J/A+A/664/A97 Galactic Center Circumnuclear disk 3D spectros. (Paumard+, 2022)
Regularized 3D spectroscopy with CubeFit:
Method and application to the Galactic Center circumnuclear disk.
Paumard T., Ciurlo A., Morris M.R., Do T., Ghez A.M.
<Astron. Astrophys. 664, A97 (2022)>
=2022A&A...664A..97P 2022A&A...664A..97P (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium; H II regions; Molecular clouds;
Spectra, infrared
Keywords: methods: data analysis - methods: numerical -
techniques: high angular resolution -
techniques: spectroscopic -
ISM: individual objects: Sgr A West Circumnuclear Disk -
Galaxy: center
Abstract:
The Galactic Center black hole and the nuclear star cluster are
surrounded by a clumpy ring of gas and dust (the circumnuclear disk,
CND) that rotates about them at a standoff distance of ∼1.5pc. The
mass and density of individual clumps in the CND are disputed. We seek
to use molecular hydrogen (H2) to characterize the clump size
distribution and to investigate the morphology and dynamics of the
interface between the ionized interior layer of the CND and the
molecular reservoir lying further out (corresponding to the inner rim
of the CND, illuminated in ultraviolet light by the central star
cluster). We have observed two fields (northeastern, NE and
southwestern, SW) of approximately 20"x20" in the CND at near-infrared
wavelengths with the OSIRIS spectro-imager at the Keck Observatory.
These two fields, located at the approaching and receding nodes of the
CND, best display this interface. Our data cover two H2 lines as
well as the Brackett gamma line of the HI spectrum (tracing HII). We
have developed the tool CubeFit, an original method to extract maps of
continuous physical parameters (such as velocity field and velocity
dispersion) from integral- field spectroscopy data, using
regularization to largely preserve spatial resolution in regions of
low signal-to-noise ratio. This original method enables us to isolate
compact, bright features in the interstellar medium of the CND.
Several clumps in the southwestern field assume the appearance of
filaments, many of which are parallel to each other. We conclude that
these clumps cannot be self-gravitating.
Description:
In this paper, we have observed two fields dubbed the northeastern
(NE) and southwestern (SW) mosaics with the OSIRIS spectro-imager. Our
spectral bandpass contains two molecular hydrogen (H2) lines, at
2.12 and 2.22 micrometers, as well as the atomic hydrogen (HI) line
Bracket gamma.
We provide here the parameter maps (Figs. 4, 5, 8, and 9) and the
associated uncertainties (Figs. B.1 to B.4). While
low-signal-two-noise and missing-data regions are masked-out in the
printed version of those maps, this electronic version includes those
regions and provides the corresponding masks in separate files. The
various panels of each figure are provided as individual FITS files
named after the following convention:
<specie>.fits
where , and have the following values:
: "NE" (for northeastern) or "SW" (for southwestern)
: "H2" (molecular hydrogen) or "HI" (Bracket gamma line)
: one of "flux", "ratio" (H2 only), "width", "velocity",
"flux_uncertainty", "ratio_uncertainty" (H2 only),
"width_uncertainty", "velocity_uncertainty", "fov", "fovinterp" and
"mask".
"flux": line flux; "ratio": flux ratio between the two considered H2
lines (only if ≡H2); "width": intrinsic line width;
"velocity": radial velocity; "flux_uncertainty", "ratio_uncertainty",
"width_uncertainty", "velocity_uncertainty": uncertainty on the above;
"fov": field-of-view mask, i.e. 1 where data where available, else 0;
"fovinterp": interpolated field-of-view mask, i.e. 1 where data where
available and where interpolation allows a reliable estimate of the
parameters (NE mosaic only); "mask": 1 where we deem the
signal-to-noise sufficient for a reliable estimate of "ratio", "width"
and "velocity" (see main text).
Objects:
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RA (2000) DE Designation(s)
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17 45 40.0 -29 00 28 Sgr A West Circumnuclear Disk = NAME CND
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 150 38 List of fits maps
fits/* . 38 Individual fits maps
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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- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 37 A10 "datime" Obs.date Observation date
39- 41 I3 Kibyte size Size of FITS file
43- 74 A32 --- FileName Name of FITS file, in subdirectory fits
76-150 A75 --- Title Title of the FITS file
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Acknowledgements:
Thibaut Paumard, thibaut.paumard(at)obspm.fr
(End) Patricia Vannier [CDS] 24-May-2022