A 100 kpc ram pressure tail trailing the group galaxy NGC 2276

¹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
² Department of Physics & Astronomy, University of Waterloo, Waterloo, ON N2L 3G1, Canada
³ Waterloo Centre for Astrophysics, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada
⁴ INAF-Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy
⁵ Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
⁶ INAF–Padova Astronomical Observatory, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁷ Department of Physics, Faculty of Science, University of Zagreb, Bijenička Cesta 32, 10000 Zagreb, Croatia

Received: 9 May 2024
Accepted: 13 June 2024

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⁻¹ for the stripped plasma across the plane of the sky, and a three-dimensional orbital velocity of 970 km s⁻¹ for NGC 2276. The orbital speed that we derive is in excellent agreement with the previous estimates from an X-ray shock analysis, despite the completely independent methodology.