271 research outputs found
Searching for compact radio sources associated to UCHII regions
Ultra-Compact (UC)HII regions represent a very early stage of massive star
formation whose structure and evolution are not yet fully understood.
Interferometric observations in recent years show that some UCHII regions have
associated compact sources of uncertain nature. Based on this, we carried out
VLA 1.3 cm observations in the A configuration of selected UCHII regions in
order to report additional cases of compact sources embedded in UCHII regions.
From the observations, we find 13 compact sources associated to 9 UCHII
regions. Although we cannot establish an unambiguous nature for the newly
detected sources, we assess some of their observational properties. According
to the results, we can distinguish between two types of compact sources. One
type corresponds to sources that probably are deeply embedded in the dense
ionized gas of the UCHII region. These sources are being photo-evaporated by
the exciting star of the region and will last for 10 yr. They may play
a crucial role in the evolution of the UCHII region as the photo-evaporated
material could replenish the expanding plasma and might provide a solution to
the so-called lifetime problem for these regions. The second type of compact
sources is not associated with the densest ionized gas of the region. A few of
these sources appear resolved and may be photo-evaporating objects such as
those of the first type but with significantly lower mass depletion rates. The
rest of sources of this second type appear unresolved and their properties are
varied. We speculate on the similarity between the sources of the second type
and those of the Orion population of radio sources.Comment: 33 pages, 6 figures, 4 tables. Accepted for publication in Ap
Multiple Sources toward the High-mass Young Star S140 IRS1
S140 IRS1 is a remarkable source where the radio source at the center of the
main bipolar molecular outflow in the region is elongated perpendicular to the
axis of the outflow, an orientation opposite to that expected if the radio
source is a thermal jet exciting the outflow. We present results of 1.3 cm
continuum and H2O maser emission observations made with the VLA in its A
configuration toward this region. In addition, we also present results of
continuum observations at 7 mm and re-analyse observations at 2, 3.5 and 6 cm
(previously published). IRS 1A is detected at all wavelengths, showing an
elongated structure. Three water maser spots are detected along the major axis
of the radio source IRS 1A. We have also detected a new continuum source at 3.5
cm (IRS 1C) located ~0.6'' northeast of IRS 1A. The presence of these two YSOs
(IRS 1A and 1C) could explain the existence of the two bipolar molecular
outflows observed in the region. In addition, we have also detected three
continuum clumps (IRS 1B, 1D and 1E) located along the major axis of IRS 1A. We
discuss two possible models to explain the nature of IRS 1A: a thermal jet and
an equatorial wind.Comment: 17 pages, 4 figures, to be published in A
The ultracompact regions G40.54+2.59 and G34.13+0.47: A new detection of compact radio sources
We report the detection of three compact ( pc) radio sources (CRSs)
at K-band (0.9 cm) in the \uchiirs G040.54+2.59 (two CRSs) and
G034.13+0.47 (one CRS). These CRSs have weak flux densities and are located at
the center of their respective \uchii regions. We found no clear association
between massive ionizing stars and CRSs but some radiative influence on the
latter, as suggested by their large emission measures (> ), typical of photo evaporating neutral objects
close to or associated with massive stars. Our modelling of G40.54+2.59 shows
that their CRSs supply enough ionized material to shape its morphology while
significantly extending its observable lifetime. On the other hand, despite the
possible relation of the CRS with the large-scale outflow signatures observed
in G034.13+0.47, the influence of this CRS on the evolution of the \uchii
region is unlikely. Our results show that the presence of CRSs can alleviate
the so-called lifetime problem of UCHII regions. Still, to address their
dynamical evolution adequately, the scenario must include additional mechanisms
like ambient confinement, or the role of the kinematics of their associated
stellar objects.Comment: Published in Publications of the Astronomical Society of Japan,
Volume 75, Issue 1, February 2023, Pages 90-102,
https://doi.org/10.1093/pasj/psac09
Cambios en el panorama televisivo español: ¿Hacia qué modelo nos encaminamos?
