TESTING DIAGNOSTICS OF NUCLEAR ACTIVITY AND STAR FORMATION IN GALAXIES AT z > 1

Journal Article · Sun Jan 20 04:00:00 EST 2013 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/763/1/L6· OSTI ID:22078328

Trump, Jonathan R; Barro, Guillermo; Koo, David C; Faber, S M ^[1]; Konidaris, Nicholas P ^[2]; Kocevski, Dale D; Yan, Renbin ^[3]; Juneau, Stephanie ^[4]; Weiner, Benjamin J ^[5]; McLean, Ian S ^[6]; Perez-Gonzalez, Pablo G; Villar, Victor ^[7]

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1. University of California Observatories/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
2. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
3. Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States)
4. Irfu/Service d'Astrophysique, CEA-Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette Cedex (France)
5. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
6. Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095 (United States)
7. Departamento de Astrofisica, Facultad de CC. Fisicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

We present some of the first science data with the new Keck/MOSFIRE instrument to test the effectiveness of different AGN/SF diagnostics at z {approx} 1.5. MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S field, resulting in 2 hr exposures of 36 emission-line galaxies. We compare X-ray data with the traditional emission-line ratio diagnostics and the alternative mass-excitation and color-excitation diagrams, combining new MOSFIRE infrared data with previous HST/WFC3 infrared spectra (from the 3D-HST survey) and multiwavelength photometry. We demonstrate that a high [O III]/H{beta} ratio is insufficient as an active galactic nucleus (AGN) indicator at z > 1. For the four X-ray-detected galaxies, the classic diagnostics ([O III]/H{beta} versus [N II]/H{alpha} and [S II]/H{alpha}) remain consistent with X-ray AGN/SF classification. The X-ray data also suggest that 'composite' galaxies (with intermediate AGN/SF classification) host bona fide AGNs. Nearly {approx}2/3 of the z {approx} 1.5 emission-line galaxies have nuclear activity detected by either X-rays or the classic diagnostics. Compared to the X-ray and line ratio classifications, the mass-excitation method remains effective at z > 1, but we show that the color-excitation method requires a new calibration to successfully identify AGNs at these redshifts.

• OSTI ID: 22078328
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 763; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CALIBRATION
COLOR
EMISSION
EXCITATION
GALAXIES
GALAXY NUCLEI
INFRARED SPECTRA
PHOTOMETRY
RED SHIFT
STARS
TESTING
X RADIATION
X-RAY DETECTION