TY - JOUR
T1 - Chemical abundance of z∼6 quasar broad-line regions in the XQR-30 sample
AU - Lai, Samuel
AU - Bian, Fuyan
AU - Onken, Christopher A.
AU - Wolf, Christian
AU - Mazzucchelli, Chiara
AU - Banados, Eduardo
AU - Bischetti, Manuela
AU - Bosman, Sarah E.I.
AU - Becker, George
AU - Cupani, Guido
AU - D'Odorico, Valentina
AU - Eilers, Anna Christina
AU - Fan, Xiaohui
AU - Farina, Emanuele Paolo
AU - Onoue, Masafusa
AU - Schindler, Jan Torge
AU - Walter, Fabian
AU - Wang, Feige
AU - Yang, Jinyi
AU - Zhu, Yongda
N1 - Funding Information:
We thank Matthew Temple for the helpful discussion and the reviewer, Yoshiki Matsuoka, for the thoughtful comments and suggestions which have improved this work. The results of this research is based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 1103.A-0817. This work is also based, in part, on observations obtained at the international Gemini Observatory, a programme of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnoloǵ?a e Innovación (Argentina), Ministério da Ciencia, Tecnologia, Inovaçoes e Comunicaços (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). SL is grateful to the Australian National University Research School of Astronomy and Astrophysics (ANU/RSAA) for funding his Ph.D. studentship and the European Southern Observatory for the research internship. CAO was supported by the Australian Research Council (ARC) through Discovery Project DP190100252. MB acknowledges support from PRIN MIUR project 'Black Hole winds and the Baryon Life Cycle of Galaxies: the stone-guest at the galaxy evolution supper', contract #2017PH3WAT. ACE acknowledges support by NASA through the NASA Hubble Fellowship grant #HF2-51434 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. SEIB acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 740246 'Cosmic Gas'). JTS acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 885301 'Quasar Chronicles').
Publisher Copyright:
© 2022 The Author(s).
PY - 2022/6/1
Y1 - 2022/6/1
N2 - The elemental abundances in the broad-line regions of high-redshift quasars trace the chemical evolution in the nuclear regions of massive galaxies in the early Universe. In this work, we study metallicity-sensitive broad emission-line flux ratios in rest-frame UV spectra of 25 high-redshift (5.8 < z < 7.5) quasars observed with the VLT/X-shooter and Gemini/GNIRS instruments, ranging over log (MBH/M⊙) = 8.4-9.8 in black hole mass and log (Lbol/erg s-1) = 46.7-47.7 in bolometric luminosity. We fit individual spectra and composites generated by binning across quasar properties: bolometric luminosity, black hole mass, and blueshift of the C iv line, finding no redshift evolution in the emission-line ratios by comparing our high-redshift quasars to lower redshift (2.0 < z < 5.0) results presented in the literature. Using cloudy-based locally optimally emitting cloud photoionization model relations between metallicity and emission-line flux ratios, we find the observable properties of the broad emission lines to be consistent with emission from gas clouds with metallicity that are at least 2-4 times solar. Our high-redshift measurements also confirm that the blueshift of the C iv emission line is correlated with its equivalent width, which influences line ratios normalized against C iv. When accounting for the C iv blueshift, we find that the rest-frame UV emission-line flux ratios do not correlate appreciably with the black hole mass or bolometric luminosity.
AB - The elemental abundances in the broad-line regions of high-redshift quasars trace the chemical evolution in the nuclear regions of massive galaxies in the early Universe. In this work, we study metallicity-sensitive broad emission-line flux ratios in rest-frame UV spectra of 25 high-redshift (5.8 < z < 7.5) quasars observed with the VLT/X-shooter and Gemini/GNIRS instruments, ranging over log (MBH/M⊙) = 8.4-9.8 in black hole mass and log (Lbol/erg s-1) = 46.7-47.7 in bolometric luminosity. We fit individual spectra and composites generated by binning across quasar properties: bolometric luminosity, black hole mass, and blueshift of the C iv line, finding no redshift evolution in the emission-line ratios by comparing our high-redshift quasars to lower redshift (2.0 < z < 5.0) results presented in the literature. Using cloudy-based locally optimally emitting cloud photoionization model relations between metallicity and emission-line flux ratios, we find the observable properties of the broad emission lines to be consistent with emission from gas clouds with metallicity that are at least 2-4 times solar. Our high-redshift measurements also confirm that the blueshift of the C iv emission line is correlated with its equivalent width, which influences line ratios normalized against C iv. When accounting for the C iv blueshift, we find that the rest-frame UV emission-line flux ratios do not correlate appreciably with the black hole mass or bolometric luminosity.
KW - galaxies: abundances
KW - galaxies: active
KW - galaxies: high-redshift
KW - quasars: emission lines
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U2 - 10.1093/mnras/stac1001
DO - 10.1093/mnras/stac1001
M3 - Article
AN - SCOPUS:85130449095
SN - 0035-8711
VL - 513
SP - 1801
EP - 1819
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -