2,335 research outputs found
Mass Distribution in Hickson Compact Groups of Galaxies
This study presents the mass distribution for a sample of 18 late-type
galaxies in nine Hickson Compact Groups. We used rotation curves from high
resolution 2D velocity fields of Fabry-Perot observations and J-band photometry
from the 2MASS survey, in order to determine the dark halo and the visible
matter distributions. The study compares two halo density profile, an
isothermal core-like distribution and a cuspy one. We also compare their
visible and dark matter distributions with those of galaxies belonging to
cluster and field galaxies coming from two samples: 40 cluster galaxies of
Barnes et al (2004) and 35 field galaxies of Spano et al. (2008). The central
halo surface density is found to be constant with respect to the total absolute
magnitude similar to what is found for the isolated galaxies. This suggests
that the halo density is independent to galaxy type and environment. We have
found that core-like density profiles fit better the rotation curves than
cuspy-like ones. No major differences have been found between field, cluster
and compact group galaxies with respect to their dark halo density profiles.Comment: 35 pages, 21 figures. Accept for publication in Astronomical Journa
Kinematics of galaxies in Compact Groups. Studying the B-band Tully-Fisher relation
We obtained new Fabry-Perot data cubes and derived velocity fields,
monochromatic and velocity dispersion maps for 28 galaxies in the Hickson
compact groups 37, 40, 47, 49, 54, 56, 68, 79 and 93. We find that one third of
the non-barred compact group galaxies have position angle misalignments between
the stellar and gaseous components. This and the asymmetric rotation curves are
clear signatures of kinematic perturbations, probably due to interactions among
compact group galaxies. A comparison between the B-band Tully-Fisher relation
for compact group galaxies and that for the GHASP field-galaxy sample shows
that, despite the high fraction of compact group galaxies with asymmetric
rotation curves, these lie on the Tully-Fisher relation defined by galaxies in
less dense environments, although with more scatter. This is in agreement with
previous results, but now confirmed for a larger sample of 41 galaxies. We
confirm the tendency for compact group galaxies at the low-mass end of the
Tully-Fisher relation (HCG 49b, 89d, 96c, 96d and 100c) to have either a
magnitude that is too bright for its mass (suggesting brightening by star
formation) and/or a low maximum rotational velocity for its luminosity
(suggesting tidal stripping). These galaxies are outside the Tully Fisher
relation, at the 1 sigma level, even when the minimum acceptable values of
inclinations are used to compute their maximum velocities. The inclusion of
such galaxies with v<100 km/s in the determination of the zero point and slope
of the compact group B-band Tully-Fisher relation would strongly change the
fit, making it different from the relation for field galaxies, a fact that has
to be kept in mind when studying scaling relations of interacting galaxies,
specially at high redshifts.Comment: 17 figures. Accepted for publication in Astronomy and Astrophysics.
Hickson compact groups Fabry-Perot data are available at
http://fabryperot.oamp.fr/PerotFabry
Estudio retrospectivo de 11 casos de fracturas de cúbito en aves salvajes
En este trabajo se describen 11 casos de fracturas de cúbito (con o sin afectación del radio) en aves salvajes, tratadas con distintas técnicas. Describimos el tratamiento conservador (vendajes) o quirúrico (agujas intramedulares, fijadores externos y placas de osteosÃntesis), indicando las razanos por las que, en cada caso, optamos por un tratamiento u otro en 4 de los casos. Acompañamos el artÃculo con imágnes radiográficas prequirúrgicas, posquirúrgicas inmediatas y de evolución de algunos de los casos
GHASP: an H{\alpha} kinematic survey of spiral and irregular galaxies -- IX. The NIR, stellar and baryonic Tully-Fisher relations
We studied, for the first time, the near infrared, stellar and baryonic
Tully-Fisher relations for a sample of field galaxies taken from an homogeneous
Fabry-Perot sample of galaxies (the GHASP survey). The main advantage of GHASP
over other samples is that maximum rotational velocities were estimated from 2D
velocity fields, avoiding assumptions about the inclination and position angle
of the galaxies. By combining these data with 2MASS photometry, optical colors,
HI masses and different mass-to-light ratio estimators, we found a slope of
4.48\pm0.38 and 3.64\pm0.28 for the stellar and baryonic Tully-Fisher relation,
respectively. We found that these values do not change significantly when
different mass-to-light ratios recipes were used. We also point out, for the
first time, that rising rotation curves as well as asymmetric rotation curves
show a larger dispersion in the Tully-Fisher relation than flat ones or than
symmetric ones. Using the baryonic mass and the optical radius of galaxies, we
found that the surface baryonic mass density is almost constant for all the
galaxies of this sample. In this study we also emphasize the presence of a
break in the NIR Tully-Fisher relation at M(H,K)\sim-20 and we confirm that
late-type galaxies present higher total-to-baryonic mass ratios than early-type
spirals, suggesting that supernova feedback is actually an important issue in
late-type spirals. Due to the well defined sample selection criteria and the
homogeneity of the data analysis, the Tully-Fisher relation for GHASP galaxies
can be used as a reference for the study of this relation in other environments
and at higher redshifts.Comment: 16 pages, 6 figures. Accepted for publication in MNRA
Concreciones carbonatadas en margas del Eoceno: consecuencias geomorfológicas
[Resumen] Las margas del Eoceno de la cuenca de Jaca (Pirineo Central) presentan, en numerosos lugares, una topografÃa de detalle muy caracterÃstica, en la que destacan un conjunto de núcleos más resistentes de aspecto frecuentemente esférico y de orden métrico, que permiten hablar de un paisaje de "margas con bolas". Se trata en realidad de concreciones dolomÃticas interestratificadas, menos susceptibles a los procesos erosivos que las propias margas. En este trabajo hemos intentado establecer si las diferencias mineralógicas entre concreciones carbonatadas y margas encajantes permiten explicar esta meteorización diferencial; para ello se ha estudiado la mineralogÃa de las concreciones, las margas y las margas alteradas. Se concluye que los procesos quÃmicos de alteración resultan insuficientes para explicar las diferentes tasas erosivas, debiendo por tanto atribuirse a causas fÃsicas (susceptibilidad ante la helada, procesos de humectación-desecación) la mayor erosionabilidad de las margas frente a las concreciones carbonatadas y areniscas interestratificadas.[Abstract] The Eocene marls from the Jaca basin (Central Pyrenees) show a conspicuous morphologic feature consisting of disperse hard cores, often with an spherical shape and metric size, surrounded by the marly matrix. These hard cores are dolomitic concretions isolated from the marls because of less intense weathering. In this paper we study the mineralogical composition of dolomitic concretionsand marls, in order to better define the differences in weathering processes. We conclude that chemical weathering processes do not fully explain the differences of erosion rates. We propose physical processes (frost susceptibility, dry-moist alternations) as the main erosion factors in the Eocene marls and, consequently, they are responsible for the greater erodibility of the marls compared to the dolomite concretions and interlayered sandstones
Digitalization, multinationals and employment: an empirical analysis of their causal relationships
This study measures the effects of digitalization related to Information and Communication Technologies (ICT) investment on employment and other economic variables according to firms' ownership. We present two computable general equilibrium models (with full employment and with unemployment) which differentiate two types of firms: National and foreign multinationals (MNEs). Both types of firms allow for the substitution between labour and ICT capital. We conclude that ICT investments significantly create jobs and raise real wages, GDP and welfare. The aggregate positive effects are stronger for ICT investment in national firms than in foreign MNEs although the sign of some sectoral effects can be negative. We also analyze the role of wage flexibility in this context, with the most favorable results related to scenarios where wages are more rigid for both cases, when investors are national firms or foreign MNEs. The model is applied to the case of Spain, a country with a high unemployment rate where ICT investment has been large since the mid 1990s.The authors acknowledge financial support from the Spanish Ministry of Economy and Competitiveness, through the projects ECO2013-46954-C3-1-R and ECO2017-86054-C3-2-R (A. G. Gómez-Plana) and ECO2013-41317-R and ECO2016-78422-R (M.C. Latorre)
Deep GeMS/GSAOI near-infrared observations of N159W in the Large Magellanic Cloud
Aims. The formation and properties of star clusters at the edge of H II
regions are poorly known, partly due to limitations in angular resolution and
sensitivity, which become particularly critical when dealing with extragalactic
clusters. In this paper we study the stellar content and star-formation
processes in the young N159W region in the Large Magellanic Cloud.
Methods. We investigate the star-forming sites in N159W at unprecedented
spatial resolution using JHKs-band images obtained with the GeMS/GSAOI
instrument on the Gemini South telescope. The typical angular resolution of the
images is of 100 mas, with a limiting magnitude in H of 22 mag (90 percent
completeness). Photometry from our images is used to identify candidate young
stellar objects (YSOs) in N159W. We also determine the H-band luminosity
function of the star cluster at the centre of the H II region and use this to
estimate its initial mass function (IMF).
Results. We estimate an age of 2 + or - 1 Myr for the central cluster, with
its IMF described by a power-law with an index of gamma = - 1.05 + or - 0.2 ,
and with a total estimated mass of 1300 solar mass. We also identify 104
candidate YSOs, which are concentrated in clumps and subclusters of stars,
principally at the edges of the H II region. These clusters display signs of
recent and active star-formation such as ultra-compact H II regions, and
molecular outflows. This suggests that the YSOs are typically younger than the
central cluster, pointing to sequential star-formation in N159W, which has
probably been influenced by interactions with the expanding H II bubble
Kinematics and morphology of ionized gas in Hickson Compact Group 18
We present new observations of emission in the Hickson Compact
Group 18 (HCG 18) obtained with a scanning Fabry-Perot interferometer. The
velocity field does not show motions of individual group members but, instead,
a complex common velocity field for the whole group. The gas distribution is
very asymmetric with clumps of maximum intensity coinciding with the optically
brightest knots. Comparing and HI data we conclude that HCG 18 is
not a compact group but instead a large irregular galaxy with several clumps of
star formation.Comment: Accepted for publication in Astronomical Journal (13p 6 figures
Estructura cristalina y molecular de la 2 etoxi isonitrosoacetanilida
In this paper, the crystal and molecular structure of the 2 ethosy isonitroseacetanilide has been solved by means of the X-ray diffraction and the direct methods. This compound is a isonitroseacetanilide derivative by sustitution of the ORTO hydrogen benzene ring by an ethoxy group. Space group: Pccn. Unit cell dimensions : n : 10.964 4 b : 21.884 A, c: 9.463 A, Z : 8
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