Evolution of emission line galaxies

Citation

Horowitz, Irwin Kenneth (1994) Evolution of emission line galaxies. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/c8r3-gs98. https://resolver.caltech.edu/CaltechETD:etd-09102008-134503

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. This thesis compares two samples of emission line galaxies, selected on the basis of the strength of their [0111]λλ4959, 5007 and/or Hβ λ4861 emission lines. The distant sample is drawn from the 4-Shooter transit survey undertaken by Schmidt, Schneider and Gunn (1994 and references therein), and consists of 370 galaxies with emission line equivalent widths in excess of 50[...] and fluxes above well-defined wavelength-dependent limits. This survey consists of 6 narrow strips of the sky covering ~ 62 square degrees. Each of these galaxies is classified by using line ratio diagnostics from the moderate resolution spectra taken to identify the emission line. The nearby sample is taken from the first CfA Northern Sky Redshift Survey, and consists of 81 galaxies from Burg (1987) with [OIII]λλ4959,5007 EW≥23.75[...] and an additional 26 Seyfert galaxies from Edelson (1987). This sample is observed on the 1.5m Oscar Meyer telescope using the Echelle Spectrograph in a low-resolution, long slit mode (McCarthy, 1988). Each of the 107 galaxies is observed twice, along perpendicular axes over a wavelength range from 4350[...] to 7200[...], which covers the emission lines of interest such as Hβ λ4861, [OIII]λλ4959,5007 and Hα λ6563. These data are used both to classify the 107 galaxies from their line ratio diagnostics as well as to model the spatial and spectral light distribution on the plane of the sky for a comparison of how each would appear in the distant survey as a function of redshift. Maximum redshifts in both the nearby and the distant survey are determined for each CfA galaxy, and predicted number counts, based on both a no-evolution model as well as a model incorporating density evolution, are made from the corresponding ratio of accessible volumes in the two surveys. Corrections are made to the predicted counts to account for sample incompletenesses and the overdensity of the CfA survey relative to the average density of galaxies in the "local" universe. These predicted counts are compared to the observed counts from the distant survey for each object class. The results from this comparison are consistent with the no-evolution model for emission line galaxies out to z~0.5, and do not support the conjecture (Broadhurst et al. 1988; Colless et al. 1990) that there is an evolving population of dwarf star-forming emission line galaxies.

Thesis Files