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Due to its proximity, the stellar populations of the Galactic bulge (GB) can be resolved and can be studied in detail. This allows tracing the bulge metallicity distribution function (MDF) for different spatial regions within the bulge, which may give us clues about the bulge formation and evolution scenarios. In this work, we developed a chemical evolution model (CEM), taking into account the mass distribution in the bulge and disc, to derive the radial dependence of this time-scale in the Galaxy. Since the infall rate depends on that time scale in the CEM, the results of the model were used to test a scenario where the bulge is formed inside-out. The obtained results for the $[\alpha/\mbox{Fe}]$ vs. [Fe/H] relationship, the MDF and the [Fe/H] radial gradient in the bulge have been compared to available data in the literature. The model is able to reproduce most of the observational data: the spread in the relation $[\alpha/\mbox{Fe}]$ vs. [Fe/H], the MDF shape in different regions of the bulge, the [Fe/H] radial gradient inside it and the age-metallicity relation, as well as the [$\alpha$/Fe] evolution with age. The results of the model point to a scenario where the bulk of the bulge stars pre-existed the boxy/peanut X-shape bar formation. As a result, the classical origin of the GB is not ruled out and this scenario may be invoked to explain the chemical properties of the Galactic bulge., Comment: 16 pages, 11 figures. Accepted for publication in MNRAS

We present a self-consistent prediction of the interstellar radiation field (ISRF), from the extreme ultraviolet (EUV) to sub-mm range, based on two chemical evolution models of a Milky Way-like galaxy (MWG). To this end, we develop a new tool called Mixclask to include gas emission, absorption and scattering from the photoionization code Cloudy into the Monte Carlo radiative transfer code Skirt. Both algorithms are invoked iteratively, until the physical properties of the ISM converge. We have designed a first test, reminiscent of a HII region, and we find that the results of Mixclask are in good agreement with a spherically symmetric Cloudy simulation. Both MWG models based on chemical evolution codes give results broadly consistent with previous empirical models reported in the literature for the ISRF of our Galaxy, albeit they systematically underestimate the mid-infrared emission. We also find significant differences between our two models in the whole ultraviolet range, not fully explored in previous ISRF models. These results show the feasibility of our method of combining radiative transfer with chemical evolution models: there is increased predictive power and the interstellar radiation field obtained provides further constraints on the model parameters. Python source code to implement our method is publicly available at https://github.com/MarioRomeroC/Mixclask., Comment: 16 pages, 7 figures, 3 tables. Accepted for publication in MNRAS

We use type Ia supernovae (SNe Ia) data obtained by the Sloan Digital Sky Survey-II Supernova Survey (SDSS-II/SNe) in combination with the publicly available SDSS DR16 fiber spectroscopy of their host galaxies to correlate SNe Ia light-curve parameters and Hubble residuals to several host galaxy properties. Fixed-aperture fiber spectroscopy suffers from aperture effects: the fraction of the galaxy covered by the fiber varies depending on its projected size on the sky, thus measured properties are not representative of the whole galaxy. The advent of Integral Field Spectroscopy has provided a way for correcting the missing light, by studying how these galaxy parameters change with the aperture size. Here we study how the standard SN host galaxy relations change once global host galaxy parameters are corrected for aperture effects. We recover previous trends on SN Hubble residuals with host galaxy properties, but we find that discarding objects with poor fiber coverage instead of correcting for aperture loss introduces biases in the sample that affect SN host galaxy relations. The net effect of applying the commonly used $g$-band fraction criterion is discarding intrinsically faint \mbox{SNe~Ia} in high-mass galaxies, thus artificially increasing the height of the mass step by 0.02 mag and its significance. Current and next generation of fixed-aperture fiber spectroscopy surveys, such as DES, DESI or TiDES in 4MOST, that aim at study SN and galaxy correlations must consider, and correct for, these effects., Comment: Accepted in A&A. 16 pages, 12 Figures

We carry out 1D hydrodynamical simulations of the evolution of a spherically symmetric supernova remnant (SNR) subject to an external radiation field (ERF) that influences the cooling and heating rates of the gas. We consider homogeneous media with ambient hydrogen number densities $n_{\rm H,0}$ of $0.1$ and $1$ cm$^{-3}$ permeated by an average radiation field including the cosmic microwave, extragalactic, and Galactic backgrounds, attenuated by an effective column density $N_{\rm H,eff}$ from $10^{18}$ to $10^{21}$~cm$^{-2}$. Our results may be classified into two broad categories: at low $N_{\rm H,eff}$, the ERF presents little absorption in the ultraviolet (ionising) regime, and all the 'unshielded' cases feature an equilibrium temperature $T_{eq} \sim 7000$~K below which the ambient gas cannot cool further. In this scenario, the SNR develops a nearly isothermal shock profile whose shell becomes thicker over time. At higher $N_{\rm H,eff}$, the ERF is heavily absorbed in the UV range, yielding a roughly constant heating function for temperatures $\lesssim 10^4$ K. These `shielded' cases develop a thin, cold and dense shell throughout their evolution. Energy and momentum injection to the medium do not change significantly between both scenarios, albeit luminosity is higher and more uniformly distributed over the shell for unshielded SNR., Comment: 12 pages, 5 figures, 2 tables. Accepted in MNRAS

We present a 2-dimensional chemical evolution code applied to a Milky Way type galaxy, incorporating the role of spiral arms in shaping azimuthal abundance variations, and confront the predicted behaviour with recent observations taken with integral field units. To the usual radial distribution of mass, we add the surface density of the spiral wave and study its effect on star formation and elemental abundances. We compute five different models: one with azimuthal symmetry which depends only on radius, while the other four are subjected to the effect of a spiral density wave. At early times, the imprint of the spiral density wave is carried by both the stellar and star formation surface densities; conversely, the elemental abundance pattern is less affected. At later epochs, however, differences among the models are diluted, becoming almost indistinguishable given current observational uncertainties. At the present time, the largest differences appear in the star formation rate and/or in the outer disc (R$\ge$ 18\,kpc). The predicted azimuthal oxygen abundance patterns for $t \le 2$\,Gyr are in reasonable agreement with recent observations obtained with VLT/MUSE for NGC 6754, Comment: 19 pages, 12 figures, MNRAS to be published

In our grid of multiphase chemical evolution models (Moll\'a & D\'iaz, 2005), star formation in the disk occurs in two steps: first, molecular gas forms, and then stars are created by cloud-cloud collisions or interactions of massive stars with the surrounding molecular clouds. The formation of both molecular clouds and stars are treated through the use of free parameters we refer to as efficiencies. In this work we modify the formation of molecular clouds based on several new prescriptions existing in the literature, and we compare the results obtained for a chemical evolution model of the Milky Way Galaxy regarding the evolution of the Solar region, the radial structure of the Galactic disk, and the ratio between the diffuse and molecular components, HI/H$_2$. Our results show that the six prescriptions we have tested reproduce fairly consistent most of the observed trends, differing mostly in their predictions for the (poorly-constrained) outskirts of the Milky Way and the evolution in time of its radial structure. Among them, the model proposed by Ascasibar et al. (2017), where the conversion of diffuse gas into molecular clouds depends on the local stellar and gas densities as well as on the gas metallicity, seems to provide the best overall match to the observed data., Comment: 14 pages, 13 figures, accepted by Monthly Notices of the Royal Astronomical Society

We summarize the results obtained from our suite of chemical evolution models for spiral disks, computed for different total masses and star formation efficiencies. Once the gas, stars and star formation radial distributions are reproduced, we analyze the Oxygen abundances radial profiles for gas and stars, in addition to stellar averaged ages and global metallicity. We examine scenarios for the potential origin of the apparent flattening of abundance gradients in the outskirts of disk galaxies, in particular the role of molecular gas formation prescriptions., Comment: 3 pages, 2 figures, Formation and evolution of galaxy outskirts Proceedings IAU Symposium No. 321, 2015, Armando Gil de Paz, Johan Knapen & Janice Lee, in press

Spiral galaxies are thought to acquire their gas through a protracted infall phase resulting in the inside-out growth of their associated discs. For field spirals, this infall occurs in the lower density environments of the cosmic web. The overall infall rate, as well as the galactocentric radius at which this infall is incorporated into the star-forming disc, plays a pivotal role in shaping the characteristics observed today. Indeed, characterising the functional form of this spatio-temporal infall in-situ is exceedingly difficult, and one is forced to constrain these forms using the present day state of galaxies with model or simulation predictions. We present the infall rates used as input to a grid of chemical evolution models spanning the mass spectrum of discs observed today. We provide a systematic comparison with alternate analytical infall schemes in the literature, including a first comparison with cosmological simulations. Identifying the degeneracies associated with the adopted infall rate prescriptions in galaxy models is an important step in the development of a consistent picture of disc galaxy formation and evolution., Comment: 12 pages, 12 figures, MNRAS, accepted

