Euclid Quick Data Release (Q1) Euclid spectroscopy of quasars. 2. Physical properties from spectral fitting

@misc{collaboration2026euclid,
  title = {{Euclid Quick Data Release (Q1) Euclid spectroscopy of quasars. 2. Physical properties from spectral fitting}},
  author = {Euclid Collaboration and J. Calhau and G. Calderone and A. Feltre and M. Scialpi and V. Allevato and H. Landt and F. Ricci and Y. Fu and L. Spinoglio and F. Shankar and L. Nicastro and A. Viitanen and G. Zamorani and M. Mezcua and F. La Franca and D. Stern and E. Lusso and J. Wolf and A. Paulino-Afonso and S. Andreon and N. Auricchio and C. Baccigalupi and M. Baldi and S. Bardelli and P. Battaglia and A. Biviano and M. Bolzonella and E. Branchini and M. Brescia and S. Camera and V. Capobianco and C. Carbone and J. Carretero and M. Castellano and G. Castignani and S. Cavuoti and K. C. Chambers and A. Cimatti and C. Colodro-Conde and G. Congedo and C. J. Conselice and L. Conversi and Y. Copin and F. Courbin and H. M. Courtois and M. Cropper and H. Degaudenzi and G. De Lucia and H. Dole and F. Dubath and X. Dupac and S. Dusini and A. Ealet and S. Escoffier and M. Farina and S. Ferriol and F. Finelli and S. Fotopoulou and N. Fourmanoit},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.20947},
  eprint = {2609.20947},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.20947},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Euclid Quick Data Release (Q1) Euclid spectroscopy of quasars. 2. Physical properties from spectral fitting
AU  - Euclid Collaboration
AU  - J. Calhau
AU  - G. Calderone
AU  - A. Feltre
AU  - M. Scialpi
AU  - V. Allevato
AU  - H. Landt
AU  - F. Ricci
AU  - Y. Fu
AU  - L. Spinoglio
AU  - F. Shankar
AU  - L. Nicastro
AU  - A. Viitanen
AU  - G. Zamorani
AU  - M. Mezcua
AU  - F. La Franca
AU  - D. Stern
AU  - E. Lusso
AU  - J. Wolf
AU  - A. Paulino-Afonso
AU  - S. Andreon
AU  - N. Auricchio
AU  - C. Baccigalupi
AU  - M. Baldi
AU  - S. Bardelli
AU  - P. Battaglia
AU  - A. Biviano
AU  - M. Bolzonella
AU  - E. Branchini
AU  - M. Brescia
AU  - S. Camera
AU  - V. Capobianco
AU  - C. Carbone
AU  - J. Carretero
AU  - M. Castellano
AU  - G. Castignani
AU  - S. Cavuoti
AU  - K. C. Chambers
AU  - A. Cimatti
AU  - C. Colodro-Conde
AU  - G. Congedo
AU  - C. J. Conselice
AU  - L. Conversi
AU  - Y. Copin
AU  - F. Courbin
AU  - H. M. Courtois
AU  - M. Cropper
AU  - H. Degaudenzi
AU  - G. De Lucia
AU  - H. Dole
AU  - F. Dubath
AU  - X. Dupac
AU  - S. Dusini
AU  - A. Ealet
AU  - S. Escoffier
AU  - M. Farina
AU  - S. Ferriol
AU  - F. Finelli
AU  - S. Fotopoulou
AU  - N. Fourmanoit
PY  - 2026
DA  - 2026/09/17
PB  - arXiv
DO  - 10.48550/arxiv.2609.20947
UR  - https://arxiv.org/abs/2609.20947
AB  - A substantial volume of spectroscopic data has become available with the Euclid Data Release (Q1), which represents a unique opportunity to study quasars (QSOs) in the Euclid Deep Fields, provide spectroscopic measurements, and estimates of their physical properties. We present results from a spectroscopic analysis of QSOs with HE < = 22.5 using Q1. We use external catalogues from surveys such as the Dark Energy Spectroscopic Instrument (DESI), Gaia, Wide-field Infrared Survey Explorer (WISE), and the QUasars as BRIght beacons for Cosmology in the Southern hemisphere (QUBRICS) for the QSO selection and redshift determination, totaling 5489 QSOs. We provide measurements of the line fluxes, full widths at half-maximum, and respective uncertainties for the emission lines of Euclid spectra based on fitting statistica and signal-to-noise ratio (S/N). Of the total 5489 QSOs, 5387 are successfully fitted. We find that 45% of the total number of successfully fitted spectra are free of problematic artefacts allowing for trustworthy measurements. Our final Euclid QSO sample spans a redshift range of 0.01 < = z < = 4.8 and shows a median spectral index of αλ = - 1.17. Finally, we estimate black hole masses with single epoch methods for 1213 sources, using the He I λ10830, Pa β, H α, H β, and Mg II emission lines, obtainning a mean logarithmc mass of log10 (MBH / Msolar) = 8.7 and mean Edigton ratio of λEdd = 0.34. The catalogue with the physical properties of this sample together with the software developed for the analysis is available online for scientific exploitation.
ER  -