Pérez González, Pablo Guillermo

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First Name
Pablo Guillermo
Last Name
Pérez González
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Astronomía y Astrofísica
UCM identifierScopus Author IDWeb of Science ResearcherIDDialnet ID

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Now showing 1 - 10 of 18
  • Publication
    The stellar mass assembly of galaxies from z=0 to z=4: Analysis of a sample selected in the rest-frame near-infrared with Spitzer
    (American Astronomical Society, 2008-03-01) Pérez González, Pablo Guillermo; Rieke, George H.;, George H.; Villar, Victor; Barro, Guillermo; Blaylock, Myra; Egami, Eiichi; Gallego Maestro, Jesús; Gil de Paz, Armando; Pascual, Sergio; Zamorano Calvo, Jaime; Donley, Jennifer L.
    Using a sample of ~28,000 sources selected at 3.6-4.5 μm with Spitzer observations of the Hubble Deep Field North, the Chandra Deep Field South, and the Lockman Hole (surveyed area ~664 arcmin^2), we study the evolution of the stellar mass content of the universe at 0 < z < 4. We calculate stellar masses and photometric redshifts, based on ~2000 templates built with stellar population and dust emission models fitting the ultraviolet to mid-infrared spectral energy distributions of galaxies with spectroscopic redshifts. We estimate stellar mass functions for different redshift intervals. We find that 50% of the local stellar mass density was assembled at 0 < z < 1 (average star formation rate [SFR] 0.048 M-☉ yr^−1 Mpc^−3), and at least another 40% at 1 < z < 4 (average SFR 0.074 M_☉ yr^−1 Mpc^−3). Our results confirm and quantify the "downsizing" scenario of galaxy formation. The most massive galaxies (M > 10^12.0 M_☉) assembled the bulk of their stellar content rapidly (in 1-2 Gyr) beyond z ~ 3 in very intense star formation events (producing high specific SFRs). Galaxies with 10^11.5 < M < 10^12.0 M_☉ assembled half of their stellar mass before z ~ 1.5, and more than 90% of their mass was already in place at z ~ 0.6. Galaxies with M < 1011.5 M☉ evolved more slowly (presenting smaller specific SFRs), assembling half of their stellar mass below z ~ 1. About 40% of the local stellar mass density of 10^9.0 < M < 10^11.0 M_☉ galaxies was assembled below z ~ 0.4, most probably through accretion of small satellites producing little star formation. The cosmic stellar mass density at z > 2.5 is dominated by optically faint (Rgsim 25) red galaxies (distant red galaxies or BzK sources), which account for ~30% of the global population of galaxies, but contribute at least 60% of the cosmic stellar mass density. Bluer galaxies (e.g., Lyman break galaxies) are more numerous but less massive, contributing less than 50% of the global stellar mass density at high redshift.
  • Publication
    The Hα-based star formation rate density of the universe at z=0.84
    (American Astronomical Society, 2008-04-10) Villar, Victor; Gallego Maestro, Jesús; Pérez González, Pablo Guillermo; Pascual, Sergio; Noeske, Kai; Koo, David C.; Barro, Guillermo; Zamorano Calvo, Jaime
    We present the results of an Hα near-infrared narrowband survey searching for star-forming galaxies at redshift z = 0.84. This work is an extension of our previous narrowband studies in the optical at lower redshifts. After removal of stars and redshift interlopers (using spectroscopic and photometric redshifts), we build a complete sample of 165 Hα emitters in the extended Groth strip and GOODS-N fields with L(Hα) > 10^41 ergs s^−1. We compute the Hα luminosity function at z = 0.84 after corrections for [N_π] flux contamination, extinction, systematic errors, and incompleteness. Our sources present an average dust extinction of A(H α) = 1.5 mag. Adopting Hα as a surrogate for the instantaneous SFR, we measure an extinction-corrected SFR density of 0.17^+0.03_−0.03 M_☉ yr^−1 Mpc^−3. Combining this result to our prior measurements at z = 0.02, 0.24, and 0.40, we derive an Hα-based evolution of the SFR density proportional to (1 + z)^β with β = 3.8 ± 0.5. This evolution is consistent with that derived by other authors using different SFR tracers.
