A 100 kpc Ram Pressure Tail Trailing the Group Galaxy NGC 2276

TL;DR

This paper reports the discovery of a 100 kpc radio tail behind NGC 2276, providing new insights into ram-pressure stripping in a low-mass galaxy group through multi-frequency radio observations and spectral ageing analysis.

Contribution

It presents the first detection of a large-scale radio tail in NGC 2276 and estimates the galaxy's orbital velocity using spectral ageing, confirming previous dynamical estimates.

Findings

The radio tail extends 100 kpc, ten times larger than previous observations.

Spectral ageing models yield a plasma velocity of 870 km/s.

Derived orbital velocity of NGC 2276 is 970 km/s, matching prior estimates.

Abstract

We present the discovery of a 100 kpc low-frequency radio tail behind the nearby group galaxy, NGC 2276. The extent of this tail is a factor of ten larger than previously reported from higher-frequency radio and X-ray imaging. The radio morphology of the galaxy disc and tail suggest that the tail was produced via ram-pressure stripping, cementing NGC 2276 as the clearest known example of ram-pressure stripping in a low-mass group. With multi-frequency imaging, we extract radio continuum spectra between ~50 MHz and 1.2 GHz as a function of projected distance along the tail. All of the spectra are well fit by a simple model of spectral ageing due to synchrotron and inverse-Compton losses. From these fits we estimate a velocity of 870 km/s for the stripped plasma across the plane of the sky, and a three-dimensional orbital velocity of 970 km/s for NGC 2276. The orbital speed that we derive is in excellent agreement with the previous estimate from Rasmussen et al., despite it being derived with a completely independent methodology.