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arXiv · 2304.02085

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

Yuzo Ishikawa·Ben Wang·Nadia L. Zakamska·Gordon T. Richards·Joseph F. Hennawi·Angelica B. Rivera
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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 ${\rm H\alpha}$, ${\rm H\beta}$, and/or ${\rm[ O~III]}$ 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 ${\rm H\alpha}/{\rm H\beta}$ ratios, and we directly observe a heavily reddened rest-frame optical continuum in several sources, suggesting high extinction ($A_V\sim7-20$ 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.

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Yuzo Ishikawa, Ben Wang, Nadia L. Zakamska, Gordon T. Richards, Joseph F. Hennawi, Angelica B. Rivera. 2023-04-04. Infrared spectroscopic confirmation of z~2 photometrically-selected obscured quasars. https://doi.org/10.1093/mnras%2Fstad1035

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