Discovery of CO absorption at z = 0.05 in G0248+430^⋆

¹ Observatoire de Paris, LERMA, College de France, CNRS, PSL Univ., Sorbonne University, UPMC, Paris, France
e-mail: francoise.combes@obspm.fr
² Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, 411007 Pune, India
³ South African Radio Astronomy Observatory, Black River Park, 2 Fir Street, Observatory, 7925 Cape Town, South Africa
⁴ Rhodes Centre for Radio Astronomy Techniques & Technologies, Dep. of Physics and Electronics, Rhodes University, PO Box 94 6140 Grahamstown, South Africa
⁵ Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
⁶ National Radio Astronomy Observatory, PO Box O 1003 Socorro, NM 87801, USA

Received: 14 January 2019
Accepted: 14 February 2019

Abstract

Absorption lines in front of distant quasars are quite rare in the millimeter domain. They can, however, bring very useful and complementary information to emission lines. We report here the detection with NOEMA of CO(1–0) and CN(1–0) lines in absorption, and the confirmation of CO emission in the quasar/galaxy pair Q0248+430/G0248+430. The system G0248+430 corresponds to two merging galaxies (a Seyfert and a LINER) at z = 0.0519 with a tidal tail just on the line of sight to the background quasar Q0248+430 at z = 1.313. Optical (CaII, NaI), H I 21 cm, and OH-1667 MHz absorption lines associated with the tidal tail of the foreground system have previously been detected toward the quasar, while four CO lines at different rotation J levels have been detected in emission from the foreground galaxies. New H I 21 cm line observations with the upgraded GMRT array are also presented. We discuss the molecular content of the merging galaxies, and the physical conditions in the absorbing interstellar medium of the tidal tail.