El presente artĂculo repasa la evoluciĂłn legislativa española en el terreno audiovisual hasta la reciente aprobaciĂłn de la Ley General de la ComunicaciĂłn Audiovisual. El texto analiza la influencia del nuevo marco en el mercado televisivo en tres aspectos fundamentales: el pluralismo, la concentraciĂłn y la contribuciĂłn a la producciĂłn audiovisual, con vistas a su incidencia en el modelo audiovisual español y, mĂĄs especĂficamente, el desarrollo de la televisiĂłn de pago. Del examen de este proceso los autores extraen un notable retroceso en estas materias.This paper reviews the legal Spanish evolution in the audiovisual context till the approval of the
new Communication Act. The text analyses the effect of this new framework in the television market from
three main perspectives: pluralism, concentration and audiovisual production, in regard to their influence in
the audiovisual Spanish model and the development of pay TV. The authors observe some important
backward movements from the study of this process.Publicad
Collision of molecular outflows in the L1448--C system
We present a study of the central zone of the star-forming region L1448 at
217--230 GHz ( 1.3 mm) using ALMA observations. Our study focuses on the
detection of proto-stellar molecular outflows and the interaction with the
surrounding medium toward sources L1448--C(N) and L1448--C(S). Both sources
exhibit continuum emission, with L1448--C(N) being the brightest one. Based on
its spectral index and the associated bipolar outflow, the continuum emission
is the most likely to be associated with a circumstellar disk. The CO(J=21) and SiO(J= 54) emissions associated with
L1448--C(N) trace a bipolar outflow and a jet oriented along the
northwest-southeast direction. The CO(J=21) outflow for
L1448--C(N) has a wide-open angle and a V-shape morphology. The SiO jet is
highly collimated and has an axial extent comparable with the CO(J=21) emission. There is not SiO(J= 54)
emission towards L1448--C(S), but there is CO(J=21)
emission. The observations revealed that the red-shifted lobes of the CO(J=21) outflows of L1448--C(N) and L1448--C(S) are
colliding. As a result of this interaction, the L1448-C(S) lobe seems to be
truncated. The collision of the molecular outflows is also hinted by the SiO(J=
54) emission, where the velocity dispersion increases
significantly in the interaction zone. We also investigated whether it could be
possible that this collision triggers the formation of new stars in the
L1448--C system.Comment: 11 pages, 7 figures, Accepted for publication in Monthly Notices of
the Royal Astronomical Society (MNRAS) DOI: 10.1093/mnras/stad98
Evolution induced by dry minor mergers onto fast-rotator S0 galaxies
We analysed collisionless N-body simulations of intermediate and minor dry
mergers onto S0s to test whether these mergers can generate S0 galaxies with
kinematics intermediate between fast and slow rotators. We find that minor
mergers induce a lower decrease of the global rotational support than
encounters of lower mass ratios, which results in S0s with properties
intermediate between fast and slow rotators. The resulting remnants are
intrinsically more triaxial, less flattened, and span the whole range of
apparent ellipticities up to . They do not show
lower apparent ellipticities in random projections than initially; on the
contrary, the formation of oval distortions and the disc thickening increase
the percentage of projections at . In the
experiments with S0b progenitor galaxies, minor mergers tend to spin up the
bulge and to decrease slightly its intrinsic ellipticity, whereas in the cases
of primary S0c galaxies they keep the rotational support of the bulge nearly
constant and decrease significantly its intrinsic ellipticity. The remnant
bulges remain nearly spherical (), but exhibit a wide range
of triaxialities (). In the plane of global anisotropy of
velocities () vs. intrinsic ellipticity (),
some of our models extend the linear trend found in previous major merger
simulations towards higher values, while others
depart from it. This is consistent with the wide dispersion exhibited by real
S0s in this diagram compared with ellipticals, which follow the linear trend
drawn by major merger simulations. The different trends exhibited by
ellipticals and S0 galaxies in the - diagram may
be pointing to the different role played by major mergers in the build-up of
each morphological type.Comment: Corrected typos. 20 pages, 14 figures. Accepted for publishing in A&
EphrinA4 plays a critical role in α4 and αL mediated survival ofhuman CLL cells during extravasation
A role of endothelial cells in the survival of CLL cells during extravasation is presently unknown. Herein we show that CLL cells but not normal B cells can receive apoptotic signals through physical contact with TNF-α activated endothelium impairing survival in transendothelial migration (TEM) assays. In addition, the CLL cells of patients having lymphadenopathy (LApos) show a survival advantage during TEM that can be linked to increased expression of α4 and αL integrin chains. Within this context, ephrinA4 expressed on the surface of CLL cells sequestrates integrins and inactivates them resulting in reduced adhesion and inhibition of apoptotic/survival signals through them. In agreement, ephrinA4 silencing resulted in increased survival of CLL cells of LApos patients but not LA neg patients. Similarly was observed when a soluble ephrinA4 isoform was added to TEM assays strongly suggesting that accumulation of this isoform in the serum of LApos patients could contribute to CLL cells dissemination and survival in vivo. In supporting, CLL lymphadenopathies showed a preferential accumulation of apoptotic CLL cells around high endothelial venules lacking ephrinA4. Moreover, soluble ephrinA4 isolated from sera of patients increased the number and viability of CLL cells recovered from the lymph nodes of adoptively transferred mice. Finally, we present evidence suggesting that soluble ephrinA4 mediated survival during TEM could enhance a transcellular TEM route of the CLL cells. Together these findings point to an important role of ephrinA4 in the nodal dissemination of CLL cells governing extravasation and survival
A Rapid and Accurate Extraction Procedure for Analysing Free Amino Acids in Meat Samples by GC-MS
This study evaluated the use of a mixer mill as the homogenization tool for the extraction of free amino acids in meat samples, with the main goal of analyzing a large number of samples in the shortest time and minimizing sample amount and solvent volume. Ground samples (0.2âg) were mixed with 1.5âmLâHCl 0.1âM and homogenized in the mixer mill. The final biphasic system was separated by centrifugation. The supernatant was deproteinized, derivatized and analyzed by gas chromatography. This procedure showed a high extracting ability, especially in samples with high free amino acid content (recovery = 88.73â104.94%). It also showed a low limit of detection and quantification (3.8 · 10â4â6.6 · 10â4âÎŒgâÎŒLâ1 and 1.3 · 10â3â2.2 · 10â2âÎŒgâÎŒLâ1, resp.) for most amino acids, an adequate precision (2.15â20.15% for run-to-run), and a linear response for all amino acids (R2 = 0.741â0.998) in the range of 1â100â”gâmLâ1. Moreover, it takes less time and requires lower amount of sample and solvent than conventional techniques. Thus, this is a cost and time efficient tool for homogenizing in the extraction procedure of free amino acids from meat samples, being an adequate option for routine analysis
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