arXiv subjects

Gustavo Bruzual A

Publications and source records attributed to Gustavo Bruzual A.

8 recordsLinked to original sources

arXiv2016

Removing biases in resolved stellar mass-maps of galaxy disks through successive Bayesian marginalization

Stellar masses of galaxies are frequently obtained by fitting stellar population synthesis models to galaxy photometry or spectra. The state of the art method resolves spatial structures within a galaxy to assess the total stellar mass content. In comparison to unresolved studies, resolved methods yield, on average, higher fractions of stellar mass for galaxies. In this work we improve the current method in order to mitigate a bias related to the resolved spatial distribution derived for the mass. The bias consists in an apparent filamentary mass distribution, and a spatial coincidence between mass structures and dust lanes near spiral arms. The improved method is based on iterative Bayesian marginalization, through a new algorithm we have named Bayesian Successive Priors (BSP). We have applied BSP to M 51, and to a pilot sample of 90 spiral galaxies from the Ohio State University Bright Spiral Galaxy Survey. By comparing quantitatively both methods, we find that the average fraction of stellar mass missed by unresolved studies is only half than previously thought. In contrast with the previous method, the output BSP mass-maps bear a better resemblance to near infrared images.

astro-ph.GA↗

arXiv2013

Revisiting binary stars in population synthesis models

We report results of a population synthesis model that follows the evolution of single and binary stars. In this model we include the 2HeWD merger channel, suggested by Han et al. (2002), for the formation of EHB stars. The physical parameters of the resulting EHB stars are derived from the BaSTI database, and are thus realistic and observationally supported. The predictions of this model are in good agreement with traditional population synthesis models, except when the spectrum of the stellar population is dominated by binary stars or their products, e.g., EHB stars in the UV of ETGs. We reproduce successfully the observed CMD and SED of the metal rich open cluster NGC 6791. The stellar population in this cluster may be archetypal of the stellar population in ETGs that show the UVX phenomenon. Our models should be appropriate to study the UV upturn in ETGs.

astro-ph.CO↗

arXiv2007

On TP-AGB stars and the mass of galaxies

Recent calculations of evolutionary tracks of TP-AGB stars of different mass and metallicity by Marigo et al. (2007) have been incorporated in the Bruzual & Charlot evolutionary population synthesis models. The mass of the stellar population in HUDF galaxies at z from 1 to 3 determined from fits to the spectro-photometric data of these galaxies is 50 to 80% lower than the mass determined from the BC03 models. The ages inferred for these populations are, with exceptions, 40 to 60% of the BC03 estimates.

astro-ph↗

arXiv2007

Stellar Populations: High Spectral Resolution Libraries. Improved TP-AGB Treatment

I present a short description of the STELIB, HNGSL, IndoUS, MILES, ELODIE, UVES-POP, and IRTF libraries of empirical stellar spectra and show some applications of their use in population synthesis models. When new calculations of the TP-AGB evolutionary phase for stars of different mass and metallicity are included in population synthesis models, the stellar mass in galaxies at z from 1 to 3 determined from spectro-photometric data can be up to 50% lower than the mass determined from the BC03 models. The ages inferred for these populations are considerably lower than the BC03 estimates.

astro-ph↗

arXiv2007

Stellar Populations in Normal Galaxies

I describe very briefly the new libraries of empirical spectra of stars covering wide ranges of values of the atmospheric parameters Teff, log g, [Fe/H], as well as spectral type, that have become available in the recent past, among them the HNGSL, MILES, UVES-POP, and Indo-US libraries. I show the results of using the HNGSL to build population synthesis models. These libraries are complementary in spectral resolution and wavelength coverage, and will prove extremely useful to describe spectral features expected in galaxy spectra from the NUV to the NIR.

astro-ph↗

arXiv2002

Spectroscopic Dating of Stellar Populations from Local Star Clusters to Distant Galaxies and the Age of the Universe

I summarize in terms of evolutionary population synthesis models our current understanding of stellar populations in different environments, from star clusters in nearby galaxies to distant galaxies in clusters or seen through gravitational lenses. Constraints on the age of the stellar populations in clusters and galaxies derived from comparing predicted and observed spectral energy distributions are examined and contrasted with the maximum ages allowed by cosmological models at the corresponding redshift.

astro-ph↗

arXiv2001

Stellar Populations in Star Clusters: The Role Played by Stochastic Effects

In this paper I combine the results of a set of population synthesis models with simple Montecarlo simulations of stochastic effects in the number of stars occupying sparsely populated stellar evolutionary phases, to show that the scatter observed in the magnitudes and colors of LMC and NGC 7252 star clusters can be understood in the framework of current stellar evolution theory, without the need to introduce ad-hoc corrections (e.g. artificially increasing the number of AGB stars).

astro-ph↗

arXiv2000

Stellar population synthesis models at low and high redshift

The basic assumptions behind Population Synthesis and Spectral Evolution models are reviewed. The numerical problems encountered by the standard population synthesis technique when applied to models with truncated star formation rates are described. The Isochrone Synthesis algorithm is introduced as a means to circumvent these problems. A summary of results from the application of this algorithm to model galaxy spectra by Bruzual and Charlot (1993, 2000) follows. I present a comparison of these population synthesis model predictions with observed spectra and color magnitude diagrams for stellar systems of various ages and metallicities. It is argued that models built using different ingredients differ in the resulting values of some basic quantities (e.g. $M/L_V$), without need to invoking violations of physical principles. The range of allowed colors in the observer frame is explored for several galaxy redshifts.

astro-ph↗