2013ApJ...763L...6T -
Astrophys. J., 763, L6 (2013/January-3)
Testing diagnostics of nuclear activity and star formation in galaxies at z > 1.
TRUMP J.R., KONIDARIS N.P., BARRO G., KOO D.C., KOCEVSKI D.D., JUNEAU S., WEINER B.J., FABER S.M., McLEAN I.S., YAN R., PEREZ-GONZALEZ P.G. and VILLAR V.
Abstract (from CDS):
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 ∼ 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]/Hβ 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]/Hβ versus [N II]/Hα and [S II]/Hα) 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 ∼2/3 of the z ∼ 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.
Abstract Copyright:
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Journal keyword(s):
galaxies: active - galaxies: fundamental parameters - galaxies: nuclei - galaxies: Seyfert
Nomenclature:
Table 1: [TKB2013b] NNNNN N=36 among (Nos 5745-13252).
Simbad objects:
37
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