Luminous mid-IR selected obscured quasars at cosmic noon in SDSS Stripe82 II: spectroscopic diversity and broad H α emissions

作者：Ben Wang, Yuzo Ishikawa, Joseph F. Hennawi, Zheng Cai, Gordon T. Richards, Nadia L. Zakamska, Da-Ming Yang, Jan–Torge Schindler · 发表于：Monthly Notices of the Royal Astronomical Society · 年份：2025 · DOI：10.1093/mnras/staf1730 · 被引用次数：2 · 研究领域：Galaxies: Formation, Evolution, Phenomena、Astronomy and Astrophysical Research、Gamma-ray bursts and supernovae

ABSTRACT We present a multiwavelength spectroscopic survey of 23 luminous mid-infrared-selected Type-2 quasars at the redshifts of $z=0.88$–3.49. The targets were selected in the SDSS Stripe 82 field based on their bright WISE 22 $\mu$m detections and extremely faint or red optical counterparts. Near-infrared (Gemini/Gemini Near-InfraRed Spectrograph) and optical (Keck/Low Resolution Imaging Spectrometer and Keck Cosmic Web Imager Integral Field Spectrograph) spectroscopy confirm 23 out of 24 candidates as Type-2 quasars, including 12 objects at $z>2$. The spectra exhibit strong rest-frame UV and optical emission lines (Ly $\alpha$, C iv, [O iii], H $\alpha$) with a wide range of line widths, indicating significant spectral diversity. Approximately one-third of the sample (8 of 23) shows broad H $\alpha$ emission (full width at half-maximum, FWHM$>2000$ km s$^{-1}$) despite their Type-2 classification, while the rest have only narrow lines (FWHM $< 2000$ km s$^{-1}$) characteristic of classical obscured quasars. Notably, these broad-line Type-2 quasars share similar spectral energy distributions with the James Webb Space Telescope (JWST)-discovered ‘little red dot’, suggesting that our sample could be lower redshift analogues of the heavily obscured broad-line AGNs uncovered by JWST. We also find that the [O iii] $\lambda$5007 emission is relatively weak for their high-bolometric luminosities, deviating from trends seen in lower-z Type-2 quasi-stellar obj...