Stellar Populations in Local Star‐forming GalaxiesAuthor(s): Pablo G. Pérez‐GonzálezSource: Publications of the Astronomical Society of the Pacific, Vol. 115, No. 813 (November2003), p. 1353Published by: The University of Chicago Press on behalf of the Astronomical Society of the PacificStable URL: http://www.jstor.org/stable/10.1086/379747 .

Accessed: 24/05/2014 01:24

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact support@jstor.org.

.

The University of Chicago Press and Astronomical Society of the Pacific are collaborating with JSTOR todigitize, preserve and extend access to Publications of the Astronomical Society of the Pacific.

http://www.jstor.org

This content downloaded from 91.229.248.157 on Sat, 24 May 2014 01:24:35 AMAll use subject to JSTOR Terms and Conditions

1353

Publications of the Astronomical Society of the Pacific, 115:1353–1353, 2003 November� 2003. The Astronomical Society of the Pacific. All rights reserved. Printed in U.S.A.

Dissertation Summary

Stellar Populations in Local Star-forming Galaxies

Pablo G. Perez-Gonzalez

Current address: University of Arizona, Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721; pgperez@as.arizona.eduThesis work conducted at Departamento de Astrofı´sica, Facultad de Ciencias Fı´sicas, Universidad Complutense de Madrid (Spain)

Ph.D. thesis directed by J. Zamorano & J. Gallego; Ph.D. degree awarded 2003 June

Received 2003 September 11; accepted 2003 September 11

One of the main issues in today’s astrophysics is how pre-sent-day galaxies formed and how they have evolved over time.A considerable observational effort is being made to studygalaxies from the earliest possible times to the present. Oneapproach to understand how present-day galaxies came intobeing is to study in detail the properties of local active star-forming galaxies, and in particular their star formation histories.In this respect, it is important to quantify the relative importanceof the current episode of star formation in comparison to theunderlying older stellar populations.

The main goal of this thesis work1 is studying the mainproperties of the stellar populations embedded in a statisticallycomplete sample of local active star-forming galaxies: the Uni-versidad Complutense de Madrid (UCM) Survey of emission-line galaxies.2 This sample contains 191 local star-forming gal-axies at an average redshift of 0.026. The survey was carriedout using an objective-prism technique centered at the wave-length of the Ha nebular emission line (a common tracer ofrecent star formation).

We have compiled an extensive multiwavelength (from theoptical to the near-infrared) photometric (in narrow- and broad-band filters) and spectroscopic data set for all the galaxies inthe sample. The analysis of this data set has been centered onthe characterization of the morphology of the objects, on the

1 The original text is written in Spanish and is available athttp://t-rex.fis.ucm.es/Publications/Repository/tesis_pag_1.ps.gz,http://t-rex.fis.ucm.es/Publications/Repository/tesis_pag_2.ps.gz.

2 http://t-rex.fis.ucm.es/UCM_Survey/index.html.

comparison of the global properties of the sample with thoseof other galaxy samples at several redshifts, and on the studyof the stellar content of the UCM galaxies. In the latter researchtopic, a special attention has been paid to the most recent star-forming bursts, which are the main characteristic of our objects.We have also developed (and tested with the data set for theUCM sample) a powerful stellar population synthesis tool(which is able to obtain robust estimates of the stellar mass, avery important parameter in the study of the evolution of gal-axies) and a technique to calculate luminosity and stellar massfunctions. These techniques may be easily used in the charac-terization of samples of galaxies at any redshift.

The main results obtained in this work point out that theUCM Survey galaxies span a broad range in properties (amongothers, the total stellar mass and the star formation rate perstellar-mass unit) between those of galaxies completely dom-inated by current/recent star formation (e.g., extreme dwarfH ii galaxies or starburst galaxies) and those of “normal” qui-escent spirals. The UCM objects present intermediate to lateHubble type spiral morphologies and a recent instantaneousburst of star formation (which occurred about 5 Myr ago) withsubsolar metallicity.These bursts involved 5% of the totalstellar mass of the UCM galaxies. An “average” UCM gal-axy has a total stellar mass of 1010 solar masses, i.e., abouta factor of 7–10 lower than a typical local spiral galaxy.Finally, we estimate that of the total baryon mass13%� 3%density in the form of stars in the local universe is associatedwith star-forming galaxies.

This content downloaded from 91.229.248.157 on Sat, 24 May 2014 01:24:35 AMAll use subject to JSTOR Terms and Conditions