The dependence on redshift of quasar black hole masses from the SLOAN survey

R. Decarli Università dell’Insubria, Como, ItalyA. Treves Università dell’Insubria, Como, ItalyR. Falomo INAF, Osservatorio Astronomico di Padova, Italy

Marzia Labita

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SMBHs and host galaxies Most (if not all) nearby (early type) galaxies host a

supermassive black hole (SMBH) at their centers- proper motion of stars (Milky Way)- rotation curves of gas clouds – MASER (22 objects)

The host galaxies of low redshift quasars contain a massive spheroidal component(observative results)

(Ferrarese 2006 for a review)

Elliptical galaxies ↔ SMBHs

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Joint formation of SMBHs and massive spheroids

According to the hierarchical merging scenario, massive spheroids should be the products of successive merging events

At low redshift, the central BH mass is strongly correlated to the properties of the host galaxy bulge (of both active and inactive galaxies)

…OUTSIDE THE SPHERE OF INFLUENCE!

Formation of Formation and fuellingElliptical galaxies of their active nuclei

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Quasar – Host Galaxy connection: Host galaxy luminosity (mass) dependence on

redshift

Study the BH – host mass correlation at low z and trace its cosmological evolution close and beyond the peak of the quasar activity

BH mass dependence on redshift

SLOAN

McLure & Dunlop SDSS

Shen et al. SDSS

Fine et al. 2dF

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SDSS Sloan Digital Sky Survey(Fifht data release) 8000 square degrees imaged 1000000 spectra 90000 quasars (0.1 < z < 4.5)

…of which:50000 quasars for which MgII line width and 3000Å monochromatic flux are available (0.35 < z < 2.3)

Uniform BH mass determinations:

(McLure & Dunlop 2004)

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Absolute magnitude and BH mass vs. redshift

?

Malmquist Bias

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The luminosity-FWHM plane

GROWING REDSHIFT

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The luminosity-FWHM plane

Constant luminosity

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The luminosity-FWHM plane

Constant luminosity

Constant BH mass

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The luminosity-FWHM plane

Constant luminosity

Constant BH mass

Constant Eddington ratio

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MMAX

EMAX

LMIN

The luminosity-FWHM plane

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MMAX

EMAX

LMIN

The luminosity-FWHM plane

PROBABILITY DENSITY:

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Focus on the lowest redshift sample:Description of the assumed probability density6 FREE PARAMETERS: LMIN

MMAX

EMAX

σL

σE

σM

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Best fit to the luminosity-FWHM distribution Construction of the discrete observed distribution:

Division in boxes with ΔlogλLλ=0.15; ΔlogFWHM=0.04

Number of objects in each box Construction of the discrete expected

distribution from the assumed probability density:

Discretization in boxes Normalization to the observed number

of objects Evaluation of the best fit parameters:

For each choice of the 6 free parameters, evaluation of the rms between the observed and the expected distributions

Minimization of the rms BEST FIT PARAMETERS

Contour plot =Levels of constant probability

Errors on the best fit parameters:MONTE CARLO SIMULATIONS

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Comparison between the observed and the expected distribution Contour plot of a sample of

quasars simulated adopting the best fit probability density (Monte Carlo simulation)

Contour plot of the observed quasar sample

Contour plot of the residuals between the observed and the simulated distributions

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Best fit parameters in function of redshift

The rms of the best fit is almost the same in all the redshift bins.

(If we assumed that MMAX is constant redshift, the fit would be awful!)

The best fit parameters MMAX(z) and EMAX(z) give the (unbiassed!) dependence on redshift of the maximum mass and Eddington ratio

LMIN is a free parameter

LMIN is a NOT a free parameter: its dependence on redshift is fixed by COSMOLOGY

GROWING REDSHIFT

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Evolution of the quasar populations with the Cosmic Time: EDDINGTON RATIO

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Evolution of the quasar populations with the Cosmic Time: EDDINGTON RATIO

This work

Simple mean

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Evolution of the quasar populations with the Cosmic Time: MASS

Log (MBH MAX/MSUN ) = 1/3 z + 9

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This workSimple meanFine et al.

Evolution of the quasar populations with the Cosmic Time: MASS

Log (MBH MAX/MSUN ) = 1/3 z + 9

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ConclusionsThe maximum mass of quasar populations seems to decrease with Cosmic Time

i.e. the more a BH is massive,

the earliest it starts its quasar activity

Future Use C IV line to study this trend till z=4.5 Compare and contrast this trend in RQQs and RLQs Compare this results with the bulge mass evolution with

redshift … WORK IN PROGRESS!