Kartaltepe, Jeyhan S. and Sanders, D. B. and Silverman, J. D. and Kashino, D. and Chu, J. and Zahid, H. and Hasinger, G. and Kewley, L. and Matsuoka, K. and Nagao, T. and Riguccini, L. and Salvato, M. and Schawinski, K. and Taniguchi, Y. and Treister, E. and Capak, P. and Daddi, E. and Ohta, K. (2015) Rest-frame Optical Emission Lines in Far-infrared-selected Galaxies at z < 1.7 from the FMOS-COSMOS Survey. Astrophysical Journal Letters, 806 (2). Art. No. L35. ISSN 2041-8205. http://resolver.caltech.edu/CaltechAUTHORS:20150722-100206292
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We have used FMOS on Subaru to obtain near-infrared spectroscopy of 123 far-infrared-selected galaxies in COSMOS and the key rest-frame optical emission lines. This is the largest sample of infrared galaxies with near-infrared spectroscopy at these redshifts. The far-infrared selection results in a sample of galaxies that are massive systems that span a range of metallicities in comparison with previous optically selected surveys, and thus has a higher active galactic nucleus (AGN) fraction and better samples the AGN branch. We establish the presence of AGNs and starbursts in this sample of (U)LIRGs selected as Herschel-PACS and Spitzer-MIPS detections in two redshift bins (z ~ 0.7 and z ~ 1.5) and test the redshift dependence of diagnostics used to separate AGNs from star formation dominated galaxies. In addition, we construct a low-redshift (z ~ 0.1) comparison sample of infrared-selected galaxies and find that the evolution from z ~ 1.5 to today is consistent with an evolving AGN selection line and a range of ISM conditions and metallicities from the models of Kewley et al. We find that a large fraction of (U)LIRGs are BPT-selected AGNs using their new redshift-dependent classification line. We compare the position of known X-ray-detected AGNs (67 in total) with the BPT selection and find that the new classification line accurately selects most of these objects (>70%). Furthermore, we identify 35 new (likely obscured) AGNs not selected as such by their X-ray emission. Our results have direct implications for AGN selection at higher redshift with either current (MOSFIRE, KMOS) or future (PFS, MOONS) spectroscopic efforts with near-infrared spectral coverage.
|Additional Information:||© 2015 The American Astronomical Society. Received 2014 November 25; accepted 2015 May 9; published 2015 June 22.|
|Subject Keywords:||cosmology: observations – galaxies: active – galaxies: evolution – galaxies: high-redshift – infrared: galaxies – surveys|
|Official Citation:||Rest-frame Optical Emission Lines in Far-infrared-selected Galaxies at z < 1.7 from the FMOS-COSMOS Survey Jeyhan S. Kartaltepe et al. 2015 ApJ 806 L35|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||22 Jul 2015 17:28|
|Last Modified:||22 Jul 2015 17:28|
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