The Quasar / Galaxy Pair PKS 1327-206 / ESO 1327-2041: Absorption Associated with a Recent Galaxy Merger

TL;DR

This study combines multi-wavelength observations to analyze the complex morphology and gas dynamics of the galaxy ESO 1327-2041, revealing absorption features linked to recent galaxy merger activity and challenging simplified models of high-redshift absorbers.

Contribution

It provides a detailed multi-wavelength case study of a galaxy merger and its associated absorption features, highlighting the complexity of galaxy-absorber relationships.

Findings

Absorption components match velocities of metal-line features.

Tidal stripping contributes to high-velocity gas.

Galaxy morphology includes an extended spiral arm and possible polar ring.

Abstract

We present HST/WFPC2 broadband and ground-based Halpha images, H I 21-cm emission maps, and low-resolution optical spectra of the nearby galaxy ESO 1327-2041, which is located 38 arcsec (14 kpc in projection) west of the quasar PKS 1327-206. Our HST images reveal that ESO 1327-2041 has a complex optical morphology, including an extended spiral arm that was previously classified as a polar ring. Our optical spectra show Halpha emission from several H II regions in this arm located ~5 arcsec from the quasar position (~2 kpc in projection) and our ground-based Halpha images reveal the presence of several additional H II regions in an inclined disk near the galaxy's center. Absorption associated with ESO 1327-2041 is found in H I 21-cm, optical, and near-UV spectra of PKS 1327-206. We find two absorption components at cz = 5255 and 5510 km/s in the H I 21-cm absorption spectrum, which match the velocities of previously discovered metal-line components. We attribute the 5510 km/s absorber to disk gas in the extended spiral arm and the 5255 km/s absorber to high-velocity gas that has been tidally stripped from the disk of ESO 1327-2041. The complexity of the galaxy/absorber relationships for these very nearby H I 21-cm absorbers suggests that the standard view of high redshift damped Lyman-alpha absorbers is oversimplified in many cases.