Star formation in emission-line galaxies between redshifts of 0.8 and 1.6

被引:29
作者
Hicks, EKS [1 ]
Malkan, MA
Teplitz, HI
McCarthy, PJ
Yan, L
机构
[1] Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA
[2] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
[3] Carnegie Inst Washington Observ, Pasadena, CA 91101 USA
[4] CALTECH, SIRTF Sci Ctr, Pasadena, CA 91125 USA
关键词
galaxies : distances and redshifts; galaxies : Seyfert; galaxies : starburst; galaxies : statistics; infrared : galaxies; surveys;
D O I
10.1086/344224
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Optical spectra of 14 emission-line galaxies representative of the 1999 NICMOS parallel grism Halpha 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]/Halpha values of our sample are found to be more than 2 times lower than expected from Jansen et al. This [O II]/Halpha ratio discrepancy is most likely explained by additional reddening in our Halpha-selected sample [on average, as much as an extra E(B-V)=0.6], as well as by a possible stronger dependence of the [O II]/Halpha ratio on galaxy luminosity than is found in local galaxies. The result is that star formation rates (SFRs) calculated from [O II]lambda3727 emission, uncorrected for extinction, are found to be on average 4+/-2 times lower than the SFRs calculated from Halpha emission. Classification of emission-line galaxies as starburst or Seyfert galaxies based on comparison of the ratios [O II]/Hbeta and [Ne III]lambda3869/Hbeta is discussed. New Seyfert 1 diagnostics using the Halpha line luminosity, H-band absolute magnitude, and Halpha equivalent widths are also presented. One galaxy is classified as a Seyfert 1 based on its broad emission lines, implying a comoving number density for Seyfert 1 galaxies of 2.5(-2.1)(+5.9)x10(-5) Mpc(-3). This comoving number density is a factor of 2.4(-2.0)(+5.5) times higher than estimated by other surveys.
引用
收藏
页码:205 / 222
页数:18
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