Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Global X-ray emission and central properties of early type galaxies   Hubble Space Telescope observations revealed that the central surface
brightness profiles of early type galaxies can be divided into two types:
"core" profiles and featureless power law profiles. On the basis of this and
previous results, early type galaxies have been grouped into two families:
coreless galaxies, which are also rapidly rotating, nearly isotropic spheroids,
and with disky isophotes, and core galaxies, which are slowly rotating and
boxy-distorted. Here I investigate the relationship between global X-ray
emission and shape of the inner surface brightness profile, for a sample of 59
early type galaxies. I find a clear dicothomy also in the X-ray properties, in
the sense that core galaxies span the whole observed range of Lx values, while
power law galaxies are confined below log Lx (erg/s)=41. Moreover, the relation
between Lx and the shape of the central profile is the strongest among the
relations of Lx with the basic properties characterizing the two families of
early type galaxies. So, a global property such as Lx, that measures the hot
gas content on a galactic scale, turns out to be surprisingly well linked to a
nuclear property. Various possible reasons are explored for the origin of the
different Lx behavior of core and power law galaxies. While a few explanations
can be imagined for the large spread in the X-ray luminosities of core
galaxies, an open problem is why power law ones never become very X-ray bright.
It is likely that the presence of a central massive black hole, and possibly
also the environment, play an important role in determining Lx.

36
The categories of this paper are: cmp-lg
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The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex