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M-σ PowerPoint PPT Presentation

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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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  • Predicted in 1998-1999 based on self-regulated BH growth

  • M ~ σ5 (Silk & Rees)

  • M ~ σ4 (Fabian)

Discovery of m

Discovery of M-σ

  • Ferrarese & Merritt (2000)

  • Gebhardt et al. (2000)

Discovery of m1

Discovery of M-σ

  • Ferrarese & Merritt (2000)

  • Gebhardt et al. (2000)

What about agns

What about AGNs?

  • Ferrarese et al. 2001

Is m sigma an upper bound

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

Gultekin et al 2011 rebuttal

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

The high mass end mcconnell et al find m 10 10 bh s

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

Mcconnell et al

McConnell et al

M-L predicts very massive BH in BCGs but sigma values are typical of other large ellipticals

The high mass end

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?

The low mass end

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

The low mass end1

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)

Xiao et al 2011 exploring the low mass end

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

Xiao et al 2011 exploring the low mass end1

Xiao et al. (2011): Exploring the low-mass end

  • Edge-on galaxies have more scatter in sigma, presumably from rotational contribution

Massive galaxies with no smbh

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

What is the intrinsic shape

What is the Intrinsic Shape?

Some questions

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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