Optical and near-infrared spectroscopy of quasars at <i>z</i> &amp;gt; 6.5: public data release and composite spectrum

ABSTRACT We present optical and near-infrared (NIR) spectroscopic observations for a sample of 45 quasars at $6.50 &amp;lt; z \le 7.64$ with absolute magnitudes at 1450 Å in the range $-28.82 \le M_{1450} \le -24.13$ and their composite spectrum. The median redshift and $M_{1450}$ of the quasars in the sample are $z_{\rm {median}}=6.71$ and $M_{1450,\rm {median}} \simeq -26.1$, respectively. The NIR spectra are taken with Echelle spectrographs, complemented with additional data from optical long slit instruments, and then reduced consistently using the open-source Python-based spectroscopic data reduction pipeline PypeIt. The median of the mean signal-to-noise ratios per 110 km s$^{-1}$ pixel in the J, H, and K band [median $\langle \rm {SNR}_{\lambda } \rangle$] is median $\langle \rm {SNR}_{J} \rangle =9.7$, median $\langle \rm {SNR}_{H} \rangle =10.3$, and median $\langle \rm {SNR}_{K} \rangle =11.7$; demonstrating the good data quality. This work presents the largest medium-/moderate-resolution sample of quasars at $z&amp;gt;6.5$ from ground-based instruments. Despite the diversity in instrumental set-ups and spectral quality, the data set is uniformly processed and well-characterized, making it ideally suited for several scientific goals, including the study of the quasar proximity zones and damping wings, the Ly $\alpha$ forest, the intergalactic medium’s metal content, as well as other properties such as the distribution of SMBH masses and Eddington ratios. Our composite spectrum is compared to others at both high and low z from the literature, showing differences in the strengths of many emission lines, probably due to differences in luminosity among the samples, but a consistent continuum slope, which proves that the same spectral features are preserved in quasars at different redshift ranges.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-05-14
DOI
https://doi.org/10.1093/mnras/staf787
Citations
5
Primary Topic
Astronomy and Astrophysical Research
Type
article
Field-Weighted Citation Impact
5.96

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Optical and near-infrared spectroscopy of quasars at z &gt; 6.5: public data release and composite spectrum

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Optical and near-infrared spectroscopy of quasars at z &gt; 6.5: public data release and composite spectrum

Masafusa Onoue, Fabian Walter, Jan–Torge Schindler, Riccardo Nanni, Joseph F. Hennawi, Aaron J. Barth, Jinyi Yang, S. Belladitta, Feige Wang, Bram Venemans, Chiara Mazzucchelli, Frederick B. Davies, Anna–Christina Eilers, Eduardo Bañados, Fabio Vito, Sarah E. I. Bosman, I.T Andika, Emanuele Paolo Farina, Silvia Onorato, Xiaohui Fan, Roberto Decarli
article en
5 citations

Abstract

ABSTRACT We present optical and near-infrared (NIR) spectroscopic observations for a sample of 45 quasars at $6.50 &amp;lt; z \le 7.64$ with absolute magnitudes at 1450 Å in the range $-28.82 \le M_{1450} \le -24.13$ and their composite spectrum. The median redshift and $M_{1450}$ of the quasars in the sample are $z_{\rm {median}}=6.71$ and $M_{1450,\rm {median}} \simeq -26.1$, respectively. The NIR spectra are taken with Echelle spectrographs, complemented with additional data from optical long slit instruments, and then reduced consistently using the open-source Python-based spectroscopic data reduction pipeline PypeIt. The median of the mean signal-to-noise ratios per 110 km s$^{-1}$ pixel in the J, H, and K band [median $\langle \rm {SNR}_{\lambda } \rangle$] is median $\langle \rm {SNR}_{J} \rangle =9.7$, median $\langle \rm {SNR}_{H} \rangle =10.3$, and median $\langle \rm {SNR}_{K} \rangle =11.7$; demonstrating the good data quality. This work presents the largest medium-/moderate-resolution sample of quasars at $z&amp;gt;6.5$ from ground-based instruments. Despite the diversity in instrumental set-ups and spectral quality, the data set is uniformly processed and well-characterized, making it ideally suited for several scientific goals, including the study of the quasar proximity zones and damping wings, the Ly $\alpha$ forest, the intergalactic medium’s metal content, as well as other properties such as the distribution of SMBH masses and Eddington ratios. Our composite spectrum is compared to others at both high and low z from the literature, showing differences in the strengths of many emission lines, probably due to differences in luminosity among the samples, but a consistent continuum slope, which proves that the same spectral features are preserved in quasars at different redshift ranges.

Monthly Notices of the Royal Astronomical SocietyVol. 540(1)
Leiden University (NL), University of Arizona (US), University of California, Santa Barbara (US), Universität Hamburg (DE), Kavli Institute for the Physics and Mathematics of the Universe (JP), Peking University (CN), University of California, Irvine (US), Heidelberg University (DE), University of Michigan (US), Kavli Institute for Particle Astrophysics and Cosmology (US), Gemini North Observatory (US), Max Planck Institute for Astrophysics (DE), Kavli Institute for Theoretical Sciences (CN), Max Planck Institute for Astronomy (DE), Instituto de Física Teórica (ES), Osservatorio di Astrofisica e Scienza dello Spazio, Technical University of Munich (DE), Massachusetts Institute of Technology (US), Heidelberg Institute for Theoretical Studies (DE), The University of Tokyo (JP), Universidad Diego Portales (CL)
National Science Foundation, National Aeronautics and Space Administration, European Commission, Deutsche Forschungsgemeinschaft, Universiteit Leiden, Nuclear Safety and Security Commission, Agencia Nacional de Investigación y Desarrollo, University of California, Santa Barbara
Openalex Percentile: Top 4%
Astronomy and Astrophysical Research
5.96
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