispersions. We also compute the ratio of gas surface density to the critical density for large-scale gravitational instabilities that would allow the formation of clouds. We compare the gas density and kinematic profiles with the surface brightness profiles of the stars before and after the break. We also compare the gas surface density profiles of these galaxies with dwarf irregulars of similar luminosity that do not have breaks in their stellar exponential disk profiles.
This research has been funded by the Lowell Research Fund.
Anderson Edward
Elmegreen Bruce G.
Hunter Deidre Ann
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