Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photodissociation regions and star formation in the Carina Nebula   We have obtained wide-field thermal infrared (IR) images of the Carina
Nebula, using the SPIREX/Abu telescope at the South Pole. Emission from
poly-cyclic aromatic hydrocarbons (PAHs) at 3.29um, a tracer of
photodissociation regions (PDRs), reveals many interesting well defined clumps
and diffuse regions throughout the complex. Near-IR images (1--2um), along with
images from the Midcourse Space Experiment (MSX) satellite (8--21um) were
incorporated to study the interactions between the young stars and the
surrounding molecular cloud in more detail. Two new PAH emission clumps have
been identified in the Keyhole Nebula and were mapped in 12CO(2--1) and (1--0)
using the SEST. Analysis of their physical properties reveals they are dense
molecular clumps, externally heated with PDRs on their surfaces and supported
by external pressure in a similar manner to the other clumps in the region. A
previously identified externally heated globule containing IRAS 10430-5931 in
the southern molecular cloud, shows strong 3.29-, 8- and 21-um emission, the
spectral energy distribution (SED) revealing the location of an ultra-compact
(UC) HII region. The northern part of the nebula is complicated, with PAH
emission inter-mixed with mid-IR dust continuum emission. Several point sources
are located here and through a two-component black-body fit to their SEDs, we
have identified 3 possible UC HII regions as well as a young star surrounded by
a circumstellar disc. This implies that star formation in this region is
on-going and not halted by the intense radiation from the surrounding young
massive stars.

24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
2
The categories of this paper are: math