Person: Gorgas García, Francisco Javier
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First Name
Francisco Javier
Last Name
Gorgas García
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física de la Tierra y Astrofísica
Area
Astronomía y Astrofísica
Identifiers
12 results
Search Results
Now showing 1 - 10 of 12
Item Evolutionary stellar population synthesis with MILES - I. The base models and a new line index system(Monthly notices of the Royal Astronomical Society, 2010) Vazdekis, A.; Sánchez Blázquez, Patricia; Falcón Barroso, J.; Cenarro, A. J.; Beasley, M. A.; Cardiel López, Nicolás; Gorgas García, Francisco Javier; Peletier, R. F.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) = 2.3 A]. 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 14 A (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.Item GUAIX: The UCM Group of Extragalactic Astrophysics and Astronomical Instrumentation(Highlights of Spanish Astrophysics, 2010) Cardiel López, Nicolás; Gallego Maestro, Jesús; Pascual Ramírez, Sergio; Eliche Moral, María del Carmen; Castillo Morales, María África; Guzmán, R.; Gil De Paz, Armando; Pérez González, Pablo Guillermo; Gorgas García, Francisco Javier; Zamorano Calvo, JaimeWe present a short summary of the activities developed by GUAIX, the Universidad Complutense de Madrid (UCM) Group of Extragalactic Astrophysics and Astronomical Instrumentation. At present we are focused in the development of data reduction pipelines for several future instruments for the Spanish 10m GTC (Gran Telescopio Canarias). The careful treatment of the random error propagation throughout the data reduction is one of the main improvements of those pipelines. The first hardware development leaded by the GUAIX group will be FISIR, a fully-cryogenic (optimized for the K band) tunable filter in the near-infrared, to be installed within CIRCE, a near-IR camera for GTC.Item New empirical fitting functions for the Lick/IDS indices using MILES(Highlights of Spanish Astrophysics, 2010) Martín Hernández, J.M.; Mármol Queraltó, E.; Gorgas García, Francisco Javier; Cardiel López, Nicolás; Sánchez Blázquez, Patricia; Cenarro, A.J.; Peletier, R. F.; Vazdekis, A.; Falcón Barroso, J.We are presenting new empirical fitting functions for the Lick/IDS line-strength indices as measured in MILES (Medium-resolution INT Library of Empirical Spectra). Following previous work in the field, these functions describe the empirical behaviour of the line-strength indices with the atmospheric stellar parameters (T_(eff), logɡ, [Fe/H]). In order to derive the fitting functions we have devised a new procedure which, being fully automatic, provides a better description of the line-strength index variations in the stellar parameter space.Item Gaseous-phase metallicities and stellar populations in the centres of barred galaxies(Monthly notices of the Royal Astronomical Society, 2014) Sánchez Blázquez, Patricia; Gorgas García, Francisco Javier; Cacho Martínez, Raúl; Perez, I.Numerical simulations predict that bars represent a very important agent for triggering gas inflows, which in turn could lead to central star formation. Bars thus are thought to contribute to the formation of the bulge. This process changes both the gaseous-phase and the stellar-phase metallicities in the centres of galaxies. With the aim of quantifying the importance of this process, we present a comparative study of the gaseous-phase and stellar-phase metallicities in the centres of members of a sample of barred and unbarred galaxies from SDSS. We do not find a significant difference in the metallicity (neither gaseous nor stellar) between barred and unbarred galaxies, but we find different trends in the metallicities of early- and late-type galaxies, with larger differences in the metallicity in the early-type subsample. Our results contradict some previous research in this field, but we find a possible origin of the discrepancies between previous works and our results.Item Erratum: Stellar kinematics and structural properties of Virgo cluster dwarf early-type galaxies from the smakced project. II. The survey and a systematic analysis of kinematic anomalies and asymmetries (vol 215, 17, 2014)(Astrophysical journal supplement series, 2015) Gorgas García, Francisco JavierItem Formation and evolution of dwarf early-type galaxies in the Virgo cluster II. Kinematic scaling relations (Corrigendum) (vol 548, pg A76, 2012)(Astronomy & Astrophysics, 2013) Toloba, E.; Boselli, A.; Peletier, R. F.; Falcón Barroso, J.; van de Ven, G.; Gorgas García, Francisco JavierItem The origin of dwarf early-type galaxies in the Virgo cluster(EAS Publications Series, 2011) Toloba, E.; Boselli, A.; Peletier, R. F.; Gorgas García, Francisco JavierWe present new medium resolution kinematic data for a sample of 21 dwarf early-type galaxies (dEs) mainly in the Virgo cluster. These data are used to study the origin of the dE population inhabiting rich clusters. Within them we detect two different subpopulations: half of the sample (52%) are rotationally supported and the other half are pressure supported. We also find that the rotationally supported dEs are located in the outer parts of the cluster, present disky morphological shapes and are younger than those pressure supported that are concentrated in the core of the cluster