Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: How to form bulges/ellipticals in dark halos as fast as central black
  holes?   Gravity is nearly a universal constant in the cusp of an NFW galaxy halo.
Inside this external field an isothermal gas sphere will collapse and trigger a
starburst if above a critical central pressure. Thus formed spheroidal stellar
systems have Sersic-profile and satisfy the Faber-Jackson relation. The process
is consistent with observed starbursts. We also recover the M_BH vs. velocity
dispersion relation, if the gas collapse is regulated or resisted by the
feedback from radiation from the central BH.

20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph