A CANDELS WFC3 Grism Study of Emission-Line Galaxies at z ~ 2: A Mix of Nuclear Activity and Low-Metallicity Star Formation
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_(0.5-10keV) 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.
Additional Information
© 2011 The American Astronomical Society. Received 2011 June 22; accepted 2011 August 30; published 2011 December 1. 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. J.R.T. and the other authors at UC Santa Cruz acknowledge support from NASA HST Grant GO12060.10-A, Chandra Grant G08-9129A, and NSF Grant AST-0808133. We thank Stephanie LaMassa for access to her data and Shelley Wright for helpful discussions. We additionally thank the anonymous referee for helpful comments which improved the quality of the manuscript. We thank A. Reiss (P.I.) and his SN team for acquiring the grism data and acknowledge support from NASA HST grant GO 12099.Attached Files
Published - Trump2011p16923Astrophys_J.pdf
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Additional details
- Eprint ID
- 29082
- Resolver ID
- CaltechAUTHORS:20120202-081919864
- GO 12060.10-A
- NASA
- G08-9129A
- NASA
- AST-0808133
- NSF
- GO-12099
- NASA
- Created
-
2012-02-02Created from EPrint's datestamp field
- Updated
-
2021-11-09Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)