Systematic effects in measurement of black hole masses by emission-line reverberation of active galactic nuclei: Eddington ratio and inclination

By S. Collin, T. Kawaguchi, B. Peterson, M. Vestergaard. 2006

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Context. Scatter around the relationship between central black hole masses in active galactic nuclei (AGNs) obtained by reverberation-mapping methods and host-galaxy bulge velocity dispersion indicates that the masses are uncertain typically by a factor of about three. Aims. In this paper, we try to identify the sources and systematics of this uncertainty. Methods. We characterize the broad Hemission-line profiles by the ratio of their full-width at half maximum (FWHM) to their line dispersion, i.e., the second moment of the line profile. We use this parameter to separate the reverberation-mapped AGNs into two populations, the first with narrower Hlines that tend to have relatively extended wings, and the second with broader lines that are relatively flat-topped. The first population is characterized by higher Eddington ratios than the second. Within each population, we calibrate the black-hole mass scale by comparison of the reverberation-based mass with that predicted by the bulge velocity dispersion. We also use the distribution of ratios of the reverberation-based mass to the velocity-dispersion mass prediction in a comparison with a "generalized thick disk" model in order to see if inclination can plausibly account for the observed distribution. Results. We find that the line dispersion is a less biased parameter in general than FWHM for black hole mass estimation, although we show that it is possible to empirically correct for the bias introduced by using FWHM to characterize the emission- line width. We also argue that inclination effects are apparent only in some small subset of the reverberation-based mass measurements; it is primarily the objects with the narrowest emission lines that seem to be most strongly affected. Conclusions. Our principal conclusion is that the Hprofile is sensitive primarily to Eddington ratio, but that inclination effects play a role in some cases.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/1346087d7d7df3f90eaeaeb23a6973faeb73d005

