XQR-30: The ultimate XSHOOTER quasar sample at the reionization epoch

Valentina D'Odorico*, E. Banados, G. D. Becker, M. Bischetti, S. E. I. Bosman, G. Cupani, R. Davies, E. P. Farina, A. Ferrara, C. Feruglio, C. Mazzucchelli, E. Ryan-Weber, J. -T. Schindler, A. Sodini, B. P. Venemans, F. Walter, H. Chen, S. Lai, Y. Zhu, F. BianS. Campo, S. Carniani, S. Cristiani, F. Davies, R. Decarli, A. Drake, A. -C. Eilers, X. Fan, P. Gaikwad, S. Gallerani, B. Greig, M. G. Haehnelt, J. Hennawi, L. Keating, G. Kulkarni, A. Mesinger, R. A. Meyer, M. Neeleman, M. Onoue, A. Pallottini, Y. Qin, S. Rojas-Ruiz, S. Satyavolu, A. Sebastian, R. Tripodi, F. Wang, M. Wolfson, J. Yang, M. V. Zanchettin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

The final phase of the reionization process can be probed by rest-frame UV absorption spectra of quasars at z>6, shedding light on the properties of the diffuse intergalactic medium within the first Gyr of the Universe. The ESO Large Programme "XQR-30: the ultimate XSHOOTER legacy survey of quasars at z~5.8-6.6" dedicated ~250 hours of observations at the VLT to create a homogeneous and high-quality sample of spectra of 30 luminous quasars at z~6, covering the rest wavelength range from the Lyman limit to beyond the MgII emission. Twelve quasar spectra of similar quality from the XSHOOTER archive were added to form the enlarged XQR-30 sample, corresponding to a total of ~350 hours of on-source exposure time. The median effective resolving power of the 42 spectra is R~11400 and 9800 in the VIS and NIR arm, respectively. The signal-to-noise ratio per 10 km/s pixel ranges from ~11 to 114 at $\lambda \simeq 1285$ \AA rest frame, with a median value of ~29. We describe the observations, data reduction and analysis of the spectra, together with some first results based on the E-XQR-30 sample. New photometry in the H and K bands are provided for the XQR-30 quasars, together with composite spectra whose characteristics reflect the large absolute magnitudes of the sample. The composite and the reduced spectra are released to the community through a public repository, and will enable a range of studies addressing outstanding questions regarding the first Gyr of the Universe.
Original languageEnglish
Pages (from-to)1399-1420
Number of pages22
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Early online date18 May 2023
Publication statusPublished - 1 Jul 2023

Keywords / Materials (for Non-textual outputs)

  • dark ages, reionization, first stars
  • galaxies: high-redshift
  • intergalactic medium
  • quasars: absorption lines
  • quasars: emission lines


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