2004A&A...416..603J


C.D.S. - SIMBAD4 rel 1.7 - 2020.01.28CET14:42:18

2004A&A...416..603J - Astronomy and Astrophysics, volume 416, 603-622 (2004/3-3)

Molecular inventories and chemical evolution of low-mass protostellar envelopes.

JORGENSEN J.K., SCHOEIER F.L. and VAN DISHOECK E.F.

Abstract (from CDS):

This paper presents the first substantial study of the chemistry of the envelopes around a sample of 18 low-mass pre- and protostellar objects for which physical properties have previously been derived from radiative transfer modeling of their dust continuum emission. Single-dish line observations of 24 transitions of 9 molecular species (not counting isotopes) including HCO+, N2H+, CS, SO, SO2, HCN, HNC, HC3N and CN are reported. The line intensities are used to constrain the molecular abundances by comparison to Monte Carlo radiative transfer modeling of the line strengths. In general the nitrogen-bearing species together with HCO+ and CO cannot be fitted by a constant fractional abundance when the lowest excitation transitions are included, but require radial dependences of their chemistry since the intensity of the lowest excitation lines are systematically underestimated in such models. A scenario is suggested in which these species are depleted in a specific region of the envelope where the density is high enough that the freeze-out timescale is shorter than the dynamical timescale and the temperature low enough that the molecule is not evaporated from the icy grain mantles. This can be simulated by a ``drop'' abundance profile with standard (undepleted) abundances in the inner- and outermost regions and a drop in abundance in between where the molecule freezes out. An empirical chemical network is constructed on the basis of correlations between the abundances of various species. For example, it is seen that the HCO+ and CO abundances are linearly correlated, both increasing with decreasing envelope mass. This is shown to be the case if the main formation route of HCO+ is through reactions between CO and H3+, and if the CO abundance still is low enough that reactions between H3+ and N2 are the main mechanism responsible for the removal of H3+. Species such as CS, SO and HCN show no trend with envelope mass. In particular no trend is seen between ``evolutionary stage'' of the objects and the abundances of the main sulfur- or nitrogen-containing species. Among the nitrogen-bearing species abundances of CN, HNC and HC3N are found to be closely correlated, which can be understood from considerations of the chemical network. The CS/SO abundance ratio is found to correlate with the abundances of CN and HC3N, which may reflect a dependence on the atomic carbon abundance. An anti-correlation is found between the deuteration of HCO+ and HCN, reflecting different temperature dependences for gas-phase deuteration mechanisms. The abundances are compared to other protostellar environments. In particular it is found that the abundances in the cold outer envelope of the previously studied class 0 protostar IRAS 16293-2422 are in good agreement with the average abundances for the presented sample of class 0 objects.

Abstract Copyright:

Journal keyword(s): stars: formation - ISM: molecules - ISM: abundances - radiative transfer - astrochemistry

Simbad objects: 25

goto Full paper

goto View the reference in ADS

Number of rows : 25

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NAME LDN 1448 IRS 2 Y*O 03 25 22.32 +30 45 13.9           ~ 114 0
2 [SDA2014] West4 Y*O 03 25 38.83 +30 44 06.2           ~ 241 1
3 NAME LDN 1448-mm Y*O 03 25 38.83 +30 44 06.2           ~ 296 0
4 IRAS 03258+3104 Y*O 03 28 55.30 +31 14 27.8           ~ 158 1
5 [JCC87] IRAS 2A Y*O 03 28 55.55 +31 14 36.7           ~ 378 3
6 [JCC87] IRAS 4A Y*O 03 29 10.49 +31 13 30.8           ~ 575 1
7 [JCC87] IRAS 4 FIR 03 29 10.9 +31 13 26           ~ 462 0
8 [JCC87] IRAS 4B Y*O 03 29 12.058 +31 13 02.05           ~ 547 0
9 LDN 1489 DNe 04 04 47.5 +26 19 42           ~ 190 0
10 HBC 393 FU* 04 31 34.077 +18 08 04.90           K3V/M3III 777 2
11 IRAS 04361+2547 Y*O 04 39 13.898 +25 53 20.63           ~ 183 1
12 IRAS 04365+2535 Y*O 04 39 35.194 +25 41 44.73           ~ 228 0
13 LDN 1527 DNe 04 39 53 +25 45.0           ~ 477 0
14 TMC-1 MoC 04 41 45.9 +25 41 27           ~ 1334 0
15 LDN 1544 DNe 05 04 16.6 +25 10 48           ~ 661 0
16 NAME [BM89] L1544 cor 05 04 22.5 +25 11 36           ~ 434 1
17 LDN 183 MoC 15 54 12.2 -02 49 42           ~ 675 1
18 NAME VLA 1623-243 Y*O 16 26 26.42 -24 24 30.0           ~ 368 0
19 [SSG2006] MMS002 smm 16 26 26.50 -24 24 30.9           ~ 241 0
20 IRAS 16293-2422 cor 16 32 22.56 -24 28 31.8           ~ 1011 1
21 LDN 1689B DNe 16 34 42.1 -24 36 11           ~ 131 0
22 LDN 483 DNe 18 17 35 -04 39.8           ~ 199 0
23 LDN 723 DNe 19 18 12 +19 13.6           ~ 153 0
24 LDN 1157 DNe 20 39 06.4 +68 02 13           ~ 469 0
25 LDN 1262 MoC 23 25 47 +74 17.6           ~ 130 0

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2004A&A...416..603J and select 'bookmark this link' or equivalent in the popup menu


2020.01.28-14:42:18

© Université de Strasbourg/CNRS

    • Contact