2,005 research outputs found
Generalized strongly increasing semigroups
In this work we present a new class of numerical semigroups called
GSI-semigroups. We see the relations between them and others families of
semigroups and we give explicitly their set of gaps. Moreover, an algorithm to
obtain all the GSI-semigroups up to a given Frobenius number is provided and
the realization of positive integers as Frobenius numbers of GSI-semigroups is
studied
Formation and evolution of dwarf early-type galaxies in the Virgo cluster II. Kinematic scaling relations (Corrigendum) (vol 548, pg A76, 2012)
© ESO, 2013Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEpu
Ultrametric spaces of branches on arborescent singularities
Let be a normal complex analytic surface singularity. We say that is
arborescent if the dual graph of any resolution of it is a tree. Whenever
are distinct branches on , we denote by their intersection
number in the sense of Mumford. If is a fixed branch, we define when and
otherwise. We generalize a theorem of P{\l}oski concerning smooth germs of
surfaces, by proving that whenever is arborescent, then is an
ultrametric on the set of branches of different from . We compute the
maximum of , which gives an analog of a theorem of Teissier. We show that
encodes topological information about the structure of the embedded
resolutions of any finite set of branches. This generalizes a theorem of Favre
and Jonsson concerning the case when both and are smooth. We generalize
also from smooth germs to arbitrary arborescent ones their valuative
interpretation of the dual trees of the resolutions of . Our proofs are
based in an essential way on a determinantal identity of Eisenbud and Neumann.Comment: 37 pages, 16 figures. Compared to the first version on Arxiv, il has
a new section 4.3, accompanied by 2 new figures. Several passages were
clarified and the typos discovered in the meantime were correcte
Quattor: Tools and Techniques for the Configuration, Installation and Management of Large-Scale Grid Computing Fabrics
This paper describes the quattor tool suite, a new system for the installation, configuration, and management of operating systems and application software for computing fabrics. At present Unix derivatives such as Linux and Solaris are supported. Quattor is a powerful, portable and modular open source solution that has been shown to scale to thousands of computing nodes and offers a significant reduction in management costs for large computing fabrics. The quattor tool suite includes innovations compared to existing solutions which make it very useful for computing fabrics integrated into grid environments. Evaluations of the tool suite in current large scale computing environments are presented
Bar pattern speeds in CALIFA galaxies: I. Fast bars across the Hubble sequence
The bar pattern speed () is defined as the rotational
frequency of the bar, and it determines the bar dynamics. Several methods have
been proposed for measuring . The non-parametric method
proposed by Tremaine \& Weinberg (1984; TW) and based on stellar kinematics is
the most accurate. This method has been applied so far to 17 galaxies, most of
them SB0 and SBa types. We have applied the TW method to a new sample of 15
strong and bright barred galaxies, spanning a wide range of morphological types
from SB0 to SBbc. Combining our analysis with previous studies, we investigate
32 barred galaxies with their pattern speed measured by the TW method. The
resulting total sample of barred galaxies allows us to study the dependence of
on galaxy properties, such as the Hubble type. We measured
using the TW method on the stellar velocity maps provided by
the integral-field spectroscopy data from the CALIFA survey. Integral-field
data solve the problems that long-slit data present when applying the TW
method, resulting in the determination of more accurate . In
addition, we have also derived the ratio of the corotation radius to
the bar length of the galaxies. According to this parameter, bars can be
classified as fast ( \cal{R}\%\cal{R}$ and the galaxy morphological
type. Our results indicate that independent of the Hubble type, bars have been
formed and then evolve as fast rotators. This observational result will
constrain the scenarios of formation and evolution of bars proposed by
numerical simulations.Comment: 17 pages, 10 figures, accepted for publication in A&
First survey of Wolf-Rayet star populations over the full extension of nearby galaxies observed with CALIFA
The search of extragalactic regions with conspicuous presence of Wolf-Rayet
(WR) stars outside the Local Group is challenging task due to the difficulties
in detecting their faint spectral features. In this exploratory work, we
develop a methodology to perform an automated search of WR signatures through a
pixel-by-pixel analysis of integral field spectroscopy (IFS) data belonging to
the Calar Alto Legacy Integral Field Area survey, CALIFA. This technique
allowed us to build the first catalogue of Wolf-Rayet rich regions with
spatially-resolved information, allowing to study the properties of these
complexes in a 2D context. The detection technique is based on the
identification of the blue WR bump (around He II 4686 {\AA}, mainly associated
to nitrogen-rich WR stars, WN) and the red WR bump (around C IV 5808 {\AA} and
associated to carbon-rich WR stars, WC) using a pixel-by-pixel analysis. We
identified 44 WR-rich regions with blue bumps distributed in 25 galaxies of a
total of 558. The red WR bump was identified only in 5 of those regions. We
found that the majority of the galaxies hosting WR populations in our sample
are involved in some kind of interaction process. Half of the host galaxies
share some properties with gamma-ray burst (GRB) hosts where WR stars, as
potential candidates to being the progenitors of GRBs, are found. We also
compared the WR properties derived from the CALIFA data with stellar population
synthesis models, and confirm that simple star models are generally not able to
