1996A&A...311..690L

Query : 1996A&A...311..690L

1996A&A...311..690L - Astronomy and Astrophysics, volume 311, 690-707 (1996/7-2)

Photodissociation of H2 and CO and time dependent chemistry in inhomogeneous interstellar clouds.

LEE H.-H., HERBST E., PINEAU DES FORETS G., ROUEFF E. and LE BOURLOT J.

Abstract (from CDS):

In this paper we present a model of time-dependent gas-phase chemistry with complex molecules in a spatially inhomogeneous cloud which is exposed on one side to an isotropic radiation field. In addition to the shielding afforded by the dust particles, we consider the shielding due to H2 and CO. The cloud is divided into 43 slabs, which are defined so that the photodissociation rate of CO, determined in a simplified chemical model, is halved as one proceeds to the next slab. The hydrogen number density is a function of cloud depth, ranging from 102cm–3 at the cloud surface to ≃104cm–3 at the cloud center, and varying as (1-cr)–2 where r is the depth into the cloud. The cloud temperature is kept constant at 30K. The chemical/radiative transfer model is solved for each slab, starting from the outermost slab. Models with three different sets of initial conditions regarding hydrogen are presented here. In the first model, we start with atomic hydrogen in all slabs, while in the second, we start with molecular hydrogen. The third model utilizes an H/H2 fraction ranging from large in the outer slabs to small in the inner ones. The variations in fractional abundance and integrated column density for selected atoms (H, C) and molecules as functions of cloud depth at different times are discussed. A comparison between total integrated column densities with observations in TMC1 is given. A plausible dynamic scenario for the material in and in front of TMC1 based on our chemical results is suggested. Alternative total integrated column densities are obtained via a weighting procedure designed for unresolved distant sources in which the outer slabs are weighted more heavily than the inner ones due to their larger radii.

Abstract Copyright: ∼

Journal keyword(s): ISM: clouds - molecules - individual: TMC 1 - molecular processes - radiative transfer

Simbad objects: 1

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Number of rows : 1
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 TMC-1 MoC 04 41 45.9 +25 41 27           ~ 1676 0

Query : 1996A&A...311..690L

Basic data :
TMC-1 -- Molecular Cloud
Origin of the objects types :

(Ref) Object type as listed in the reference "Ref"
(acronym) Object type linked to the acronym according to the original reference
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Other object types: 		PoC (MLB,[MOH94]), MoC (TMC), Cld (HCL)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
ICRS coord. (ep=J2000) : 		04 41 45.9 +25 41 27 [ ] D 1983ApJ...264..517M
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
FK4 coord. (ep=B1950 eq=1950) : 		04 38 42.0 +25 35 45 [ ]
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
Gal coord. (ep=J2000) : 		174.3852 -13.4312 [ ]
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', {sourceSize:12, color:'#30a090'})); aladin.on('objectClicked', function(object) { var objName=object.data.MAIN_ID; aladin.showPopup(object.ra,object.dec,'',''+ objName+''); });" title="Show Simbad objects"> Overlay Simbad points in this preview
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HCL 2 MLB 3-28 TMC-1 [MOH94] 6

References (1676 between 1850 and 2024) (Total 1676)
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