Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Imaging the molecular gas in a submm galaxy at z = 4.05: cold mode
  accretion or a major merger?   We present a high resolution (down to 0.18"), multi-transition imaging study
of the molecular gas in the z = 4.05 submillimeter galaxy GN20. GN20 is one of
the most luminous starburst galaxy known at z > 4, and is a member of a rich
proto-cluster of galaxies at z = 4.05 in GOODS-North. We have observed the CO
1-0 and 2-1 emission with the VLA, the CO 6-5 emission with the PdBI
Interferometer, and the 5-4 emission with CARMA. The H_2 mass derived from the
CO 1-0 emission is 1.3 \times 10^{11} (\alpha/0.8) Mo. High resolution imaging
of CO 2-1 shows emission distributed over a large area, appearing as partial
ring, or disk, of ~ 10kpc diameter. The integrated CO excitation is higher than
found in the inner disk of the Milky Way, but lower than that seen in high
redshift quasar host galaxies and low redshift starburst nuclei. The VLA CO 2-1
image at 0.2" resolution shows resolved, clumpy structure, with a few brighter
clumps with intrinsic sizes ~ 2 kpc. The velocity field determined from the CO
6-5 emission is consistent with a rotating disk with a rotation velocity of ~
570 km s^{-1} (using an inclination angle of 45^o), from which we derive a
dynamical mass of 3 \times 10^{11} \msun within about 4 kpc radius. The star
formation distribution, as derived from imaging of the radio synchrotron and
dust continuum, is on a similar scale as the molecular gas distribution. The
molecular gas and star formation are offset by ~ 1" from the HST I-band
emission, implying that the regions of most intense star formation are highly
dust-obscured on a scale of ~ 10 kpc. The large spatial extent and ordered
rotation of this object suggests that this is not a major merger, but rather a
clumpy disk accreting gas rapidly in minor mergers or smoothly from the
proto-intracluster medium. ABSTRACT TRUNCATED

3
The categories of this paper are: physics
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
16
The categories of this paper are: stat
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg