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Dive into the research topics where I. G. de la Rosa is active.

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Featured researches published by I. G. de la Rosa.


Monthly Notices of the Royal Astronomical Society | 2013

SPIDER VIII – constraints on the stellar initial mass function of early-type galaxies from a variety of spectral features

F. La Barbera; Ignacio Ferreras; A. Vazdekis; I. G. de la Rosa; R. R. de Carvalho; M. Trevisan; J. Falcón-Barroso; E. Ricciardelli

We perform a spectroscopic study to constrain the stellar initial mass function (IMF) by using a large sample of 24 781 early-type galaxies from the Sloan Digital Sky Survey-based Spheroids Panchromatic Investigation in Different Environmental Regions survey. Clear evidence is found of a trend between IMF and central velocity dispersion (σ0), evolving from a standard Kroupa/Chabrier IMF at σ0 ~ 100 km s-1 towards a more bottom-heavy IMF with increasing σ0, becoming steeper than the Salpeter function at σ0 > 220 km s-1. We analyse a variety of spectral indices, combining gravity-sensitive features, with age- and metallicitysensitive indices, and we also consider the effect of non-solar abundance variations. The indices, corrected to solar scale by means of semi-empirical correlations, are fitted simultaneously with the (nearly solar-scaled) extended MILES (MIUSCAT) stellar population models. Similar conclusions are reached when analysing the spectra with a hybrid approach, combining constraints from direct spectral fitting in the optical with those from IMF-sensitive indices. Our analysis suggests that σ0, rather than [a/Fe], drives the variation of the IMF. Although our analysis cannot discriminate between a single power-law (unimodal) IMF and a low-mass (<0.5Mȯ) tapered (bimodal) IMF, robust constraints can be inferred for the fraction in lowmass stars at birth. This fraction (by mass) is found to increase from ~20 per cent at σ0 ~ 100 km s-1, up to ~80 per cent at σ0 ~ 300 km s-1. However, additional constraints can be provided with stellar mass-to-light (M/L) ratios: unimodal models predict M/L significantly larger than dynamical M/L, across the whole σ0 range, whereas a bimodal IMF is compatible. Our results are robust against individual abundance variations. No significant variation is found in Na and Ca in addition to the expected change from the correlation between [s-1/Fe] and σ0.


Monthly Notices of the Royal Astronomical Society | 2013

The impact of a non-universal initial mass function on the star formation histories of early-type galaxies

A. Ferré-Mateu; A. Vazdekis; I. G. de la Rosa

Recent results on the non-universality of the Initial Mass Function (IMF) have shown strong evidence of IMF variations with galaxy velocity dispersion, with a corresponding impact on other stellar population parameters, line indices and colours. Using a set of stellar population models with varying IMF slopes, we provide additional caveats on the assumption of a universal IMF. The present study shows that the derived star formation histories of early-type galaxies vary significantly with the IMF slope. For instance, a steepening in the slope of a single power-law IMF decreases substantially, by a factor of up to four, the contribution of the old stellar populations to the total light/mass. This trend is milder for a segmented-like IMF shape, where the contribution of the very low mass stars is decreased. It is also shown that, by tuning each IMF slope to its prescribed value according to each galaxy velocity dispersion, a sample of early-type galaxies covering a range of masses yield comparable star formation histories. On the one hand, a small contribution from relatively young stellar populations appear in the star formation histories of most massive elliptical galaxies when adopting a steep IMF. On the other hand, we find that low mass early-type galaxies that look like genuinely young objects with a standard IMF (i.e. ``baby elliptical galaxies``), turn out to be older when a slightly flatter IMF is employed. In summary, the use of a non-universal IMF, tuned according to the velocity dispersion of the galaxy, seems to provide more consistent results.


