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Journal article
Connecting Low- and High-redshift Weak Emission-line Quasars via Hubble Space Telescope Spectroscopy of Ly alpha Emission
The Astrophysical journal, v 929(1), p78
01 Apr 2022
Abstract
We present ultraviolet spectroscopy covering the Ly alpha + N v complex of six candidate low-redshift (0.9 < z < 1.5) weak emission-line quasars (WLQs) based on observations with the Hubble Space Telescope. The original systematic searches for these puzzling Type 1 quasars with intrinsically weak broad emission lines revealed an N approximate to 100 WLQ population from optical spectroscopy of high-redshift (z > 3) quasars, defined by a Ly alpha + N v rest-frame equivalent width (EW) threshold <15.4 angstrom. Identification of lower-redshift (z < 3) WLQ candidates, however, has relied primarily on optical spectroscopy of weak broad emission lines at longer rest-frame wavelengths. With these new observations expanding existing optical coverage into the ultraviolet, we explore unifying the low- and high-z WLQ populations via EW[Ly alpha+N v]. Two objects in the sample unify with high-z WLQs, three others appear consistent with the intermediate portion of the population connecting WLQs and normal quasars, and the final object is consistent with typical quasars. The expanded wavelength coverage improves the number of available line diagnostics for our individual targets, allowing a better understanding of the shapes of their ionizing continua. The ratio of EW[Ly alpha+N v] to EW[Mg ii] in our sample is generally small but varied, favoring a soft ionizing continuum scenario for WLQs, and we find a lack of correlation between EW[Ly alpha+N v] and the X-ray properties of our targets, consistent with a "slim-disk" shielding gas model. We also find indications that weak absorption may be a more significant contaminant in low-z WLQ populations than previously thought.
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Details
- Title
- Connecting Low- and High-redshift Weak Emission-line Quasars via Hubble Space Telescope Spectroscopy of Ly alpha Emission
- Creators
- Jeremiah D. Paul - Univ Nevada, Dept Phys, Reno, NV 89557 USARichard M. Plotkin - Univ Nevada, Dept Phys, Reno, NV 89557 USAOhad Shemmer - Univ North Texas, Dept Phys, Denton, TX 76203 USAScott F. Anderson - Univ Washington, Dept Astron, Box 351580, Seattle, WA 98195 USAW. N. Brandt - Penn State Univ, Dept Astron & Astrophys, Davey Lab 525, University Pk, PA 16802 USAXiaohui Fan - Univ Arizona, Steward Observ, 933 N Cherry Ave, Tucson, AZ 85721 USAElena Gallo - Univ Michigan, Dept Astron, 1085 S Univ Ave, Ann Arbor, MI 48109 USABin Luo - Nanjing Univ, Sch Astron & Space Sci, Nanjing 210093, Jiangsu, Peoples R ChinaQingling Ni - Penn State Univ, Dept Astron & Astrophys, Davey Lab 525, University Pk, PA 16802 USAGordon T. Richards - Drexel UniversityDonald P. Schneider - Penn State Univ, Dept Astron & Astrophys, Davey Lab 525, University Pk, PA 16802 USAJianfeng Wu - Xiamen Univ, Dept Astron, Xiamen 361005, Fujian, Peoples R ChinaWeimin Yi - Penn State Univ, Dept Astron & Astrophys, Davey Lab 525, University Pk, PA 16802 USA
- Publication Details
- The Astrophysical journal, v 929(1), p78
- Publisher
- IOP Publishing Ltd
- Number of pages
- 15
- Grant note
- Max Planck Society; Foundation CELLEX NAS5-26555 / NASA; National Aeronautics & Space Administration (NASA) National Science Foundation; National Science Foundation (NSF) U.S. Department of Energy; United States Department of Energy (DOE) HST-GO-13298.001 / NASA from the Space Telescope Science Institute National Aeronautics and Space Administration; National Aeronautics & Space Administration (NASA) CMS-CSST-2021-A05; CMS-CSST-2021-A06 / China Manned Space Project GO0-21080X / Chandra X-ray Center 11991053 / National Natural Science Foundation of China; National Natural Science Foundation of China (NSFC) Alfred P. Sloan Foundation Higher Education Funding Council for England; UK Research & Innovation (UKRI); Higher Education Funding Council for England (HEFCE) Japanese Monbukagakusho; Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Physics
- Web of Science ID
- WOS:000782505000001
- Scopus ID
- 2-s2.0-85128806732
- Other Identifier
- 991019169673104721
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- Collaboration types
- Domestic collaboration
- International collaboration
- Web of Science research areas
- Astronomy & Astrophysics