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Title:
Optical and Near-Infrared Spectroscopy of a High-Redshift Hard X-Ray-emitting Spiral Galaxy
Authors:
Dawson, Steve; McCrady, Nate; Stern, Daniel; Eckart, Megan E.; Spinrad, Hyron; Liu, Michael C.; Graham, James R.
Affiliation:
AA(Department of Astronomy, University of California at Berkeley, Mail Code 3411, Berkeley, CA 94720; , , , .), AB(Department of Astronomy, University of California at Berkeley, Mail Code 3411, Berkeley, CA 94720; , , , .), AC(Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 169-327, Pasadena, CA 91109; .), AD(Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Mail Stop 220-47, Pasadena, CA 91125; .), AE(Department of Astronomy, University of California at Berkeley, Mail Code 3411, Berkeley, CA 94720; , , , .), AF(Currently Beatrice Watson Parrent Fellow, Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822; .), AG(Department of Astronomy, University of California at Berkeley, Mail Code 3411, Berkeley, CA 94720; , , , .)
Publication:
The Astronomical Journal, Volume 125, Issue 3, pp. 1236-1246. (AJ Homepage)
Publication Date:
03/2003
Origin:
UCP
AJ Keywords:
Galaxies: High-Redshift, Galaxies: Individual: Alphanumeric: CXOHDFN J123635.6+621424, Galaxies: Seyfert, Galaxies: Spiral, Galaxies: Quasars: Emission Lines
DOI:
10.1086/367792
Bibliographic Code:
2003AJ....125.1236D

Abstract

We present optical and near-infrared Keck spectroscopy of CXOHDFN J123635.6+621424 (HDFX 28), a hard X-ray source at a redshift of z=2.011 in the flanking fields of the Hubble Deep Field North (HDF-N). HDFX 28 is a red source (R-Ks=4.74) with extended steep-spectrum (α8.41.4 GHz>0.87 GHz) microjansky radio emission and significant emission (441 μJy) at 15 μm. Accordingly, initial investigations prompted the interpretation that HDFX 28 is powered by star formation. Subsequent Chandra imaging, however, revealed hard (Γ=0.30) X-ray emission indicative of absorbed active galactic nucleus (AGN) activity, implying that HDFX 28 is an obscured type II AGN. The optical and near-infrared spectra presented herein corroborate this result; the near-infrared emission lines cannot be powered by star formation alone, and the optical emission lines indicate a buried AGN. HDFX 28 is identified with a face-on moderately late-type spiral galaxy. Multiwavelength morphological studies of the HDF-N have heretofore revealed no galaxies with any kind of recognizable spiral structure beyond z>2. We present a quantitative analysis of the morphology of HDFX 28, and we find the measures of central concentration and asymmetry to be indeed consistent with those expected for a rare high-redshift spiral galaxy.

Based on observations made at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

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