Patricia Sanchez-Blazquez

Bio: Patricia Sanchez-Blazquez is an academic researcher from Complutense University of Madrid. The author has contributed to research in topics: Galaxy & Metallicity. The author has an hindex of 65, co-authored 295 publications receiving 18059 citations. Previous affiliations of Patricia Sanchez-Blazquez include University of Central Lancashire & Swinburne University of Technology.

Medium-resolution isaac newton telescope library of empirical spectra

Abstract: A new stellar library developed for stellar population synthesis modelling is presented. The library consists of 985 stars spanning a large range in atmospheric parameters. The spectra were obtained at the 2.5-m Isaac Newton Telescope and cover the range λλ 3525–7500 A at 2.3 A (full width at half-maximum) spectral resolution. The spectral resolution, spectral-type coverage, flux-calibration accuracy and number of stars represent a substantial improvement over previous libraries used in population-synthesis models.

MILES: A Medium resolution INT Library of Empirical Spectra

Abstract: A new stellar library developed for stellar population synthesis modeling is presented. The library consist of 985 stars spanning a large range in atmospheric parameters. The spectra were obtained at the 2.5m INT telescope and cover the range 3525-7500A at 2.3A (FWHM) spectral resolution. The spectral resolution, spectral type coverage, flux calibration accuracy and number of stars represent a substantial improvement over previous libraries used in population synthesis models.

CALIFA, the Calar Alto Legacy Integral Field Area survey : I. Survey presentation

Abstract: The final product of galaxy evolution through cosmic time is the population of galaxies in the local universe. These galaxies are also those that can be studied in most detail, thus providing a stringent benchmark for our understanding of galaxy evolution. Through the huge success of spectroscopic single-fiber, statistical surveys of the Local Universe in the last decade, it has become clear, however, that an authoritative observational description of galaxies will involve measuring their spatially resolved properties over their full optical extent for a statistically significant sample. We present here the Calar Alto Legacy Integral Field Area (CALIFA) survey, which has been designed to provide a first step in this direction. We summarize the survey goals and design, including sample selection and observational strategy. We also showcase the data taken during the first observing runs (June/July 2010) and outline the reduction pipeline, quality control schemes and general characteristics of the reduced data. This survey is obtaining spatially resolved spectroscopic information of a diameter selected sample of similar to 600 galaxies in the Local Universe (0.005 < z < 0.03). CALIFA has been designed to allow the building of two-dimensional maps of the following quantities: (a) stellar populations: ages and metallicities; (b) ionized gas: distribution, excitation mechanism and chemical abundances; and (c) kinematic properties: both from stellar and ionized gas components. CALIFA uses the PPAK integral field unit (IFU), with a hexagonal field-of-view of similar to 1.3 square', with a 100% covering factor by adopting a three-pointing dithering scheme. The optical wavelength range is covered from 3700 to 7000 angstrom, using two overlapping setups (V500 and V1200), with different resolutions: R similar to 850 and R similar to 1650, respectively. CALIFA is a legacy survey, intended for the community. The reduced data will be released, once the quality has been guaranteed. The analyzed data fulfill the expectations of the original observing proposal, on the basis of a set of quality checks and exploratory analysis: (i) the final datacubes reach a 3 sigma limiting surface brightness depth of similar to 23.0 mag/arcsec(2) for the V500 grating data (similar to 22.8 mag/arcsec(2) for V1200); (ii) about similar to 70% of the covered field-of-view is above this 3 sigma limit; (iii) the data have a blue-to-red relative flux calibration within a few percent in most of the wavelength range; (iv) the absolute flux calibration is accurate within similar to 8% with respect to SDSS; (v) the measured spectral resolution is similar to 85 km s(-1) for V1200 (similar to 150 km s(-1) for V500); (vi) the estimated accuracy of the wavelength calibration is similar to 5 km s(-1) for the V1200 data (similar to 10 km s(-1) for the V500 data); (vii) the aperture matched CALIFA and SDSS spectra are qualitatively and quantitatively similar. Finally, we show that we are able to carry out all measurements indicated above, recovering the properties of the stellar populations, the ionized gas and the kinematics of both components. The associated maps illustrate the spatial variation of these parameters across the field, reemphasizing the redshift dependence of single aperture spectroscopic measurements. We conclude from this first look at the data that CALIFA will be an important resource for archaeological studies of galaxies in the Local Universe.

