Galaxy group-associated distances to very high energy gamma-ray emitting BL Lacs KUV 00311−1938 and S2 0109+22

: Koljonen, Karri I. I.; Lindfors, Elina; Nilsson, Kari; Heinämäki, Pekka; Kotilainen, Jari

Publisher: Oxford University Press

: 2024

: Monthly Notices of the Royal Astronomical Society

: 531

: 4

: 5084

: 5096

: 0035-8711

: 1365-2966

DOI: https://doi.org/10.1093/mnras/stae1512(external)

: https://doi.org/10.1093/mnras/stae1512(external)

: https://research.utu.fi/converis/portal/detail/Publication/457147080(external)

: https://arxiv.org/abs/2406.13786(external)

: The VLT/FORS2 data analysed here are available at the European Southern Observatory Science Archive Facility (http://archive.eso.org). The Gemini data is available at the Gemini Observatory archive (https://archive.gemini.edu). The SDSS data is available at the SDSS website: https://www.sdss4.org. The simulation data produced as part of this work are available from the authors on request.

Blazars constitute the most numerous source class in the known extragalactic population of very high energy (VHE) gamma-ray sources. However, determining their redshifts is often challenging due to weak or non-existent emission lines in their spectra. This study focuses on two BL Lacs, KUV 00311−1938 and S2 0109+22, where previous attempts at redshift determination have faced difficulties. By combining spectroscopic observations with photometric redshift estimates, we tentatively assign a redshift of z = 0.634 to KUV 00311−1938 and a likely redshift of z = 0.49 to S2 0109+22. Establishing redshift estimates for high-redshift blazars is crucial for understanding extragalactic VHE gamma-ray sources and their interactions with the surrounding Universe.

Key words: BL Lacertae objects: general – galaxies: distances and redshifts – galaxies: groups: general.

stae1512.pdf

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Research funded by European Research Council (101002352) | Academy of Finland (306531,317636,320045,346071)