2,199 research outputs found
Spitzer observations of the HH 1/2 system. The discovery of the counterjet
We present unpublished Spitzer IRAC observations of the HH 1/2 young stellar outow processed
with a high angular resolution deconvolution algorithm, that produces sub-arcsecond (~ 0.6 - 0.8”)
images. In the resulting mid-infrared images, the optically invisible counterjet is detected for the first
time. The counterjet is approximately half as bright as the jet at 4.5 µm (the IRAC band that best
traces young stellar outows) and has a length of ~ 10”. The NW optical jet itself can be followed back
in the mid-IR to the position of the exciting VLA 1 source. An analysis of the IRAC colors indicates
that the jet/counterjet emission is dominated by collisionally excited H_2 pure rotational lines arising
from a medium with a neutral Hydrogen gas density of ~ 1000-2000 cm^(-3) and a temperature ~ 1500
K. The observed jet/counterjet brightness asymmetry is consistent with an intrinsically symmetric
outow with extinction from a dense, circumstellar structure of ~ 6” size (along the outow axis),
and with a mean visual extinction, A_V ~ 11 mag
New Variable Jet Models for HH 34
We consider newly derived proper motions of the HH 34 jet to reconstruct the evolution of this outflow. We first extrapolate ballistic trajectories for the knots (starting from their present-day positions and velocities) and find that at ~1000 yr in the future most of them will merge to form a larger-mass structure. This mass structure will be formed close to the present-day position of the HH 34S bow shock. We then carry out a fit to the ejection velocity versus time reconstructed from the observed proper motions (assuming that the past motion of the knots was ballistic) and use this fit to compute axisymmetric jet simulations. We find that the intensity maps predicted from these simulations do indeed match reasonably well the [S II] structure of HH 34 observed in Hubble Space Telescope images
Beta decays with momentum space Majorana spinors
We construct and apply to beta decays a truly neutral local quantum field
that is entirely based upon momentum space Majorana spinors. We make the
observation that theory with momentum space Majorana spinors of real C parities
is equivalent to Dirac's theory. For imaginary C parities, the neutrino mass
can drop from the single beta decay trace and reappear in 0\nu \beta \beta, a
curious and in principle experimentally testable signature for a non-trivial
impact of Majorana framework in experiments with polarized sources.Comment: 7 pages, 1 figure; needs svjour.cls, svepj.cl
Proper Motions of Young Stellar Outflows in the Mid-Infrared with Spitzer. II. HH 377/Cep E
We have used multiple mid-infrared observations at 4.5 micron obtained with
the Infrared Array Camera, of the compact (~1.4 arcmin) young stellar bipolar
outflow Cep E to measure the proper motion of its brightest condensations. The
images span a period of ~6 yr and have been reprocessed to achieve a higher
angular resolution (~0.8 arcsec) than their normal beam (2 arcsec).
We found that for a distance of 730 pc, the tangential velocities of the
North and South outflow lobes are 62+/-29 and 94+/-6 km/s respectively, and
moving away from the central source roughly along the major axis of the flow. A
simple 3D hydrodynamical simulation of the H2 gas in a precessing outflow
supports this idea. Observations and model confirm that the molecular Hydrogen
gas, traced by the pure rotational transitions, moves at highly supersonic
velocities without being dissociated. This suggests either a very efficient
mechanism to reform H2 molecules along these shocks or the presence of some
other mechanism (e.g. strong magnetic field) that shields the H2 gas.Comment: Accepted for publication in New Journal of Physics (Special Issue
article
Expanded Very Large Array Observations of the Nebula Around G79.29+0.46
We have observed the radio nebula surrounding the Galactic luminous blue variable candidate G79.29+0.46 with the Expanded Very Large Array (EVLA) at 6 cm. These new radio observations allow a morphological comparison between the radio emission, which traces the ionized gas component, and the mid-IR emission, a tracer of the dust component. The InfraRed Array Camera (8 ÎĽm) and the Multiband Imaging Photometer for Spitzer (24 ÎĽm and 70 ÎĽm) images have been reprocessed and compared with the EVLA map. We confirm the presence of a second shell at 24 ÎĽm and also provide evidence for its detection at 70 ÎĽm. The differences between the spatial morphology of the radio and mid-IR maps indicate the existence of two dust populations, the cooler one emitting mostly at longer wavelengths. Analysis of the two dusty, nested shells have provided us with an estimate of the characteristic timescales for shell ejection, providing important constraints for stellar evolutionary models. Finer details of the ionized gas distribution can be appreciated thanks to the improved quality of the new 6 cm image, most notably the highly structured texture of the nebula. Evidence of interaction between the nebula and the surrounding interstellar medium can be seen in the radio map, including brighter features that delineate regions where the shell structure is locally modified. In particular, the brighter filaments in the southwest region appear to frame the shocked southwestern clump reported from CO observations
The X-ray Luminosities of HH Objects
The recent detection of X-ray emission from HH 2 and HH 154 with the Chandra
and XMM-Newton satellites (respectively) have opened up an interesting, new
observational possibility in the field of Herbig-Haro objects. In order to be
able to plan further X-ray observations of other HH objects, it is now of
interest to be able to estimate their X-ray luminosities in order to choose
which objects to observe. This paper describes a simple, analytic model for
predicting the X-ray luminosity of a bow shock from the parameters of the flow
(i.e., the size of the bow shock, its velocity, and the pre-shock density). The
accuracy of the analytic model is analyzed through a comparison with the
predictions obtained from axisymmetric, gasdynamic simulations of the leading
working surface of an HH jet. We find that our analytic model reproduces the
observed X-ray luminosities of HH 2 and HH 154, and we propose that HH~80/81 is
a good candidate for future observations with Chandra.Comment: 10 pages (8 text, 2 figures
Crecimiento postraumático en padres de niños y adolescentes con cáncer.
El cáncer puede provocar reacciones psicológicas
negativas. No obstante, la lucha al abordar los problemas
oncológicos también puede dar lugar a cambios
psicolĂłgicos positivos que demuestran la fortaleza del
ser humano, siendo una de ellas el crecimiento postraumático
(CPT). El objetivo de esta revisiĂłn narrativa fue
revisar y analizar los artĂculos, publicados durante los
años 2000 a 2018 y disponibles en distintas bases de
datos, sobre el CPT en padres y madres de niños y adolescentes
con cáncer en el ámbito pediátrico.
Se identificaron 20 estudios que incluĂan 2.422 sujetos,
mayoritariamente madres (n=1.788), y que analizaban
el CPT en funciĂłn del parentesco, evoluciĂłn y tipo
de enfermedad del hijo, asĂ como factores predictores
del mismo. Tanto padres como madres, son capaces de
desarrollar CPT como consecuencia de la experiencia
del cáncer de sus hijos, siendo ellas quienes experimentan
mayores niveles. En comparaciĂłn con otras muestras
como progenitores de niños con diabetes tipo I o
de niños sanos, o pacientes adultos con osteosarcoma,
los padres y madres de niños con cáncer refieren mayor
CPT. Asimismo, se observan factores que influyen en el
desarrollo del CPT, como el contexto cultural, el procesamiento
cognitivo, el ajuste a la enfermedad y ciertos
rasgos de personalidad.
La evidencia cientĂfica publicada avala la existencia
de CPT en madres y padres de hijos con cáncer. No
obstante, serĂa necesario realizar estudios objetivos,
longitudinales, con muestras homogéneas de mayor
tamaño, para diseñar intervenciones dirigidas a promocionar
ese CPT y no centrarse solo en los aspectos
negativos de la enfermedad.post-print213 K
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