Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence for ram pressure stripping in a cluster of galaxies at z=0.7   MUSE observations of the cluster of galaxies CGr32 ($M_{200}$ $\simeq$ 2
$\times$ 10$^{14}$ M$_{\odot}$) at $z$ = 0.73 reveal the presence of two
massive star forming galaxies with extended tails of diffuse gas detected in
the [OII]$\lambda\lambda$3727-3729 A emission-line doublet. The tails, which
have a cometary shape with a typical surface brightness of a few 10$^{-18}$ erg
s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$, extend up to $\simeq$ 100 kpc (projected
distance) from the galaxy discs and are not associated to any stellar
component. All this observational evidence suggests that the gas has been
removed during a ram-pressure stripping event. This observation is thus the
first evidence that dynamical interactions with the intracluster medium were
active when the Universe had only half of its present age. The density of the
gas derived using the observed [OII]$\lambda$3729/[OII]$\lambda$3726 line ratio
implies a very short recombination time, suggesting that a source of ionisation
is necessary to keep the gas ionised within the tail.

2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph