J/A+A/592/A142 Reduced high-resolution HI and CO data cubes (Roehser+, 2016)
High-resolution HI and CO observations of high-latitude intermediate-velocity
clouds.
Roehser T., Kerp J., Ben Bekhti N., Winkel B.
<Astron. Astrophys. 592, A142 (2016)>
=2016A&A...592A.142R 2016A&A...592A.142R (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Interstellar medium ; H I data ; Carbon monoxide ;
Spectroscopy
Keywords: instrumentation: high angular resolution - Galaxy: halo -
ISM: clouds - ISM: structure - ISM: molecules
Abstract:
Intermediate-velocity clouds (IVCs) are HI halo clouds that are likely
related to a Galactic fountain process. In-falling IVCs are candidates
for the re-accretion of matter onto the Milky Way. Aims. We study the
evolution of IVCs at the disk-halo interface, focussing on the
transition from atomic to molecular IVCs. We compare an atomic IVC to
a molecular IVC and characterise their structural differences in order
to investigate how molecular IVCs form high above the Galactic plane.
With high-resolution HI observations of the Westerbork Synthesis Radio
Telescope and 12CO(1-0) and 13CO(1-0) observations with the IRAM
30m telescope, we analyse the small-scale structures within the two
clouds. By correlating HI and far-infrared (FIR) dust continuum
emission from the Planck satellite, the distribution of molecular
hydrogen (H2) is estimated. We conduct a detailed comparison of the
HI, FIR, and CO data and study variations of the XCO conversion
factor. The atomic IVC does not disclose detectable CO emission. The
atomic small-scale structure, as revealed by the high-resolution HI
data, shows low peak HI column densities and low HI fluxes as compared
to the molecular IVC. The molecular IVC exhibits a rich molecular
structure and most of the CO emission is observed at the eastern edge
of the cloud. There is observational evidence that the molecular IVC
is in a transient and, thus, non- equilibrium phase. The average XCO
factor is close to the canonical value of the Milky Way disk. We
propose that the two IVCs represent different states in a gradual
transition from atomic to molecular clouds. The molecular IVC appears
to be more condensed allowing the formation of H2 and CO in shielded
regions all over the cloud. Ram pressure may accumulate gas and thus
facilitate the formation of H2. We show evidence that the atomic IVC
will evolve also into a molecular IVC in a few Myr.
Description:
The spectral data cubes of the reduced high-resolution observations
are provided for both clouds (mIVC and aIVC) in standard FITS format.
For more details, compare with Table 1 of the corresponding
publication.
(1) The high-resolution 21-cm emission of neutral atomic hydrogen was
observed with the Westerbork Synthesis Radio Telescope (Netherlands).
The mIVC was covered with a single pointing, the aIVC with two
pointings (denoted as aIVC1 and aIVC2). The Westerbork HI data is
provided in Equatorial Coordinates with SIN projection, satisfying the
WCS standard (Greisen & Calabretta, 2002A&A...395.1061G 2002A&A...395.1061G, Calabretta &
Greisen, 2002A&A...395.1077C 2002A&A...395.1077C, Greisen et al., 2006A&A...446..747G 2006A&A...446..747G).
(2) The rotational emission lines 12CO(1-0) and 13CO(1-0) were
observed with the IRAM 30-m telescope (Spain) using the FTS
spectrometer (Klein et. al, 2012A&A...542L...3K 2012A&A...542L...3K). For the aIVC, the
empty 12CO(1-0) data cube is provided. The IRAM CO data is gridded
in Equatorial Coordinates with GLS projection, satisfying the WCS
standard.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 138 6 List of fits datacubes
fits/* . 6 Individual data cubes
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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 (J2000) of data cube center
10- 18 F9.5 deg DEdeg Declination (J2000) of data cube center
20- 23 I4 pix Nx Number of pixels along X-axis
25- 28 I4 pix Ny Number of pixels along Y-axis
30- 32 I3 pix Nz Number of slices
34- 59 A26 --- Obs.Date Observation date (YYYY-MM-DDThh:mm:ss.ssssss)
61- 67 F7.2 km/s VLSRl Lower value of LSR velocity interval
69- 73 F5.2 km/s VLSRu Upper value of LSR velocity interval
75- 78 F4.2 km/s dVLSR Spectral resolution in LSR velocity
80- 85 I6 Kibyte size Size of FITS file
87-107 A21 --- FileName Name of the FITS file in subdirectory fits
109-138 A30 --- Title Title of the fits file
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Acknowledgements:
Tobias Roehser, troehser(at)astro.uni-bonn.de
(End) Patricia Vannier [CDS] 04-Aug-2016