Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: NGC922 - A new drop-through ring galaxy   We have found the peculiar galaxy NGC922 to be a new drop-through ring galaxy
using multi-wavelength (UV-radio) imaging and spectroscopic observations. Its
`C'-shaped morphology and tidal plume indicate a recent strong interaction with
its companion which was identified with these observations. Using numerical
simulations we demonstrate that the main properties of the system can be
generated by a high-speed off-axis drop-through collision of a small galaxy
with a larger disk system, thus making NGC922 one of the nearest known
collisional ring galaxies. While these systems are rare in the local Universe,
recent deep HST images suggest they were more common in the early Universe.

15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th