J/A+A/666/A168 Elias 2-27 CO and CN ALMA datacubes (Paneque-Carreno+, 2022)
Vertically extended and asymmetric CN emission in the Elias 2-27
protoplanetary disk.
Paneque-Carreno T., Miotello A., van Dishoeck E.F., Perez L.M., Facchini S.,
Izquierdo A.F., Tychoniec L., Testi L.
<Astron. Astrophys. 666, A168 (2022)>
=2022A&A...666A.168P 2022A&A...666A.168P (SIMBAD/NED BibCode)
ADC_Keywords: YSOs ; Millimetric/submm sources
Keywords: protoplanetary disks - stars: formation
Abstract:
Cyanide (CN) emission is expected to originate in the upper layers of
protoplanetary disks, tracing UV-irradiated regions. This hypothesis,
however, has been observationally tested only in a handful of disks.
Elias 2-27 is a young star that hosts an extended, bright, and
inclined disk of dust and gas. The inclination and extreme flaring of
the disk make Elias 2-27 an ideal target to study the vertical
distribution of molecules, particularly CN.
Our aim is to directly trace the emission of CN in the disk around
Elias 2-27 and compare it to previously published CO isotopolog data
of the system. The two tracers can be combined and used to constrain
the physical and chemical properties of the disk. Through this
analysis we can test model predictions of CN emission and compare
observations of CN in other objects to the massive, highly flared,
asymmetric, and likely gravitationally unstable protoplanetary disk
around Elias 2-27.
We analyzed CN N=3-2 emission in two different transitions J=7/2-5/2
and J=5/2-3/2, for which we detect two hyperfine group transitions.
The vertical location of CN emission was traced directly from the
channel maps, following geometrical methods that had been previously
used to analyze the CO emission of Elias 2-27. Simple analytical
models were used to parameterize the vertical profile of each molecule
and study the extent of each tracer. From the radial intensity
profiles we computed radial profiles of column density and optical
depth.
We show that the vertical location of CN and CO isotopologs in Elias
2-27 is layered and consistent with predictions from thermochemical
models. A north--south asymmetry in the radial extent of the CN
emission is detected, which is likely due to shadowing on the north
side of the disk. Combining the information from the peak brightness
temperature and vertical structure radial profiles, we find that the
CN emission is mostly optically thin and constrained vertically to a
thin slab at z/r∼0.5. A column density of 1014cm-2 is measured in
the inner disk, which for the north side decreases to 1012cm-2 and
for the south side to 1013cm-2 in the outer regions.
In Elias 2-27, CN traces a vertically elevated region above the
midplane, very similar to that traced by 12CO. The inferred CN
column densities, low optical depth (τ≤1), and location near the
disk surface are consistent with thermo-chemical disk models in which
CN formation is initiated by the reaction of N with UV-pumped H2.
The observed north-south asymmetry may be caused by either ongoing
infall or by a warped inner disk. This study highlights the importance
of tracing the vertical location of various molecules to constrain the
disk physical conditions.
Description:
We provide the reduced datacubes of 13CO (J=3-2) , C18O (J=3-2)
and CN (N=3-2) ALMA observations of Elias 2-27. The units are Jy/beam.
Objects:
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RA (2000) DE Designation(s)
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16 26 45.03 -24 23 07.79 Elias 2-27 = GSS 39
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 188 4 List of fits datacubes
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- 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
34- 59 A26 "datime" Obs.date Observation date
61- 67 F7.3 GHz bFreq Lower value of frequency interval
69- 75 F7.3 GHz BFreq Upper value of frequency interval
77- 82 I6 Hz dFreq Frequency resolution
84- 90 I7 Kibyte size Size of FITS file
92-136 A45 --- FileName Name of FITS file, in subdirectory fits
138-188 A51 --- Title Title of the FITS file
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Acknowledgements:
Teresa Paneque-Carreno, tpaneque(at)eso.org
(End) Patricia Vannier [CDS] 17-Aug-2022