The metallicity of the progenitor system producing a type Ia supernova (SN Ia) could play a role in its maximum luminosity, as suggested by theoretical predictions. We present an observational study to investigate if such a relationship there exists. Using the 4.2m WHT we have obtained intermediate-resolution spectroscopy data of a sample of 28 local galaxies hosting SNe Ia, for which distances have been derived using methods independent to those based on the own SN Ia parameters. From the emission lines observed in their optical spectrum, we derived the gas-phase oxygen abundance in the region where each SN Ia exploded. Our data show a trend, with a 80% of chance not to be due to random fluctuation, between SNe Ia absolute magnitudes and the oxygen abundances of the host galaxies, in the sense that luminosities tend to be higher for galaxies with lower metallicities. This result seems like to be in agreement with both the theoretically expected behavior, and with other observational results. This dependence $M_{B}$-Z might induce to systematic errors when is not considered in deriving SNe Ia luminosities and then using them to derive cosmological distances., Comment: 9 pages, 4 figures, accepted for publication in ApJ Letters

We present a set of 144 galactic chemical evolution models applied to a Milky Way analogue, computed using four sets of low and intermediate star nucleosynthetic yields, six massive star yield compilations, and six functional forms for the initial mass function. The integrated or true yields for each combination are derived. A comparison is made between a grid of multiphase chemical evolution models computed with these yield combinations and empirical data drawn from the Milky Way's disc, including the solar neighbourhood. By means of a chi2 methodology, applied to the results of these multiphase models, the best combination of stellar yields and initial mass function capable of reproducing these observations is identified., Comment: 16 pages, 13 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

We summarize the updated set of multiphase chemical evolution models performed with 44 theoretical radial mass initial distributions and 10 possible values of efficiencies to form molecular clouds and stars. We present the results about the infall rate histories, the formation of the disk, and the evolution of the radial distributions of diffuse and molecular gas surface density, stellar profile, star formation rate surface density and elemental abundances of C,N, O and Fe, finding that the radial gradients for these elements begin very steeper, and flatten with increasing time or decreasing redshift, although the outer disks always show a certain flattening for all times. With the resulting star formation and enrichment histories, we calculate the spectral energy distributions (SEDs) for each radial region by using the ones for single stellar populations resulting from the evolutive synthesis model {\sc popstar}. With these SEDs we may compute finally the broad band magnitudes and colors radial distributions in the Johnson and in the SLOAN/SDSS systems which are the main result of this work. We present the evolution of these brightness and color profiles with the redshift., Comment: 22 pages, 18 figures, accepted in Advances in Astronomy

We argue that isolated gas-rich dwarf galaxies -- in particular, dwarf irregular (dIrr) galaxies -- do not necessarily undergo significant gas loss. Our aim is to investigate whether the observed properties of isolated, gas-rich dwarf galaxies, not affected by external environmental processes, can be reproduced by self-consistent chemo-photometric infall models with continuous star formation histories and no mass or metals loss. The model is characterized by the total mass of primordial gas available to the object, its characteristic collapse timescale, and a constant star formation efficiency. A grid of 144 such models has been computed by varying these parameters, and their predictions (elemental abundances, stellar and gas masses, photometric colors) have been compared with a set of observations of dIrr galaxies obtained from the literature. It is found that the models with moderate to low efficiency are able to reproduce most of the observational data, including the relative abundances of nitrogen and oxygen., Comment: 12 pages, 8 figures. Accepted to MNRAS

We have computed with a fine time grid the evolution of the elemental abundances of He, C, N and O ejected by a young (t < 20 Myr) and massive (M$=10^{6}$\,\Msun) coeval stellar cluster with a Salpeter initial mass function (IMF) over a wide range of initial abundances. Our computations incorporate the mass loss from massive stars (M >30 Msun) during their wind phase including the Wolf-Rayet phase and the ejecta from the core collapse supernovae. We find that during the Wolf-Rayet phase (t <5 Myr) the cluster ejecta composition suddenly becomes vastly over-abundant in N for all initial abundances and in He, C and O for initial abundances higher than 1/5th Solar. The C and O abundance in the cluster ejecta can reach over 50 times the solar value with important consequences for the chemical and hydrodynamical evolution of the surrounding ISM., Comment: 13 pages, 10 figures, 7 tables, accepted by MNRAS

We present OASIS observations obtained at the Canada-France-Hawaii Telescope for the SB(rs)c galaxy NGC 4900. About 800 spectra in the wavelength range 4700-5500 AA and 6270- 7000 AA have been collected with a spatial resolution of ~50 pc. This galaxy is part of a sample to study the stellar populations and their history in the central region of galaxies. In this paper, we present our iterative technique developed to describe consistently the different stellar com- ponents seen through emission and absorption lines. In NGC 4900 we find many young bursts of star formation distributed along the galaxy large scale bar on each side of the nucleus. They represent nearly 40 per cent of the actual stellar mass in the field of view. The age for these bursts ranges from 5.5 to 8 Myr with a metallicity near and above 2 Zsun . The extinction map gives E(B-V) values from 0.19+/-0.01 near the youngest bursts to 0.62+/-0.06 in a dusty internal bar perpendicular to the large scale bar. The Mg 2 and Fe I absorption lines indicate the superposition of a background stellar population with an age between 100 Myr to 3 Gyr and a sub-solar metallicity on average. We propose that all these episodes of star formation are the consequence of a secular evolution. In this scenario, the galactic large scale bar plays an important role with respect to the recent bursts and the dusty nuclear bar observed. The iterative technique allows us to improve the determination of the stellar population parameters, mainly an older age is obtained for the old component and more reliable stellar population masses are found. A composite/transition type activity in the galaxy nucleus is also revealed with this technique., Comment: 19 pages, accepted in MNRAS

ABRIDGED We present measurements of the Type Ia supernova (SN) rate in galaxy clusters based on data from the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. The cluster SN Ia rate is determined from 9 SN events in a set of 71 C4 clusters at z <0.17 and 27 SN events in 492 maxBCG clusters at 0.1 < z < 0.3$. We find values for the cluster SN Ia rate of $({0.37}^{+0.17+0.01}_{-0.12-0.01}) \mathrm{SNu}r h^{2}$ and $({0.55}^{+0.13+0.02}_{-0.11-0.01}) \mathrm{SNu}r h^{2}$ ($\mathrm{SNu}x = 10^{-12} L_{x\sun}^{-1} \mathrm{yr}^{-1}$) in C4 and maxBCG clusters, respectively, where the quoted errors are statistical and systematic, respectively. The SN rate for early-type galaxies is found to be $({0.31}^{+0.18+0.01}_{-0.12-0.01}) \mathrm{SNu}r h^{2}$ and $({0.49}^{+0.15+0.02}_{-0.11-0.01})$ $\mathrm{SNu}r h^{2}$ in C4 and maxBCG clusters, respectively. The SN rate for the brightest cluster galaxies (BCG) is found to be $({2.04}^{+1.99+0.07}_{-1.11-0.04}) \mathrm{SNu}r h^{2}$ and $({0.36}^{+0.84+0.01}_{-0.30-0.01}) \mathrm{SNu}r h^{2}$ in C4 and maxBCG clusters. The ratio of the SN Ia rate in cluster early-type galaxies to that of the SN Ia rate in field early-type galaxies is ${1.94}^{+1.31+0.043}_{-0.91-0.015}$ and ${3.02}^{+1.31+0.062}_{-1.03-0.048}$, for C4 and maxBCG clusters. The SN rate in galaxy clusters as a function of redshift...shows only weak dependence on redshift. Combining our current measurements with previous measurements, we fit the cluster SN Ia rate data to a linear function of redshift, and find $r_{L} = $ $[(0.49^{+0.15}_{-0.14}) +$ $(0.91^{+0.85}_{-0.81}) \times z]$ $\mathrm{SNu}B$ $h^{2}$. A comparison of the radial distribution of SNe in cluster to field early-type galaxies shows possible evidence for an enhancement of the SN rate in the cores of cluster early-type galaxies... we estimate the fraction of cluster SNe that are hostless to be $(9.4^+8._3-5.1)%$., Comment: 46 pages. ApJ in press. v2 fixes some references.

