J/A+A/606/A35 Barnard 1b-N and 1b-S 350GHz images (Gerin+, 2017)
Evidence for disks at an early stage in class 0 protostars?
Gerin M., Pety J., Commercon B., Fuente A., Cernicharo J., Marcelino N.,
Ciardi A., Lis D.C., Roueff E., Wootten H.A., Chapillon E.
<Astron. Astrophys. 606, A35 (2017)>
=2017A&A...606A..35G 2017A&A...606A..35G (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds ;
Photometry, millimetric/submm
Keywords: stars: formation - ISM: clouds - submillimeter: ISM -
ISM: individual objects: Barnard 1b - ISM: molecules
Abstract:
The formation epoch of protostellar disks is debated because of the
competing roles of rotation, turbulence, and magnetic fields in the
early stages of low-mass star formation. Magnetohydrodynamics
simulations of collapsing cores predict that rotationally supported
disks may form in strongly magnetized cores through ambipolar
diffusion or misalignment between the rotation axis and the magnetic
field orientation. Detailed studies of individual sources are needed
to cross check the theoretical predictions. We present 0.06-0.1arcsec
resolution images at 350GHz toward B1b-N and B1b-S, which are young
class 0 protostars, possibly first hydrostatic cores. The images have
been obtained with ALMA, and we compare these data with
magnetohydrodynamics simulations of a collapsing turbulent and
magnetized core. The submillimeter continuum emission is spatially
resolved by ALMA. Compact structures with optically thick 350GHz
emission are detected toward both B1b-N and B1b-S, with 0.2 and
0.35arcsec radii (46 and 80au at the Perseus distance of 230pc),
within a more extended envelope. The flux ratio between the compact
structure and the envelope is lower in B1b-N than in B1b-S, in
agreement with its earlier evolutionary status. The size and
orientation of the compact structure are consistent with 0.2arcsec
resolution 32GHz observations obtained with the Very Large Array as a
part of the VANDAM survey, suggesting that grains have grown through
coagulation. The morphology, temperature, and densities of the compact
structures are consistent with those of disks formed in numerical
simulations of collapsing cores. Moreover, the properties of B1b-N are
consistent with those of a very young protostar, possibly a first
hydrostatic core. These observations provide support for the early
formation of disks around low-mass protostars.
Description:
The data are provided as two separate FITS files, one for B1b-N and
one for B1b-S. The data have been obtained with ALMA in continuum
mode. Four continuum basebands with 2 GHz bandwidth, 128 channels each
have been combined. Central sky frequencies on each band are 2336.5
and 338.4GHz in the lower side band and 3548.5 and 350.5GHz in the
upper side band. The images have been produced by combining two
observing sessions in two ALMA configurations C36-7 and C40-4, for a
total of 30 minutes on source. The data processing and calibration is
described in the article. The image units are Jy/beam.
Objects:
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RA (2000) DE Designation(s)
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03 33 20.32 +31 07 21.5 Barnard 1b = [HKM99] B1-b
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 97 2 List of fits images
fits/* . 2 Individual fits images
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See also:
J/A+A/577/L2 : Barnard 1b-N and 1b-S nascent bipolar outflows (Gerin+, 2015)
J/A+A/606/L3 : Barnard 1b CO, NH2D and SO images (Fuente+, 2017)
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- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 52 A23 --- Obs.Date Observation date (YYYY-MM-DDThh:mm:ss.sss)
54- 60 F7.3 GHz Freq Observed frequency
62- 66 I5 Kibyte size Size of FITS file
68- 85 A18 --- FileName Name of FITS file, in subdirectory fits
87- 97 A11 --- Title Title of the FITS file
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Acknowledgements:
Maryvonne Gerin, maryvonne.gerin(at)lra.ens.fr
(End) Patricia Vannier [CDS] 25-Aug-2017