The Astrophysical Journal | 2011

ON THE RADIAL STELLAR CONTENT OF EARLY-TYPE GALAXIES AS A FUNCTION OF MASS AND ENVIRONMENT

F. La Barbera; Ignacio Ferreras; R. R. de Carvalho; P. A. A. Lopes; Anna Pasquali; I. G. de la Rosa; G. De Lucia

Using optical-optical and optical-NIR colors, we analyze the radial dependence of age and metallicity inside massive (M{sub *} {approx}> 10{sup 10.5} M{sub sun}), low-redshift (z < 0.1), early-type galaxies (ETGs), residing in both high-density group regions and the field. On average, internal color gradients of ETGs are mainly driven by metallicity, consistent with previous studies. However, we find that group galaxies feature positive age gradients, {nabla} {sub t}, i.e., a younger stellar population in the galaxy center, and steeper metallicity gradients, compared to the field sample, whose {nabla} {sub t} ranges from negative in lower mass galaxies to positive gradients at higher mass. These dependencies yield new constraints on models of galaxy formation and evolution. We speculate that age and metallicity gradients of group ETGs result from (either gas-rich or minor-dry) mergers and/or cold-gas accretion, while field ETGs exhibit the characteristic flatter gradients expected from younger, more metal-rich stars formed inside-out by later gas cooling.


Monthly Notices of the Royal Astronomical Society | 2014

SPIDER X - Environmental effects in central and satellite early-type galaxies through the stellar fossil record

F. La Barbera; Anna Pasquali; Ignacio Ferreras; Anna Gallazzi; R. R. de Carvalho; I. G. de la Rosa

A detailed analysis of how environment affects the star formation history of earlytype galaxies (ETGs) is undertaken via high signal to noise ratio stacked spectra obtained from a sample of 20,977 ETGs (morphologically selected) from the SDSSbased SPIDER survey. Two major parameters are considered for the study: the central velocity dispersion (σ), which relates to local drivers of star formation, and the mass of the host halo, which relates to environment-related effects. In addition, we separate the sample between centrals (the most massive galaxy in a halo) and satellites. We derive trends of age, metallicity, and [α/Fe] enhancement, with σ. We confirm that the major driver of stellar population properties in ETGs is velocity dispersion, with a secondorder effect associated to the central/satellite nature of the galaxy. No environmental dependence is detected for satellite ETGs, except at low σ – where satellites in groups or in the outskirts of clusters tend to be younger than those in the central regions of clusters. In contrast, the trends for centrals show a significant dependence on halo mass. Central ETGs in groups (i.e. with a halo mass > 10 12.5 M⊙) have younger ages, lower [α/Fe], and higher internal reddening, than “isolated” systems (i.e. centrals residing in low-mass, < 10 12.5 M⊙, halos). Our findings imply that central ETGs in groups formed their stellar component over longer time scales than “isolated” centrals, mainly because of gas-rich interactions with their companion galaxies.


Monthly Notices of the Royal Astronomical Society | 2010

SPIDER – I. Sample and galaxy parameters in the grizYJHK wavebands

F. La Barbera; R. R. de Carvalho; I. G. de la Rosa; P. A. A. Lopes; J. L. Kohl-Moreira; H. V. Capelato


The Astronomical Journal | 2010

SPIDER. IV. OPTICAL AND NEAR-INFRARED COLOR GRADIENTS IN EARLY-TYPE GALAXIES: NEW INSIGHT INTO CORRELATIONS WITH GALAXY PROPERTIES

F. La Barbera; R. R. de Carvalho; I. G. de la Rosa; Roy R. Gal; R. Swindle; P. A. A. Lopes


Monthly Notices of the Royal Astronomical Society | 2010

SPIDER – II. The Fundamental Plane of early-type galaxies in grizYJHK

F. La Barbera; R. R. de Carvalho; I. G. de la Rosa; P. A. A. Lopes


Monthly Notices of the Royal Astronomical Society | 2010

SPIDER – III. Environmental dependence of the Fundamental Plane of early-type galaxies

F. La Barbera; P. A. A. Lopes; R. R. de Carvalho; I. G. de la Rosa; Andreas A. Berlind


Monthly Notices of the Royal Astronomical Society | 2012

Young ages and other intriguing properties of massive compact galaxies in the local Universe

A. Ferré-Mateu; A. Vazdekis; Ignacio Trujillo; P. Sánchez-Blázquez; E. Ricciardelli; I. G. de la Rosa


The Astrophysical Journal | 2012

Constraints on Feedback Processes during the Formation of Early-type Galaxies

M. Trevisan; Ignacio Ferreras; I. G. de la Rosa; F. La Barbera; R. R. de Carvalho

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R. R. de Carvalho

National Institute for Space Research

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P. A. A. Lopes

Federal University of Rio de Janeiro

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A. Vazdekis

University of La Laguna

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M. Trevisan

University of São Paulo

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P. Sánchez-Blázquez

Autonomous University of Madrid

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