Morphological properties of star-forming galaxies: Connecting the morphological evolution of galaxies and the decline of the star formation rate density of the Universe in the past 9 billion years
by Zamojski, Michel A., Ph.D., COLUMBIA UNIVERSITY, 2008, 160 pages; 3305281

Abstract:

In this dissertation, we present results connecting the morphological evolution of galaxies and the decline of the star formation rate density in the Universe since z ∼ 2. For our study, we used the high-resolution HST/ACS images of the COSMOS survey to perform non-parametric automated morphological measurements on all objects with brightness IF814W ≤ 23 mag (AB) in the 2 □° field, and combined these data with UV-photometry extracted from GALEX imaging to trace objects with moderate to high star formation rates. By first looking at the morphological properties of a sub-sample of z ∼ 0.7 galaxies, we discover that the morphological bimodality is already in place, that z ∼ 0.7 galaxies have masses, sizes and morphologies similar to that of local galaxies, but that they have star formation rates higher than local galaxies by a factor 2.5–3.5, independently of their other physical properties. We infer that the decline of the star formation rate density in the past 6 Gyrs can be mostly accounted for by a global fading of the galaxy population. We discover that morphology correlates well with UV-optical color, but that there also exists a population of red and dusty star-forming galaxies with bulge-like morphologies. We conclude that bulge growth is linked with episodes of high star formation, and interpret these objects as late-phase mergers. By studying the evolution of the luminosity function at 1500Å, we confirm the fading of the characteristic FUV magnitude of galaxies since z = 2.0, and discover a flattening of the faint-end slope at z < 0.7. We interpret this flattening as due to a decrease in the birth rate of galaxies. The morphological composition of our UV-sources indicates that disk galaxies dominate the FUV-luminosity function at all redshifts and all luminosities while interacting systems and galaxies with bulges contribute significantly mostly at the bright-end. Early-type disks appear to be the ones to evolve the most since z ∼ 0.7, an epoch through which their faint-end slope steepens. We interpret this as an indication that most small to intermediate-size disk galaxies formed their bulges in the last 6 Gyrs. Finally, we observe, at z > 1, a progressive increase, with redshift, of the contribution of bulge-dominated galaxies to the bright-end of the FUV-luminosity function, a likely signature of the epoch of bulge formation.

 
AdviserDavid Schiminovich
SchoolCOLUMBIA UNIVERSITY
SourceDAI/B 69-03, p. , Jun 2008
Source TypeDissertation
SubjectsAstronomy
Publication Number3305281
Adobe PDF Access the complete dissertation:
 

» Find an electronic copy at your library.
  Use the link below to access a full citation record of this graduate work:
  http://gateway.proquest.com/openurl%3furl_ver=Z39.88-2004%26res_dat=xri:pqdiss%26rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation%26rft_dat=xri:pqdiss:3305281
  If your library subscribes to the ProQuest Dissertations & Theses (PQDT) database, you may be entitled to a free electronic version of this graduate work. If not, you will have the option to purchase one, and access a 24 page preview for free (if available).

About ProQuest Dissertations & Theses
With over 2.3 million records, the ProQuest Dissertations & Theses (PQDT) database is the most comprehensive collection of dissertations and theses in the world. It is the database of record for graduate research.

The database includes citations of graduate works ranging from the first U.S. dissertation, accepted in 1861, to those accepted as recently as last semester. Of the 2.3 million graduate works included in the database, ProQuest offers more than 1.9 million in full text formats. Of those, over 860,000 are available in PDF format. More than 60,000 dissertations and theses are added to the database each year.

If you have questions, please feel free to visit the ProQuest Web site - http://www.proquest.com - or call ProQuest Hotline Customer Support at 1-800-521-3042.