2,669 research outputs found
Stellar population analysis of two ellipticals
The spatial distributions of the mean luminosity-weighted stellar age,
metallicity, and alpha/Fe ratio along both photometric axes of two nearby
elliptical galaxies have been obtained using Lick index measurements on long
slit spectra in order to reconstruct the star formation history in their
kinematically distinct subsystems. Lick indexes were compared with those of
single-aged stellar population (SSP) models. A population synthesis method was
also applied in order to help disentangling the age-metallicity degeneracy. The
stars characteristics are associated with their kinematics: they are older and
alpha-enhanced in the not rotating bulge of NGC 1052 and counter rotating core
of NGC 7796, while they show a strong spread of alpha/Fe and age along the
rotating disk of NGC 1052 and an outwards radial decreasing of them outside the
core of NGC 7796.Comment: 2 pages, to appear in the Proceedings of IAU Symposium 241 "Stellar
populations as building blocks of galaxies", A. Vazdekis & R. Peletier, ed
Direct determination of the collective pinning radius in high temperature superconductors
We study finite-size effects at the onset of the irreversible magnetic
behaviour of micron-sized BiSrCaCuO single crystals by
using silicon micro-oscillators. We find an irreversibility line appearing well
below the thermodynamic Bragg-glass melting line at a magnetic field which
increases both with increasing the sample radius and with decreasing the
temperature. We show that this size-dependent irreversibility line can be
identified with the crossover between the Larkin and the random manifold
regimes of the vortex lattice transverse roughness. Our method allows to
determine the three-dimensional weak collective pinning Larkin radius in a {\it
direct way}.Comment: 4 pages, 3 fig
Polycyclic Aromatic Hydrocarbon in the Central Region of the Seyfert 2 Galaxy NGC1808
We present mid infrared (MIR) spectra of the Seyfert 2 (Sy 2) galaxy NGC
1808, obtained with the Gemini's Thermal-Region Camera Spectrograph (T-ReCS) at
a spatial resolution of 26 pc. The high spatial resolution allowed us to detect
bright polycyclic aromatic hydrocarbons (PAHs) emissions at 8.6micron and
11.3micron in the galaxy centre (26 pc) up to a radius of 70 pc from the
nucleus. The spectra also present [Ne ii]12.8micron ionic lines, and H2
S(2)12.27micron molecular gas line. We found that the PAHs profiles are similar
to Peeters's A class, with the line peak shifted towards the blue. The
differences in the PAH line profiles also suggests that the molecules in the
region located 26 pc NE of the nucleus are more in the neutral than in the
ionised state, while at 26 pc SW of the nucleus, the molecules are mainly in
ionised state. After removal of the underlying galaxy contribution, the nuclear
spectrum can be represented by a Nenkova's clumpy torus model, indicating that
the nucleus of NGC 1808 hosts a dusty toroidal structure with an angular cloud
distribution of sigma = 70degree, observer's view angle i = 90degree, and an
outer radius of R0 = 0.55 pc. The derived column density along the line of
sight is NH = 1.5 x 10^24 cm-2, which is sufficient to block the hard radiation
from the active nucleus, and would explain the presence of PAH molecules near
to the NGC 1808's active nucleus.Comment: Accepted by MNRAS 2012 December
High resolution imaging of the early-type galaxy NGC 1380: an insight into the nature of extended extragalactic star clusters
NGC 1380 is a lenticular galaxy located near the centre of the Fornax Cluster
northeast of NGC 1399. The globular cluster system of this galaxy was
previously studied only from the ground. Recent studies of similar early-type
galaxies, specially lenticular ones, reveal the existence of star clusters that
apparently break up the traditional open/globular cluster dichotomy. With
higher quality photometry from HST/WFPC2 we study the star clusters in NGC
1380, measuring their magnitudes, colours, sizes and projected distances from
the centre of the galaxy. We used deep archival HST/WFPC2 in the B and V bands.
We built colour magnitude diagrams from which we selected a sample of cluster
candidates. We also analysed their colour distribution and measured their
sizes. Based on their location in the luminosity-size diagram we estimated
probabilities of them being typical globular clusters as those found in the
Galaxy. A total of about 570 cluster candidates were found down to V=26.5. We
measured sizes for approximately 200 of them. The observed colour distribution
has three apparent peaks. Likewise for the size distribution. We identified the
smaller population as being mainly typical globular clusters, while the more
extended objects have small probabilities of being such objects. Different
correlations between absolute magnitudes, sizes, colours and location were
inferred for these cluster sub-populations. Most extended clusters (Reff > 4
pc) share similar properties to the diffuse star clusters reported to inhabit
luminous early-type galaxies in the Virgo galaxy cluster such as being of low
surface brightness and fainter than MV ~ -8. We also report on a small group of
(Reff ~ 10 pc), -8< MV < -6, red clusters located near the centre of NGC 1380,
which may be interpreted as faint fuzzies.Comment: accepted for publication in A&
Community building and memberships realtions in spanish law of the nineteenth century
El presente trabajo se ocupa de la problemática del sujeto y su pertenencia a la comunidad política en el Derecho español del siglo XIX. Se trata de indagar la trayectoria que, arrancando del orden tradicional de la Monarquía católica, desembocó en la "nacionalidad" como institución fundamental para el Estado. Para ello, se presta atención tanto a la semántica de las relaciones de pertenencia, como al cuerpo legislativo del siglo XIX, problematizado en tres espacios -público, doméstico, y nacional (por oposición a extranjero)- esenciales para el Estado en construcción. En ellos se revela una intención de monopolizar el acceso de los sujetos a la comunidad política.This paper deals with the problems of the legal subject and its political membership in Spanish law of the nineteenth century. It wants to investigate the path that starts from the traditional law of the Catholic Monarchy and leads to nationality as a fundamental legal category for the new State. For that purpose, we study both the new semantics of membership relations and the Spanish legal corpus of the ninetheenth century, divided in three problematic areas that became essential for the State-buiding process: public, domestic and national (as opposed to foreigner). They reveal an intention to monolopize the access of subjects to the political communit
Anisotropic response of the moving vortex lattice in superconducting MoGe amorphous films
We have performed magnetic susceptibility measurements in MoGe
amorphous thin films biased with an electrical current using anisotropic coils.
We tested the symmetry of the vortex response changing the relative orientation
between the bias current and the susceptibility coils. We found a region in the
DC current - temperature phase diagram where the dynamical vortex structures
behave anisotropically. In this region the shielding capability of the
superconducting currents measured by the susceptibility coils is less effective
along the direction of vortex motion compared to the transverse direction. This
anisotropic response is found in the same region where the peak effect in the
critical current is developed. On rising temperature the isotropic behavior is
recovered.Comment: 10 pages, 4 figure
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