A CANDELS WFC3 GRISM STUDY OF EMISSION-LINE GALAXIES AT z similar to 2: A MIX OF NUCLEAR ACTIVITY AND LOW-METALLICITY STAR FORMATION

Jonathan R. Trump, Benjamin J. Weiner, Claudia Scarlata, Dale D. Kocevski, Eric F. Bell, Elizabeth J. McGrath, David C. Koo, S. M. Faber, Elise S. Laird, Mark Mozena, Cyprian Rangel, Renbin Yan, Hassen Yesuf, Hakim Atek, Mark Dickinson, Jennifer L. Donley, James S. Dunlop, Henry C. Ferguson, Steven L. Finkelstein, Norman A. GroginNimish P. Hathi, Stephanie Juneau, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Kirpal Nandra, Jeffrey A. Newman, Steven A. Rodney, Amber N. Straughn, Harry I. Teplitz

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

We present Hubble Space Telescope Wide Field Camera 3 (WFC3) slitless grism spectroscopy of 28 emission-line galaxies at z similar to 2, in the GOODS-S region of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. The high sensitivity of these grism observations, with > 1 sigma detections of emission lines to f > 2.5 x 10(-18) erg s(-1) cm(-2), means that the galaxies in the sample are typically similar to 7 times less massive (median M-* = 10(9.5) M-circle dot) than previously studied z similar to 2 emission-line galaxies. Despite their lower mass, the galaxies have [O III]/H beta ratios which are very similar to previously studied z similar to 2 galaxies and much higher than the typical emission-line ratios of local galaxies. The WFC3 grism allows for unique studies of spatial gradients in emission lines, and we stack the two-dimensional spectra of the galaxies for this purpose. In the stacked data the [O III] emission line is more spatially concentrated than the H beta emission line with 98.1% confidence. We additionally stack the X-ray data (all sources are individually undetected), and find that the average L-[O III]/L0.5-10 (keV) ratio is intermediate between typical z similar to 0 obscured active galaxies and star-forming galaxies. Together the compactness of the stacked [O III] spatial profile and the stacked X-ray data suggest that at least some of these low-mass, low-metallicity galaxies harbor weak active galactic nuclei.

Original languageEnglish
Article number144
Pages (from-to)-
Number of pages8
JournalAstrophysical Journal
Volume743
Issue number2
DOIs
Publication statusPublished - 20 Dec 2011

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