1. M-σ

2. Predicted in 1998-1999 based on self- regulated BH growth M ~ σ 5 (Silk & Rees) M ~ σ 4 (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 r i = GM bh /σ 2 ; θ i = r i /D < 1” for almost all galaxies Selection effect: If r i < telescope resolution, we skip that galaxy Using list of all galaxies with M<100 Mpc and measured σ, assign a random M bh 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 θ i ; 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=10 10 BH’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 “virial estimate”. 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 – M bh = fRv 2 /G (f accounts for unknown geometry of BLR)

13. Xiao et al. (2011): Exploring the low- mass end Greene & Ho measured M BH with SDSS Add 71 AGNs with M=10 5 – 10 7 BHs 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?