2013A&A...560A..41L


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.04CEST04:34:15

2013A&A...560A..41L - Astronomy and Astrophysics, volume 560A, 41-41 (2013/12-1)

Gas-phase CO depletion and N2H+ abundances in starless cores.

LIPPOK N., LAUNHARDT R., SEMENOV D., STUTZ A.M., BALOG Z., HENNING T., KRAUSE O., LINZ H., NIELBOCK M., PAVLYUCHENKOV Ya.N., SCHMALZL M., SCHMIEDEKE A. and BIEGING J.H.

Abstract (from CDS):

In the dense and cold interiors of starless molecular cloud cores, a number of chemical processes allow for the formation of complex molecules and the deposition of ice layers on dust grains. Dust density and temperature maps of starless cores derived from Herschel continuum observations constrain the physical structure of the cloud cores better than ever before. We use these to model the temporal chemical evolution of starless cores. We derive molecular abundance profiles for a sample of starless cores. We then analyze these using chemical modeling based on dust temperature and hydrogen density maps derived from Herschel continuum observations. We observed the 12CO(2-1), 13CO(2-1), C18O(2-1) and N2H+(1-0) transitions towards seven isolated, nearby low-mass starless molecular cloud cores. Using far infrared (FIR) and submillimeter (submm) dust emission maps from the Herschel key program Earliest Phases of Star formation (EPoS) and by applying a ray-tracing technique, we derived the physical structure (density, dust temperature) of these cores. Based on these results we applied time-dependent chemical modeling of the molecular abundances. We modeled the molecular emission profiles with a line-radiative transfer code and compared them to the observed emission profiles. CO is frozen onto the grains in the center of all cores in our sample. The level of CO depletion increases with hydrogen density and ranges from 46% up to more than 95% in the core centers of the three cores with the highest hydrogen density. The average hydrogen density at which 50% of CO is frozen onto the grains is 1.1±0.4x105cm–3. At about this density, the cores typically have the highest relative abundance of N2H+. The cores with higher central densities show depletion of N2H+ at levels of 13% to 55%. The chemical ages for the individual species are on average (2±1)x105yr for 13CO, (6±3)x104yr for C18O, and (9±2)x104yr for N2H+. Chemical modeling indirectly suggests that the gas and dust temperatures decouple in the envelopes and that the dust grains are not yet significantly coagulated. We observationally confirm chemical models of CO-freezeout and nitrogen chemistry. We find clear correlations between the hydrogen density and CO depletion and the emergence of N2H+. The chemical ages indicate a core lifetime of less than 1Myr.

Abstract Copyright:

Journal keyword(s): astrochemistry - ISM: abundances - submillimeter: ISM - infrared: ISM - stars: formation - stars: low-mass

Simbad objects: 13

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Number of rows : 13

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 [DB2002b] G121.03-9.97 MoC 00 39 03 +52 51.5           ~ 19 0
2 LDN 1389 MoC 04 04 38 +56 56.2           ~ 81 0
3 NAME Tau-Aur Complex SFR 04 30 +25.0           ~ 1216 0
4 LDN 1439 DNe 05 00 09 +52 04.9           ~ 77 0
5 LDN 1512 MoC 05 04 09.7 +32 43 09           ~ 160 0
6 LDN 57 DNe 17 22 38.2 -23 49 34           ~ 283 1
7 NAME the Pipe Nebula DNe 17 30 -25.0           ~ 333 1
8 LDN 507 MoC 18 16 15 -02 32.8           ~ 28 0
9 NAME Aql Rift DNe 18 32 -01.0           ~ 234 1
10 NAME Cas A SNR 23 23 24.000 +58 48 54.00           ~ 2413 1
11 LDN 1262 MoC 23 25 47 +74 17.6           ~ 130 0
12 NAME Cep Flare MoC 23 34 +72.0           ~ 102 0
13 NAME Gould Belt PoG ~ ~           ~ 711 1

    Equat.    Gal    SGal    Ecl

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2020.07.04-04:34:15

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