J/A+A/629/A75 HD 97048 H13CO+ and HC15N first detections (Booth+, 2019)
First detections of H13CO+ and HC15N in the disk around HD 97048:
Evidence for a cold gas reservoir in the outer disk.
Booth A.S., Walsh C., Ilee J.D.
<Astron. Astrophys. 629, A75 (2019)>
=2019A&A...629A..75B 2019A&A...629A..75B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, pre-main sequence ;
Photometry, millimetric/submm
Keywords: astrochemistry - stars: individual: HD 97048 -
stars: individual: HD 100546 - stars: pre-main sequence -
protoplanetary disks - submillimetre: planetary systems
Abstract:
Observations of different molecular lines in protoplanetary disks
provide valuable information on the gas kinematics, as well as
constraints on the radial density and temperature structure of the
gas. With ALMA we have detected H13CO+ (J=4-3) and HC15N (J=4-3) in
the HD 97048 protoplanetary disk for the first time. We compare these
new detections to the ringed continuum mm-dust emission and the
spatially resolved CO (J=3-2) and HCO+ (J=4-3) emission. The radial
distributions of the H13CO+ and HC15N emission show hints of
ringed sub-structure whereas, the optically thick tracers, CO and
HCO+, do not. We calculate the HCO+/H13CO+ intensity ratio
across the disk and find that it is radially constant (within our
uncertainties). We use a physio-chemical parametric disk structure of
the HD 97048 disk with an analytical prescription for the HCO+
abundance distribution to generate synthetic observations of the
HCO+ and H13CO+ disk emission assuming LTE. The best by-eye fit
models require radial variations in the HCO+/H13CO+ abundance
ratio and an overall enhancement in H13CO+ relative to HCO+.
This highlights the need to consider isotope selective chemistry and
in particular low temperature carbon isotope exchange reactions. This
also points to the presence of a reservoir of cold molecular gas in
the outer disk (T<10K, R>200au). Chemical models are required to
confirm that isotope-selective chemistry alone can explain the
observations presented here. With these data, we cannot rule out that
the known dust substructure in the HD 97048 disk is responsible for
the observed trends in molecular line emission, and higher spatial
resolution observations are required to fully explore the potential of
optically thin tracers to probe planet-carved dust gaps. We also
report non-detections of H13CO+ and HC15N in the HD 100546
protoplanetary disk.
Description:
Reduced data cubes (in FITS format) of ALMA observations of 12CO
(J=3-2), HCO+ (J=4-3) , H13CO+ (J=4-3) and HC15N (J=4-3)
(projects 2011.0.00863.S and 2012.1.00031.S). `
Objects:
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RA (2000) DE Designation(s)
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11 08 03.31 -77 39 17.5 HD 97048 = HIP 54413
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 147 4 List of fits data cubes
fits/* . 4 Individual fits datacubes
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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- 30 I3 --- Nz Number of slices
32- 54 A23 "datime" Obs.Date Observation date (DD-MM-YYYY)
56- 63 F8.4 GHz bFreq Lower value of frequency interval
65- 72 F8.4 GHz BFreq Upper value of frequency interval
74- 83 F10.4 Hz dFreq Frequency resolution
85- 89 I5 Kibyte size Size of FITS file
91-105 A15 --- FileName Name of FITS file, in subdirectory fits
107-147 A41 --- Title Title of the FITS file
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Acknowledgements:
Alice S. Booth, pyasb(at)leeds.ac.uk
(End) Alice Booth [University of Leeds], Patricia Vannier [CDS] 23-Jul-2019