Infrared spectroscopic confirmation of z~2 photometrically-selected obscured quasars

Abstract

The census of obscured quasar populations is incomplete, and remains a major unsolved problem, especially at higher redshifts, where we expect a greater density of galaxy formation and quasar activity. We present Gemini GNIRS near-infrared spectroscopy of 24 luminous obscured quasar candidates from the Sloan Digital Sky Survey's Stripe 82 region. The targets were photometrically selected using a WISE/W4 selection technique that is optimized to identify IR-bright and heavily-reddened/optically-obscured targets at $z>1$. We detect emission lines of $\mathrm{H}\alpha$, $\mathrm{H}\beta$, and/or $[\mathrm{O}\mathrm{III}]$ in 23 sources allowing us to measure spectroscopic redshifts in the range $1<z<3$ with bolometric luminosities spanning $L=10^{46.3}-10^{47.3}$ erg s${}^{-1}$. We observe broad $10^3-10^4$ km s${}^{-1}$ Balmer emissions with large $\mathrm{H}\alpha /\mathrm{H}\beta$ ratios, and we directly observe a heavily reddened rest-frame optical continuum in several sources, suggesting high extinction ($A_V\sim 7-20$ mag). Our observations demonstrate that such optical/infrared photometric selection successfully recovers high-redshift obscured quasars. The successful identification of previously undetected red, obscured high-redshift quasar candidates suggests that there are more obscured quasars yet to be discovered.

Accepted by MNRAS, 13 pages, 8 figures, 2 tables

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