  • Publication
    Luminosity and stellar mass functions of local star-forming galaxies
    (American Astronomical Society, 2003-04-10) Pérez González, Pablo Guillermo; Gallego Maestro, Jesús; Zamorano Calvo, Jaime; Alonso Herrero, A.; Gil de Paz, Armando; Aragón Salamanca, A.
    We present the optical and near-infrared luminosity and mass functions of the local star-forming galaxies in the Universidad Complutense de Madrid (UCM) Survey. A bivariate method that explicitly deals with the Hα selection of the survey is used when estimating these functions. Total stellar masses have been calculated on a galaxy-by-galaxy basis taking into account differences in star formation histories. The main difference between the luminosity distributions of the UCM sample and the luminosity functions of the local galaxy population is a lower normalization (φ *), indicating a lower global volume density of UCM galaxies. The typical near-infrared luminosity (L*) of local star-forming galaxies is fainter than that of normal galaxies. This is a direct consequence of the lower stellar masses of our objects. However, at optical wavelengths (B and r), the luminosity enhancement arising from the young stars leads to M* values that are similar to those of normal galaxies. The fraction of the total optical and near-infrared luminosity density in the local universe associated with star-forming galaxies is 10%-20%. Fitting the total stellar mass function using a Schechter parameterization, we obtain α = -1.15 ± 0.15, log M* = 10.82 ± 0.17 M_☉, and log φ * = -3.04 ± 0.20 Mpc^-3. This gives an integrated total stellar mass density of 10^7.83±0.07 M_☉ Mpc-3 in local star-forming galaxies (H_0 = 70 km s^-1 Mpc^-1, Ω_M = 0.3, and Λ = 0.7). The volume-averaged burst strength of the UCM galaxies is b = 0.04 ± 0.01, defined as the ratio of the mass density of stars formed in recent bursts (with an age of <10 Myr) to the total stellar mass density in UCM galaxies. Finally, we derive that in the local universe, 13% ± 3% of the total baryon mass density in the form of stars is associated with star-forming galaxies.
  • Publication
    Radial distribution of stars, gas, and dust in sings galaxies. II. Derived dust properties
    (American Astronomical Society, 2009-08-20) Muñoz Mateos, J. C.; Gil de Paz, Armando; Boissier, S.; Zamorano Calvo, Jaime; Dale, D. A.; Pérez González, Pablo Guillermo; Gallego Maestro, Jesús; Madore, B. F.; Bendo, G.; Thornley, M. D.; Draine, B. T.; Boselli, A.; Buat, V.; Calzetti, D.; Moustakas, J.; Kennicutt, R. C. Jr.
    We present a detailed analysis of the radial distribution of dust properties in the SINGS sample, performed on a set of ultraviolet (UV), infrared (IR), and Hi surface brightness profiles, combined with published molecular gas profiles and metallicity gradients. The internal extinction, derived from the total-IR (TIR)-to-far-UV (FUV) luminosity ratio, decreases with radius, and is larger in Sb-Sbc galaxies. The TIR-to-FUV ratio correlates with the UV spectral slope β, following a sequence shifted to redder UV colors with respect to that of starbursts. The star formation history (SFH) is identified as the main driver of this departure. Both L_TIR)/L_FUV and β correlate well with metallicity, especially in moderately face-on galaxies. The relation shifts to redder colors with increased scatter in more edge-on objects. By applying physical dust models to our radial spectral energy distributions, we have derived radial profiles of the total dust mass surface density, the fraction of the total dust mass contributed by polycyclic aromatic hydrocarbons (PAHs), and the intensity of the radiation field heating the grains. The dust profiles are exponential, their radial scale length being constant from Sb to Sd galaxies (only ~ 10% larger than the stellar scale length). Many S0/a-Sab galaxies have central depressions in their dust radial distributions. The PAH abundance increases with metallicity for 12 + log(O/H) < 9, and at larger metallicities the trend flattens and even reverses, with the SFH being a plausible underlying driver for this behavior. The dust-to-gas ratio is also well correlated with metallicity and therefore decreases with galactocentric radius. Although most of the total emitted IR power (especially in the outer regions of disks) is contributed by dust grains heated by diffuse starlight with a similar intensity as the local Milky Way radiation field, a small amount of the dust mass (~ 1%) is required to be exposed to very intense starlight in order to reproduce the observed fluxes at 24 μ m, accounting for ~ 10% of the total integrated IR power.