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Citations in the corpus

The Effect of Radiation Pressure on Virial Black Hole Mass Estimates and the Case of Narrow-Line Seyfert 1 Galaxies (2008, background): “This possibility has generated a debate about thereliability of virial BH masses (e.g. Peterson & Wandel 2000; Krolik 2001; Onken & Peterson 2002; Collin et al. 2006; Vestergaard & Peterson 2006) which is beyond the scope of this paper.”
THE LICK AGN MONITORING PROJECT: BROAD-LINE REGION RADII AND BLACK HOLE MASSES FROM REVERBERATION MAPPING OF Hβ (2009, background): “There is no reason to expect that thef value is the same from object to object, and differingf values in individual objects may be the main source of scatter in the AGNMBH − σ⋆ relationship (e.g., Collin et al. 2006).”
C IV λ1549 as an Eigenvector 1 Parameter for Active Galactic Nuclei (2007, background): “…with FWHM(H BC) 4000 km s 1, which is also appreciable in, e.g., Figure 6 ofWang et al. (1996), Figure 2 of Boller (2004), Figure 1 of Sulentic et al. (2000b), Figure 3 of Baskin & Laor (2005), and most impressively in Figure 7 (right) of Corbin & Boroson (1996); see also Collin et al. (2006).”
THE LICK AGN MONITORING PROJECT 2011: SPECTROSCOPIC CAMPAIGN AND EMISSION-LINE LIGHT CURVES (2015, background): “The width of broad Hβ is typically found to be slightly narrower in rms profiles than in mean profiles (e.g., Sergeev et al. 1999; Collin et al. 2006; Bentz et al. 2010a).”
THE LICK AGN MONITORING PROJECT: THE MBH–σ* RELATION FOR REVERBERATION-MAPPED ACTIVE GALAXIES (2010, methodology): “In an empirical study LAMP: MBH − σ∗ RELATION 11 of the systematic effects of emission-line profiles, Collin et al. (2006) showed that it was necessary to use a smaller value of the virial coefficient for AGNs with larger VFWHM.”
Black Holes in Pseudobulges and Spheroidals: A Change in the Black Hole-Bulge Scaling Relations at Low Mass (2008, background): “Finally, the technical measurement details can seriously and systematically impact the derived BH masses (e.g., Collin et al. 2006; Shen et al. 2008b).”
Determining Inclinations of Active Galactic Nuclei Via Their Narrow-Line Region Kinematics (2012, background): “These results can thus provide valuable constraints on specific torus models (e.g. Fritz et al. 2006; Ramos Almeida et al. 2009; Roth et al. 2012; Stalevski et al. 2012) and BLR models (e.g. Collin et al. 2006; Denney 2012; Pancoast et al. 2012).”
A Reverberation-based Mass for the Central Black Hole in NGC 4151 (2006, background): “(1) depends on the structure, kinematics, and inclination of the BLR (cf. Collin et al. 2006) and is expected to be different for each AGN.”
DWARF GALAXIES WITH OPTICAL SIGNATURES OF ACTIVE MASSIVE BLACK HOLES (2013, background): “Whether the geometry depends on fundamental parameters of the BH remains uncertain (Collin et al. 2006).”
A CATALOG OF QUASAR PROPERTIES FROM SLOAN DIGITAL SKY SURVEY DATA RELEASE 7 (2010, background): “…dex) associated with these estimates and the systematics involved in the calibration and usage, which will potentially lead to significant biases of these BH mass estimates (e.g., Collin et al. 2006; Shen et al. 2008b; Marconi et al. 2008; Denney et al. 2009; Kelly et al. 2009; Shen & Kelly 2010).”
COMPARING SINGLE-EPOCH VIRIAL BLACK HOLE MASS ESTIMATORS FOR LUMINOUS QUASARS (2012, background): “Arguablyσline is a better surrogate for the virial velocity (e.g., Collin et al. 2006), although the evidence is not very strong.”
Selection bias in dynamically measured supermassive black hole samples: its consequences and the quest for the most fundamental relation (2016, background): “…in the literature vary between averagvalues of fvir ∼ 1 andfvir ∼ 4, depending, respectively, on whether the emission-line profile which enters the virial equation is measured via its full-width at half maximum or its line dispersion (e.g., Collin et al. 2006; Park et al. 2012b; Ho & Kim 2014).”
UNIFICATION OF LUMINOUS TYPE 1 QUASARS THROUGH C iv EMISSION (2010, neutral): “The general idea of our two-component model is similar to that of Collin et al. (2006) and one possible manifestation is illustrated in Figure 15 of Leighly (2004), except that here we assume that there is always a wind component (which simply may not always be dominated by radiation line driving)…”
REVERBERATION MAPPING MEASUREMENTS OF BLACK HOLE MASSES IN SIX LOCAL SEYFERT GALAXIES (2010, methodology): “Because the rms profile is weak and poorly-defined, we measure the line widths from the mean spectrum and use the Collin et al. (2006) calibration of the scale factor determined for the line dispersion measured from the mean spectrum, f = 3.85.”
Broad-line Balmer decrements in blue active galactic nuclei (2007, background): “Collin et al. (2006) characterize the broad-line profiles by the ratio of FWHM to σline, based on which the broad-line profiles of AGN are separated into two categories: the first, having F WHM σline < 2.35, are narrower lines with relatively extended wings; the second, having F WHM σline > 2.35,…”
An expanded Mbh–σ diagram, and a new calibration of active galactic nuclei masses (2010, background): “Thin discs, thickened discs or composites of planar and random motions have all been modelled by various groups (see discussions by Krolik 2001; Collin et al. 2006; Labita et al. 2006; Decarli et al. 2008b).”
The AGN Black Hole Mass Database (2014, methodology): “We caution the user that, in general, other combinations of time delay and line width measurements will require the adoption of other values of〈 f 〉 (e.g., Collin et al. 2006).”
Piecing together the X-ray background : bolometric corrections for active galactic nuclei (2007, background): “There are also potential systematics in the estimation of NLS1 masses, possibly due to the flattening and inclinatioto the line of sight of the broad-line region; this could cause NLS1 BH masses to be underestimated under the reverberation mapping method (Collin et al. 2006).”