Issue |
A&A
Volume 684, April 2024
|
|
---|---|---|
Article Number | A147 | |
Number of page(s) | 15 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/202347423 | |
Published online | 16 April 2024 |
Polarimetry of the Lyα envelope of the radio-quiet quasar SDSS J124020.91+145535.6⋆
1
Institut de Physique, Laboratoire d’astrophysique, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, 1290 Versoix, Switzerland
e-mail: pierre.north@epfl.ch
2
Stockholm University, Albanova University Center, Department of Astronomy, 106 91 Stockholm, Sweden
3
Kavli Institute for Particle Astrophysics and Cosmology and Department of Physics, Stanford University, Stanford, CA 94305, USA
4
Observatoire de Sauverny, Université de Genève, Chemin Pegasi 51, 1290 Sauverny, Switzerland
5
Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700AV Groningen, The Netherlands
6
Univ. Lyon, Univ. Lyon 1, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, 69230 Saint-Genis-Laval, France
7
Department of Physics, Faculty of Natural Sciences, University of Haifa, Haifa 31905, Israel
Received:
11
July
2023
Accepted:
5
January
2024
The radio quiet quasar SDSS J1240+1455 lies at a redshift of z = 3.11, is surrounded by a Lyα blob (LAB), and is absorbed by a proximate damped Lyα system. In order to better define the morphology of the blob and determine its emission mechanism, we gathered deep narrow-band images isolating the Lyα line of this object in linearly polarized light. We provide a deep intensity image of the blob, showing a filamentary structure extending up to 16″ (or 122 physical kpc) in diameter. No significant polarization signal could be extracted from the data, but 95% probability upper limits were defined through simulations. They vary between ∼3% in the central 0.75″ disk (after subtraction of the unpolarized quasar continuum) and ∼10% in the 3.8 − 5.5″ annulus. The low polarization suggests that the Lyα photons are emitted mostly in situ, by recombination and de-excitation in a gas largely ionized by the quasar ultraviolet light, rather than by a central source and scattered subsequently by neutral hydrogen gas. This blob shows no detectable polarization signal, contrary to LAB1, a brighter and more extended blob that is not related to the nearby active galactic nucleus (AGN) in any obvious way, and where a significant polarization signal of about 18% was detected.
Key words: quasars: emission lines / quasars: general / quasars: individual: SDSS J124020.91 + 145535.6
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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