The Lop-sided Spiral Galaxy NGC 247: Clues to a Possible Interaction with NGC 253

TL;DR

This study uses multi-wavelength observations to analyze asymmetries in NGC 247, revealing its lop-sided morphology and suggesting past interactions with NGC 253 influenced its structure and star formation history.

Contribution

It provides new evidence of NGC 247's lop-sided nature and links morphological features to possible galaxy interactions, supported by multi-wavelength data and dynamical age estimates.

Findings

Northern arm is over-luminous at all wavelengths.

Presence of large kpc-scale bubbles in the disk.

Morphological similarities with NGC 4027 indicating interaction.

Abstract

Observations that span a broad range of wavelengths are used to examine asymmetries in the disk of the nearby late-type spiral galaxy NGC 247. The northern spiral arm is over-luminous at all wavelengths when compared with other parts of the galaxy at similar galactocentric radii, while the density of very luminous red stars in the void that is immediately south of this arm matches that in other parts of the disk at the same galactocentric radius. Two bubbles with spatial extents of many kpc are identified in the disk, and many of the young stars in the southern disk of NGC 247 are located in the walls of one of these structures. Dynamical age estimates of these bubbles coincide with the last large-scale star formation event in the nucleus, suggesting that there was large-scale star formation throughout the disk of NGC 247 a few hundred Myr in the past. Morphological similarities are seen with the classical lop-sided galaxy NGC 4027, and it is concluded that NGC 247 is a significantly lop-sided spiral galaxy. The void in the northern disk is then the area between the main body of the disk and the northern arm viewed in projection. The implications of a lop-sided morphology for NGC 247 in the context of interactions with its nearby starburst galaxy companion NGC 253 are discussed.