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M-σ

M-σ. M-σ. Predicted in 1998-1999 based on self-regulated BH growth M ~ σ 5 (Silk & Rees) M ~ σ 4 (Fabian). Discovery of M-σ. Ferrarese & Merritt (2000) Gebhardt et al. (2000). Discovery of M-σ. Ferrarese & Merritt (2000) Gebhardt et al. (2000). What about AGNs ?.

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M-σ

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  1. M-σ

  2. M-σ • Predicted in 1998-1999 based on self-regulated BH growth • M ~ σ5 (Silk & Rees) • M ~ σ4 (Fabian)

  3. Discovery of M-σ • Ferrarese & Merritt (2000) • Gebhardt et al. (2000)

  4. Discovery of M-σ • Ferrarese & Merritt (2000) • Gebhardt et al. (2000)

  5. What about AGNs? • Ferrarese et al. 2001

  6. Is M-sigma an upper bound? • Batcheldor (2010) argues that using “sphere of influence” argument to limit which galaxies to include in M-σ can lead to a false relationship • ri = GMbh/σ2 ; θi = ri/D < 1” for almost all galaxies • Selection effect: If ri < telescope resolution, we skip that galaxy • Using list of all galaxies with M<100 Mpc and measured σ, assign a random Mbh then plot M-σ with low and high cutoffs

  7. Gultekin et al. (2011) rebuttal • “We find that this hypothesis can be rejected … for early type galaxies with relatively high velocity dispersions, that comprise most of our sample.” • M-σ is basically unchanged when incorporating a general procedure to account for observational selection effects • Consider 325 < sigma < 385; G09 contains 4 galaxies; expect ~ 40 galaxies if M randomized; there are only 3 upper limits. Could this be because observers don’t publish nondetections, or have other clues to BH existence, e.g. weak AGN? • Construct “top 50” list by predicted θi ; choose top 30 from these, 15 have measured Mbh. Run statistical tests against “upper envelope” model

  8. The high mass end …McConnell et al. find M=1010BH’s

  9. McConnell et al M-L predicts very massive BH in BCGs but sigma values are typical of other large ellipticals

  10. The high-mass end • A special formation history for BCGs? • Multiple generations of gas-poor mergers • These are the most massive & luminous galaxies; with the most massive BH’s • Anisotropic infall (along cosmological filamets?); unique assembly history leads to displacement from M-sigma?

  11. The Low-mass end • Important for understanding BH seeds • Models include: • “light seeds” from pop III stars • Predict wide range of present-day BH masses, inc. v. low mass systems • High “occupation fraction” • “heavy seeds” from collapse of massive gas clouds in halos • Low “occupation fraction” • Minimum BH mass is higher (no v. low mass BHs) • Current observations don’t distinguish between these models – need more low-mass BH measurements

  12. The Low-mass end • It is difficult to measure stellar-dynamical BH masses for low-mass galaxies AGNs are a better place to look • Approximate low-mass BH mass with “virialestimate”. Low precision, but widely applicable. • Get BLR velocity dispersion from line width • Guess BLR radius based on AGN luminosity • This relation is calibrated by reverberation mapping from a sample of ~ 30 galaxies • Mbh = fRv2/G (f accounts for unknown geometry of BLR)

  13. Xiao et al. (2011): Exploring the low-mass end • Greene & Ho measured MBH with SDSS • Add 71 AGNs with M=105 – 107BHs • Follow trend of inactive galaxies • Slightly flatter slope; similar scatter • Barred/Unbarred similar

  14. Xiao et al. (2011): Exploring the low-mass end • Edge-on galaxies have more scatter in sigma, presumably from rotational contribution

  15. Massive galaxies with no SMBH? • High-mass BH growth is driven by mergers • Mergers  binary BHs • If viscosity/dynamical friction leads to small separation, grav radiation can lead to merger • BHs with unequal masses can lead to recoil  up to 200 km/s • BHs with aligned spins can recoil up to ~ 4000 km/s; escape velocity < 1000 km/s SMBH on the loose!! • These ejections predict increased scatter in M-sigma at low mass, where escape velocity is lower • Gas-poor mergers cannot reestablish the M-σ relation by growing a new BH

  16. What is the Intrinsic Shape?

  17. Some questions • How does slope and intrinsic scatter vary for different classes of galaxies, and what does this tell us? • E.g. classical vs. pseudo bulges; morphological types • Do differences of slope/scatter in host galaxy types account for most of the scatter at the low-mass end? • What can M-sigma tell us about formation of BH seeds? • How do the very massive BHs detected at high redshift evolve? Present day BCDs? • Can we detect escaped SMBHs?

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