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SUMMARY:Selection bias in dynamically-measured super-massive black hole sa
 mples: its consequences and the quest for the most fundamental relation - 
 Francesco Shankar (Southampton)
DTSTART:20160415T103000Z
DTEND:20160415T113000Z
UID:TALK65261@talks.cam.ac.uk
CONTACT:Martin Haehnelt
DESCRIPTION:We compare the set of local galaxies having dynamically measur
 ed black holes with a large\, unbiased sample of galaxies extracted from t
 he Sloan Digital Sky Survey. We confirm earlier work showing that the majo
 rity of black hole hosts have significantly higher velocity dispersions si
 gma than local galaxies of similar stellar mass. We use Monte-Carlo simula
 tions to illustrate the effect on black hole scaling relations if this bia
 s arises from the requirement that the black hole sphere of influence must
  be resolved to measure black hole masses with spatially resolved kinemati
 cs. We find that this selection effect artificially increases the normaliz
 ation of the Mbh-sigma relation by a factor of at least 3\; the bias for t
 he Mbh-Mstar relation is even larger. Our Monte Carlo simulations and anal
 ysis of the residuals from scaling relations both indicate that sigma is m
 ore fundamental than Mstar or effective radius. In particular\, the Mbh-Ms
 tar relation is mostly a consequence of the Mbh-sigma and sigma-Mstar rela
 tions\, and is heavily biased by up to a factor of 50 at small masses. Thi
 s helps resolve the discrepancy between dynamically-based black hole-galax
 y scaling relations versus those of active galaxies. Our simulations also 
 disfavour broad distributions of black hole masses at fixed sigma. I will 
 discuss how correcting for this bias suggests that the calibration factor 
 used to estimate black hole masses in active galaxies should be reduced to
  values of fvir of about unity. Our work also suggests that black hole mas
 s densities should be proportionally smaller\, perhaps implying significan
 tly higher radiative efficiencies/black hole spins. I will conclude showin
 g how our reduced average black hole masses also significantly reduce the 
 gravitational wave signal expected from black hole mergers.
LOCATION:Kavli LMR\, IoA
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