Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...421..434x&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 421, no. 2, p. 434-452
Astronomy and Astrophysics
Astronomy
21
Carbon Monoxide, Carbon 12, Carbon 13, Galactic Evolution, Galactic Nuclei, Interstellar Gas, Radio Astronomy, Spiral Galaxies, Astronomical Models, Carbon Compounds, Radio Telescopes, Star Formation, Sulfur Compounds
Scientific paper
We present observations of the (12)CO and (13)CO J = 2 goes to 1 and 1 goes to 0, as well as CS J = 2 goes to 1 lines in the nuclear regions of NGC 2146 and IC 342, made with the 14 m Five College Radio Astronomy Observatory (FCRAO) telescope. Through comparisons with radiative transfer calculations, we find that the (12)CO/(13)CO J = 1 goes to 0 line ratio, in conjunction with the (13)CO J = 2 goes to 1/J = 1 goes to 0 line ratio, provides significant constraints on the physical conditions of the bulk of molecular gas. The densities and temperatures in the nuclear regions of the two actively star-forming galaxies are found to be higher than the typical values of the disk giant molecular clouds (GMCs) in the Milky Way but similar to those in the molecular clouds of the Galactic center. The derived physical conditions of the gas depend on the abundance ratio of (12)CO/H2 used in the model calculations. With (12)CO/H2 = 10-4 and (12)CO/(13)CO = 60, the average temperature in the nuclear region of NGC 2146 is estimated to be around 55 K, and the average density is about 2 x 104/cc. The average temperature and density ascertained in the nuclear region of IC 342 are lower than those in NGC 2146, with T approximately 25 K and nH2 approximately 4 x 103/cc. In spite of the difference in the physical conditions of these two galaxies, the values of the N(H2)/ICO conversion factor, which depends on the (square root of n(H2))/TCO ratio, seem to be within a factor of 2 of the Galactic value at the centers of the two galaxies, provided that they have the same CO abundance. CS J = 2 goes to 1 emission is detected toward the centers of NGC 2146 and IC 342, confirming the conclusion reached in previous works that a large amount of dense gas (with n(H2) greater than or approximately equal to 104/cc) exists in the centers of many galaxies.
Schloerb Peter F.
Xie Shuding
Young Judith
No associations
LandOfFree
A (12)CO, (13)CO, and CS study of NGC 2146 and IC 342 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A (12)CO, (13)CO, and CS study of NGC 2146 and IC 342, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A (12)CO, (13)CO, and CS study of NGC 2146 and IC 342 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1013881