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Black Hole Growth and Quasars
Stephen Fine, Scott Croom (University of Sydney IoA) Philip Hopkins, Lars Hernquist (Harvard CFA)


Overview
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Lifecycle of quasars Simulations of galaxy mergers · Quasar light curves · Resulting models of the quasar and active black hole (BH) populations Ways to test these models · Measuring the BH mass in quasars · Measuring the BH mass in 100,000 quasars Results · How do the models do? · Other results

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Lifecycle of a quasar


Luminosity history of a quasar
· Simulated quasar light curves give t/L the time spent by a quasar at a given luminosity. · This is a function not only of L but also the peak luminosity a quasar will attain in its lifetime. · Convolving this model for quasar lifetimes with a `birth' rate function gives the luminosity function.
Springel, Di Matteo & Hernquist (2005)


The Luminosity Function
Low mass BHs accreting rapidly, and High mass BHs with low accretion rates.

Only higher mass BHs accreting at or near the Eddington rate. Mass limited by steep BH mass function. Accretion rate constrained by Eddington limit.


Broad lines and Quasars


Mass estimation with the virial method
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Broad-line emission region is assumed to be virialised and so the width of a line gives vBLR. The radius-luminosity relation derived from reverberation mapping campaigns gives rBLR.
Kaspi et al. (2005)

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Virial problems
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Broad-line region may not be virialised Radius-luminosity relation poorly defined (in particular for bright quasars) We want the dispersion in BH mass at a given luminosity so: · We bin our sample of QSOs by L and z and calculate the dispersion in Log(line width). · Then for a given bin:
Dispersion in Log(BH mass) = 2 x Dispersion in log(line widths)

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Data
Survey
SDSS

No. of objects
77,000

Mag. range
~19>Mi>~15

2QZ

23,000

20.85>Mbj>18.25

2SLAQ

8,000

21.85>Mg>18.0


QSO spectrum

Croom et al. (2002)


The Results


Dispersion Results


Comparison with Models


Dispersion Results


Geometry of the Broad-Line Region


Geometry of the BLR
Disk? Polar wind?

Line width



sin()

Line width

cos()


Geometry of the BLR

Line width

asin() + (1-a)

Line width

acos() + (1-a)


Summary
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There is very little variation in broad-line width between QSOs. There is a significant decreases in this variation towards larger luminosities. We find an almost identical trend in the dispersion of our line widths as predicted for the dispersion in BH masses. The low level of dispersion in line width at high luminosities implies: 1) There is an important aspect of the virial method for BH mass estimation we are yet to understand. 2) The velocity field of the broad-line region in high luminosity quasars is largely spherically symmetric.

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Same with CIV?


Same with CIV?


Measuring the MgII line


Measuring the MgII line


Same with CIV?


Geometry of the Broad-Line Region


The life and death of a quasar
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Lifecycle of QSOs · galaxy mergers starburst quasar activity BH growth feedback spheroid formation BH ­ spheroid correlations (e.g. Tremaine et al. 2002) Energetics (e.g. Silk & Rees 1998) Simulations of galaxy mergers (e.g. Hopkins et al. 2006)

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The radius-luminosity relation

Kaspi et al. (2005)