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

## TL;DR

This paper reports the first detection of CO absorption at z=0.05 in a merging galaxy system, providing insights into the molecular content and physical conditions of the interstellar medium in the tidal tail.

## Contribution

It presents the discovery of CO(1-0) and CN(1-0) absorption lines in a galaxy merger system, complementing previous emission and absorption observations across multiple wavelengths.

## Key findings

- Detection of CO and CN absorption lines at z=0.05
- Confirmation of CO emission in the merging galaxies
- Insights into the molecular content of the tidal tail

## Abstract

Absorption lines in front of distant quasars are quite rare in the millimeter domain. They can however bring a 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 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), HI-21cm 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 HI 21-cm line observations with the upgraded GMRT array are presented. We discuss the molecular content of the merging galaxies, and the physical conditions in the absorbing interstellar medium of the tidal tail.