The Relationship of Hard X-Ray and Optical Line Emission in Low-Redshift Active Galactic Nuclei

By T. Heckman, A. Ptak, A. Hornschemeier, G. Kauffmann. 2005

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In this paper we assess the relationship of the population of active galactic nuclei (AGNs) selected by hard X-rays to the traditional population of AGNs with strong optical emission lines. First, we study the emission-line properties of a new hard-X-ray-selected sample of 47 local AGNs (classified optically as Type 1 and 2 AGNs). We find that the hard X-ray (3-20 keV) and [O III] λ5007 optical emission-line luminosities are well-correlated over a range of about 4 orders of magnitude in luminosity (mean luminosity ratio 2.15 dex with a standard deviation of σ = 0.51 dex). Second, we study the hard X-ray properties of a sample of 55 local AGNs selected from the literature on the basis of the flux in the [O III] line. The correlation between the hard X-ray (2-10 keV) and [O III] luminosity for the Type 1 AGNs is consistent with what is seen in the hard-X-ray-selected sample. However, the Type 2 AGNs have a much larger range in the luminosity ratio, and many are very weak in hard X-rays (as expected for heavily absorbed AGNs). We then compare the hard X-ray (3-20 keV) and [O III] luminosity functions of AGNs in the local universe. These have similar faint-end slopes, with a luminosity ratio of 1.60 dex (0.55 dex smaller than the mean value for individual hard-X-ray-selected AGNs). We conclude that at low redshift, selection by narrow optical emission lines will recover most AGNs selected by hard X-rays (with the exception of BL Lac objects). However, selection by hard X-rays misses a significant fraction of the local AGN population with strong emission lines.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/9596330de488d65d3bb05b806f0e30ae1e4bf0b7

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Citations in the corpus

A NEW DIAGNOSTIC OF ACTIVE GALACTIC NUCLEI: REVEALING HIGHLY ABSORBED SYSTEMS AT REDSHIFT >0.3 (2011, methodology): “We reproduce this result in Figure 9(a) where we combine samples of Seyferts from Heckman et al. (2005) and Bassani et al. (1999).”
Galaxy pairs in the Sloan Digital Sky Survey – VIII. The observational properties of post-merger galaxies (2013, background): “The correction of the [OIII] luminosity to a bolometric luminosity is highly uncertain, and depends on (among other factors) how (or if) dust is accounted for and whether the AGN is a type I or type II (e.g. Heckman et al. 2005).”
Ultraviolet Detection of the Tidal Disruption of a Star by a Supermassive Black Hole (2006, background): “The correlation be-42 1L 1 # 10X tweenL([O iii]) and (3–20 keV) observed for local AGNsLX (Heckman et al. 2005) predicts erg s , which39 1L([O iii]) !”
On the X-ray, optical emission line and black hole mass properties of local Seyfert galaxies ! (2006, background): “More recently, Heckman et al. (2005) have found that LX and L[OIII] are well correlated in a sample of hard X-ray selected AGN (both type 1 and type 2).”
The host galaxies and classification of active galactic nuclei (2006, background): “Heckman et al. (2005) found that the L[OIII] and hard X- ray (3-20 keV) luminosities of AGN are correlated over four orders of magnitude.”
Timing the starburst–AGN connection (2010, background): “For obscured (Type 2) AGN, [O III] luminosity correlates well with hard X-ray luminosity for Compton thin AGN, with a scatter of 0.51dex over 4 orders of magnitude in luminosity (Heckman et al. 2005).”
Star formation and AGN activity in SDSS cluster galaxies (2009, background): “At least in the local universe, this AGN population correlates well with X-ray selected AGN (Heckman et al. 2005), which are thus also likely linked to ongoi g star formation.”
ONGOING AND CO-EVOLVING STAR FORMATION IN zCOSMOS GALAXIES HOSTING ACTIVE GALACTIC NUCLEI (2008, methodology): “…by the 0.5-10 keV band thus limiting the inclusion of more heavily absorbed type 2 AGN such as the Compton-thick population (Fiore et al. 2008), for which this correlation is less evident if the X-ray luminosities are not corrected for X-ray absorption (Heckman et al. 2005) as is the case here.”
Nuclear Activity in Nearby Galaxies (2008, methodology): “Because of the wide range of ionization levels among LLAGNs, a bolometric correction based on Hα should be more stable than one tied to [O III] λ5007 (e.g., Heckman et al. 2005).”
The Coevolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe (2014, background): “The problem with the hard X-ray luminosity is that many of the Type 2 AGN in the SDSS-OIII and IRAS-MIR samples are Compton-thick and significantly obscured even in the Swift BAT band (14-195 keV) – see also Heckman et al. (2005), Winter et al. (2010).”
Swift BAT Survey of AGNs (2007, background): “While it is commonly believed that extinction-corrected [O iii] can be used as an ‘‘unbiased’’ tracer of AGN activity (Risaliti et al. 1999), there is a large scatter between [O iii] and 2Y10 keV X-ray flux (Heckman et al. 2005) and between [O iii] and BAT flux (Meléndez et al. 2008).”
Narrow-line region gas kinematics of 24 264 optically selected AGN: the radio connection (2013, background): “…III] λ5007 luminosity (hereafter L[O III]) is thought to be a proxy measure of the bolometric AGN luminosity (e.g. Maiolino & Rieke 1995; Bassani et al. 1999; Risaliti, Maiolino & Salvati 1999; Heckman et al. 2005), so here we investigate the relationship between [O III] λ5007 profile and L[O III].”
SPACE DENSITY OF OPTICALLY SELECTED TYPE 2 QUASARS (2008, methodology): “Hao et al. (2005b) found that type 2 AGNs make up about 60% of the AGN population at L[O iii] ∼ 106 L , and about 30% at ∼3 × 107 L .”
A CONTINUUM OF H- TO He-RICH TIDAL DISRUPTION CANDIDATES WITH A PREFERENCE FOR E+A GALAXIES (2014, background): “We detect X-ray flux at the position of PTF09axc, which is marginally consistent with an extremely weak AGN given our measured [O III] luminosity (Heckman et al. 2005) and highly inconsistent with an accreting binary origin (Hornschemeier et al. 2005).”
Accretion-driven evolution of black holes: Eddington ratios, duty cycles and active galaxy fractions (2011, background): “…and active galaxies have found evidence for time evolution of λc, and in some cases for mass-dependence (e.g., McLure & Dunlop 2004; Vestergaard 2004; Heckman et al. 2005; Ballo et al. 2007; Babić et al. 2007; Bundy et al. 2008; Rovilos & Georgantopoulos 2007; Cao & Li 2008; Fine et al. 2008;…”
Determining Inclinations of Active Galactic Nuclei Via Their Narrow-Line Region Kinematics (2012, methodology): “…luminosities were obtained by integrating across all available spectral energy distribution (SED) flux points (Woo & Urry 2002) or derived from [O III] (log(LBol) ≈ log(L[OIII])+ log(3500); Heckman et al. 2004, 2005; Meléndez et al. 2008) or 2-10 keV X-ray (Malaguti et al. 1998) luminosities.”