J/A+A/646/A18 The Bok globule CB 26 (Zhang+, 2021)
Pebbles in an embedded protostellar disk: the case of CB 26..
Zhang C.-P., Launhardt R., Liu Y., Tobin J.J., Henning T.
<Astron. Astrophys. 646, A18 (2021)>
=2021A&A...646A..18Z 2021A&A...646A..18Z (SIMBAD/NED BibCode)
ADC_Keywords: Globules ; Millimetric/submm sources
Keywords: protoplanetary disks - radiative transfer - stars: individual: CB 26 -
circumstellar matter
Abstract:
Planetary cores are thought to form in proto-planetary disks via the
growth of dusty solid material. However, it is unclear how early this
process begins.
We study the physical structure and grain growth in the edge-on disk
that surrounds the ∼1Myr old low-mass (∼0.55M☉) protostar
embedded in the Bok Globule CB26 to examine how much grain growth has
already occurred in the protostellar phase.
We combine the SED between 0.9um and 6.4cm with high angular
resolution continuum maps at 1.3, 2.9, and 8.1mm, and use the
radiative transfer code RADMC-3D to conduct a detailed modelling of
the dust emission from the disk and envelope of CB 26.
We infer inner and outer disk radii of around 16au and 172±22au,
respectively. The total gas mass in the disk is ∼0.076M☉, which
amounts to ∼14% of the mass of the central star. The inner disk
contains a compact free-free emission region, which could be related
to either a jet or a photoevaporation region. The thermal dust
emission from the outer disk is optically thin at mm wavelengths,
while the emission from the inner disk midplane is moderately
optically thick. Our best-fit radiative transfer models indicate that
the dust grains in the disk have already grown to pebbles with
diameters of the order of 10cm in size. Residual 8.1mm emission
suggests the presence of even larger particles in the inner disk. For
the optically thin mm dust emission from the outer disk, we derive a
mean opacity slope of βmm~=0.7±0.4, which is consistent with
the presence of large dust grains.
The presence of cm-sized bodies in the CB 26 disk indicates that
solids grow rapidly already during the first million years in a
protostellar disk. It is thus possible that Class II disks are already
seeded with large particles and may contain even planetesimals.
Description:
The Bok globule CB 26 harbors a young (∼1Myr) low-mass (∼0.55M☉)
star that is surrounded by a massive circumstellar disk seen nearly
edge-on, which is in turn still embedded in a thin remnant envelope.
Combining the well-sampled SED between 0.9um and 6.4cm,
high-angular-resolution millimeter continuum observations at 1.1, 1.3,
2.9, and 8.1mm, and using the radiative transfer code RADMC-3D, we
conduct a detailed modeling of the dust emission from the CB 26
circumstellar disk. The models are fitted simultaneously to the
complete SED and to the image plane data of the interferometric dust
continuum emission maps at 1.3, 2.9, and 8.1mm.
Objects:
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RA (2000) DE Designation(s)
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05 00 09 +52 04.9 CB 26 = [CB88] 26
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 50 27 Photometric data points for CB 26
table2.dat 38 4 Beam sizes and noise levels of the millimeter
table3.dat 90 22 Overview of parameter ranges used in the modeling
list.dat 96 4 List of fits images
fits/* . 4 Individual fits images
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 F8.2 um lambda Wavelength
10- 18 F9.3 mJy Flux Flux at each Wavelength
20- 27 F8.3 mJy e_Flux Flux at each Wavelength error
29- 31 I3 arcsec Aperture Aperture for each observation
33- 48 A16 -- Inst Observational Instrument
50 I1 -- Ref [1/4] Referece for photometric data (1)
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Note (1): References as follows:
1 = Stecklum et al. (2004ApJ...617..418S 2004ApJ...617..418S)
2 = Sauter et al. (2009A&A...505.1167S 2009A&A...505.1167S)
3 = Launhardt et al. (2013A&A...551A..98L 2013A&A...551A..98L)
4 = This work
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Inst Observational Instrument
11- 13 F3.1 mm lambda Observational Wavelength
15- 19 F5.3 arcsec HPBWa Beam size, major axis
20 A1 --- --- [x]
21- 25 F5.3 arcsec HPBWb Beam size, minor axis
27- 31 F5.1 deg HPBWPA Beam size, position angle
33- 38 F6.4 mJy/beam rms Observational rms
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- Env Environment (1)
25- 37 A13 --- Param Fitted Parameter (2)
39- 45 A7 --- Unit Unit for each Fitted Parameter
47- 53 E7.3 --- Range1 Range for each Parameter
54 A1 --- --- [~]
55- 61 E7.3 --- Range2 ? Range for each Parameter
62- 68 E7.3 --- Bestfit Best-fit Parameter
70- 76 E7.3 --- E_Param ? Upper value of Param uncertainty (3)
78- 84 E7.3 --- e_Param ? Lower value of Param uncertainty (3)
86- 90 A5 ---- n_Param [Fixed ] Fixed when uncertainty fixed
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Note (1): Environmenta are Disk, Envelope, Star and Grain size distribution.
Note (2): Explanations for Fitted Parameter:
rin : Inner radius of the disk
rout : Outer radius of the disk
hout/rout : Ratio of the pressure scale height to the radius at rout
p : Power exponent of the radial surface density distribution
k : Flare index
Sigmaout : Surface density of the disk at the outer radius
phi : Inclination angle of the disk
Rin : Inner radius of the envelope
Rout : Outer radius of the envelope
rhoout : Density of the envelope at the outer radius
gamma : Radial density distribution power exponent
P.C. : Radius of the polar cavity in the envelope
r* : Radius of the star
M* : Mass of the star, fitted with a Keplerian disk in
the 12CO J=2-1 velocity field
T* : Effective surface temperature of the star
P.A. : The rotation of the major axis in the image plane
AV : Visual extinction
Distance : The distance to the Sun
amaxdisk : Maximum dust grain size in the disk
amaxenv : Maximum dust grain size in the envelope
amindisk : Minimum dust grain size in the disk
aminenv : Minimum dust grain size in the envelope
Note (3): Uncertainties: Defined by χ2total-χ2best<3.
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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- 48 A21 "datime" Obs.date Observation date
50- 53 I4 Kibyte size Size of FITS file
55- 65 A11 --- FileName Name of FITS file, in subdirectory fits
67- 96 A30 --- Title Title of the FITS file
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Acknowledgements:
Chuan-Peng Zhang, zcp0507(at)nao.cas.cn
(End) Chuan-Peng Zhang [NAOC, Beijing], Patricia Vannier [CDS] 25-Dec-2020