J/A+A/603/A68 Images of molecular and ionized gas around Sgr A* (Moser+, 2017)
Approaching hell's kitchen: Molecular daredevil clouds in the vicinity of
Sagittarius A*.
Moser L., Sanchez-Monge A., Eckart A., Requena-Torres M.A.,
Garcia-Marin M., Kunneriath D., Zensus A., Britzen S., Sabha N.,
Shahzamanian B., Borkar A., Fischer S.
<Astron. Astrophys. 603, A68 (2017)>
=2017A&A...603A..68M 2017A&A...603A..68M (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Molecular clouds ; Millimetric/submm sources
Keywords: Galaxy: center - Galaxy: nucleus - submillimeter: ISM -
ISM: molecules - ISM: clouds - ISM: kinematics and dynamics
Abstract:
We report serendipitous detections of line emission with the Atacama
Large Millimeter/submillimeter Array (ALMA) in bands 3, 6, and 7 in
the central parsec down to within 1" around Sgr A* at an up to
now highest resolution (<0.5") view of the Galactic center (GC)
in the submillimeter (sub-mm) domain. From the 100GHz continuum and
the H39α emission we obtain a uniform electron temperature
around Te∼6000K for the minispiral. The spectral index
(S∝να) of Sagittarius A* (Sgr A*) is ∼0.5 at
100-250GHz and ∼0.0 at 230-340GHz. The bright sources in the center
show spectral indices around -0.1 implying Bremsstrahlung emission,
while dust emission is emerging in the minispiral exterior.
Apart from CS, which is most widespread in the center, H13CO+,
HC3N, SiO, SO, C2H, CH3OH, 13CS and N2H+ are also detected.
The bulk of the clumpy emission regions is at positive velocities and
in a region confined by the minispiral northern arm (NA), bar, and the
sources IRS 3 and 7. Although partly spatially overlapping with the
radio recombination line (RRL) emission at same negative velocities,
the relation to the minispiral remains unclear. A likely explanation
is an infalling clump consisting of denser cloud cores embedded in
diffuse gas. This central association (CA) of clouds shows three times
higher CS/X (X: any other observed molecule) ratios than the
circumnuclear disk (CND) suggesting a combination of higher
excitation, by a temperature gradient and/or infrared (IR) pumping,
and abundance enhancement due to UV and/or X-ray emission. Hence, we
conclude that this CA is closer to the center than the CND. Moreover,
we find molecular line emission at velocities up to 200km/s.
Apart from the CA, we identified two intriguing regions in the CND.
One region shows emission in all molecular species and higher energy
levels tested in this and previous observations and contains a
methanol class I maser. The other region shows similar behavior of the
line ratios such as the CA. Outside the CND, we find the traditionally
quiescent gas tracer N2H+ coinciding with the largest IR dark
clouds (IRDC) in the field. Methanol emission is found at and around
previously detected methanol class I masers in the same region. We
propose to make these particular regions subject to further studies in
the scope of hot core, cold core, and extreme photon and/or X-ray
dominated region (PDR/XDR) chemistry and consequent star formation in
the central few parsecs.
Description:
ALMA Cycle 0 data of band 3, 6, and 7 around the frequencies 100GHz,
250GHz, and 340GHz tuning (PI: Falcke) for a single pointing on
Sgr A* (17h45m40.04s, -29d00m28.12s).
XXXXXip: primary beam corrected image/cube
XXXXXpb: primary beam image/cube (needed to restore uncorrected image for
noise clipping)
s0 - s3: spectral windows (spw) 0 - 3 (TDM setup)
XXXsXXX: cube of an entire spw for natural weighting
XXXcnXX: continuum for natural weighting
XXXcuXX: continuum for uniform weighting
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 220 30 List of fits datacubes and images
fits/* . 30 Individual fits datacubes and images
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See also:
J/A+A/502/91 : Proper motions of stars near SgrA* (Schoedel+, 2009)
J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+, 2010)
J/A+A/534/A117 : NIR polarimetry of sources near SgrA* (Buchholz+, 2011)
J/ApJ/755/90 : [NeII] emission line obs. from SgrA West (Irons+, 2012)
J/MNRAS/428/2731 : SgrA* emission at 7mm (Beaklini+, 2013)
J/A+A/582/A118 : OH-streamer in SgrA at 1665 and 1667MHz (Karlsson+, 2015)
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 --- Nz ? Number of slices
32- 57 A26 --- Obs.Date Observation date (YYYY-MM-DDThh:mm:ss.ssssss)
59- 69 E11.6 Hz Freq Observed frequency, or lower value of
frequency interval for datacubes
71- 81 E11.6 Hz BFreq ? Upper value of observed frequency for
datacubes
83- 92 E10.5 Hz dFreq ? Frequency resolution for datacubes
94- 99 I6 Kibyte size Size of FITS file
101-111 A11 --- FileName Name of FITS file, in subdirectory fits
113-220 A108 --- Title Title of the FITS file
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Acknowledgements:
Lydia Moser, moser(at)astro.uni-bonn.de
This data is based on the following ALMA data:
ADS/JAO.ALMA#2011.0.00887.S. ALMA is a partnership of ESO
(representing its member states), NSF (USA) and NINS (Japan), together
with NRC (Canada) and NSC and ASIAA (Taiwan) and KASI (Republic of
Korea), in cooperation with the Republic of Chile. The Joint ALMA
Observatory is operated by ESO, AUI/NRAO, and NAOJ.
(End) Lydia Moser [AIfA, Bonn, Germany], Patricia Vannier [CDS] 16-Mar-2017