Evolution of Emission Line Galaxies from z$<$0.5 to the present

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Session 23 -- Emission-Line, Starburst and Ultra-Luminous Galaxies
Oral presentation, Monday, 2:30-4:00, Wheeler Room

[23.01] Evolution of Emission Line Galaxies from z$<$0.5 to the present

I.K. Horowitz, M.Schmidt (Caltech), D.P.Schneider (IAS)

A comparison of the predicted and observed number counts of two samples of emission line galaxies is made so as to determine the extent to which evolutionary effects play a role in these objects from z$<$0.5 to the present. The distant sample of objects is taken from the 4-Shooter transit surveys of Schmidt, Schneider and Gunn (hereafter SSG). It consists of 371 galaxies whose inclusion by SSG was based on the detection of either the H$\beta$4861 or the [OIII]$\lambda\lambda$4959,5007 emission line. The nearby sample is taken from the CfA Northern Sky Redshift Survey (Davis, et.al., 1983). From the work of Burg (1987), a subset of 81 galaxies with strong [OIII] emission (EW$>$25\AA) has been selected. Added to that list are 26 additional Seyfert galaxies from Edelson (1987).

This group of 107 CfA galaxies represents an initial sample that has been observed on the 1.5m Oscar Meyer telescope at Palomar Observatory using the Echelle Spectrograph, which was operated in a low-resolution mode. Spectra were taken along both the major and minor axes of each CfA galaxy. The data were analyzed so as to determine how each galaxy would appear in the transit survey as a function of redshift. Having determined the maximum observable redshift for each CfA galaxy, based on the transit survey criteria, a prediction is made of the number of similar galaxies expected in the transit survey through a comparison of the accessible volumes in both the CfA survey as well as the transit survey. This is then compared to the observed numbers of galaxies in the transit survey, and a statement is made on the effects of evolution on various sub-classes of emission line galaxies.

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