Spectacular X-ray tails, intracluster star formation and ULXs in A3627

TL;DR

This paper reports the discovery and detailed analysis of spectacular X-ray tails in two galaxies within Abell 3627, revealing insights into intracluster star formation, ULXs, and the effects of ram pressure stripping.

Contribution

It provides the first detailed spatial and spectral analysis of double X-ray tails in ESO137-001 and the discovery of a hot X-ray tail in ESO137-002, linking high-pressure environments to tail brightness and star formation.

Findings

Double X-ray tails in ESO137-001 with little temperature variation.

Identification of intracluster ULXs with luminosities up to 2.5x10^40 erg/s.

Active star formation occurs in stripped cold ISM, contributing to intracluster light.

Abstract

We present the discovery of spectacular double X-ray tails associated with ESO137-001 and a possibly heated X-ray tail associated with ESO137-002, both late-type galaxies in the closest rich cluster Abell 3627. A deep Chandra observation of ESO137-001 allows us for the first time to examine the spatial and spectral properties of such X-ray tails in detail. Besides the known bright tail that extends to ~ 80 kpc from ESO137-001, a fainter and narrower secondary tail with a similar length was surprisingly revealed. There is little temperature variation along both tails. We also identified six X-ray point sources as candidates of intracluster ULXs with L(0.3-10 keV) of up to 2.5x10^40 erg s^-1. Gemini spectra of intracluster HII regions downstream of ESO137-001 are also presented, as well as the velocity map of these HII regions that shows the imprint of ESO137-001's disk rotation. For the first time, we unambiguously know that active star formation can happen in the cold ISM stripped by ICM ram pressure and it may contribute a significant amount of the intracluster light. We also report the discovery of a 40 kpc X-ray tail of another late-type galaxy in A3627, ESO137-002. Its X-ray tail seems hot, ~ 2 keV (compared to ~ 0.8 keV for ESO137-001's tails). We conclude that the high pressure environment around these two galaxies is important for their bright X-ray tails and the intracluster star formation.