We present a measurement of the volumetric Type Ia supernova (SN Ia) rate based on data from the Sloan Digital Sky Survey II (SDSS-II) Supernova Survey. The adopted sample of supernovae (SNe) includes 516 SNe Ia at redshift z \lesssim 0.3, of which 270 (52%) are spectroscopically identified as SNe Ia. The remaining 246 SNe Ia were identified through their light curves; 113 of these objects have spectroscopic redshifts from spectra of their host galaxy, and 133 have photometric redshifts estimated from the SN light curves. Based on consideration of 87 spectroscopically confirmed non-Ia SNe discovered by the SDSS-II SN Survey, we estimate that 2.04+1.61-0.95 % of the photometric SNe Ia may be misidentified. The sample of SNe Ia used in this measurement represents an order of magnitude increase in the statistics for SN Ia rate measurements in the redshift range covered by the SDSS-II Supernova Survey. If we assume a SN Ia rate that is constant at low redshift (z < 0.15), then the SN observations can be used to infer a value of the SN rate of rV = (2.69+0.34+0.21-0.30-0.01) x10^{-5} SNe yr^{-1} Mpc-3 (H0 /(70 km s^{-1} Mpc^{-1}))^{3} at a mean redshift of ~ 0.12, based on 79 SNe Ia of which 72 are spectroscopically confirmed. However, the large sample of SNe Ia included in this study allows us to place constraints on the redshift dependence of the SN Ia rate based on the SDSS-II Supernova Survey data alone. Fitting a power-law model of the SN rate evolution, r_V(z) = A_p x ((1 + z)/(1 + z0))^{\nu}, over the redshift range 0.0 < z < 0.3 with z0 = 0.21, results in A_p = (3.43+0.15-0.15) x 10^{-5} SNe yr^{-1} Mpc-3 (H0 /(70 km s^{-1} Mpc^{-1}))^{3} and \nu = 2.04+0.90-0.89., Comment: 80 pages. v2 updates a few references.

We describe an SPH model for chemical enrichment and radiative cooling in cosmological simulations of structure formation. This model includes: i) the delayed gas restitution from stars by means of a probabilistic approach designed to reduce the statistical noise and, hence, to allow for the study of the inner chemical structure of objects with moderately high numbers of particles; ii) the full dependence of metal production on the detailed chemical composition of stellar particles by using, for the first time in SPH codes, the Qij matrix formalism that relates each nucleosynthetic product to its sources; and iii) the full dependence of radiative cooling on the detailed chemical composition of gas particles, achieved through a fast algorithm using a new metallicity parameter zeta(T) that gives the weight of each element on the total cooling function. The resolution effects and the results obtained from this SPH chemical model have been tested by comparing its predictions in different problems with known theoretical solutions. We also present some preliminary results on the chemical properties of elliptical galaxies found in self-consistent cosmological simulations. Such simulations show that the above zeta-cooling method is important to prevent an overestimation of the metallicity-dependent cooling rate, whereas the Qij formalism is important to prevent a significant underestimation of the [alpha/Fe] ratio in simulated galaxy-like objects., Comment: 19 pages, 22 figures, 2 tables; accepted for publication in MNRAS

We present a new set of theoretical evolutionary synthesis models, PopStar. This grid of Single Stellar Populations covers a wide range in both, age and metallicity. The models use the most recent evolutionary tracks together with the use of new NLTE atmosphere models for the hot stars (O, B, WR, post-AGB stars, planetary nebulae) that dominate the stellar cluster's ionizing spectra. The results of the models in VO format can be used through VOSpec., Comment: 2 pages, 1 figure, proceeding of Astronomical Spectroscopy and Virtual Observatory workshop, Villafranca del Castillo, Madrid

We show observations obtained with the integral field spectrometer OASIS for the central regions of a sample of barred galaxies. The high spatial resolution of the instrument allows to distinguish various structures within these regions as defined by stellar populations of different ages and metallicities. From these data we obtain important clues about the star formation history. But we advise that, in order to obtain adequately the evolutionary sequence, a combination of chemical and synthesis models may be necessary., Comment: 4 pages, 2 figures, submitted to the IAU245 Symposium Formation and Evolution of Galaxy Bulges

