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E. K. S. Hicks, M. A. Malkan (University of California, Los Angeles), H. I. Teplitz (NASA Goddard Space Flight Center), P. J. McCarthy (Observatories of the Carnegie Institution of Washington), L. Yan (SIRTF Science Center, California Institute of Technology)
Optical spectra of 14 emission-line galaxies representative of the 1999 NICMOS parallel grism Ha survey of McCarthy et al. are presented. Of the 14, 9 have emission lines confirming the redshifts found in the grism survey. The higher resolution of our optical spectra improves the redshift accuracy by a factor of 5. The [O II]/Ha values of our sample are found to be more than two times lower than expected from Jansen et al. This [O II]/Ha ratio discrepancy is most likely explained by additional reddening in our Ha-selected sample [on average, as much as an extra E(B-V) = 0.6], as well as to a possible stronger dependence of the [O II]/Ha ratio on galaxy luminosity than is found in local galaxies. The result is that star formation rates (SFRs) calculated from [O II]3727 emission, uncorrected for extinction, are found to be on average 4 +/- 2 times lower than the SFRs calculated from Ha emission. Classification of emission-line galaxies as starburst or Seyfert galaxies based on comparison of the ratios [O II]/Hb and [Ne III]3869/Hb will be discussed. New Seyfert 1 diagnostics using the Ha line luminosity, H-band absolute magnitude, and Ha equivalent widths will also be presented. One galaxy is classified as a Seyfert 1 based on its broad emission lines, implying a comoving number density for Seyfert 1s of 2.5{+5.9, -2.1} x 10-5 Mpc-3. This comoving number density is a factor of 2.4{+5.5,-2.0} times higher than estimated by other surveys.
The author(s) of this abstract have provided an email address for comments about the abstract: ehicks@astro.ucla.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.