J/A+A/642/A76 California molecular cloud CO datacubes (Zhang+, 2020)
Fragmentation of star-forming filaments in the X-shaped nebula of the
California molecular cloud.
Zhang G.-Y., Andre P., Men'shchikov A., Wang K.
<Astron. Astrophys. 642, A76 (2020)>
=2020A&A...642A..76Z 2020A&A...642A..76Z (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Carbon monoxide
Keywords: stars: formation - ISM: clouds - (ISM:) dust, extinction -
ISM: kinematics and dynamics
Abstract:
Dense molecular filaments are central to the star formation process,
but the detailed manner in which they fragment into prestellar cores
is not well understood yet.
Here, we investigate the fragmentation properties and dynamical state
of several star-forming filaments in the X-shaped nebula region of the
California molecular cloud in an effort to shed some light on this
issue.
We used multiwavelength far-infrared images from Herschel as well as
the getsources and getfilaments extraction methods to identify dense
cores and filaments in the region and derive their basic properties.
We also used a map of 13CO(2-1) emission from the Arizona 10m
Submillimeter Telescope (SMT) to constrain the dynamical state of the
filaments.
We identified ten filaments with aspect ratios of AR>4 and column
density contrasts of C>0.5, as well as 57 dense cores, including two
protostellar cores, 20 robust prestellar cores, 11 candidate
prestellar cores, and 24 unbound starless cores. All ten filaments
have roughly the same deconvolved full width at half maximum (FWHM),
with a median value of 0.12±0.03pc, which is independent of their
column densities ranging from <1021cm-2 to >1022cm-2. Two
star-forming filaments (# 8 and # 10) stand out since they harbor
quasi-periodic chains of dense cores with a typical projected core
spacing of ∼0.15pc. These two filaments have thermally supercritical
line masses and are not static. Filament 8 exhibits a prominent
transverse velocity gradient, suggesting that it is accreting gas from
the parent cloud gas reservoir at an estimated rate of
∼40±10M☉/Myr/pc. Filament 10 includes two embedded protostars
with outflows and it is likely at a somewhat later evolutionary stage
than filament 8. In both cases, the observed (projected) core spacing
is similar to the filament width and significantly shorter than the
canonical separation of ∼4 times the filament width predicted by
classical cylinder fragmentation theory. It is unlikely that
projection effects can explain this discrepancy. We suggest that the
continuous accretion of gas onto the two star-forming filaments, as
well as the geometrical bending of the filaments, may account for the
observed core spacing.
Our findings suggest that the characteristic fragmentation lengthscale
of molecular filaments is quite sensitive to external perturbations
from the parent cloud, such as the gravitational accretion of ambient
material.
Description:
XCalif_12CO21.fits and XCalif_13CO21.fits are 12CO(2-1) and
13CO(2-1) data cubes of the X-shaped nebula of the California
molecular cloud observed by SMT 10m submillimeter telescope and
processed by GILDAS CLASS.
The SMT data presented here are based on the ESO-ARO programme ID
196.C-0999(A).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 233 2 List of fits datacube
fits/* . 2 Indivudal 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- 30 I3 --- Nz Number of pixels along Z-axis
32- 39 F8.1 m/s bVRAD Lower value of VRAD interval
41- 47 F7.1 m/s BVRAD Upper value of VRAD interval
49- 55 F7.3 m/s dVRAD VRAD resolution
57- 61 I5 Kibyte size Size of FITS file
63- 80 A18 --- FileName Name of FITS file, in subdirectory fits
82-233 A152 --- Title Title of the FITS file
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Acknowledgements:
Guo-Yin Zhang, zgyin(at)nao.cas.cn
(End) Patricia Vannier [CDS] 08-Sep-2020