A 3x10^9 solar mass black hole in the quasar SDSS J1148+5251 at z=6.41

TL;DR

This paper reports the discovery of a supermassive black hole of 3 billion solar masses in a high-redshift quasar at z=6.41, using near-infrared spectroscopy to analyze emission lines and estimate black hole mass and accretion rate.

Contribution

It provides a precise redshift measurement and estimates the mass and accretion rate of the black hole in a very distant quasar, demonstrating the existence of massive black holes early in the universe.

Findings

Black hole mass estimated at 3x10^9 solar masses.

Quasar is accreting at the Eddington limit.

Redshift determined to be z=6.41±0.01.

Abstract

We present near-infrared H and K-band spectra of the z=6.41 quasar SDSS J114816.64+525150.3. The spectrum reveals a broad MgII 2799 emission line with a full-width half-maximium of 6000 km/s. From the peak wavelength of this emission line we obtain a more accurate redshift than is possible from the published optical spectrum and determine a redshift of z=6.41+/-0.01. If the true peak of the Lyman alpha emission is at the same redshift, then a large fraction of the flux blueward of the peak is absorbed. The equivalent width of the MgII emission line is similar to that of lower redshift quasars, suggesting that the UV continuum is not dominated by a beamed component. Making basic assumptions about the line-emitting gas we derive an estimate for the central black hole in this quasar of 3x10^9 solar masses. The very high luminosity of the quasar shows that it is accreting at the maximal allowable rate for a black hole of this mass adopting the Eddington limit criterion.