J/A+A/620/A80 Signatures of an incipient hot corino in B1b-S (Marcelino+, 2018)
ALMA observations of the young protostellar system Barnard 1b:
Signatures of an incipient hot corino in B1b-S.
Marcelino N., Gerin M., Cernicharo J., Fuente A., Wootten H.A.,
Chapillon E., Pety J., Lis D.C., Roueff E., Commercon B., Ciardi A.
<Astron. Astrophys. 620, A80 (2018)>
=2018A&A...620A..80M 2018A&A...620A..80M (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Line Profiles ; Spectroscopy
Keywords: astrochemistry - ISM: clouds - SM: individual objects: Barnard 1b -
ISM: abundances - stars: formation - stars: low-mass
Abstract:
The Barnard 1b core shows signatures of being at the earliest stages
of low- mass star formation, with two extremely young and deeply
embedded proto- stellar objects. Hence, this core is an ideal target
to study the structure and chemistry of the first objects formed in
the collapse of prestellar cores. We present ALMA Band 6 spectral line
observations at ∼0.6" of angular resolution towards Barnard 1b. We
have extracted the spectra towards both protostars, and used a local
thermodynamic equilibrium (LTE) model to reproduce the observed line
profiles. B1b-S shows rich and complex spectra, with emission from
high energy transitions of complex molecules, such as CH3OCOH and
CH3CHO, including vibrational level transitions. We have tentatively
detected for the first time in this source emission from NH2CN,
NH2CHO, CH3CH2OH, CH2OHCHO, CH3CH2OCOH and both aGg' and
gGg' conformers of (CH2OH)2. This is the first detection of ethyl
formate (CH3CH2OCOH) towards a low-mass star forming region. On
the other hand, the spectra of the FHSC candidate B1b-N are free of
COMs emission. In order to fit the observed line profiles in B1b-S, we
used a source model with two components: an inner hot and compact
component (200K, 0.35") and an outer and colder one (60K, 0.6"). The
resulting COM abundances in B1b-S range from 10-13 for NH2CN and
NH2CHO, up to 10-9 for CH3OCOH. Our ALMA Band 6 observations
reveal the presence of a compact and hot component in B1b-S, with
moderate abundances of complex organics. These results indicate that a
hot corino is being formed in this very young Class 0 source.
Description:
Table B.2 contains the detected molecular transitions in the B1b-S
protostar ordered by observed frequency. The table includes the
molecule formula and transition, rest frequency, spectroscopic data,
and line parameters obtained from Gaussian fits.
Objects:
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RA (2000) DE Designation(s)
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03 33 21.3 +31 07 28 B1b-S = [HKM99] B1-bS
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb2.dat 149 241 *Observed transitions in B1b-S
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Note on tableb2.dat: Line parameters are obtained from Gaussian fits.
Rest frequencies and spectroscopic data are taken from the MADEX catalogue
(Cernicharo et al., 2012EAS....58..251C 2012EAS....58..251C)
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Byte-by-byte Description of file: tableb2.dat
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Bytes Format Units Label Explanations
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1- 9 F9.2 MHz ObsFreq ? Observed frequency
12- 24 A13 --- Mol Molecule formula
26- 48 A23 --- Trans Quantum numbers of the transition
51- 60 F10.3 MHz RestFreq ? Rest frequency from the catalogues
62- 66 F5.3 MHz e_RestFreq ? Uncertainty for the rest frequency
69- 73 F5.1 K Eup ? Upper state energy
76- 81 F6.2 --- Sij ? Line strength
84- 90 E7.3 s-1 Aij ? Einstein coefficient
94- 98 F5.3 K.km/s IntArea ? Integrated area of the line
100-104 F5.3 K.km/s e_IntArea ? Uncertainty for the integrated area
107-111 F5.3 km/s vLSR ? LSR velocity
113-117 F5.3 km/s e_vLSR ? Uncertainty for the LSR velocity
120-124 F5.3 km/s Deltav ? Line width
126-130 F5.3 km/s e_Deltav ? Uncertainty for the line width
133-137 F5.3 K TB ? Brightness temperature
139-143 F5.3 K rms ? rms of the spectra near the line
146-149 A4 --- Notes Note (1)
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Note (1): Note as follows:
Abs = line observed in absorption
Blen = line blended with others
CP = line with complex line profile
Edge = line at the edge of the spectral window
Ext = line with extended emission
Ori = unidentified line also detected in Orion-KL
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Acknowledgements:
Nuria Marcelino, nuria.marcelino(at)csic.es
(End) Nuria Marcelino [CSIC, Spain], Patricia Vannier [CDS] 15-Oct-2018