reproduce the observations. We conclude that other effects, such as the binary
star channel (which could extend the WR phase up to 10 Myr), fast rotation or
other physical processes that causes the loss of observed Lyman continuum
photons, are very likely affecting the derived WR properties, and hence should
be considered when modelling the evolution of massive stars.Comment: 33 pages, accepted for publication in A&
Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters
We present a homogeneous set of stellar atmospheric parameters (T-eff, log g, [Fe/H]) for MILES, a new spectral stellar library covering the range lambda lambda 3525-7500 angstrom at 2.3 angstrom (FWHM) spectral resolution. The library consists of 985 stars spanning a large range in atmospheric parameters, from super-metal-rich, cool stars to hot, metal-poor stars. The spectral resolution, spectral type coverage and number of stars represent a substantial improvement over previous libraries used in population synthesis models. The atmospheric parameters that we present here are the result of a previous, extensive compilation from the literature. In order to construct a homogeneous data set of atmospheric parameters we have taken the sample of stars of Soubiran, Katz & Cayrel, which has very well determined fundamental parameters, as the standard reference system for our field stars, and have calibrated and bootstrapped the data from other papers against it. The atmospheric parameters for our cluster stars have also been revised and updated according to recent metallicity scales, colour-temperature relations and improved set of isochrones
The O3N2 and N2 abundance indicators revisited: improved calibrations based on CALIFA and Te-based literature data
The use of IFS is since recently allowing to measure the emission line fluxes
of an increasingly large number of star-forming galaxies both locally and at
high redshift. The main goal of this study is to review the most widely used
empirical oxygen calibrations, O3N2 and N2, by using new direct abundance
measurements. We pay special attention to the expected uncertainty of these
calibrations as a function of the index value or abundance derived and the
presence of possible systematic offsets. This is possible thanks to the
analysis of the most ambitious compilation of Te-based HII regions to date.
This new dataset compiles the Te-based abundances of 603 HII regions extracted
from the literature but also includes new measurements from the CALIFA survey.
Besides providing new and improved empirical calibrations for the gas
abundance, we also present here a comparison between our revisited calibrations
with a total of 3423 additional CALIFA HII complexes with abundances derived
using the ONS calibration by Pilyugin et al. (2010). The combined analysis of
Te-based and ONS abundances allows us to derive their most accurate calibration
to date for both the O3N2 and N2 single-ratio indicators, in terms of all
statistical significance, quality and coverage of the space of parameters. In
particular, we infer that these indicators show shallower abundance
dependencies and statistically-significant offsets compared to those of Pettini
and Pagel (2004), Nagao et al. (2006) and P\'erez-Montero and Contini (2009).
The O3N2 and N2 indicators can be empirically applied to derive oxygen
abundances calibrations from either direct abundance determinations with random
errors of 0.18 and 0.16, respectively, or from indirect ones (but based on a
large amount of data) reaching an average precision of 0.08 and 0.09 dex
(random) and 0.02 and 0.08 dex (systematic; compared to the direct
estimations),respectively.Comment: 12 pages, 5 figures, accepted for publication in A&
Observational hints of radial migration in disc galaxies from CALIFA
Context. According to numerical simulations, stars are not always kept at their birth galactocentric distances but they have a tendency to migrate. The importance of this radial migration in shaping galactic light distributions is still unclear. However, if radial migration is indeed important, galaxies with different surface brightness (SB) profiles must display differences in their stellar population properties.
Aims: We investigate the role of radial migration in the light distribution and radial stellar content by comparing the inner colour, age, and metallicity gradients for galaxies with different SB profiles. We define these inner parts, avoiding the bulge and bar regions and up to around three disc scale lengths (type I, pure exponential) or the break radius (type II, downbending; type III, upbending).
Methods: We analysed 214 spiral galaxies from the CALIFA survey covering different SB profiles. We made use of GASP2D and SDSS data to characterise the light distribution and obtain colour profiles of these spiral galaxies. The stellar age and metallicity profiles were computed using a methodology based on full-spectrum fitting techniques (pPXF, GANDALF, and STECKMAP) to the Integral Field Spectroscopic CALIFA data.
Results: The distributions of the colour, stellar age, and stellar metallicity gradients in the inner parts for galaxies displaying different SB profiles are unalike as suggested by Kolmogorov-Smirnov and Anderson-Darling tests. We find a trend in which type II galaxies show the steepest profiles of all, type III show the shallowest, and type I display an intermediate behaviour.
Conclusions: These results are consistent with a scenario in which radial migration is more efficient for type III galaxies than for type I systems, where type II galaxies present the lowest radial migration efficiency. In such a scenario, radial migration mixes the stellar content, thereby flattening the radial stellar properties and shaping different SB profiles. However, in light of these results we cannot further quantify the importance of radial migration in shaping spiral galaxies, and other processes, such as recent star formation or satellite accretion, might play a role
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