J/A+A/673/A76 Polaris Flare CO enhancement by MHD waves (Skalidis+, 2023)
CO enhancement by magnetohydrodynamic waves. Striations in the Polaris Flare.
Skalidis R., Gkimisi K., Tassis K. Panopoulou G.V., Pelgrims V.,
Tritsis A., Goldsmith P.F.
<Astron. Astrophys. 673, A76 (2023)>
=2023A&A...673A..76S 2023A&A...673A..76S (SIMBAD/NED BibCode)
ADC_Keywords: Polarization ; Interstellar medium ; Magnetic fields ;
Carbon monoxide
Keywords: ISM: magnetic fields - polarization - ISM: kinematics and dynamics -
ISM: clouds - ISM: individual objects: Polaris Flare - ISM: abundances
Abstract:
The formation of molecular gas in interstellar clouds is a slow
process, but can be enhanced by gas compression. Magnetohydrodynamic
(MHD) waves can create compressed quasiperiodic linear structures,
referred to as striations. Striations are observed at column densities
where the atomic to molecular gas transition takes place. We explore
the role of MHD waves in the CO chemistry in regions with striations
within molecular clouds. We target a region with striations in the
Polaris Flare cloud. We conduct a CO J=2-1 survey in order to probe
the molecular gas properties. We use archival starlight polarization
data and dust emission maps in order to probe the magnetic field
properties and compare against the CO morphological and kinematic
properties. We assess the interaction of compressible MHD wave modes
with CO chemistry by comparing their characteristic timescales. The
estimated magnetic field is 38-76uG. In the CO integrated intensity
map, we observe a dominant quasi-periodic intensity structure, which
tends to be parallel to the magnetic field orientation and has a
wavelength of one parsec approximately. The periodicity axis is ∼17
degrees off from the mean magnetic field orientation and is also
observed in the dust intensity map. The contrast in the CO integrated
intensity map is ∼2.4 times larger than the contrast of the column
density map, indicating that CO formation is enhanced locally. We
suggest that a dominant slow magnetosonic mode with estimated period
2.1-3.4Myr, and propagation speed 0.30-0.45km/s, is likely to have
enhanced the formation of CO, hence created the observed periodic
pattern. We also suggest that, within uncertainties, a fast
magnetosonic mode with period 0.48Myr and velocity 2.0km/s could have
played some role in increasing the CO abundance.
Description:
We carried out CO (1-0) observations toward the target cloud with the
Purple Mountain Observatory 13.7m telescope (PMO-13.7m). We used the
Heinrich Hertz Submillimeter Telescope on Mt. Graham, Arizona, to
measure the J=2-1 transition of CO toward the target cloud. We upload
the position-position-velocity (PPV) data in a fits format.
Objects:
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RA (2000) DE Designation(s)
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11 00 14.79 +86 10 52.0 Polaris Flare = NAME Polaris Flare
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 131 1 Informations of CO (1-0) datacube
fits/* . 1 fits datacube
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See also:
J/MNRAS/452/715 : Optical polarization of the Polaris Flare (Panopoulou+, 2015)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [G]
2- 10 F9.5 deg GLON Galactic longitude of center (J2000)
11- 19 F9.5 deg GLAT Galactic latitude of center (J2000)
21- 23 I3 --- Nx Number of pixels along X-axis
25- 27 I3 --- Ny Number of pixels along Y-axis
29- 31 I3 --- Nz Number of slices
33- 40 F8.1 m/s bVELO-LSR Lower value of VELO-LSR
42- 48 F7.1 m/s BVELO-LSR Upper value of VELO-LSR
50- 56 F7.3 m/s dVELO-LSR VELO-LSR resolution
58- 63 I6 Kibyte size Size of FITS file
65- 75 A11 --- FileName Name of FITS file, in subdirectory fits
77-131 A55 --- Title Title of the FITS file
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Acknowledgements:
Raphael Skalidis, skalidis(at)caltech.edu
(End) Patricia Vannier [CDS] 10-Apr-2023