5,730 research outputs found
Unveiling the inner morphology and gas kinematics of NGC 5135 with ALMA
The local Seyfert 2 galaxy NGC5135, thanks to its almost face-on appearance,
a bulge overdensity of stars, the presence of a large-scale bar, an AGN and a
Supernova Remnant, is an excellent target to investigate the dynamics of
inflows, outflows, star formation and AGN feedback. Here we present a
reconstruction of the gas morphology and kinematics in the inner regions of
this galaxy, based on the analysis of Atacama Large Millimeter Array (ALMA)
archival data. To our purpose, we combine the available 100 pc resolution
ALMA 1.3 and 0.45 mm observations of dust continuum emission, the spectroscopic
maps of two transitions of the CO molecule (tracer of molecular mass in star
forming and nuclear regions), and of the CS molecule (tracer of the dense star
forming regions) with the outcome of the SED decomposition. By applying the
BAROLO software (3D-Based Analysis of Rotating Object via Line
Observations), we have been able to fit the galaxy rotation curves
reconstructing a 3D tilted-ring model of the disk. Most of the observed
emitting features are described by our kinematic model. We also attempt an
interpretation for the emission in few regions that the axisymmetric model
fails to reproduce. The most relevant of these is a region at the northern edge
of the inner bar, where multiple velocity components overlap, as a possible
consequence of the expansion of a super-bubble.Comment: 15 pages, 13 figures, resubmitted to MNRAS after moderate revision
A timeline for massive star-forming regions via combined observation of o-HD and ND
Context: In cold and dense gas prior to the formation of young stellar
objects, heavy molecular species (including CO) are accreted onto dust grains.
Under these conditions H and its deuterated isotopologues become more
abundant, enhancing the deuterium fraction of molecules such as NH that
are formed via ion-neutral reactions. Because this process is extremely
temperature sensitive, the abundance of these species is likely linked to the
evolutionary stage of the source.
Aims: We investigate how the abundances of o-HD and ND vary
with evolution in high-mass clumps.
Methods: We observed with APEX the ground-state transitions of o-HD
near 372 GHz, and ND(3-2) near 231 GHz for three massive clumps in
different evolutionary stages. The sources were selected within the
G351.77-0.51 complex to minimise the variation of initial chemical conditions,
and to remove distance effects. We modelled their dust continuum emission to
estimate their physical properties, and also modelled their spectra under the
assumption of local thermodynamic equilibrium to calculate beam-averaged
abundances.
Results: We find an anticorrelation between the abundance of o-HD and
that of ND, with the former decreasing and the latter increasing with
evolution. With the new observations we are also able to provide a qualitative
upper limit to the age of the youngest clump of about 10 yr, comparable to
its current free-fall time.
Conclusions: We can explain the evolution of the two tracers with simple
considerations on the chemical formation paths, depletion of heavy elements,
and evaporation from the grains. We therefore propose that the joint
observation and the relative abundance of o-HD and ND can act
as an efficient tracer of the evolutionary stages of the star-formation
process
Thermodynamic investigation of asynchronous open inverse air cycle integrated with compressed air energy storage
Temperature dependence of the thermal boundary resistivity of glass-embedded metal nanoparticles
The temperature dependence of the thermal boundary resistivity is
investigated in glass-embedded Ag particles of radius 4.5 nm, in the
temperature range from 300 to 70 K, using all-optical time-resolved
nanocalorimetry. The present results provide a benchmark for theories aiming at
explaining the thermal boundary resistivity at the interface between metal
nanoparticles and their environment, a topic of great relevance when tailoring
thermal energy delivery from nanoparticles as for applications in nanomedicine
and thermal management at the nanoscaleComment: 4 pages, 3 figure
Physical properties of high-mass clumps in different stages of evolution
(Abridged) Aims. To investigate the first stages of the process of high-mass
star formation, we selected a sample of massive clumps previously observed with
the SEST at 1.2 mm and with the ATNF ATCA at 1.3 cm. We want to characterize
the physical conditions in such sources, and test whether their properties
depend on the evolutionary stage of the clump.
Methods. With ATCA we observed the selected sources in the NH3(1,1) and (2,2)
transitions and in the 22 GHz H2O maser line. Ammonia lines are a good
temperature probe that allow us to accurately determine the mass and the
column-, volume-, and surface densities of the clumps. We also collected all
data available to construct the spectral energy distribution of the individual
clumps and to determine if star formation is already occurring, through
observations of its most common signposts, thus putting constraints on the
evolutionary stage of the source. We fitted the spectral energy distribution
between 1.2 mm and 70 microns with a modified black body to derive the dust
temperature and independently determine the mass.
