2008ApJ...679..481P


C.D.S. - SIMBAD4 rel 1.7 - 2021.04.15CEST08:12:04

2008ApJ...679..481P - Astrophys. J., 679, 481-496 (2008/May-3)

CO isotopologues in the Perseus molecular cloud complex: the X-factor and regional variations.

PINEDA J.E., CASELLI P. and GOODMAN A.A.

Abstract (from CDS):

We use data gathered by the COMPLETE survey of star-forming regions to find new calibrations of the ``X-factor'' and 13CO abundance within the Perseus molecular cloud. We divide Perseus into six subregions, using groupings in a dust temperature vs. LSR velocity plot. The standard X-factor, X≡N(H2)/W(12CO), is derived both for the whole Perseus complex and for each of the six subregions with values consistent with previous estimates. However, the X-factor is heavily affected by the saturation of the emission above AV∼4 mag, and variations are also found between regions. Linear fits to relate W(12CO) and AV using only points below 4 mag of extinction yield a better estimate of the AV than the X-factor. Linear relations of W(13CO), N(13CO), and W(C18O) with AV are derived. The extinction thresholds above which 13CO(1-0) and C18O(1-0) are detected are about 1 mag larger than previous estimates, so that a more efficient shielding is needed for the formation of CO than previously thought. The 12CO and 13CO lines saturate above 4 and 5 mag, respectively, whereas C18O(1-0) never saturates in the whole AV range probed by our study (up to 10 mag). Approximately 60% of the positions with 12CO(1-0) emission have subthermally excited lines, and almost all positions have excitation temperatures below the dust temperature. PDR models, using the Meudon code, can explain the 12CO(1-0) and 13CO(1-0) emission with densities ranging between 103 and 104/cm3. In general, local variations in the volume density and nonthermal motions (linked to different star formation activity) can explain the observations. Higher densities are needed to reproduce CO data toward active star-forming sites, such as NGC 1333, where the larger internal motions driven by the young protostars allow more photons from the embedded high-density cores to escape the cloud. In the most quiescent region, B5, the 12CO and 13CO emission appears to arise from an almost uniform thin layer of molecular material at densities around 104/cm3, and in this region the integrated intensities of the two CO isotopologues are the lowest in the whole complex.

Abstract Copyright:

Journal keyword(s): ISM: Dust, Extinction - ISM: Abundances - ISM: Individual: Name: Perseus - ISM: Molecules

Simbad objects: 15

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Number of rows : 15

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 LDN 1448 DNe 03 22.5 +30 35           ~ 479 0
2 LDN 1455 DNe 03 28 00.6480 +30 07 58.800           ~ 172 1
3 NGC 1333 OpC 03 29 11 +31 18.6           ~ 1258 1
4 Barnard 1 MoC 03 33 16.3 +31 07 51           ~ 276 0
5 NAME Perseus Cloud SFR 03 35.0 +31 13           ~ 1131 0
6 IC 348 OpC 03 44 34 +32 09.8           ~ 1252 1
7 NAME [BM89] B5 DNe 03 47 38.3 +32 52 43           ~ 221 0
8 LDN 1471 DNe 03 48.0 +32 54           ~ 289 0
9 NAME [BM89] L1495 PoC 04 14 08.2 +28 09 31           ~ 170 0
10 LDN 1495 DNe 04 18.1 +27 37           ~ 303 1
11 LDN 1517 DNe 04 55 45 +30 33.0           ~ 103 0
12 NAME UMa Region reg 11 00 +50.0           ~ 318 0
13 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3156 1
14 NAME the Pipe Nebula DNe 17 30 -25.0           ~ 351 1
15 IC 5146 OpC 21 53 24 +47 16.0           ~ 400 2

    Equat.    Gal    SGal    Ecl

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