34,101 research outputs found
Fibers in the NGC1333 proto-cluster
Are the initial conditions for clustered star formation the same as for
non-clustered star formation? To investigate the initial gas properties in
young proto-clusters we carried out a comprehensive and high-sensitivity study
of the internal structure, density, temperature, and kinematics of the dense
gas content of the NGC1333 region in Perseus, one of the nearest and best
studied embedded clusters. The analysis of the gas velocities in the
Position-Position-Velocity space reveals an intricate underlying gas
organization both in space and velocity. We identified a total of 14
velocity-coherent, (tran-)sonic structures within NGC1333, with similar
physical and kinematic properties than those quiescent, star-forming (aka
fertile) fibers previously identified in low-mass star-forming clouds. These
fibers are arranged in a complex spatial network, build-up the observed total
column density, and contain the dense cores and protostars in this cloud. Our
results demonstrate that the presence of fibers is not restricted to low-mass
clouds but can be extended to regions of increasing mass and complexity. We
propose that the observational dichotomy between clustered and non-clustered
star-forming regions might be naturally explained by the distinct spatial
density of fertile fibers in these environments.Comment: 25 pages, 17 figures; Accepted for publication in A&
Gravitational collapse of the OMC-1 region
We have investigated the global dynamical state of the Integral Shaped
Filament in the Orion A cloud using new NH (1-0) large-scale, IRAM30m
observations. Our analysis of its internal gas dynamics reveals the presence of
accelerated motions towards the Orion Nebula Cluster, showing a characteristic
blue-shifted profile centred at the position of the OMC-1 South region. The
properties of these observed gas motions (profile, extension, and magnitude)
are consistent with the expected accelerations for the gravitational collapse
of the OMC-1 region and explain both the physical and kinematic structure of
this cloud.Comment: 5 pages, 2 figures; Accepted by A&
The Musca cloud: A 6 pc-long velocity-coherent, sonic filament
Filaments play a central role in the molecular clouds' evolution, but their
internal dynamical properties remain poorly characterized. To further explore
the physical state of these structures, we have investigated the kinematic
properties of the Musca cloud. We have sampled the main axis of this
filamentary cloud in CO and CO (2--1) lines using APEX
observations. The different line profiles in Musca shows that this cloud
presents a continuous and quiescent velocity field along its 6.5 pc of
length. With an internal gas kinematics dominated by thermal motions (i.e.,
) and large-scale velocity gradients, these results
reveal Musca as the longest velocity-coherent, sonic-like object identified so
far in the ISM. The transonic properties of Musca present a clear departure
from the predicted supersonic velocity dispersions expected in the Larson's
velocity dispersion-size relationship, and constitute the first observational
evidence of a filament fully decoupled from the turbulent regime over
multi-parsec scales.Comment: 12 pages, 6 figures; Accepted for publication in A&
Unparticle inspired corrections to the Gravitational Quantum Well
We consider unparticle inspired corrections of the type
to the Newtonian potential in the context of the
gravitational quantum well. The new energy spectrum is computed and bounds on
the parameters of these corrections are obtained from the knowledge of the
energy eigenvalues of the gravitational quantum well as measured by the GRANIT
experiment.Comment: Revtex4 file, 4 pages, 2 figures and 1 table. Version to match the
one published at Physical Review
HP2 survey: III The California Molecular Cloud--A Sleeping Giant Revisited
We present new high resolution and dynamic range dust column density and
temperature maps of the California Molecular Cloud derived from a combination
of Planck and Herschel dust-emission maps, and 2MASS NIR dust-extinction maps.
We used these data to determine the ratio of the 2.2 micron extinction
coefficient to the 850 micron opacity and found the value to be close to that
found in similar studies of the Orion B and Perseus clouds but higher than that
characterizing the Orion A cloud, indicating that variations in the fundamental
optical properties of dust may exist between local clouds. We show that over a
wide range of extinction, the column density probability distribution function
(PDF) of the cloud can be well described by a simple power law with an
index that represents a steeper decline with column density than found in
similar studies of the Orion and Perseus clouds. Using only the protostellar
population of the cloud and our extinction maps we investigate the Schmidt
relation within the cloud. We show that the protostellar surface density,
, is directly proportional to the ratio of the protostellar and cloud
pdfs. We use the cumulative distribution of protostars to infer the functional
forms for both and PDF. We find that is best
described by two power-law functions with steeper indicies than found in other
local GMCs. We find that the protostellar pdf is a declining function of
extinction also best described by two power-laws whose behavior mirrors that of
. Our observations suggest that variations both in the slope of the
Schmidt relation and in the sizes of the protostellar populations between GMCs
are largely driven by variations in the slope of the cloud pdf. This confirms
earlier studies suggesting that cloud structure plays a major role in setting
the global star formation rates in GMCs.Comment: Accepted for publication in Astronomy and Astrophysics. Corrected
typos in source coordinates in table A.
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