J/A+A/627/L6 ALMA Long Baseline maps of G17.64+0.16 (Maud+, 2019)
Substructures in the Keplerian disc around the O-type (proto)star G17.64+0.16.
Maud L.T., Cesaroni R., Kumar M.S.N., Rivilla V.M., Ginsburg A.,
Klaassen P.D., Harsono D., Sanchez-Monge A., Ahmadi A., Allen V.,
Beltran M.T., Beuther H., Galvan-Madrid R., Goddi C., Hoare M.G.,
Hogerheijde M.R., Johnston K.G., Kuiper R., Moscadelli L., Peters T.,
Testi L., van det Tak F.F.S., de Wit W.J.
<Astron. Astrophys. 627, L6 (2019)>
=2019A&A...627L...6M 2019A&A...627L...6M (SIMBAD/NED BibCode)
ADC_Keywords: Infrared sources ; Millimetric/submm sources ; Interferometry;
YSOs
Keywords: stars: formation - stars: protostars - stars: massive -
stars: winds, outflows - stars: pre-main sequence -
submillimeter: stars
Abstract:
We present the highest angular resolution (20x15mas - 44x33au)
Atacama Large Millimeter/sub-millimeter Array (ALMA) observations
currently possible of the proto-O-star G17.64+0.16 in Band 6. The
Cycle 5 observations with baselines out to 16 km probes scales <50au
and reveal the rotating disc around G17.64+0.16, a massive forming
O-type star. The disc has a ring-like enhancement in the dust
emission, especially visible as arc structures to the north and south.
The Keplerian kinematics are most prominently seen in the
vibrationally excited water line, H2O (Eu=3461.9K). The mass of the
central source found by modelling the Keplerian rotation is consistent
with 45±10M☉. The H30alpha (231.9GHz) radio-recombination line
and the SiO (5-4) molecular line were detected at up to the 10-sigma
level. The estimated disc mass is 0.6-2.6M☉ under the optically
thin assumption. Analysis of the Toomre Q parameter, in the optically
thin regime, indicates that the disc stability is highly dependent on
temperature. The disc currently appears stable for temperatures >150K,
this does not preclude that the substructures formed earlier through
disc fragmentation.
Description:
The ALMA 12m observations consist of one execution block (EB)
conducted during Cycle 5 on 4 October 2017 (project ID: 2017.1.00098.S
- PI: Maud) in configuration C43-10, with 43 antennas. The on-source
time was 30.6minutes. Here we provide the continuum map of G17.64+0.16
before and after the removal of a point-source (that accounts for the
free-free contamination. A possible maximal and minumal value are
used. We also provide the image cubes for H20, SIO, and H30alpha.
The resulting resolution of the continuum images made with robust=0.0
was 20x15mas. For the H20 line robust=1.5 was use and the resulting
resolution was 28x23mas. The SIO map also used robust=1.5 and has a
resolution 30x24mas, while the H30alpha used robust=0.0 and has a
resolution 20x18mas. All data use the ALMA 12m main array with the
long baseline configuration C43-10. All data are selfcalibrated with
the pointing centre shifted to be centred on G17.64+0.16.
Objects:
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RA (2000) DE Designation(s)
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18 22 26.386 -13 30 11.972 AFGL 2136 IRS 1 = MSX6C G017.6380+00.1566
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 151 6 List of fits files
fits/* . 6 Individual fits files
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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- 2 I2 h RAh Right ascension (J2000.0)
4- 5 I2 min RAm Right ascension (J2000.0)
7- 12 F6.3 s RAs Right ascension (J2000.0)
14 A1 --- DE- Declination sign (J2000.0)
15- 16 I2 deg DEd Declination (J2000.0)
18- 19 I2 arcmin DEm Declination (J2000.0)
21- 25 F5.2 arcsec DEs Declination (J2000.0)
27- 30 I4 --- Nx Number of pixels along X-axis
32- 35 I4 --- Ny Number of pixels along Y-axis
37- 39 I3 --- Nz ? Number of slices
41- 63 A23 "datime" Obs.date Observation date (YYYY-MM-DDThh:mm:ss.sss)
65- 71 F7.3 GHz RestFreq Reference frequency of the cube at Nz=0
73- 78 F6.1 kHz dFreq ? Frequency resolution for datacubes
80- 86 I7 Kibyte size Size of FITS file
88-112 A25 --- FileName Name of FITS file, in subdirectory fits
114-151 A38 --- Title Description of FITS image
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Acknowledgements:
Luke Maud, lmaud(at)eso.org
(End) Luke Maud [ESO], Patricia Vannier [CDS] 02-Jul-2019