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Ram-pressure stripped radio tail and two ULXs in the spiral galaxy HCG 97b.

Authors :
Hu, Dan
Zajaček, Michal
Werner, Norbert
Grossová, Romana
Jáchym, Pavel
Roberts, Ian D
Ignesti, Alessandro
Kenney, Jeffrey D P
Plšek, Tomáš
Breuer, Jean-Paul
Shimwell, Timothy
Tasse, Cyril
Zhu, Zhenghao
Wu, Linhui
Source :
Monthly Notices of the Royal Astronomical Society. Jan2024, Vol. 527 Issue 1, p1062-1080. 19p.
Publication Year :
2024

Abstract

We report LOFAR and Very Large Array (VLA) detections of extended radio emission in the spiral galaxy HCG 97b, hosted by an X-ray bright galaxy group. The extended radio emission detected at 144 MHz, 1.4 GHz, and 4.86 GHz is elongated along the optical disc and has a tail that extends 27 kpc in projection towards the centre of the group at GHz frequencies or 60 kpc at 144 MHz. Chandra X-ray data show two off-nuclear ultra-luminous X-ray sources (ULXs), with the farther one being a plausible candidate for an accreting intermediate-mass black hole (IMBH). The asymmetry observed in both CO emission morphology and kinematics indicates that HCG 97b is undergoing ram-pressure stripping, with the leading side at the south-eastern edge of the disc. Moreover, the VLA 4.86 GHz image reveals two bright radio blobs near one ULX, aligning with the disc and tail, respectively. The spectral indices in the disc and tail are comparable and flat (α > −1), suggesting the presence of recent outflows potentially linked to ULX feedback. This hypothesis gains support from estimates showing that the bulk velocity of the relativistic electrons needed for transport from the disc to the tail is approximately |${\sim}1300\, \rm km~s^{-1}$|⁠. This velocity is much higher than those observed in ram-pressure stripped galaxies (⁠|$100{-}600\, \rm km~s^{-1}$|⁠), implying an alternative mechanism aiding the stripping process. Therefore, we conclude that HCG 97b is subject to ram pressure, with the formation of its stripped radio tail likely influenced by the putative IMBH activities. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00358711
Volume :
527
Issue :
1
Database :
Academic Search Index
Journal :
Monthly Notices of the Royal Astronomical Society
Publication Type :
Academic Journal
Accession number :
174419393
Full Text :
https://doi.org/10.1093/mnras/stad3219