Selection bias in dynamically measured supermassive black hole samples : its consequences and the quest for the most fundamental relation

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Shankar , F , Bernardi , M , Sheth , R K , Ferrarese , L , Graham , A W , Savorgnan , G , Allevato , V , Marconi , A , Läsker , R & Lapi , A 2016 , ' Selection bias in dynamically measured supermassive black hole samples : its consequences and the quest for the most fundamental relation ' Monthly Notices of the Royal Astronomical Society , vol. 460 , no. 3 , pp. 3119-3142 . DOI: 10.1093/mnras/stw678

Title: Selection bias in dynamically measured supermassive black hole samples : its consequences and the quest for the most fundamental relation
Author: Shankar, Francesco; Bernardi, Mariangela; Sheth, Ravi K.; Ferrarese, Laura; Graham, Alister W.; Savorgnan, Giulia; Allevato, Viola; Marconi, Alessandro; Läsker, Ronald; Lapi, Andrea
Contributor: University of Helsinki, Division of Geophysics and Astronomy
Date: 2016-08-11
Language: eng
Number of pages: 24
Belongs to series: Monthly Notices of the Royal Astronomical Society
ISSN: 0035-8711
URI: http://hdl.handle.net/10138/183979
Abstract: We compare the set of local galaxies having dynamically measured black holes with a large, unbiased sample of galaxies extracted from the Sloan Digital Sky Survey. We confirm earlier work showing that the majority of black hole hosts have significantly higher velocity dispersions sigma than local galaxies of similar stellar mass. We use Monte Carlo simulations to illustrate the effect on black hole scaling relations if this bias arises from the requirement that the black hole sphere of influence must be resolved to measure black hole masses with spatially resolved kinematics. We find that this selection effect artificially increases the normalization of the M-bh-sigma relation by a factor of at least similar to 3; the bias for the M-bh-M-star relation is even larger. Our Monte Carlo simulations and analysis of the residuals from scaling relations both indicate that sigma is more fundamental than M-star or effective radius. In particular, the M-bh-M-star relation is mostly a consequence of the M-bh-sigma and sigma-M-star relations, and is heavily biased by up to a factor of 50 at small masses. This helps resolve the discrepancy between dynamically based black hole-galaxy scaling relations versus those of active galaxies. Our simulations also disfavour broad distributions of black hole masses at fixed sigma. Correcting for this bias suggests that the calibration factor used to estimate black hole masses in active galaxies should be reduced to values of f(vir) similar to 1. Black hole mass densities should also be proportionally smaller, perhaps implying significantly higher radiative efficiencies/black hole spins. Reducing black hole masses also reduces the gravitational wave signal expected from black hole mergers.
Subject: black hole physics
galaxies: fundamental parameters
galaxies: nuclei
galaxies: structure
ACTIVE GALACTIC NUCLEI
EARLY-TYPE GALAXIES
M-BH-SIGMA
STELLAR MASS FUNCTIONS
STAR-FORMATION RATE
DIGITAL SKY SURVEY
DARK-MATTER HALOS
SEYFERT 1 GALAXIES
GRAVITATIONAL-WAVE SIGNAL
NEAR-INFRARED LUMINOSITY
115 Astronomy, Space science
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