J/A+A/618/A35 ALMA images of the CND and SgrA* (Goicoechea+, 2018)
High-speed molecular cloudlets around the Galactic center's supermassive
black hole.
Goicoechea J.R., Pety J., Chapillon E., Cernicharo J., Gerin M.,
Herrera C., Requena-Torres M.A., Santa-Maria M.G.
<Astron. Astrophys. 618, A35 (2018)>
=2018A&A...618A..35G 2018A&A...618A..35G (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds ; Interferometry
Keywords: ISM: clouds - ISM: kinematics and dynamics - ISM: molecules -
Galaxy: center - radiolines: ISM
Abstract:
We present 1"-resolution ALMA observations of the circumnuclear disk
(CND) and the environment around SgrA*. The images unveil the presence
of small spatial scale CO (J=3-2) molecular "cloudlets" within the
central pc of the Milky Way, moving at high speeds, up to 300km/s
along the line-of-sight. The CO-emitting structures show intricate
morphologies: extended and filamentary at high negative-velocities
(vLSR←150km/s), more localized and clumpy at extreme
positive-velocities (vLSR>+200km/s).
Based on the pencil-beam CO absorption spectrum toward SgrA*
synchrotron emission, we also present evidence for a diffuse gas
component producing absorption features at more extreme
negative-velocities (vLSR←200km/s).
The CND shows a clumpy spatial distribution. Its motion requires a
bundle of non-uniformly rotating streams of slightly different
inclinations. The inferred gas density peaks are lower than the local
Roche limit. This supports that CND molecular cores are transient.
We apply the two standard orbit models, spirals vs. ellipses, invoked
to explain the kinematics of the ionized gas streamers around SgrA*.
The location and velocities of the CO cloudlets are inconsistent with
the spiral model, and only two of them are consistent with the
Keplerian ellipse model. Most cloudlets, however, show similar
velocities that are incompatible with the motions of the ionized
streamers or with gas bounded to the central gravity. We speculate
that they are leftovers of more massive, tidally disrupted, clouds
that fall into the cavity, or that they originate from instabilities
in the inner rim of the CND and infall from there.
Molecular cloudlets, all together with a mass of several 10M☉,
exist around SgrA*. Most of them must be short-lived: photoevaporated
by the intense stellar radiation field, blown away by winds from
massive stars, or disrupted by strong gravitational shears.
Description:
The FITS files contain total integrated line intensity maps of CO
(3-2), H13CN (4-3) and SO (89-78) emission lines shown in
Figures 1, 3, 4 and A1 and A4 of the article. The integrated velocity
range goes from vLSR=-150 to +150km/s for H13CN and SO and from
-400 to +280 for CO. The intensity scale of the images is in K.km/s
units.
Objects:
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RA (2000) DE Designation(s)
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17 45 40.04 -29 00 28.2 Sgr A* = NAME Sgr A*
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 101 3 List of fits images
fits/* . 3 Individual fits images
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See also:
J/MNRAS/428/2731 : SgrA* emission at 7mm (Beaklini+, 2013)
J/ApJ/820/90 : 4yr 1.3mm VLBI observations of SgrA* with EHT (Fish+, 2016)
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
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 Kibyte size Size of FITS file
32- 55 A24 --- FileName Name of FITS file, in subdirectory fits
57-101 A45 --- Title Title of the FITS file
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Acknowledgements:
Javier R. Goicoechea, javier.r.goicoechea(at)csic.es
(End) Javier Goicoehcea [CSIC, Spain], Patricia Vannier [CDS] 20-Aug-2018