Shaken, Not Stirred: The Disrupted Disk of the Starburst Galaxy NGC 253

TL;DR

This study uses near-infrared imaging to analyze the disrupted disk and star formation history of NGC 253, revealing asymmetries, diffuse structures, and evidence of a recent tidal encounter affecting its evolution.

Contribution

It provides new insights into the recent star formation activity, disk asymmetry, and the impact of tidal interactions on NGC 253's structure and stellar populations.

Findings

Asymmetric distribution of AGB stars in the disk

Detection of extraplanar stellar populations up to 15 kpc

Evidence of a recent tidal encounter within the past 0.2 Gyr

Abstract

Near-infrared images obtained with the CFHT WIRCam are used to investigate the recent history of the nearby Sculptor Group spiral NGC 253. The distribution of stars in the disk is lop-sided, in the sense that the projected density of AGB stars in the north east portion of the disk between 10 and 20 kpc from the galaxy center is ~ 0.5 dex higher than on the opposite side of the galaxy. With the exception of the central 2 kpc, the north east portion of the disk appears to have been the site of the highest levels of star-forming activity in the galaxy during the past ~ 0.1 Gyr. Diffuse stellar structures are found in the periphery of the disk, and the most prominent of these is to the south and east of the galaxy. Bright AGB stars are detected out to 15 kpc above the disk plane, and these are part of a diffusely distributed, flattened extraplanar component. Comparisons between observed and model luminosity functions suggest that the extraplanar regions contain stars that formed throughout much of the age of the Universe. It is suggested that the disk of NGC 253 was disrupted by a tidal encounter with a now defunct companion. The ages of the youngest extraplanar stars suggests that the event that produced the extraplanar population, and presumably induced the starburst, occured within the past ~ 0.2 Gyr.