A Connection between Obscuration and Star Formation in Luminous Quasars

TL;DR

This study investigates the link between obscuration in quasars and star formation activity, revealing that obscured quasars exhibit higher star formation rates and dust content, supporting models of galaxy evolution involving dust-enshrouded starburst phases.

Contribution

It provides the first comprehensive analysis of star formation properties in a uniform sample of obscured and unobscured quasars using spectral energy distribution decomposition.

Findings

Obscured quasars have higher far-IR detection rates and luminosities than unobscured ones.

The obscured fraction of quasars increases with infrared luminosity.

X-ray absorption correlates with the presence of far-IR emitting dust.

Abstract

We present a measurement of the star formation properties of a uniform sample of mid-IR selected, unobscured and obscured quasars (QSO1s and QSO2s) in the Bo\"otes survey region. We use an spectral energy distribution (SED) analysis for photometric data spanning optical to far-IR wavelengths to decompose AGN and host galaxy components. We find that when compared to a matched sample of QSO1s, the QSO2s have higher far-IR detection fractions, far-IR fluxes and infrared star formation luminosities ($L_{\rm IR}^{\rm SF}$) by a factor of $\sim2$. Correspondingly, we show that the AGN obscured fraction rises from 0.3 to 0.7 between $4-40\times10^{11}L_\odot$. We also find evidence associating the absorption in the X-ray emission with the presence of far-IR emitting dust. Overall, these results are consistent with galaxy evolution models in which quasar obscurations can be associated with a dust-enshrouded starburst galaxies.