J/A+A/608/A133 Gas and dust in star-forming region rho OphA (Larsson+, 2017)
Gas and dust in the star-forming region rho OphA
II. The gas in the PDR and in the dense cores.
Larsson B., Liseau R.
<Astron. Astrophys. 608, A133 (2017)>
=2017A&A...608A.133L 2017A&A...608A.133L (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Interstellar medium ; Nebulae ; YSOs ;
Abundances ; Radio lines ; Spectroscopy ; Models
Keywords: ISM: individual objects: rho Oph A - ISM: molecules -
ISM: abundances - photon-dominated region (PDR) -
stars: formation - ISM: general
Abstract:
We investigate to what degree local physical and chemical conditions
are related to the evolutionary status of various objects in
star-forming media. rho Oph A displays the entire sequence of low-mass
star formation in a small volume of space. Using spectrophotometric
line maps of H2, H2O, NH3, N2H+, O2, OI, CO, and CS, we
examine the distribution of the atomic and molecular gas in this dense
molecular core. The physical parameters of these species are derived,
as are their relative abundances in rho Oph A. Using radiative
transfer models, we examine the infall status of the cold dense cores
from their resolved line profiles of the ground state lines of H2O
and NH3, where for the latter no contamination from the VLA 1623
outflow is observed and line overlap of the hyperfine components is
explicitly taken into account. The stratified structure of this photon
dominated region (PDR), seen edge-on, is clearly displayed. Polycyclic
aromatic hydrocarbons (PAHs) and OI are seen throughout the region
around the exciting star S1. At the interface to the molecular core
0.05pc away, atomic hydrogen is rapidly converted into H2, whereas
OI protrudes further into the molecular core. This provides oxygen
atoms for the gas-phase formation of O2 in the core SM1, where
X(O2)∼5x10-8.
There, the ratio of the O2 to H2O abundance [X(H2O)∼5x10-9] is
significantly higher than unity. Away from the core, O2 experiences
a dramatic decrease due to increasing H2O formation. Outside the
molecular core, on the far side as seen from S1, the intense radiation
from the 0.5pc distant early B-type star HD147889 destroys the
molecules. Towards the dark core SM1, the observed abundance ratio
X(O2)/X(H2O)>1, which suggests that this object is extremely
young, which would explain why O2 is such an elusive molecule
outside the solar system.
Description:
Atomic and molecular line data from different telescope towards the
star-forming region rho OphA is presented.
From the Infrared Space Observatory (ISO) archive, H2 lines have
been extracted from three frames of spectrophotometric data using the
ISOCAM-CVF (Circular Variable Filter, Cesarsky et al.,
1996A&A...315L..32C 1996A&A...315L..32C).
The sub-millimetre molecular data have been obtained with the
Heterodyne Instrument for the Far Infrared (HIFI, de Graauw et al.,
2010A&A...518L...6D 2010A&A...518L...6D) on board the ESA spacecraft Herschel (Pilbratt et
al., 2010A&A...518L...1P 2010A&A...518L...1P).
Mapping in H2O of the rho Oph cloud was done with the Odin satellite
(Nordh et al., 2003A&A...402L..21N 2003A&A...402L..21N).
The Photodetector Array Camera and Spectrometer (PACS, Poglitsch et
al., 2010A&A...518L...2P 2010A&A...518L...2P) was used to map the fine structure line of
oxygen.
Low level transitions of CS was observed with the Swedish ESO
Submillimetre Telescope (SEST) on La Silla.
Objects:
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RA (2000) DE Designation(s)
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16 26 24.6 -24 23 54 rho Oph A (in L1688) = HD 147933
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 172 25 List of FITS files
fits/* . 25 Individual fits files
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See also:
J/ApJ/613/393 : X-ray and radio sources in ρ Oph Core A (Gagne+, 2004)
J/A+A/510/A98 : 12C18O(3-2) map of rho Oph A (Liseau+, 2010)
J/A+A/578/A131 : Gas & dust in the star-forming region rho OphA (Liseau+, 2015)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 31 I4 --- Nz ? Number of slices
33- 43 E11.6 Hz bFreq ? Lower value of frequency interval
45- 55 E11.6 Hz BFreq ? Upper value of frequency interval
57- 67 E11.6 Hz dFreq ? Frequency resolution
69- 72 I4 Kibyte size Size of FITS file
74- 96 A23 --- FileName Name of FITS file, in subdirectory fits
98-103 A6 --- Fig Figure number in the paper
105-112 A8 --- Mol Species
114-140 A27 --- Trans Transition
142-172 A31 --- Title Title of the FITS file
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Acknowledgements:
Bengt Larsson, bem(at)astro.su.se
References:
Liseau et al., Paper I 2015A&A...578A.131L 2015A&A...578A.131L, Cat. J/A+A/578/A131
(End) Patricia Vannier [CDS] 07-Sep-2017