J/A+A/668/A183 Central Molecular Zone cloud complexes datacubes (Busch+, 2022)
Living on the edge of the Milky Way's central molecular zone:
G1.3 is the more likely candidate for gas accretion into the CMZ.
Busch L.A., Riquelme D., Guesten R., Menten K.M., Pillai T.G.S.,
Kauffmann J.
<Astron. Astrophys. 668, A183 (2022)>
=2022A&A...668A.183B 2022A&A...668A.183B (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds ;
Spectra, millimetric/submm
Keywords: ISM: clouds - ISM: molecules - Galaxy: center
Abstract:
The 1.3deg (G1.3) and 1.6deg (G1.6) cloud complexes in the Central
Molecular Zone (CMZ) of our Galaxy have been proposed to possibly
reside at the intersection region of the X1 and X2 orbits for several
reasons. This includes the detection of co-spatial low- and
high-velocity clouds, high velocity dispersion, high fractional
molecular abundances of shock-tracing molecules, and kinetic
temperatures that are higher than for usual CMZ clouds. We mapped both
cloud complexes in molecular lines in the frequency range from 85 to
475GHz with the IRAM 30m and the APEX 12m telescopes. The kinematic
structure of G1.3 reveals an `emission bridge' at intermediate
velocities (∼150km/s) connecting low-velocity (∼100km/s) and
high-velocity (∼180km/s) gas and an overall fluffy shell-like
structure. These may represent observational evidence of cloud-cloud
interactions. Low- and high-velocity gas components in G1.6 do not
show such evidence of interaction, suggesting that they are spatially
separated. We selected three positions in each cloud complex for
further analysis. Based on non-LTE modelling of an ensemble of CH3CN
lines, we derived kinetic temperatures of 60-100K and H2 volume
densities of 104-105cm-3 in both complexes. Molecular abundances
relative to H2 suggest a similar chemistry of the two clouds, which is
moreover similar to that of other GC clouds. We conclude that G1.3 may
indeed exhibit signs of cloud-cloud interactions. We propose an
interaction of gas that is accreted from the near-side dust lane to
the CMZ, with gas pre-existing at this location. Low- and
high-velocity components in G1.6 are rather coincidentally observed
along the same line of sight. They may be associated with either
overshot decelerated gas from the far-side dust line or actual CMZ gas
and high-velocity gas moving on a dust lane. These scenarios would be
in agreement with numerical simulations.
Description:
We mapped both cloud complexes in molecular lines in the frequency
range from 85 to 117GHz with the IRAM 30m telescope. The APEX 12m
telescope was used to observe higher frequency transitions between 210
and 475GHz (provided here are data covered in frequency range
265-475GHz) from selected molecules that are emitted from higher
energy levels. The maps extend over an area of a couple hundred arcsec
each. The reduced data are provided in main beam temperature scale,
have a common angular resolution of 30'', a common spectral resolution
of 1km/s, and pixel size of 14.5''.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 125 69 List of fits files
fits/* . 69 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 of center (J2000)
4- 5 I2 min RAm Right Ascension of center (J2000)
7- 11 F5.2 s RAs Right Ascension of center (J2000)
12 A1 --- DE- Declination sign of center (J2000)
13- 14 I2 deg DEd Declination of center (J2000)
16- 17 I2 arcmin DEm Declination of center (J2000)
19- 22 F4.1 arcsec DEs Declination of center (J2000)
24- 25 I2 --- Nx Number of pixels along X-axis
27- 28 I2 --- Ny Number of pixels along Y-axis
30- 32 I3 --- Nz Number of channels along the spectral axis
34- 40 F7.3 GHz bFreq Minimum frequency of spectral axis
42- 48 F7.3 GHz BFreq Maximum frequency of spectral axis
50- 54 F5.3 MHz dFreq Frequency resolution
56- 59 F4.2 Mbyte size Size of FITS file
61- 84 A24 --- FileName Name of FITS file, in subdirectory fits
(SourceNameSpeciesTransitionTelescope.fits)
86-125 A40 --- Title Title
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Acknowledgements:
Laura Ann Busch, labusch(at)mpifr-bonn.mpg.de
(End) Patricia Vannier [CDS] 30-Nov-2022