The Competing Influence of Ram Pressure and Tidal Interaction in NGC 2276

TL;DR

This study investigates the influence of ram pressure and tidal interactions on galaxy NGC 2276, using multiwavelength data to analyze stellar populations and morphology, concluding ram pressure likely dominates its peculiar shape.

Contribution

First detailed multiwavelength analysis of NGC 2276 assessing the roles of ram pressure and tidal forces in its morphology and stellar distribution.

Findings

Younger stars are concentrated on the leading side, indicating gas compression from ram pressure.

Asymmetrical stellar distribution suggests ram pressure influences galaxy morphology.

Pitch angles of spiral features increase with radius, supporting ram pressure effects.

Abstract

The evolution of galaxies in groups is profoundly influenced by a variety of physical processes, with ram pressure and tidal interactions playing pivotal roles in shaping their structural and evolutionary pathways. The relative influence of these two processes is still debated in groups compared to clusters, as ram pressure is less understood there. We study NGC 2276, a nearby galaxy (z$\sim$0.0079) where the dominant process is still an open question. We examine the distribution of stellar populations in NGC 2276 using multiwavelength data to assess potential evidence of tidal interactions and ram-pressure stripping. We present the first HST WFC3/UVIS images of NGC 2276, and use them to investigate the distribution of stellar populations across the disk of NGC 2276, where we assume that the bluer broadband filters mainly trace younger stellar populations, while the redder filters trace mainly older stellar populations. Furthermore, by comparing HST images with maps of H$\alpha$ emission from Calar Alto's PMAS/PPAK integral field unit (IFU) and near-IR maps from Spitzer's IRAC, we identify arm-like overdensity features that trace the spiral structure of this galaxy and tracked the variation of their pitch angle with radius. Our results indicate that the distribution of the stellar populations is asymmetrical. The youngest stellar populations (up to $\sim$100 Myr) show higher concentration on the leading side of the galaxy and are more diffuse on the trailing side, consistent with gas compression due to ram-pressure. This asymmetry is visible in the red filters as well. We also show that the average pitch angles of the overdensity features increase with galactocentric distance. Our findings are consistent with the fact that ram pressure is the leading mechanism for the peculiar morphology of NGC 2276, but do not exclude the possibility that tidal interactions could have played a role.