A CANDELS WFC3 Grism Study of Emission-line Galaxies at z ~ 2: A Mix of Nuclear Activity and Low-metallicity Star Formation

December 2011 • 2011ApJ...743..144T

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

Abstract • We present Hubble Space Telescope Wide Field Camera 3 (WFC3) slitless grism spectroscopy of 28 emission-line galaxies at z ~ 2, in the GOODS-S region of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. The high sensitivity of these grism observations, with >1σ detections of emission lines to f > 2.5 × 10^-18 erg s^-1 cm^-2, means that the galaxies in the sample are typically ~7 times less massive (median M _* = 10^9.5 M _⊙) than previously studied z ~ 2 emission-line galaxies. Despite their lower mass, the galaxies have [O III]/Hβ ratios which are very similar to previously studied z ~ 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 Hβ 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]}/L _{0.5-10 keV} ratio is intermediate between typical z ~ 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.

Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555.

Links

• PREPRINT http://arxiv.org/abs/1108.6075
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2011ApJ...743..144T
• ELECTR https://doi.org/10.1088%2F0004-637X%2F743%2F2%2F144
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2011ApJ...743..144T
• PDF https://iopscience.iop.org/article/10.1088/0004-637X/743/2/144/pdf
• PDF https://stacks.iop.org/0004-637X/743/144/pdf
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2011ApJ...743..144T
• DATA https://cda.harvard.edu/chaser?obsid=441,581,582,1431,1672,2239,2312,2313,2405,2406,2409,8591,8592,8593,8594,8595,8596,8597,9575,9578,9593,9596,9718,12043,12044,12045,12046,12047,12048,12049,12050,12051,12052,12053,12054,12055,12123,12128,12129,12135,12137,12138,12213,12218,12219,12220,12222,12223,12227,12230,12231,12232,12233,12234
• DATA https://hst.esac.esa.int/ehst/#/pages/search;bibcode=2011ApJ...743..144T