Journal article
Luminous Mid-IR Selected Obscured Quasars at Cosmic Noon in SDSS Stripe82 II: Spectroscopic Diversity and Broad Hα Emissions
Monthly notices of the Royal Astronomical Society, v 544(1), pp 687-707
Nov 2025
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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 μm detections and extremely faint or red optical counterparts. Near-infrared (Gemini/GNIRS) and optical (Keck/LRIS and KCWI) 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 (Lyα, C IV, [O III], Hα) with a wide range of line widths, indicating significant spectral diversity. Approximately one-third of the sample (8 of 23) shows broad Hα emission (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 JWST-discovered “little red dot” (LRD), 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] λ5007 emission is relatively weak for their high bolometric luminosities, deviating from trends seen in lower-z Type-2 QSOs. A new composite spectrum for Type-2 QSOs is built using our sample. Overall, our results demonstrate that mid-IR selection efficiently uncovers diverse populations of obscured quasars and that spectroscopic follow-up is crucial for revealing their true nature. This study provides new insights into heavily obscured SMBH growth at cosmic noon and bridges the gap to the obscured AGN populations being revealed by JWST.
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Details
- Title
- Luminous Mid-IR Selected Obscured Quasars at Cosmic Noon in SDSS Stripe82 II: Spectroscopic Diversity and Broad Hα Emissions
- Creators
- Ben Wang (Corresponding Author) - Tsinghua UniversityYuzo Ishikawa - Massachusetts Institute of TechnologyJoseph F Hennawi - Leiden UniversityZheng Cai - Tsinghua UniversityGordon T Richards - Drexel UniversityNadia L Zakamska - Johns Hopkins UniversityDaming Yang - Leiden UniversityJan-Torge Schindler - Universität Hamburg
- Publication Details
- Monthly notices of the Royal Astronomical Society, v 544(1), pp 687-707
- Publisher
- Oxford University Press
- Number of pages
- 21
- Grant note
- Tsinghua University: 20223080023 National Science Foundation of China: 12073014 National Key Research and Development Program of China: 2023YFA1605600
BW and ZC were supported by the National Key R&D Program of China (grant no. 2023YFA1605600), the National Science Foundation of China (grant no. 12073014), the science research grants from the China Manned Space Project with No. CMS-CSST-2021-A05, and Tsinghua University Initiative Scientific Research Program (No. 20223080023).
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Physics
- Web of Science ID
- WOS:001606519600001
- Other Identifier
- 991022123483104721