Results. The clumps are cold (T~10-30 K), massive (M~10^2-10^3 Mo), and dense
(n(H2)>~10^5 cm^-3) and they have high column densities (N(H2)~10^23 cm^-2).
All clumps appear to be potentially able to form high-mass stars. The most
massive clumps appear to be gravitationally unstable, if the only sources of
support against collapse are turbulence and thermal pressure, which possibly
indicates that the magnetic field is important in stabilizing them.
Conclusions. After investigating how the average properties depend on the
evolutionary phase of the source, we find that the temperature and central
density progressively increase with time. Sources likely hosting a ZAMS star
show a steeper radial dependence of the volume density and tend to be more
compact than starless clumps.Comment: Published in A&A, Vol. 556, A1
Disentangling the electronic and phononic glue in a high-Tc superconductor
Unveiling the nature of the bosonic excitations that mediate the formation of
Cooper pairs is a key issue for understanding unconventional superconductivity.
A fundamen- tal step toward this goal would be to identify the relative weight
of the electronic and phononic contributions to the overall frequency (\Omega)
dependent bosonic function, \Pi(\Omega). We perform optical spectroscopy on
Bi2212 crystals with simultaneous time- and frequency-resolution; this
technique allows us to disentangle the electronic and phononic contributions by
their different temporal evolution. The strength of the interaction
({\lambda}~1.1) with the electronic excitations and their spectral distribution
fully account for the high critical temperature of the superconducting phase
transition.Comment: 9 pages, 4 figure
Schöpf-Schulz-Passarge syndrome: further delineation of the phenotype and genetic considerations.
Schöpf-Schulz-Passarge syndrome is a rare ectodermal dysplasia, characterized chiefly by multiple eyelid apocrine hidrocystomas, palmo-plantar keratoderma, hypodontia, hypotrichosis and nail dystrophy. The clinical spectrum and the most likely inheritance pattern(s) have not yet been completely defined. We report here on two, unrelated patients presenting with additional, previously unreported features, including hypoplastic nipples and optic atrophy. Both individuals were born to consanguineous parents, and one also has affected siblings. A literature review identified 23 additional cases. Multiple eyelid apocrine hidrocystomas, described in all of the cases, are the hallmark of this condition, although they usually appear in adulthood. The concomitant presence of eccrine syringofibroadenoma in most patients and of other adnexal skin tumours in 44% of affected subjects indicates that Schöpf-Schulz-Passarge is a genodermatosis with skin appendage neoplasms. However, the risk of skin and visceral malignancies is not increased. Pedigree study demonstrates that 9 of the 13 published familial cases may be explained by an autosomal recessive mutation, while the remaining pedigrees show apparent vertical transmission compatible with genetic heterogeneity. The benign disease course and advanced age at diagnosis could also suggest locus homogeneity for a recessive mutation with instances of pseudodominant inheritance
ATLASGAL-selected massive clumps in the inner Galaxy: VI. Kinetic temperature and spatial density measured with formaldehyde
We aim to directly determine the kinetic temperature and spatial density with
formaldehyde for the 100 brightest ATLASGAL-selected clumps at 870 m
representing various evolutionary stages of high-mass star formation. Ten
transitions ( = 3-2 and 4-3) of ortho- and para-HCO near 211, 218, 225,
and 291 GHz were observed with the APEX 12 m telescope. Using non-LTE models
with RADEX, we derive the gas kinetic temperature and spatial density using the
measured p-HCO 3-2/3-2,
4-3/4-3, and 4-3/3-2
ratios. The gas kinetic temperatures derived from the p-HCO
3-2/3-2 and 4-3/4-3
line ratios are high, ranging from 43 to 300 K with an unweighted average of
91 4 K. Deduced values from the = 3-2 and 4-3
transitions are similar. Spatial densities of the gas derived from the
p-HCO 4-3/3-2 line ratios yield 0.6-8.3
10 cm with an unweighted average of 1.5 (0.1)
10 cm. A comparison of kinetic temperatures derived from p-HCO,
NH, and the dust emission indicates that p-HCO traces a distinctly
higher temperature than the NH (2,2)/(1,1) transitions and the dust,
tracing heated gas more directly associated with the star formation process.
The HCO linewidths are found to be correlated with bolometric luminosity
and increase with the evolutionary stage of the clumps, which suggests that
higher luminosities tend to be associated with a more turbulent molecular
medium. It seems that the spatial densities measured with HCO do not vary
significantly with the evolutionary stage of the clumps. However, averaged gas
kinetic temperatures derived from HCO increase with time through the
evolution of the clumps.Comment: Accepted for publication in A&
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