2,329 research outputs found
Inner and outer star forming regions over the disks of spiral galaxies. I. Sample characterization
Context. The knowledge of abundance distributions is central to understanding
the formation and evolution of galaxies. Most of the relations employed for the
derivation of gas abundances have so far been derived from observations of
outer disk HII regions, despite the known differences between inner and outer
regions. Aims. Using integral field spectroscopy (IFS) observations we aim to
perform a systematic study and comparison of two inner and outer HII regions
samples. The spatial resolution of the IFS, the number of objects and the
homogeneity and coherence of the observations allow a complete characterization
of the main observational properties and differences of the regions. Methods.
We analyzed a sample of 725 inner HII regions and a sample of 671 outer HII
regions, all of them detected and extracted from the observations of a sample
of 263 nearby, isolated, spiral galaxies observed by the CALIFA survey.
Results. We find that inner HII regions show smaller equivalent widths, greater
extinction and luminosities, along with greater values of
[NII]{\lambda}6583/H{\alpha} and [OII]{\lambda}3727/[OIII]{\lambda}5007
emission-line ratios, indicating higher metallicites and lower ionization
parameters. Inner regions have also redder colors and higher photometric and
ionizing masses, although Mion/Mphot is slighty higher for the outer regions.
Conclusions. This work shows important observational differences between inner
and outer HII regions in star forming galaxies not previously studied in
detail. These differences indicate that inner regions have more evolved stellar
populations and are in a later evolution state with respect to outer regions,
which goes in line with the inside-out galaxy formation paradigm.Comment: 16 page
Understanding chemical evolution in resolved galaxies -- I The local star fraction-metallicity relation
This work studies the relation between gas-phase oxygen abundance and
stellar-to-gas fraction in nearby galaxies. We first derive the theoretical
prediction, and argue that this relation is fundamental, in the sense that it
must be verified regardless of the details of the gas accretion and star
formation histories. Moreover, it should hold on "local" scales, i.e. in
regions of the order of 1 kpc. These predictions are then compared with a set
of spectroscopic observations, including both integrated and resolved data.
Although the results depend somewhat on the adopted metallicity calibration,
observed galaxies are consistent with the predicted relation, imposing tight
constraints on the mass-loading factor of (enriched) galactic winds. The
proposed parametrization of the star fraction-metallicity relation is able to
describe the observed dependence of the oxygen abundance on gas mass at fixed
stellar mass. However, the "local" mass-metallicity relation also depends on
the relation between stellar and gas surface densities.Comment: 10 pages, 4 figures. Matches accepted version (significant typo
corrected
Glomospirella cantabrica n. sp., and other benthic foraminifera from Lower Cretaceous Urgonian-type carbonates of Cantabria, Spain : biostratigraphic implications
A new benthic foraminifer is described as Glomospirella cantabrica n. sp. from several sections of the Upper Aptian Reocín Formation and one occurrence in the lowermost Albian Las Peñosas Formation of Cantabria (northern Spain). It represents a rather large-sized Glomospirella with up to eight planispiral whorls observed in lagoonal wackestones and packstones. The Upper Aptian (Late Gargasian-Clansayesian) age of the Reocín Formation is indicated by the co-occurrence with other benthic foraminifers, i.e., orbitolinids. Further data for the biostratigraphy of the Aptian-p.p. Albian shallow-water carbonates of the North Cantabrian Basin are provided. The rareness of dasycladalean green algae in these deposits is also highlighted
Supersymmetric Barotropic FRW Model and Dark Energy
Using the superfield approach we construct the supersymmetric
lagrangian for the FRW Universe with barotropic perfect fluid as matter field.
The obtained supersymmetric algebra allowed us to take the square root of the
Wheeler-DeWitt equation and solve the corresponding quantum constraint. This
model leads to the relation between the vacuum energy density and the energy
density of the dust matter.Comment: 11 pages, minor corrections, published versio
Affine convex body semigroups
In this paper we present a new kind of semigroups called convex body
semigroups which are generated by convex bodies of R^k. They generalize to
arbitrary dimension the concept of proportionally modular numerical semigroup
of [7]. Several properties of these semigroups are proven. Affine convex body
semigroups obtained from circles and polygons of R^2 are characterized. The
algorithms for computing minimal system of generators of these semigroups are
given. We provide the implementation of some of them
Cyclostratigraphy and chemostratigraphy of a bioclastic storm-dominated carbonate ramp (late Pliensbachian, Iberian Basin)
Deposition of regressive successions and coeval positive trend in the oxygen stable isotope record in relatively deep marine successions of the upper Pliensbachian of western European basins have been related to a cooling interlude within the warm greenhouse conditions of the Pliensbachian. Sedimentological, cyclostratigraphic and chemostratigraphic analyses carried out in two upper Pliensbachian successions exposed in the Iberian Chain (Obón and San Pedro localities, Spain) allowed the characterization of the imprint of this cooling interlude on the relatively shallow areas of the Iberian carbonate ramp. The upper Pliensbachian succession is characterized by skeletal limestones and encompasses proximal mid-ramp to proximal outer-ramp facies, in which resedimentation and reworking by storm-induced flows controlled the accumulation of bioclastic debris. Two orders of high-frequency, metre-scale sequences have been identified: bundles of beds, and deepening-shallowing sets of bundles. According to the age calibration (previous biostratigraphic data and new strontium isotopes data) and correlation with nearby sections, these sequences are suggested as formed in tune with the short-term and long-term eccentricity Milankovitch cycles. The isotopic data from brachiopod shells and belemnite rostra indicate progressively increasing d18O and slightly decreasing d13C trends for the uppermost Pliensbachian Spinatum Zone, reflecting the influence of cooling conditions. However, facies analysis reflects that the expected coeval long-term regression was interrupted by a tectonically driven transgressive event in the uppermost part of the Spinatum Zone
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