2012A&A...537A...7R


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.06CET00:49:58

2012A&A...537A...7R - Astronomy and Astrophysics, volume 537A, 7-7 (2012/1-1)

Observing a column-dependent ζ in dense interstellar sources: the case of the Horsehead Nebula.

RIMMER P.B., HERBST E., MORATA O. and ROUEFF E.

Abstract (from CDS):

Observations of small carbon-bearing molecules such as CCH, C4H, c-C3H2, and HCO in the Horsehead nebula have shown these species to have higher abundances towards the edge of the source than towards the center. Given the determination of a wide range of values for ζ (s–1), the total ionization rate of hydrogen atoms, and the proposal of a column-dependent ζ(NH), where NH is the total column of hydrogen nuclei, we desire to determine if the effects of ζ(NH) in a single object with spatial variation can be observable. We chose the Horsehead nebula because of its geometry and high density. We model the Horsehead nebula as a near edge-on photon dominated region (PDR), using several choices for ζ, both constant and as a function of column. The column-dependent ζ functions are determined by a Monte Carlo model of cosmic ray penetration, using a steep power-law spectrum and accounting for ionization and magnetic field effects. We consider a case with low-metal elemental abundances as well as a sulfur-rich case. We show that use of a column-dependent ζ(NH) of 5x10–15s–1 at the surface and 7.5x10–16s–1 at AV=10 on balance improves agreement between measured and theoretical molecular abundances, compared with constant values of ζ.

Abstract Copyright:

Journal keyword(s): astrochemistry - molecular processes - ISM: abundances - ISM: molecules - ISM: individual objects: Horsehead nebula

Simbad objects: 8

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Number of rows : 8

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 IC 63 HII 00 59 01.37 +60 53 17.8   13.33       ~ 86 1
2 TMC-1 MoC 04 41 45.9 +25 41 27           ~ 1399 0
3 NAME Orion Bright Bar reg 05 35 22.30 -05 24 33.0           ~ 743 0
4 NAME sigma Orionis Cluster MGr 05 38 42 -02 36.0           ~ 498 0
5 NAME Horsehead Nebula DNe 05 40 59.0 -02 27 30           ~ 457 0
6 IC 434 HII 05 41 -02.5           ~ 79 1
7 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3138 1
8 NAME Sgr B2 MoC 17 47 20.4 -28 23 07           ~ 1981 1

    Equat.    Gal    SGal    Ecl

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