2009A&A...505.1199P


Query : 2009A&A...505.1199P

2009A&A...505.1199P - Astronomy and Astrophysics, volume 505, 1199-1211 (2009/10-3)

C2H in prestellar cores.

PADOVANI M., WALMSLEY C.M., TAFALLA M., GALLI D. and MUELLER H.S.P.

Abstract (from CDS):

We study the abundance of C2H in prestellar cores both because of its role in the chemistry and because it is a potential probe of the magnetic field. We also consider the non-LTE behaviour of the N=1-0 and N=2-1 transitions of C2H and improve current estimates of the spectroscopic constants of C2H. We used the IRAM 30m radiotelescope to map the N=1-0 and N=2-1 transitions of C2H towards the prestellar cores L1498 and CB246. Towards CB246, we also mapped the 1.3 mm dust emission, the J=1-0 transition of N2H+ and the J=2-1 transition of C18O. We used a Monte Carlo radiative transfer program to analyse the C2H observations of L1498. We derived the distribution of C2H column densities and compared with the H2 column densities inferred from dust emission. We find that while non-LTE intensity ratios of different components of the N=1-0 and N=2-1 lines are present, they are of minor importance and do not impede C2H column density determinations based upon LTE analysis. Moreover, the comparison of our Monte-Carlo calculations with observations suggest that the non-LTE deviations can be qualitatively understood. For extinctions less than 20 visual magnitudes, we derive toward these two cores (assuming LTE) a relative abundance [C2H]/[H2] of (1.0±0.3)x10–8 in L1498 and (0.9±0.3)x10–8 in CB246 in reasonable agreement with our Monte-Carlo estimates. For L1498, our observations in conjunction with the Monte Carlo code imply a C2H depletion hole of radius 9x1016 cm similar to that found for other C-containing species. We briefly discuss the significance of the observed C2H abundance distribution. Finally, we used our observations to provide improved estimates for the rest frequencies of all six components of the C2H (1-0) line and seven components of C2H (2-1). Based on these results, we compute improved spectroscopic constants for C2H. We also give a brief discussion of the prospects for measuring magnetic field strengths using C2H.

Abstract Copyright:

Journal keyword(s): ISM: abundances - ISM: clouds - ISM: molecules - ISM: general - radio lines: ISM - molecular data

Simbad objects: 12

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Number of rows : 12
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 NAME [BM89] L1498 PoC 04 10 51.4 +25 09 58           ~ 187 0
2 LDN 1498 DNe 04 11.0 +24 58           ~ 271 0
3 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 4102 0
4 TMC-1 MoC 04 41 45.9 +25 41 27           ~ 1568 0
5 NAME [BM89] L1517B cor 04 55 18.8 +30 38 04           ~ 139 0
6 LDN 1544 DNe 05 04 16.6 +25 10 48           ~ 805 0
7 NAME [BM89] L1544 cor 05 04 22.5 +25 11 36           ~ 436 1
8 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2209 1
9 LDN 183 MoC 15 54 12.2 -02 49 42           ~ 729 1
10 NAME Cepheus Flare MoC 23 34 +72.0           ~ 124 0
11 LDN 1253 DNe 23 56 32 +58 31.7           ~ 55 0
12 2MASS J23563433+5834043 NIR 23 56 34.338 +58 34 04.34           ~ 1 0

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2023.02.09-10:42:23

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