J/A+A/644/A120 HL TAU and IRAS04302+2247 H2CS ALMA images (Codella+, 2020)
ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT).
IV. Thioformaldehyde (H2CS) in protoplanetary disks:
spatial distributions and binding energies.
Codella C., Podio L., Garufi A., Perrero J., Ugliengo P., Fedele D.,
Favre C., Bianchi E., Ceccarelli C., Mercimek S., Bacciotti F.,
Rygl K.L.J., Testi L.
<Astron. Astrophys. 644, A120 (2020)>
=2020A&A...644A.120C 2020A&A...644A.120C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence ; Radio continuum ; Radio lines
Keywords: astrochemistry - protoplanetary discs - methods: numerical -
ISM: individual objects: HL Tau -
ISM: individual objects: IRAS 04302+2247
Abstract:
Planet formation starts around Sun-like protostars with ages ≤1Myr,
but the chemical compositions of the surrounding discs remains
unknown.
We aim to trace the radial and vertical spatial distribution of a key
species of S-bearing chemistry, namely H2CS, in protoplanetary discs.
We also aim to analyse the observed distributions in light of the H2CS
binding energy in order to discuss the role of thermal desorption in
enriching the gas disc component.
In the context of the ALMA chemical survey of disk-outflow sources in
the Taurus star forming region (ALMA-DOT), we observed five Class I or
early Class II sources with the o-H2CS(71,6-61,5) line.
ALMA-Band 6 was used, reaching spatial resolutions ~=40au, that is,
Solar System spatial scales. We also estimated the binding energy of
H2CS using quantum mechanical calculations, for the first time, for an
extended, periodic, crystalline ice.
We imaged H2CS emission in two rotating molecular rings in the HL Tau
and IRAS04302+2247 discs, the outer radii of which are ∼140au (HL Tau)
and 115 au (IRAS 04302+2247). The edge-on geometry of IRAS 04302+2247
allows us to reveal that H2CS emission peaks at radii of 60-115au, at
z=±50au from the equatorial plane. Assuming LTE conditions, the
column densities are 1014cm-2. We estimate upper limits of a few
1013cm-2 for the H2CS column densities in DG Tau, DG Tau B, and
Haro 6-13 discs. For HL Tau, we derive, for the first time, the
[H2CS]/[H] abundance in a protoplanetary disc (∼10-14). The
binding energy of H2CS computed for extended crystalline ice and
amorphous ices is 4258K and 3000-4600K, respectively, implying thermal
evaporation where dust temperatures are 50-80K.
H2CS traces the so-called warm molecular layer, a region previously
sampled using CS and H2CO. Thioformaldehyde peaks closer to the
protostar than H2CO and CS, plausibly because of the relatively high
excitation level of the observed 71,6-61,5 line (60K). The H2CS
binding energy implies that thermal desorption dominates in thin,
au-sized, inner and/or upper disc layers, indicating that the observed
H2CS emitting up to radii larger than 100au is likely injected in the
gas phase due to non-thermal processes.
Description:
The sample consists of four well-known Class I and one early Class II
sources: DG Tau, DG Tau B, HL Tau, IRAS 04302+2247, and Haro 6-13
(also known as V806 Tau). The sources are observed in the context of
the ALMA-DOT project.
DG Tau and DG Tau B and Cycle 6 observations of HL Tau, IRAS
04302+2247, and Haro 6-13 (projects 2016.1.00846.S and 2018.1.01037.S,
PI: L. Podio).
Objects:
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RA (2000) DE Designation(s)
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04 31 38.47 +18 13 58.1 HL TAU = Haro 6-14
04 33 16.50 +22 53 20.4 IRAS 04302+2247 = 2MASS J04331650+2253204
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 204 2 List of fits images
fits/* . 2 Individual fits images
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See also:
J/A+A/636/A65 : DG Tau B ALMA observations (Garufi+, 2020)
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- 34 I5 Kibyte size Size of FITS file
36- 60 A25 --- FileName Name of FITS file, in subdirectory fits
62-204 A143 --- Title Title of the FITS file
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Acknowledgements:
Claudio Codella, codella(at)arcetri.inaf.it
References:
Garufi et al., Paper I 2020A&A...636A..65G 2020A&A...636A..65G, Cat. J/A+A/636/A65
Podio et al., Paper II 2020A&A...642L...7P 2020A&A...642L...7P
(End) Patricia Vannier [CDS] 10-Nov-2020