Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Detections of CO in Late-Type, Low Surface Brightness Spiral Galaxies   Using the IRAM 30-m telescope, we have obtained 12CO J=1-0 and 2-1 spectral
line observations toward the nuclear regions of 15 edge-on, low surface
brightness (LSB) spiral galaxies. Our sample comprises extreme late-type LSB
spirals with disk-dominated morphologies and rotational velocities V_rot<~120
km/s. We report detections of four galaxies in at least one transition
(>5sigma); for the remainder of the sample we provide upper limits on the
nuclear CO content. Adopting a standard Galactic I_CO-to-H_2 conversion factor
implies molecular gas masses of (3.3-9.8)x10**6 M_sun in the nuclear regions
(inner 1.1-1.8 kpc) of the detected galaxies. Combining our new data with
samples of late-type spirals from the literature, we find that the CO-detected
LSB spirals adhere to the same M_H2-FIR correlation as more luminous and higher
surface brightness galaxies. The amount of CO in the central regions of
late-type spirals appears to depend more strongly on mass than on central
optical surface brightness, and CO detectability declines significantly for
moderate-to-low surface brightness spirals with V_rot<~90 km/s; no LSB spirals
have so far been detected in CO below this threshold. Metallicity effects alone
are unlikely to account for this trend, and we speculate that we are seeing the
effects of a decrease in the mean fraction of a galaxy disk able to support
giant molecular cloud formation with decreasing galaxy mass.

18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
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The categories of this paper are: eess
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph