X-ray Tail in NGC 7619

TL;DR

This study uses Chandra and XMM-Newton data to analyze the X-ray tail and surface brightness discontinuity of NGC 7619, revealing insights into its motion, gas composition, and possible origin of its tail.

Contribution

First identification of a sharp X-ray surface brightness discontinuity and detailed analysis of gas properties in NGC 7619's tail using high-resolution X-ray observations.

Findings

Detected a long X-ray tail extending SW from NGC 7619.

Identified a NE surface brightness discontinuity with a Mach number ~1.

Found higher Iron abundance near the galaxy center and in the tail.

Abstract

We present new observational results of NGC 7619, an elliptical galaxy with a prominent X-ray tail and a dominant member of the Pegasus group. With Chandra and XMM-Newton observations, we confirm the presence of a long X-ray tail in the SW direction; moreover, we identify for the first time a sharp discontinuity of the X-ray surface brightness in the opposite (NE) side of the galaxy. The density, temperature and pressure jump at the NE discontinuity suggest a Mach number ~1, corresponding to a galaxy velocity of ~500 km s-1, relative to the surrounding hot gas. Spectral analysis of these data shows that the Iron abundance of the hot gaseous medium is much higher (1-2 solar) near the center of NGC 7619 and in the tail extending from the core than in the surrounding regions (< 1/2 solar), indicating that the gas in the tail is originated from the galaxy. The possible origin of the head-tail structure is either on-going ram-pressure stripping or sloshing. The morphology of the structure is more in line with a ram pressure stripping phenomenon, while the position of NGC 7619 at the center of the Pegasus I group, and its dominance, would prefer sloshing.