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arXiv · 1412.1148

The Host Galaxies of X-ray Quasars Are Not Strong Star Formers

A. J. Barger·L. L. Cowie·F. N. Owen·C. -C. Chen·G. Hasinger·L. -Y. Hsu·Y. Li
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Abstract

We use ultradeep SCUBA-2 850um observations (~0.37 mJy rms) of the 2 Ms Chandra Deep Field-North (CDF-N) and 4 Ms Chandra Deep Field-South (CDF-S) X-ray fields to examine the amount of dusty star formation taking place in the host galaxies of high-redshift X-ray AGNs. Supplementing with COSMOS, we measure the submillimeter fluxes of the 4-8 keV sources at z>1, finding little flux at the highest X-ray luminosities but significant flux at intermediate luminosities. We determine gray body and MIR luminosities by fitting spectral energy distributions to each X-ray source and to each radio source in an ultradeep Karl G. Jansky Very Large Array (VLA) 1.4 GHz (11.5uJy at 5-sigma) image of the CDF-N. We confirm the FIR-radio and MIR-radio correlations to z=4 using the non-X-ray detected radio sources. Both correlations are also obeyed by the X-ray less luminous AGNs but not by the X-ray quasars. We interpret the low FIR luminosities relative to the MIR for the X-ray quasars as being due to a lack of star formation, while the MIR stays high due to the AGN contribution. We find that the FIR luminosity distributions are highly skewed and the means are dominated by a small number of high-luminosity galaxies. Thus, stacking or averaging analyses will overestimate the level of star formation taking place in the bulk of the X-ray sample. We conclude that most of the host galaxies of X-ray quasars are not strong star formers, perhaps because their star formation is suppressed by AGN feedback.

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A. J. Barger, L. L. Cowie, F. N. Owen, C. -C. Chen, G. Hasinger, L. -Y. Hsu, Y. Li. 2015-03-03. The Host Galaxies of X-ray Quasars Are Not Strong Star Formers. https://doi.org/10.1088/0004-637x%2F801%2F2%2F87

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