Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Secular Evolution in Disk Galaxies: Pseudobulge Growth and the Formation
  of Spheroidal Galaxies   Updating Kormendy & Kennicutt (2004, ARAA, 42, 603), we review internal
secular evolution of galaxy disks. One consequence is the growth of
pseudobulges that often are mistaken for true (merger-built) bulges. Many
pseudobulges are recognizable as cold, rapidly rotating, disky structures.
Bulges have Sersic function brightness profiles with index n > 2; most
pseudobulges have n <= 2. Recognition of pseudobulges makes the biggest problem
with cold dark matter galaxy formation more acute: How can hierarchical
clustering make so many pure disk galaxies with no evidence for merger-built
bulges? E. g., the giant Scd galaxies M101 and NGC 6946 have rotation
velocities of V ~ 200 km/s but nuclear star clusters with velocity dispersions
of 25 to 40 km/s. Within 8 Mpc of us, 11 of 19 galaxies with V > 150 km/s show
no evidence for a classical bulge, while only 7 are ellipticals or have
classical bulges. It is hard to understand how bulgeless galaxies could form as
the quiescent tail of a distribution of merger histories. Our second theme is
environmental secular evolution. We confirm that spheroidal galaxies have
fundamental plane (FP) correlations that are almost perpendicular to those for
bulges and ellipticals. Spheroidals are not dwarf ellipticals. Rather, their
structural parameters are similar to those of late-type galaxies. We suggest
that spheroidals are defunct late-type galaxies transformed by internal
processes such as supernova-driven gas ejection and environmental processes
such as secular harassment and ram-pressure stripping. Minus spheroidals, the
FP of ellipticals and bulges has small scatter. With respect to these,
pseudobulges are larger and less dense.

12
The categories of this paper are: nucl-th
3
The categories of this paper are: physics
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
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The categories of this paper are: comp-gas
36
The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci