J/A+A/647/A138 Taffy system CO(1-0) datacube (Vollmer+, 2021)
Low star formation efficiency due to turbulent adiabatic compression in the
Taffy bridge.
Vollmer B., Braine J., Mazzilli-Ciraulo B., Schneider B.
<Astron. Astrophys. 647, A138 (2021)>
=2021A&A...647A.138V 2021A&A...647A.138V (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, optical ; Interstellar medium ; Carbon monoxide
Keywords: galaxies: interactions - galaxies: ISM
Abstract:
The Taffy system (UGC 12914/15) consists of two massive spiral
galaxies which had a head-on collision about 20Myr ago. New
sensitive, high-resolution CO(1-0) observations of the Taffy system
with the IRAM PdBI are presented. About 25% of the total
interferometric CO luminosity stems from the bridge region. Assuming a
Galactic N(H2)/ICO conversion factor for the galactic disks and a
third of this value for the bridge gas, about 10% of the molecular gas
mass is located in the bridge region. The giant HII region close to
UGC 12915 is located at the northern edge of the high-surface
brightness giant molecular cloud association (GMA), which has the
highest velocity dispersion among the bridge GMAs. The bridge GMAs are
clearly not virialized because of their high velocity dispersion.
Three dynamical models are presented and while no single model
reproduces all of the observed features, they are all present in at
least one of the models. Most of the bridge gas detected in CO does
not form stars. We suggest that turbulent adiabatic compression is
responsible for the exceptionally high velocity dispersion of the
molecular ISM and the suppression of star formation in the Taffy
bridge. In this scenario the turbulent velocity dispersion of the
largest eddies and turbulent substructures/clouds increase such that
giant molecular clouds are no longer in global virial equilibrium. The
increase of the virial parameter leads to a decrease of the star
formation efficiency. Most of the low-surface density, CO-emitting gas
will disperse without forming stars but some of the high-density gas
will probably collapse and form dense star clusters, such as the
luminous HII region close to UGC 12915. We suggest that globular
clusters and super star clusters formed and still form through the
gravitational collapse of gas previously compressed by turbulent
adiabatic compression during galaxy interactions.
Description:
Observations of the 12CO(1-0) emission were carried out with the
IRAM Plateau de Bure Interferometer (PdBI) in summer 2014 using all
six antennas in C and D configuration. The system was covered by a
mosaic of 11 PdBI primary beams.
Each position was observed during 55 min.
The bandpasses calibration was on 3C454.3 on May 30 and Nov 21 and on
1749+096 on May 29.
Phase and amplitude calibrations were performed on 2319+272 (every
day), 0007+171 (21 nov), and 0006+243 (May 29 and 30).
The absolute flux scale was checked on MWC 349 every day. A total
bandwidth of 640MHz with a spectral resolution of 2.5MHz was used.
We reach an rms of ∼5mJy in 6.5km/s wide velocity channels. Applying
robust weighting in the mapping process, a beam size of 2.7" (∼800pc)
was derived.
Objects:
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RA (2000) DE Designation(s)
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00 01 40.12 +23 29 23.0 NAME Taffy System = VV 254
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 116 1 Information on fits datacube
fits/* . 1 Fits datacube
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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- 30 I3 --- Nz Number of slices
32- 42 E11.6 m/s bVRAD Lower value of VRAD interval
44- 54 E11.6 m/s BVRAD Upper value of VRAD interval
56- 61 F6.1 m/s dVRAD VRAD resolution
63- 68 I6 Kibyte size Size of FITS file
70- 82 A13 --- FileName Name of FITS file, in subdirectory fits
84-116 A33 --- Title Title of the FITS file
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Acknowledgements:
Based on observations carried out with the IRAM Plateau de Bure
Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany)
and IGN (Spain).
From Bernd Vollmer, Bernd.Vollmer(at)astro.unistra.fr
(End) Patricia Vannier [CDS] 27-Jan-2021