J/A+A/488/579 Millimetric maps of IRAS 18151-1208 (Marseille+, 2008)
Evolution of massive protostars: the IRAS 18151-1208 region.
Marseille M., Bontemps S., Herpin F., van der Tak F.F.S., Purcell C.R.
<Astron. Astrophys. 488, 579 (2008)>
=2008A&A...488..579M 2008A&A...488..579M
ADC_Keywords: Infrared sources ; Millimetric/submm sources
Keywords: ISM: individual objects: IRAS 18151-1208 - ISM: abundances -
stars: formation - line: profiles
Abstract:
The study of physical and chemical properties of massive protostars is
critical to better understand the evolutionary sequence which leads to
the formation of high-mass stars. IRAS 18151-1208 is a nearby massive
region (d=3kpc, L∼2x104L☉) which splits into three cores :
MM1, MM2 and MM3 (separated by 1arcmin-2arcmin). We aim at (1)
studying the physical and chemical properties of the individual MM1,
MM2 and MM3 cores; (2) deriving their evolutionary stages; (3) using
these results to improve our view of the evolutionary sequence of
massive cores. The region was observed in the CS, C34S, H2CO,
HCO+ H13CO+, and N2H+ lines at mm wavelengths with the IRAM
30m and Mopra telescopes. We use 1D and 2D modeling of the dust
continuum to derive the density and temperature distributions, which
are then used in the RATRAN code to model the lines and constrain the
abundances of the observed species. All the lines were detected in MM1
and MM2. MM3 shows weaker emission, or even is undetected in HCO+
and all isotopic species. MM2 is driving a newly discovered CO outflow
and hosts a mid-IR-quiet massive protostar. The abundance of CS is
significantly larger in MM1 than in MM2, but smaller than in a
reference massive protostar such as AFGL 2591. In contrast the
N2H+ abundance decreases from MM2 to MM1, and is larger than in
AFGL 2591. Both MM1 and MM2 host an early phase massive protostar, but
MM2 (and mid-IR-quiet sources in general) is younger and more
dominated by the host protostar than MM1 (mid-IR-bright). The MM3
core is probably in a pre-stellar phase. We find that the
N2H+/C34S ratio varies systematically with age in the massive
protostars for which the data are available. It can be used to
identify young massive protostars.
Description:
Data available are the channel maps in FITS format of the IRAS
18151-1208 region presented in the Fig. 2 of the paper. The files are
named accordingly to the molecular transition observed : CS(2-1),
N2H+(1-0), HCO+(1-0), H13CO+(1-0), H2CO(322-221) and CO(2-1) lines.
Objects:
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RA (2000) DE Designation(s)
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18 17 58.2 -12 07 28 IRAS 18151-1208 = GAL 018.34+01.77
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
maps.dat 49 6 Map list (files contained in "fits" subdirectory)
fits/* . 6 FITS maps
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Byte-by-byte Description of file: maps.dat
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Bytes Format Units Label Explanations
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1- 37 A37 --- Title Title of the map
40- 49 A10 --- FileName Name of the FITS file in subdirectory fits
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Acknowledgements:
Matthieu Marseille, Mathieu.Marseille(at)obs.u-bordeaux1.fr
Historical notes:
* 02-Sep-2008: In fits subdirectory, H2CO.fit file in GILDAS format
* 18-Nov-2008: In fits subdirectory, H2CO.fit file in FITS format
(End) Patricia Vannier [CDS] 06-Jun-2008