J/A+A/597/A85 NGC3627S and NGC3627N CO(1-0) data cubes (Beuther+, 2017)
Interactions of the Galactic bar and spiral arm in NGC 3627.
Beuther H., Meidt S., Schinnerer E., Paladino R., Leroy A.
<Astron. Astrophys. 597, A85 (2017)>
=2017A&A...597A..85B 2017A&A...597A..85B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Carbon monoxide ; Radial velocities
Keywords: stars: formation - galaxy: individual: NGC 3627 - stars: massive -
ISM: clouds - ISM: structure
Abstract:
To gain insight into the expected gas dynamics at the interface of the
Galactic bar and spiral arms in our own MilkyWay galaxy, we examine as
an extragalactic counterpart the evidence for multiple distinct
velocity components in the cold, dense molecular gas populating a
comparable region at the end of the bar in the nearby galaxy NGC 3627.
We assemble a high resolution view of molecular gas kinematics traced
by CO(2-1) emission and extract line-of-sight velocity profiles from
regions of high and low gas velocity dispersion.
The high velocity dispersions arise with often double-peaked or
multiple line-profiles. We compare the centroids of the different
velocity components to expectations based on orbital dynamics in the
presence of bar and spiral potential perturbations. A model of the
region as the interface of two gas-populated orbits families
supporting the bar and the independently rotating spiral arms provides
an overall good match to the data. An extent of the bar to the
corotation radius of the galaxy is favored.
Using NGC 3627 as an extragalactic example, we expect situations like
this to favor strong star formation events such as observed in our own
Milky Way since gas can pile up at the crossings between the orbit
families. The relative motions of the material following these orbits
is likely even more important for the build up of high density in the
region. The surface densities in NGC 3627 are also so high that shear
at the bar end is unlikely to significantly weaken the star formation
activity. We speculate that scenarios in which the bar and spiral
rotate at two different pattern speeds may be the most favorable for
intense star formation at such interfaces.
Description:
Paladino et al. (2008A&A...485..679P 2008A&A...485..679P) present the PdBI for the first
time, however, they focus on the CO(1-0) observations and do not
complement the data with short spacing information. The PdBI
observations were carried out on March 20, 2005 with 6 antennas in the
C configuration. At that time, 1.3 and 2.6mm data could be taken
simultaneously, and the observations targeted the CO(1-0) and (2-1)
lines, respectively. The two frequencies were centered at 114.997 and
229.88GHz which are the transition rest frequencies at an assumed
vlsr of ∼712.6km/s. With four overlapping 160MHz spectral units, the
correlator covered 580MHz for each line (corresponding to 1512 and
756km/s for the (1-0) and (2-1) lines, respectively). Bandpass and
flux calibration were conducted with 1055+018 and MWC349, and the
gains were calibrated with regular observations of 1116+128.
To complement the PdBI CO(2-1) data with the missing short spacing
information, we used the IRAM 30m single-dish observations from the
HERACLES survey (Leroy et al., 2009AJ....137.4670L 2009AJ....137.4670L). These data are
available for download at www.mpia.de/HERACLES. The HERACLES CO(2-1)
data were further processed in GILDAS/CLASS and finally combined and
imaged with the PdBI data within the mapping part of the GILDAS
package.
Objects:
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RA (2000) DE Designation(s)
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11 20 15.03 +12 59 28.6 NGC 3627 = M 66
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 120 2 List of fits datacubes
fits/* . 2 Individual fits datacubes
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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- 29 I2 --- Nz Number of slices
31- 33 I3 km/s b_VRAD Lower value of VRAD interval
35- 37 I3 km/s B_VRAD Upper value of VRAD interval
39 I1 km/s dVRAD VRAD resolution
41- 45 I5 Kibyte size Size of FITS file
47- 73 A27 --- FileName Name of FITS file, in subdirectory fits
75-120 A46 --- Title Title of the FITS file
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Acknowledgements:
Henrik Beuther, beuther(at)mpia.de
(End) Patricia Vannier [CDS] 22-Sep-2016