  • Publication
    Star Formation Rate estimators: [O II]λ3727 vs. Hα for local star-forming galaxies
    (Astronomical Society of the Pacific, 2003) Aragón Salamanca, A.; Alonso Herrero, A.; Gallego Maestro, Jesús; García Dabó, C. E.; Pérez González, Pablo Guillermo; Zamorano Calvo, Jaime; Gil de Paz, Armando
    The [O ii]λ3727 emission line is frequently used as an indicator of the star formation rate (SFR) despite its complex dependence on metallicity and excitation conditions. We have analysed the properties of the [O II] and Hα emission lines for a complete sample of local Hα-selected galaxies, the Universidad Complutense de Madrid (UCM) survey. We find a large scatter in the [O II]/Hα line ratios, although the scatter in the extinction-corrected [O II]^0/Hα^0 ratio is considerably smaller. We also find that the [O II]/Hα ratios are reasonably well correlated with the absolute B- and K-band magnitudes and with EW([O II]). However, the extinction-corrected [O II]^0/Hα^0 ratio is largely independent of these quantities, indicating that extinction is the main driver of the correlations. These correlations allow us to statistically predict-with varying degrees of accuracy-the observed and extinction-corrected Hα fluxes from the observed [O II] flux using the information contained in EW([O II]) and/or the absolute magnitudes, but extreme caution is needed to make sure that the sample selection effects are correctly taken into account.
  • Publication
    Stellar populations in local star-forming galaxies - II. Recent star formation properties and stellar masses
    (Wiley, 2003-01-11) Pérez González, Pablo Guillermo; Gil de Paz, Armando; Zamorano Calvo, Jaime; Gallego Maestro, Jesús; Alonso Herrero, A.; Aragón Salamanca, A.
    We present the integrated properties of the stellar populations in the Universidad Complutense de Madrid (UCM) Survey galaxies. Applying the techniques described in the first paper of this series, we derive ages, burst masses and metallicities of the newly formed stars in our sample galaxies. The population of young stars is responsible for the Halpha emission used to detect the objects in the UCM Survey. We also infer total stellar masses and star formation rates in a consistent way taking into account the evolutionary history of each galaxy. We find that an average UCM galaxy has a total stellar mass of ∼10^10 M_⨀, of which about 5 per cent was formed in an instantaneous burst that occurred about 5 Myr ago, and subsolar metallicity. Less than 10 per cent of the sample shows massive starbursts involving more than half of the total mass of the galaxy. Several correlations are found among the derived properties. The burst strength is correlated with the extinction and with the integrated optical colours for galaxies with low obscuration. The current star formation rate is correlated with the gas content. A stellar mass-metallicity relation is also found. Our analysis indicates that the UCM Survey galaxies span a broad range in properties between those of galaxies completely dominated by current/recent star formation and those of normal quiescent spirals. We also find evidence indicating that star formation in the local Universe is dominated by galaxies considerably less massive than L^*.