We characterize the stellar populations in the nuclear region of the barred spiral galaxy NGC 4900 using the integral field spectrometer OASIS and the synthesis code LavalSB and the code from Moll\'{a} & Garc\'{\i}a-Vargas (2000) for the young ($< 10$ Myr) and the old stellar populations, respectively. The high spatial resolution of the instrument allows us to find an old population uniformely distributed and younger regions located at the end of the galaxy bar and on each side of a nuclear bar., Comment: 2 pages, 1 fig. contribution to the IAU Symp. 241 Stellar Populations as building blocks of galaxies

We show autoconsistent chemical and spectro-photometric evolution models applied to spiral and irregular galaxies. Evolutionary synthesis models usually used to explain the stellar component spectro-photometric data, are combined with chemical evolution models, to determine precisely the evolutionary history of spiral and irregular galaxies. In this piece of work we will show the results obtained for a wide grid of modeled theoretical galaxies, Comment: 6 pages, 5 figures, contribution to the VII spanich astronomical society scientific meeting (Barcelona, Spain)

We study the evolution of nitrogen resulting from a set of spiral and irregular galaxy models computed for a large number of input mass radial distributions and with various star formation efficiencies. We show that our models produce a nitrogen abundance evolution in good agreement with the observational data. In particular, low N/O values for high-redshift objects, such as those obtained for Damped Lyman Alpha galaxies can be obtained with our models simultaneously to higher and constant values of N/O as those observed for irregular and dwarf galaxies, at the same low oxygen abundances $\rm 12+log(O/H) \sim 7$ dex. The differences in the star formation histories of the regions and galaxies modeled are essential to reproduce the observational data in the N/O-O/H plane., Comment: 7 pages, 5 figures. contribution to the conference Metal Rich Universe, Eds. G. Israelian & G. Meynet, Cambridge University Press

We have computed a grid of chemical evolution models for a large set of spiral and irregular theoretical galaxies of different total mass. In our models, the gas phase has two components, the diffuse and the molecular one ($\rm H_{2}$). It is possible, therefore, to follow the time (or redshift) evolution of the expected density of the $\rm H_{2}$ phase. We will show the predictions of this gas density at hight redshift, which might be detected with ALMA, in this type of galaxies., Comment: 4 pages, 4 figures, contribution to the conference {\sl Science with ALMA: a new era for Astrophysics}

We present a grid of 440 spectro-photometric models for simulating spiral and irregular galaxies. They have been consistently calculated with evolutionary synthesis models which use as input the information proceeding from chemical evolution models. The model predictions are spectral energy distributions, brightness and color profiles and radial distributions of spectral absorption stellar indices which are in agreement with observations., Comment: 2 pages, 1 fig, contribution to IAU 241 Symp. Stellar Populations as buildinng blocks of Galaxies

We analyze the impact on the Galactic nitrogen abundances of using a new set of low and intermediate mass star yields. These yields have a significant yield of primary nitrogen from intermediate mass stars. We use these yields as an input to a Galactic Chemical Evolution model and study the nitrogen abundances in the halo and in the disc, and compare them with models obtained using other yield sets and with a large amount of observational data. We find that, using these new yields, our model adequately reproduce the observed trends. In particular, these yields solve the historical problem of the evolution of nitrogen, giving the right level of relative abundance N/O by the production of a primary component in intermediate mass stars. Moreover, using different evolutionary rates in each radial region of the Galaxy, we may explain the observed N dispersion., Comment: 13 pages, 13 figures

A generalization of the multiphase chemical evolution model applied to a wide set of theoretical galaxies is shown. This set of models has been computed by using the so-called Universal Rotation Curve from Persic, Salucci & Steel to calculate the radial mass distributions of each theoretical galaxy. By assuming that the molecular cloud and star formation efficiencies depend on the morphological type of each galaxy, we construct a bi-parametric grid of models whose results are valid in principle for any spiral galaxy, of given maximum rotation velocity or total mass, and morphological type., Comment: Proceedings of the Euroconference "The Evolution of Galaxies. III..." (Kiel 2002)

We study the old problem of the uniqueness of chemical evolution models by analyzing a set of multiphase models for the galaxy NGC 4303 computed for a variety of plausible physical input parameters. Our aim is to determine if the input parameters may be strongly constrained when nebular abundances and stellar spectral indices radial distributions are used. We run a large number of models (500) for NGC 4303 varying the input parameters. Less than 4% of the models (19) fit the present day observational data within a region of 95% probability. The number of models reduces to ~1% (6) when we also ask them to reproduce the time-averaged abundances represented by the spectral indices. Thus, by proving that only a small fraction of models are favored in reproducing the present day radial abundance distributions and the spectral indices data simultaneously, we show that these spectral indices provide strong time-dependent additional constraints to the possible star formation and chemical histories of spiral disks., Comment: 35 pages, 6 figures, accepted for publication in AJ

