The UV--mid-IR Spectral Energy Distribution of a z=1.7 Quasar Host Galaxy

TL;DR

This study measures the spectral energy distribution of a z=1.7 quasar host galaxy, revealing its stellar mass, star formation rate, and black hole properties, providing insights into galaxy and black hole co-evolution at high redshift.

Contribution

First detailed UV to mid-IR SED measurement of a high-redshift quasar host galaxy with resolved imaging, enabling analysis of stellar and black hole properties.

Findings

Host galaxy has stellar mass log(M_stars/M_sun)=11.09±0.28.

Black hole mass is approximately 10^8.6 M_sun, radiating at 24% of Eddington limit.

The stellar-to-black hole mass ratio is marginally inconsistent with local universe relations.

Abstract

We have measured the spectral energy distribution (SED) of the host galaxy of the z_s=1.7 gravitationally lensed quasar SDSS J1004+4112 from 0.44-8.0 micron (0.16-3.0 micron in the rest frame). The large angular extent of the lensed images and their separation from the centralgalaxy of this cluster lens allows the images to be resolved even with the Spitzer Space Telescope. Based on the SED, the host galaxy is a mixture of relatively old and intermediate age stars with an inferred stellar mass of log(M_stars/M_sun)=11.09+/-0.28 and a star formation rate of log(Mdot/1 M_sun per yr)=1.21+/-0.26. Given the estimated black hole mass of M_BH ~10^8.6 M_sun from locally-calibrated correlations of black hole masses with line widths and luminosities, the black hole represents a fraction log(M_BH/M_stars) = -2.49+/-0.28 of the stellar mass and it is radiating at 0.24+/-0.05 of the Eddington limit. The ratio of the host stellar mass to the black hole mass is only marginally consistent with the locally observed ratio.