Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published December 2007 | Published
Journal Article Open

The UV-Optical Color Magnitude Diagram. II. Physical Properties and Morphological Evolution On and Off of a Star-forming Sequence

Abstract

We use the UV-optical color magnitude diagram in combination with spectroscopic and photometric measurements derived from the SDSS spectroscopic sample to measure the distribution of galaxies in the local universe (z < 0.25) and their physical properties as a function of specific star formation rate (SFR/M_*) and stellar mass (M_*). Throughout this study our emphasis is on the properties of galaxies on and off of a local "star-forming sequence." We discuss how the physical characteristics of galaxies along this sequence are related to scaling relations typically derived for galaxies of different morphological types. We find, among other trends, that our measure of the star formation rate surface density, Σ_(SFR), is nearly constant along this sequence. We discuss this result and implications for galaxies at higher redshift. For the first time, we report on measurements of the local UV luminosity function versus galaxy structural parameters, as well as inclination. We also split our sample into disk-dominated and bulge-dominated subsamples using the i-band Sersic index and find that disk-dominated galaxies occupy a very tight locus in SFR/M_* vs. M_* space, while bulge-dominated galaxies display a much larger spread of SFR/M_* at fixed stellar mass. A significant fraction of galaxies with SFR/M_* and Σ_(SFR) above those on the "star-forming sequence" are bulge-dominated. We can use our derived distribution functions to ask whether a significant fraction of these galaxies may be experiencing a final episode of star formation (possibly induced by a merger or other burst), soon to be quenched, by determining whether this population can explain the growth rate of the non-star-forming galaxies on the "red sequence." We find that this is a plausible scenario for bulge-dominated galaxies near the characteristic transition mass under reasonable assumptions regarding quenching timescales. Similarly, we use this technique to estimate the rate of mergers/starbursts that take galaxies off of the star-forming sequence and show that the implied merger rates are consistent with local measurements.

Additional Information

© 2007 American Astronomical Society. Print publication: Issue 2 (2007 December); received 2007 August 2; accepted for publication 2007 October 16. D. S. gratefully acknowledges discussions with Eric Bell and Michael Blanton and the hospitality of the Max Planck Institut fu¨r Astronomie in Heidelberg and the Aspen Center for Physics. This work has made extensive use of the idlutils, kcorrect, and Goddard IDL libraries, as well as the MPA/JHU and the NYU SDSS value-added catalogs. GALEX (Galaxy Evolution Explorer) is a NASA Small Explorer, launched in April 2003. We gratefully acknowledge NASA's support for the construction, operation, and science analysis for the GALEX mission, developed in cooperation with the Centre National d'Etudes Spatiales of France and the Korean Ministry of Science and Technology. Facilities: GALEX

Attached Files

Published - SCHIapjss07b.pdf

Files

SCHIapjss07b.pdf
Files (4.8 MB)
Name Size Download all
md5:3655a5de2a7de5d5ae24c80bd7115d42
4.8 MB Preview Download

Additional details

Created:
August 22, 2023
Modified:
October 19, 2023