Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008aipc.1035..163k&link_type=abstract
THE EVOLUTION OF GALAXIES THROUGH THE NEUTRAL HYDROGEN WINDOW. AIP Conference Proceedings, Volume 1035, pp. 163-168 (2008).
Astronomy and Astrophysics
Astronomy
8
Star Formation, Interstellar Medium And Nebulae In Milky Way, Infall, Accretion, And Accretion Disks, Galaxy Clusters, Astronomical And Space-Research Instrumentation, Spectroscopy And Spectrophotometry
Scientific paper
We relate various measures of galaxy mass, using new data for the Nearby Field Galaxy Survey (NFGS). (1) Key mass and velocity transition scales previously identified in the literature are put on a common scale, indicating that the ``bimodality mass'' at M*~a few×1010 Msolar corresponds to V~190 km s-1 and is distinct from the gas-richness ``threshold mass'' at M*~several×109 Msolar, which roughly corresponds to V~120 km s-1. This value of the threshold mass is based on ionized gas detections and HI data for the NFGS, a smaller but statistically better-defined sample than that used for the original identification of the gas-richness threshold. (2) We argue that R-band light is the best available photometric tracer of dynamical mass over a wide range in mass and morphology, whereas U and K more closely trace just gas and stellar mass, respectively. The NFGS confirms evidence for an incredibly tight correlation between U-K color and atomic-gas-to-stellar mass ratio Matomic gas/Mstars, yielding rms scatter σ~= a factor of 2 (FWHM ~= a factor of 5) in Matomic gas/Mstars. (3) We examine why U band light from recent star formation correlates so well with atomic gas, when stars form in molecular gas. We propose that time-averaged molecular-to-atomic gas ratios stay within a factor of ~5 range over the 100+Myr timescales to which the U band is sensitive, due to episodic gas inflow events that replenish molecular gas, and we show evidence for such events. Finally, we consider the implications of these results for the design of the RESOLVE Survey, a mass census of the z = 0 cosmic web.
Kannappan Sheila J.
Wei Lisa H.
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