Co-evolution of Extreme Star Formation and Quasar: hints from {\it Herschel} and the Sloan Digital Sky Survey

Zhiyuan Ma; Haojing Yan

doi:10.1088/0004-637X/811/1/58

paper

Co-evolution of Extreme Star Formation and Quasar: hints from {\it Herschel} and the Sloan Digital Sky Survey

arXiv:1501.01240 · doi:10.1088/0004-637X/811/1/58

Abstract

Using the public data from the Herschel wide field surveys, we study the far-infrared properties of optical-selected quasars from the Sloan Digital Sky Survey. Within the common area of $\sim 172 d e g^{2}$ , we have identified the far-infrared counterparts for 354 quasars, among which 134 are highly secure detections in the Herschel $250 μ m$ band (signal-to-noise ratios $\geq 5$ ). This sample is the largest far-infrared quasar sample of its kind, and spans a wide redshift range of $0.14 \leq z \leq 4.7$ . Their far-infrared spectral energy distributions, which are due to the cold dust components within the host galaxies, are consistent with being heated by active star formation. In most cases ( $≳ 80$ \%), their total infrared luminosities as inferred from only their far-infrared emissions ( $L_{I R}^{(c d)}$ ) already exceed $1 0^{12} L_{⊙}$ , and thus these objects qualify as ultra-luminous infrared galaxies. There is no correlation between $L_{I R}^{(c d)}$ and the absolute magnitudes, the black hole masses or the X-ray luminosities of the quasars, which further support that their far-infrared emissions are not due to their active galactic nuclei. A large fraction of these objects ( $≳ 50 - 60%$ ) have star formation rates $≳ 300 M_{⊙} y r^{- 1}$ . Such extreme starbursts among optical quasars, however, is only a few per cent. This fraction varies with redshift, and peaks at around $z \approx 2$ . Among the entire sample, 136 objects have secure estimates of their cold-dust temperatures ( $T$ ), and we find that there is a dramatic increasing trend of $T$ with increasing $L_{I R}^{(c d)}$ . We interpret this trend as the envelope of the general distribution of infrared galaxies on the ( $T$ , $L_{I R}^{(c d)}$ ) plane.

arXiv comment26 pages, 20 figures, Accepted for publication in ApJ

Co-evolution of Extreme Star Formation and Quasar: hints from {\it Herschel} and the Sloan Digital Sky Survey

Abstract

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