Evolutionary stellar population synthesis with MILES: I. The base models and a new line index system

Abstract: We present synthetic spectral energy distributions (SEDs) for single-age, single-metallicity stellar populations (SSPs) covering the full optical spectral range at moderately high resolution [full width at half-maximum (FWHM) = 2.3A]. These SEDs constitute our base models, as they combine scaled-solar isochrones with an empirical stellar spectral library [Medium resolution INT Library of Empirical Spectra (MILES)], which follows the chemical evolution pattern of the solar neighbourhood. The models rely as much as possible on empirical ingredients, not just on the stellar spectra, but also on extensive photometric libraries, which are used to determine the transformations from the theoretical parameters of the isochrones to observational quantities. The unprecedented stellar parameter coverage of the MILES stellar library allowed us to safely extend our optical SSP SED predictions from intermediate- to very-old-age regimes and the metallicity coverage of the SSPs from super-solar to [M/H] = -2.3. SSPs with such low metallicities are particularly useful for globular cluster studies. We have computed SSP SEDs for a suite of initial mass function shapes and slopes. We provide a quantitative analysis of the dependence of the synthesized SSP SEDs on the (in)complete coverage of the stellar parameter space in the input library that not only shows that our models are of higher quality than those of other works, but also in which range of SSP parameters our models are reliable. The SSP SEDs are a useful tool to perform the analysis of stellar populations in a very flexible manner. Observed spectra can be studied by means of full spectrum fitting or by using line indices. For the latter, we propose a new line index system to avoid the intrinsic uncertainties associated with the popular Lick/IDS system and provide more appropriate, uniform, spectral resolution. Apart from constant resolution as a function of wavelength, the system is also based on flux-calibrated spectra. Data can be analysed at three different resolutions: 5, 8.4 and 14A (FWHM), which are appropriate for studying globular cluster, low- and intermediate-mass galaxies, and massive galaxies, respectively. Furthermore, we provide polynomials to transform current Lick/IDS line index measurements to the new system. We provide line index tables in the new system for various popular samples of Galactic globular clusters and galaxies. We apply the models to various stellar clusters and galaxies with high-quality spectra, for which independent studies are available, obtaining excellent results. Finally, we designed a web page from which not only these models and stellar libraries can be downloaded but which also provides a suite of on-line tools to facilitate the handling and transformation of the spectra.

An updated MILES stellar library and stellar population models (Research Note)

Abstract: Aims: We present a number of improvements to the MILES library and stellar population models. We correct some small errors in the radial velocities of the stars, measure the spectral resolution of the library and models more accurately, and give a better absolute flux calibration of the models. Methods: We use cross-correlation techniques to correct the radial velocities of the offset stars and the penalised pixel-fitting method, together with different sets of stellar templates, to re-assess the spectral resolution of the MILES stellar library and models. We have also re-calibrated the zero-point flux level of the models using a new calibration scheme. Results: The end result is an even more homogeneously calibrated stellar library than the originally released one, with a measured spectral resolution of ~2.5 A, almost constant with wavelength, for both the MILES stellar library and models. Furthermore, the new absolute flux calibration for the spectra excellently agrees with predictions based on independent photometric libraries. Conclusions: This improved version of the MILES library and models (version 9.1) is available at the project's website (http://miles.iac.es).

The EAGLE project: Simulating the evolution and assembly of galaxies and their environments

Abstract: We introduce the Virgo Consortium's EAGLE project, a suite of hydrodynamical simulations that follow the formation of galaxies and black holes in representative volumes. We discuss the limitations of such simulations in light of their finite resolution and poorly constrained subgrid physics, and how these affect their predictive power. One major improvement is our treatment of feedback from massive stars and AGN in which thermal energy is injected into the gas without the need to turn off cooling or hydrodynamical forces, allowing winds to develop without predetermined speed or mass loading factors. Because the feedback efficiencies cannot be predicted from first principles, we calibrate them to the z~0 galaxy stellar mass function and the amplitude of the galaxy-central black hole mass relation, also taking galaxy sizes into account. The observed galaxy mass function is reproduced to ≲0.2 dex over the full mass range, 108

Star Formation in the Milky Way and Nearby Galaxies

Abstract: We review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies. Methods of measuring gas contents and star-formation rates are discussed, and updated prescriptions for calculating star-formation rates are provided. We review relations between star formation and gas on scales ranging from entire galaxies to individual molecular clouds.

Monthly Notices of the Royal Astronomical Society

Abstract: Monthly Notices is one of the three largest general primary astronomical research publications. It is an international journal, published by the Royal Astronomical Society. This article 1 describes its publication policy and practice.

