J/A+A/646/A72 Resolved molecular line observations (Harsono+, 2021)
Resolved molecular line observations reveal an inherited molecular layer in the
young disk around TMC1A.
Harsono D., van der Wiel M.H.D., Bjerkeli P., Ramsey J.P., Calcutt H.,
Kristensen L.E., Joergensen J.K.
<Astron. Astrophys. 646, A72 (2021)>
=2021A&A...646A..72H 2021A&A...646A..72H
ADC_Keywords: Protostars ; Abundances ; Spectra, millimetric/submm
Keywords: stars: formation - stars: protostars - ISM: abundances -
astrochemistry - ISM: individual objects: TMC1A - protoplanetary disks
Abstract:
Physical processes that govern the star and planet formation sequence
influence the chemical composition and evolution of protoplanetary
disks. Recent studies allude to an early start to planet formation
already ongoing during the formation of a disk. To understand the
chemical composition of protoplanets, we need to constrain the
composition and structure of the disks from whence they are formed.
We aim to determine the molecular abundance structure of the young
disk around the TMC1A protostar on au scales in order to understand
its chemical structure and any possible implications for disk
formation.
We present spatially resolved Atacama Large Millimeter/submillimeter
Array observations of CO, HCO+, HCN, DCN, and SO line emission, as
well as dust continuum emission, in the vicinity of TMC1A. Molecular
column densities are estimated both under the assumption of optically
thin emission from molecules in local thermodynamical equilibrium
(LTE) as well as through more detailed non-LTE radiative transfer
calculations.
From the derived HCO+ abundance, we estimate the ionization fraction
of the disk surface and find values that imply that the accretion
process is not driven by the magneto-rotational instability. The
molecular abundances averaged over the TMC1A disk are similar to its
protostellar envelope and other, older Class II disks. We meanwhile
find a discrepancy between the young disk's molecular abundances
relative to Solar System objects.
Abundance comparisons between the disk and its surrounding envelope
for several molecular species reveal that the bulk of planet-forming
material enters the disk unaltered. Differences in HCN and H2O
molecular abundances between the disk around TMC1A, Class II disks,
and Solar System objects trace the chemical evolution during disk and
planet formation.
Description:
ALMA observations of TMC1A at a spatial resolution of 6au. The FITS
files of the dust thermal emission at 220GHz, 230GHz, 240GHz and
265GHz are uploaded. The spectral cubes of 12CO, 13CO, C18O,
DCN, HCN, HCNv2, HCO+, and SO are also presented.
Objects:
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RA (2000) DE Designation(s)
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04 39 35.19 +25 41 44.7 TMC1A = TMC-1A
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 82 17 Properties of the ALMA images including noise
and integrated flux density
list.dat 173 14 List of fits datacubes and images
fits/* . 14 Individual fits datacubes and images
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Name Name of the data
25- 32 F8.4 GHz Freq Frequency of the data
34- 40 F7.2 K Eup ?=- Upper enery level (1)
42- 46 F5.2 [s-1] LogAij ?=- Logarithmic of the Einstein A
48- 52 F5.3 arcsec Beam1 Beam information, FWHM of the major axis
53 A1 --- --- [x]
54- 58 F5.3 arcsec Beam2 Beam information, FWHM of the minor axis
60- 63 F4.1 deg PA [] Beam information, position angle
65- 68 F4.2 mJy/beam Noise Noise level
70- 72 I3 s Time The final integrated time based on the
visibilities
74 A1 --- l_Int Limit flag on Int
75- 78 I4 mJy.km/s Int Integrated flux inside 1" (2)
80- 82 I3 mJy.km/s e_Int ?=- Error on integrated flux inside 1" (2)
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Note (1): Upper limits are calculated over the size of the dust continuum
emission.
Note (2): We report the noise to be 10% of the integrated flux density unless
the measured noise is larger than 10%.
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
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- 32 I3 --- Nz ?=- Number of slices for the datacubes
34- 59 A26 "datime" Obs.date Observation date
61- 68 F8.1 m/s bVRAD ?=- Lower value of VRAD interval for datacubes
70- 76 F7.1 m/s BVRAD ?=- Upper value of VRAD interval for datacubes
78- 84 F7.2 m/s dVRAD ?=- VRAD resolution for datacubes
86- 92 F7.3 GHz Freq Observed frequency
94-101 I8 Kibyte size Size of FITS file
103-140 A38 --- FileName Name of FITS file, in subdirectory fits
142-173 A32 --- Title Title of the FITS file
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Acknowledgements:
Daniel Harsono, dsharsono(at)asiaa.sinica.edu.tw
(End) Daniel Harsono [ASIAA, Taiwan], Patricia Vannier [CDS] 08-Dec-2020