The oxygen and nitrogen abundances in the HII regions of the nine Virgo spirals of the sample from Skillman et al (1996) and in nine field spiral galaxies are re-determined with the recently suggested P - method. We confirm that there is an abundance segregation in the sample of Virgo spirals in the sense that the HI deficient Virgo spirals near the core of the cluster have higher oxygen abundances in comparison to the spirals at the periphery of the Virgo cluster. At the same time both the Virgo periphery and core spirals have counterparts among field spirals. We conclude that if there is a difference in the abundance properties of the Virgo and field spirals, this difference appears to be small and masked by the observational errors., Comment: 16 pages, 10 figures, accepted for publication in Astronomy and Astrophysics

We show a grid of multiphase models whose results are valid for any spiral galaxy, using as input the luminosity or the rotation velocity and the morphological type, measured by the classical index T from 1 to 10., Comment: 4 pag., 2 figures, contribution to "IV Reunion Cientifica de la SEA"

We show our results from the application of the Multiphase chemical evolution model to a set of Bulges of spiral galaxies, Comment: 1 pag, contribution to the Euroconference "The Evolution of Galaxies. I. Observational Clues"

We have computed a grid of multiphase chemical evolution models whose results are valid for any spiral galaxy, using as input the maximum rotation velocity and the morphological type or index T., Comment: 2 pag., contribution to the conference Cosmic Evolution (Paris, Nov. 2000)

The spectral energy distribution (SED) of recent star formation regions is dominated by the more massive and early stars (O and B types). These stars show large and very significant absorption features, the most prominent being the recombination lines of H, HeI and HeII. In particular, the shape of their profiles are very dependent on the luminosity of the star. We have explored the potential use of high resolution profiles to discriminate between different luminosity classes and spectral types, by using profiles of the He and Balmer lines. We have calculated growth curves for each of the lines and their dependence on gravity and effective temperature. We show some of these theoretical growth curves and our preliminary conclusions are analyzed and discussed., Comment: 1 pag, Contribution to the conference "Cosmic Evolution and Galaxy Formation: Structure, Interactions and Feedback", Nov. 1999 (Puebla, Mexico), to be published in ASP. Conf. Series, Eds. J. Franco, E. Terlevich. O. Lopez-Cruz, I. Aretxaga

We show that the multiphase chemical evolution model reproduces the correlations obtained along the spiral sequence, dwarf galaxies included. However the apparent spatial chemical uniformity observed in some irregular galaxies cannot be reproduced with it. An evolutionary model has been developed and tested to explain flat gradients. Preliminary results, obtained with a new code including supernova winds and radial flows, suggest that radial flows are probably responsably for this uniformity, Comment: 5 pages,5 figures, to be published in the proceedings of the ESO "Chemical Evolution from Zero to High Redshift" workshop, Eds. M.Rosa and J.R. Walsh (Springer-Verlag)

The distribution of element abundances with redshift in Damped Ly-alpha (DLA) systems can be adequately reproduced by the same model reproducing the halo and disk components of the Milky Way Galaxy at different galactocentric distances: DLA systems are well represented by normal spiral galaxies in their early evolutionary stages., Comment: 2 pages, 1 figure, proceedings of X Rencontres de Blois, "The Birth of Galaxies"

NGC 1313 is the most massive disk galaxy showing a flat radial abundance distribution in its interstellar gas, a behavior generally observed in magellanic and irregular galaxies. We have attempted to reproduce this flat abundance distribution using a multiphase chemical evolution model, which has been previously used sucessfully to depict other spiral galaxies along the Hubble morphological sequence. We found that it is not possible to reproduce the flat radial abundance distribution in NGC 1313, and at the same time, be consistent with observed radial distributions of other key parameters such the surface gas density and star formation profiles. We conclude that a more complicated galactic evolution model including radial flows, and possibly mass loss due to supernova explosions and winds, is necessary to explain the apparent chemical uniformity of the disk of NGC 1313, Comment: 14 paginas, 4 figures, to be published in ApJ, april