The Epochs of Early-Type Galaxy Formation as a Function of Environment

Abstract: The aim of this paper is to set constraints on the epochs of early-type galaxy formation through the archaeology of the stellar populations in local galaxies. Using our models of absorption-line indices that account for variable abundance ratios, we derive ages, total metallicities, and element ratios of 124 early-type galaxies in high- and low-density environments. The data are analyzed by comparison with mock galaxy samples created through Monte Carlo simulations taking the typical average observational errors into account, in order to eliminate artifacts caused by correlated errors. We find that all three parameters, age, metallicity, and ?/Fe ratio, are correlated with velocity dispersion. We show that these results are robust against recent revisions of the local abundance pattern at high metallicities. To recover the observed scatter we need to assume an intrinsic scatter of about 20% in age, 0.08?dex in [Z/H], and 0.05?dex in [?/Fe]. All low-mass objects with M* 1010 M? (? 130 km s-1) show evidence for the presence of intermediate-age stellar populations with low ?/Fe ratios. About 20% of the intermediate-mass objects with 1010 M*/M? 1011 [110 ?/(km s-1) 230; both elliptical and lenticular galaxies] must have either a young subpopulation or a blue horizontal branch. On the basis of the above relationships, valid for the bulk of the sample, we show that the Mg-? relation is mainly driven by metallicity, with similar contributions from the ?/Fe ratio (23%) and age (17%). We further find evidence for an influence of the environment on the stellar population properties. Massive early-type galaxies in low-density environments seem on average ~2?Gyr younger and slightly (~0.05-0.1?dex) more metal-rich than their counterparts in high-density environments. No offsets in the ?/Fe ratios are instead detected. With the aid of a simple chemical evolution model, we translate the derived ages and ?/Fe ratios into star formation histories. We show that most star formation activity in early-type galaxies is expected to have happened between redshifts ~3 and 5 in high-density environments and between redshifts 1 and 2 in low-density environments. We conclude that at least 50% of the total stellar mass density must have already formed at z ~ 1, in good agreement with observational estimates of the total stellar mass density as a function of redshift. Our results suggest that significant mass growth in the early-type galaxy population below z ~ 1 must be restricted to less massive objects, and a significant increase of the stellar mass density between redshifts 1 and 2 should be present, caused mainly by the field galaxy population. The results of this paper further imply the presence of vigorous star formation episodes in massive objects at z ~ 2-5 and evolved elliptical galaxies around z ~ 1, both observationally identified as SCUBA galaxies and extremely red objects, respectively.

Grids of stellar models with rotation - I. Models from 0.8 to 120 M⊙ at solar metallicity (Z = 0.014)

Abstract: Aims. Many topical astrophysical research areas, such as the properties of planet host stars, the nature of the progenitors of different types of supernovae and gamma ray bursts, and the evolution of galaxies, require complete and homogeneous sets of stellar models at different metallicities in order to be studied during the whole of cosmic history. We present here a first set of models for solar metallicity, where the effects of rotation are accounted for in a homogeneous way.Methods. We computed a grid of 48 different stellar evolutionary tracks, both rotating and non-rotating, at Z = 0.014, spanning a wide mass range from 0.8 to 120 M ⊙ . For each of the stellar masses considered, electronic tables provide data for 400 stages along the evolutionary track and at each stage, a set of 43 physical data are given. These grids thus provide an extensive and detailed data basis for comparisons with the observations. The rotating models start on the zero-age main sequence (ZAMS) with a rotation rate υ ini /υ crit = 0.4. The evolution is computed until the end of the central carbon-burning phase, the early asymptotic giant branch (AGB) phase, or the core helium-flash for, respectively, the massive, intermediate, and both low and very low mass stars. The initial abundances are those deduced by Asplund and collaborators, which best fit the observed abundances of massive stars in the solar neighbourhood. We update both the opacities and nuclear reaction rates, and introduce new prescriptions for the mass-loss rates as stars approach the Eddington and/or the critical velocity. We account for both atomic diffusion and magnetic braking in our low-mass star models.Results. The present rotating models provide a good description of the average evolution of non-interacting stars. In particular, they reproduce the observed main-sequence width, the positions of the red giant and supergiant stars in the Hertzsprung-Russell (HR) diagram, the observed surface compositions and rotational velocities. Very interestingly, the enhancement of the mass loss during the red-supergiant stage, when the luminosity becomes supra-Eddington in some outer layers, help models above 15−20 M ⊙ to lose a significant part of their hydrogen envelope and evolve back into the blue part of the HR diagram. This result has interesting consequences for the blue to red supergiant ratio, the minimum mass for stars to become Wolf-Rayet stars, and the maximum initial mass of stars that explode as type II−P supernovae.