without any underlying structures. Our analysis reveals that the rotationally supported objects have rotation curves similarly shaped to those of star forming galaxies of similar luminosities and follow the Tully-Fisher relation. This is expected if dE galaxies are the descendant of low luminosity star forming systems which recently entered the cluster and lost their gas due to a ram pressure stripping event, quenching their star formation activity and transforming them into quiescent systems, but conserving their angular momentum.Item An updated MILES stellar library and stellar population models (Research Note)(Astronomy & Astrophysics, 2011) Falcón Barroso, J.; Sánchez Blázquez, Patricia; Vazdekis, A.; Ricciardelli, E.; Cardiel López, Nicolás; Cenarro, A. J.; Gorgas García, Francisco Javier; Peletier, R. F.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 similar to 2.5 angstrom, 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).Item Stellar kinematics and structural properties of virgo cluster dwarf early-type galaxies from the smakced project. II. The survey and a systematic analysis of kinematic anomalies and asymmetries(Astrophysical journal supplement series, 2014) Toloba, E.; Guhathakurta, P.; Peletier, R. F.; Boselli, A.; Lisker, T.; Falcón Barroso, J.; Simón, J. D.; van de Ven, G.; Paudel, S.; Emsellem, E.; Janz, J.; den Brok, M.; Gorgas García, Francisco Javier; Hensler, G.; Laurikainen, E.; Niemi, S. M.; Rys, A.; Salo, H.We present spatially resolved kinematics and global stellar populations and mass-to-light ratios for a sample of 39 dwarf early-type (dE) galaxies in the Virgo cluster studied as part of the SMAKCED stellar absorption-line spectroscopy and imaging survey. This sample is representative of the early-type population in the Virgo cluster in the absolute magnitude range -19.0 < M-r < -16.0 and of all morphological subclasses found in this galaxy population. For each dE, we measure the rotation curve and velocity dispersion profile and fit an analytic function to the rotation curve. We study the significance of the departure of the rotation curve from the best-fit analytic function (poorly fit) and of the difference between the approaching and receding sides of the rotation curve (asymmetry). Our sample includes two dEs with kinematically decoupled cores that have been previously reported. We find that 62 +/- 8% (23 out of the 39) of the dEs have a significant anomaly in their rotation curve. Analysis of the images reveals photometric anomalies for most galaxies. However, there is no clear correlation between the significance of the photometric and kinematic anomalies. We measure age-sensitive (H-beta and H-gamma A) and metallicity sensitive (Fe4668 and Mgb) Lick spectral indices in the LIS-5 angstrom system. This population of galaxies exhibits a wide range of ages and metallicities; we also find that 4 dEs show clear evidence of emission partially filling in the Balmer absorption lines. Finally, we estimate the total masses and dark matter fractions of the dEs and plot them in the mass-size, themass-velocity dispersion, and the fundamental plane scaling relations. The dEs seem to be the bridge between massive early-type galaxies and dSphs, and have a median total mass within the R-e of logM(e) = 9.1 +/- 0.2 and a median dark matter fraction within the R-e of f(DM) = 46 +/- 18%. Any formation model for the dE galaxy class must account for this diversity of kinematic and photometric anomalies and stellar populations.Item Formation and evolution of dwarf early-type galaxies in the Virgo cluster II. Kinematic scaling relations(Astronomy & Astrophysics, 2012) Toloba, E.; Boselli, A.; Peletier, R. F.; Falcón Barroso, J.; van de Ven, G.; Gorgas García, Francisco JavierWe place our sample of 18 Virgo dwarf early-type galaxies (dEs) on the (V - K)_e-velocity dispersion, Faber-Jackson, and fundamental plane (FP) scaling relations for massive early-type galaxies (Es). We use a generalized velocity dispersion, which includes rotation, to be able to compare the location of both rotationally and pressure supported dEs with those of early and late-type galaxies. We find that dEs seem to bend the Faber-Jackson relation of Es to lower velocity dispersions, being the link between Es and dwarf spheroidal galaxies (dSphs). Regarding the FP relation, we find that dEs are significantly offset with respect to massive hot stellar systems, and re-casting the FP into the so-called.-space suggests that this offset is related to dEs having a total mass-to-light ratio higher than Es but still significantly lower than dSph galaxies. Given a stellar mass-to-light ratio based on the measured line indices of dEs, the FP offset allows us to infer that the dark matter fraction within the half light radii of dEs is on average ≳42% (uncertainties of 17% in the K band and 20% in the V band), fully consistent with an independent estimate in an earlier paper in this series. We also find that dEs in the size-luminosity relation in the near-infrared, like in the optical, are offset from early-type galaxies, but seem to be consistent with late-type galaxies. We thus conclude that the scaling relations show that dEs are different from Es, and that they further strengthen our previous findings that dEs are closer to and likely formed from late-type galaxies.