INDICATORS OF INTRINSIC ACTIVE GALACTIC NUCLEUS LUMINOSITY: A MULTI-WAVELENGTH APPROACH

Journal Article · Wed Sep 01 04:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/720/1/786· OSTI ID:21460084

LaMassa, Stephanie M; Heckman, Tim M; Sonnentrucker, Paule ^[1]; Ptak, Andrew ^[2]; Martins, Lucimara ^[3]; Wild, Vivienne ^[4]

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1. Johns Hopkins University, Baltimore, MD 21210 (United States)
2. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
3. NAT-Universidade Cruziero do Sul, Sao Paulo (Brazil)
4. Institut d'Astrophysique de Paris, 75014 Paris (France)

Active galactic nuclei (AGNs) consist of an accretion disk around a supermassive black hole which in turn is surrounded by an obscuring torus of dust and gas. As the resulting geometry of this system affects the observable properties, quantifying isotropic indicators of intrinsic AGN luminosity is important in selecting unbiased samples of AGNs. In this paper, we consider five such proxies: the luminosities of the [O III]{lambda}5007 line, the [O IV]25.89 {mu}m line, the mid-infrared (MIR) continuum emission by the torus, and the radio and hard X-ray (E > 10 keV) continuum emission. We compare these different proxies using two complete samples of low-redshift Type 2 AGNs selected in a homogeneous way based on different indicators: an optically selected [O III] sample and an MIR-selected 12 {mu}m sample. To assess the relative merits of these proxies, we have undertaken two analyses. First, we examine the correlations between all five different proxies, and find better agreement for the [O IV], MIR, and [O III] luminosities than for the hard X-ray and radio luminosities. Next, we compare the ratios of the fluxes of the different proxies to their values in unobscured Type 1 AGNs. The agreement is best for the ratio of the [O IV] and MIR fluxes, while the ratios of the hard X-ray to [O III], [O IV], and MIR fluxes are systematically low by about an order of magnitude in the Type 2 AGNs, indicating that hard X-ray-selected samples do not represent the full Type 2 AGN population. In a similar spirit, we compare different optical and MIR diagnostics of the relative energetic contributions of AGN and star formation processes in our samples of Type 2 AGNs. We find good agreement between the various diagnostic parameters, such as the equivalent width of the MIR polycyclic aromatic hydrocarbon features, the ratio of the MIR [O IV]/[Ne II] emission lines, the spectral index of the MIR continuum, and the commonly used optical emission-line ratios. Finally, we test whether the presence of cold gas associated with star formation leads to an enhanced conversion efficiency of AGN ionizing radiation into [O III] or [O IV] emission. We find that no compelling evidence exists for this scenario for the luminosities represented in this sample (L{sub bol} {approx}10{sup 9} - 8 x 10{sup 11} L{sub sun}).

• OSTI ID: 21460084
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 720; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
AROMATICS
BLACK HOLES
ELECTROMAGNETIC RADIATION
GALAXIES
GALAXY NUCLEI
HARD X RADIATION
HYDROCARBONS
IONIZING RADIATIONS
LUMINOSITY
OPTICAL PROPERTIES
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
POLYCYCLIC AROMATIC HYDROCARBONS
RADIATIONS
RED SHIFT
SEYFERT GALAXIES
STARS
X RADIATION