Letter to the Editor

The rich galactic environment of a H₂-absorption-selected quasar

Lyα mapping down to the inner kiloparsecs via perfect natural coronagraphy and integral field spectroscopy^⋆

¹ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
² Institut d’Astrophysique de Paris, CNRS-SU, UMR 7095, 98bis bd Arago, 75014 Paris, France
³ French-Chilean Laboratory for Astronomy, IRL 3386, CNRS and U. de Chile, Casilla 36-D, Santiago, Chile
⁴ National Research Council Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V8Z 6M7, Canada
⁵ Ioffe Institute, Polyteknicheskaya 26, 194021 Saint-Petersburg, Russia
⁶ European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla, 19001 Santiago, Chile

Received: 24 June 2024
Accepted: 23 July 2024

Abstract

We present the first Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) observations of a quasar featuring a proximate molecular absorption system, SDSS J125917.31+030922.5. The proximate damped Lyα absorption acts as a natural coronagraph, removing the quasar emission over ∼40 Å in wavelength, and allows us to detect extended Lyα emission without the necessity of subtracting the quasar emission. This natural coronagraph permits the investigation of the quasar environment down to its inner regions (r < 20 kpc), where galaxy interactions or feedback processes should have the most noticeable effects. Our observations reveal a dense environment, with a highly asymmetric Lyα emission within 2″ (∼15 kpc), possibly shaped by a companion galaxy, and a southern extension of the nebulae to about 50 kpc, with rotation-like kinematic signature. The width of the Lyα emission is broadest closer to the quasar, indicating perturbed kinematics as expected if interactions and significant gas flows are present. The foreground absorbing system itself is redshifted by ≈400 km/s relative to the background quasar, and therefore is likely arising from gas moving toward the quasar. Finally two additional Lyα emitters are detected with > 10σ significance at 96 and 223 kpc from the quasar, making this field overdense relative to other similar observations of quasars at z ∼ 3. Our results support the hypothesis that quasars with proximate neutral and molecular absorption trace rich environments where galaxy interactions are at play and motivates further studies of H₂-selected quasars to shed light on feeding and feedback processes.