2,915 research outputs found
The Coldest Place in the Universe: Probing the Ultra-Cold Outflow and Dusty Disk in the Boomerang Nebula
Our Cycle 0 ALMA observations confirmed that the Boomerang Nebula is the
coldest known object in the Universe, with a massive high-speed outflow that
has cooled significantly below the cosmic background temperature. Our new CO
1-0 data reveal heretofore unseen distant regions of this ultra-cold outflow,
out to AU. We find that in the ultra-cold outflow, the
mass-loss rate (dM/dt) increases with radius, similar to its expansion velocity
() - taking , we find . The mass in
the ultra-cold outflow is Msun, and the Boomerang's main-sequence
progenitor mass is Msun. Our high angular resolution (0".3) CO
J=3-2 map shows the inner bipolar nebula's precise, highly-collimated shape,
and a dense central waist of size (FWHM) 1740 AU AU. The
molecular gas and the dust as seen in scattered light via optical HST imaging
show a detailed correspondence. The waist shows a compact core in thermal dust
emission at 0.87-3.3 mm, which harbors Msun~of very large
(mm-to-cm sized), cold ( K) grains. The central waist
(assuming its outer regions to be expanding) and fast bipolar outflow have
expansion ages of yr and yr: the "jet-lag" (i.e.,
torus age minus the fast-outflow age) in the Boomerang supports models in which
the primary star interacts directly with a binary companion. We argue that this
interaction resulted in a common-envelope configuration while the Boomerang's
primary was an RGB or early-AGB star, with the companion finally merging into
the primary's core, and ejecting the primary's envelope that now forms the
ultra-cold outflow.Comment: accepted ApJ, 12 Apr, 201
The Breathing Modes of the Skyrmion and the Spin-Orbit Interaction
The coupling of the breathing and rotational modes of the skyrmion-skyrmion
system leads to a nucleon-nucleon spin-orbit interaction of short range, as
well as to spin-orbit potentials for the transitions , and . The longest range behaviour of these
spin-orbit potentials is calculated in closed form.Comment: Latex, figures not include
Minimally-destructive detection of magnetically-trapped atoms using frequency-synthesised light
We present a technique for atomic density measurements by the off-resonant
phase-shift induced on a two-frequency, coherently-synthesised light beam. We
have used this scheme to measure the column density of a magnetically trapped
atom cloud and to monitor oscillations of the cloud in real time by making over
a hundred non-destructive local density measurments. For measurements using
pulses of 10,000-100,000 photons lasting ~10 microsecond, the precision is
limited by statistics of the photons and the photodiode avalanche. We explore
the relationship between measurement precision and the unwanted loss of atoms
from the trap and introduce a figure of merit that characterises it. This
method can be used to probe the density of a BEC with minimal disturbance of
its phase.Comment: Submitted to New Journal of Physic
Anomalous radio emission from dust in the Helix
A byproduct of experiments designed to map the CMB is the recent detection of
a new component of foreground Galactic emission. The anomalous foreground at ~
10--30 GHz, unexplained by traditional emission mechanisms, correlates with
100um dust emission. We report that in the Helix the emission at 31 GHz and
100um are well correlated, and exhibit similar features on sky images, which
are absent in H\beta. Upper limits on the 250 GHz continuum emission in the
Helix rule out cold grains as candidates for the 31 GHz emission, and provide
spectroscopic evidence for an excess at 31 GHz over bremsstrahlung. We estimate
that the 100um-correlated radio emission, presumably due to dust, accounts for
at least 20% of the 31 GHz emission in the Helix. This result strengthens
previous tentative interpretations of diffuse ISM spectra involving a new dust
emission mechanism at radio frequencies. Very small grains have not been
detected in the Helix, which hampers interpreting the new component in terms of
spinning dust. The observed iron depletion in the Helix favors considering the
identity of this new component to be magnetic dipole emission from hot
ferromagnetic grains. The reduced level of free-free continuum we report also
implies an electronic temperature of Te=4600\pm1200K for the free-free emitting
material, which is significantly lower than the temperature of 9500\pm500K
inferred from collisionally-excited lines (abridged).Comment: Accepted for publication in Ap
The evolutionary state of the southern dense core Cha-MMS1
Aims: Our goal is to set constraints on the evolutionary state of the dense
core Cha-MMS1 in the Chamaeleon I molecular cloud. Methods: We analyze
molecular line observations carried out with the new submillimeter telescope
APEX. We look for outflow signatures around the dense core and probe its
chemical structure, which we compare to predictions of models of gas-phase
chemistry. We also use the public database of the Spitzer Space Telescope (SST)
to compare Cha-MMS1 with the two Class 0 protostars IRAM 04191 and L1521F,
which are at the same distance. Results: We measure a large deuterium
fractionation for N2H+ (11 +/- 3 %), intermediate between the prestellar core
L1544 and the very young Class 0 protostar L1521F. It is larger than for HCO+
(2.5 +/- 0.9 %), which is probably the result of depletion removing HCO+ from
the high-density inner region. Our CO(3-2) map reveals the presence of a
bipolar outflow driven by the Class I protostar Ced 110 IRS 4 but we do not
find evidence for an outflow powered by Cha-MMS1. We also report the detection
of Cha-MMS1 at 24, 70 and 160 microns by the instrument MIPS of the SST, at a
level nearly an order of magnitude lower than IRAM 04191 and L1521F.
Conclusions: Cha-MMS1 appears to have already formed a compact object, either
the first hydrostatic core at the very end of the prestellar phase, or an
extremely young protostar that has not yet powered any outflow, at the very
beginning of the Class 0 accretion phase.Comment: Accepted by Astronomy & Astrophysics as a letter, to appear in the
special issue on the APEX first result
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