Physics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008phdt........13k&link_type=abstract
Proquest Dissertations And Theses 2008. Section 0036, Part 0606 220 pages; [Ph.D. dissertation].United States - - California: Un
Physics
1
Emission Lines, Massive Early-Type Red Galaxies, Galaxies
Scientific paper
This thesis performs a look-back study on the forbidden [O II ] l3727 Å emission line in massive early-type red galaxies (MERGs) at z ~ 0.1 and z ~ 0.8. At z ~ 0, MERGs show young stellar populations. By looking back in time, at z ~ 0.8 MERGs it is possible to find signs of these young stars being formed. It is commonly thought, that [O II] luminosity traces the star formation rate; however, for z ~ 0.1 and z ~ 0.8 MERGs this is largely not the case. A variety of techniques are brought to bear on this issue. First, the evolution of the average [O II] luminosity density in MERGs from z ~ 0.8 to z ~ 0.1is (1 + z) ~1-2 , which evolves less than the global evolution of star formation of (1 + z) 4 . Second, a new star formation diagnostic is created based on line ratios. Ideally, our z ~ 0.8 MERG spectra would allow us to create a full diagnostic diagram (Ha/[NII] versus [O III]/Hb). Instead of using Ha, which is redshifted out of the visible, out new technique is calibrated on mass, color, and the emission line [O III]/Hb ratio in z ~ 0.1 massive red galaxies. The z ~ 0.8 MERGs are similar in mass, color, and [O III]/Hb ratio to the z ~ 0.1 massive red galaxies that are not forming stars. Third, the [O II] emission line is found to be physically extended in a deeply observed sample of z ~ 0.8 MERGs, suggesting that [O II] is produced by both nuclear and extended sources. In conclusion, I argue that the young stellar populations found in local MERGs are produced either by the continual addition of galaxies with young stars added to the MERG population. Or if they are form in the MERGs themselves, are formed during rare bursts.
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