TY - JOUR
T1 - The stripping of a galaxy group diving into the massive cluster A2142
AU - Eckert, D.
AU - Molendi, S.
AU - Owers, M.
AU - Gaspari, M.
AU - Venturi, T.
AU - Rudnick, L.
AU - Ettori, S.
AU - Paltani, S.
AU - Gastaldello, F.
AU - Rossetti, M.
N1 - Publisher Copyright:
© ESO, 2014.
PY - 2014/10/1
Y1 - 2014/10/1
N2 - Structure formation in the current Universe operates through the accretion of group-scale systems onto massive clusters. The detection and study of such accreting systems is crucial to understand the build-up of the most massive virialized structures we see today. We report the discovery with XMM-Newton of an irregular X-ray substructure in the outskirts of the massive galaxy cluster Abell 2142. The tip of the X-ray emission coincides with a concentration of galaxies. The bulk of the X-ray emission of this substructure appears to be lagging behind the galaxies and extends over a projected scale of at least 800 kpc. The temperature of the gas in this region is 1.4 keV, which is a factor of ~4 lower than the surrounding medium and is typical of the virialized plasma of a galaxy group with a mass of a few 1013 M⊙. For this reason, we interpret this structure as a galaxy group in the process of being accreted onto the main dark-matter halo. The X-ray structure trailing behind the group is due to gas stripped from its original dark-matter halo as it moves through the intracluster medium (ICM). This is the longest X-ray trail reported to date. For an infall velocity of ~1200 km s-1 we estimate that the stripped gas has been surviving in the presence of the hot ICM for at least 600 Myr, which exceeds the Spitzer conduction timescale in the medium by a factor of ≳ 400. Such a strong suppression of conductivity is likely related to a tangled magnetic field with small coherence length and to plasma microinstabilities. The long survival time of the low-entropy intragroup medium suggests that the infalling material can eventually settle within the core of the main cluster.
AB - Structure formation in the current Universe operates through the accretion of group-scale systems onto massive clusters. The detection and study of such accreting systems is crucial to understand the build-up of the most massive virialized structures we see today. We report the discovery with XMM-Newton of an irregular X-ray substructure in the outskirts of the massive galaxy cluster Abell 2142. The tip of the X-ray emission coincides with a concentration of galaxies. The bulk of the X-ray emission of this substructure appears to be lagging behind the galaxies and extends over a projected scale of at least 800 kpc. The temperature of the gas in this region is 1.4 keV, which is a factor of ~4 lower than the surrounding medium and is typical of the virialized plasma of a galaxy group with a mass of a few 1013 M⊙. For this reason, we interpret this structure as a galaxy group in the process of being accreted onto the main dark-matter halo. The X-ray structure trailing behind the group is due to gas stripped from its original dark-matter halo as it moves through the intracluster medium (ICM). This is the longest X-ray trail reported to date. For an infall velocity of ~1200 km s-1 we estimate that the stripped gas has been surviving in the presence of the hot ICM for at least 600 Myr, which exceeds the Spitzer conduction timescale in the medium by a factor of ≳ 400. Such a strong suppression of conductivity is likely related to a tangled magnetic field with small coherence length and to plasma microinstabilities. The long survival time of the low-entropy intragroup medium suggests that the infalling material can eventually settle within the core of the main cluster.
KW - Galaxies: clusters: general
KW - Galaxies: clusters: intracluster medium
KW - Galaxies: groups: general
KW - Large-scale structure of Universe
KW - X-rays: galaxies: clusters
UR - http://www.scopus.com/inward/record.url?scp=84908502174&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84908502174&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/201424259
DO - 10.1051/0004-6361/201424259
M3 - Article
AN - SCOPUS:84908502174
SN - 0004-6361
VL - 570
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A119
ER -