  • Publication
    Stellar populations in local star-forming galaxies - I. Data and modelling procedure
    (Wiley, 2003-01-11) Pérez González, Pablo Guillermo; Gil de Paz, Armando; Zamorano Calvo, Jaime; Gallego Maestro, Jesús; Alonso Herrero, A.; Aragón Salamanca, A,
    We present an analysis of the integrated properties of the stellar populations in the Universidad Complutense de Madrid (UCM) Survey of Halpha-selected galaxies. In this paper, the first of a series, we describe in detail the techniques developed to model star-forming galaxies using a mixture of stellar populations, and taking into account the observational uncertainties. We assume a recent burst of star formation superimposed on a more evolved population. The effects of the nebular continuum, line emission and dust attenuation are taken into account. We also test different model assumptions, including the choice of specific evolutionary synthesis model, initial mass function, star formation scenario and the treatment of dust extinction. Quantitative tests are applied to determine how well these models fit our multiwavelength observations for the UCM sample. Our observations span the optical and near-infrared, including both photometric and spectroscopic data. Our results indicate that extinction plays a key role in this kind of study, revealing that low- and high-obscured objects may require very different extinction laws and must be treated differently. We also demonstrate that the UCM Survey galaxies are best described by a short burst of star formation occurring within a quiescent galaxy, rather than by continuous star formation. A detailed discussion on the inferred parameters, such as the age, burst strength, metallicity, star formation rate, extinction and total stellar mass for individual objects, is presented in Paper II of this series.
  • Publication
    Radial distribution of stars, gas and dust in sings galaxies. I. Surface photometry and morphology
    (American Astronomical Society, 2009-10-01) Muñoz Mateos, J. C.; Gil de Paz, Armando; Zamorano Calvo, Jaime; Boissier, S.; Dale, D. A.; Pérez González, Pablo Guillermo; Gallego Maestro, Jesús; Madore, B. F.; Bendo, G.; Boselli, A.; Buat, V.; Calzetti, D.; Moustakas, J.; Kennicutt, R. C. Jr.
    We present ultraviolet through far-infrared (FIR) surface brightness profiles for the 75 galaxies in the Spitzer Infrared Nearby Galaxies Survey (SINGS). The imagery used to measure the profiles includes Galaxy Evolution Explorer UV data, optical images from Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and Sloan Digital Sky Survey, near-IR data from Two Micron All Sky Survey, and mid- and FIR images from Spitzer. Along with the radial profiles, we also provide multi-wavelength asymptotic magnitudes and several nonparametric indicators of galaxy morphology: the concentration index (C42), the asymmetry (A), the Gini coefficient (G), and the normalized second-order moment of the brightest 20% of the galaxy’s flux (M20). In this paper, the first of a series, we describe the technical aspects regarding the surface photometry, and present a basic analysis of the global and structural properties of the SINGS galaxies at different wavelengths. The homogeneity in the acquisition, reduction, and analysis of the results presented here makes these data ideal for multiple unanticipated studies on the radial distribution of the properties of stars, dust, and gas in galaxies. Our radial profiles show a wide range of morphologies and multiple components (bulges, exponential disks, inner and outer disk truncations, etc.) that vary not only from galaxy to galaxy but also with wavelength for a given object. In the optical and near-IR, the SINGS galaxies occupy the same regions in the C42–A-G-M20 parameter space as other normal galaxies in previous studies. However, they appear much less centrally concentrated, more asymmetric, and with larger values of G when viewed in the UV (due to star-forming clumps scattered across the disk) and in the mid-IR (due to the emission of polycyclic aromatic hydrocarbons at 8.0 μm and very hot dust at 24 μm). In an accompanying paper by Mu˜noz-Mateos et al., we focus on the radial distribution of dust properties in the SINGS galaxies, providing a detailed analysis of the radial variation of the attenuation, the dust column density, the dust-to-gas ratio, the abundance of PAHs, and the intensity of the heating starlight.
  • Publication
    Optical photometry of the UCM lists I and II - II. B band surface photometry and morphological discussion
    (EDP Sciencies, 2001-01) Pérez González, Pablo Guillermo; Gallego Maestro, Jesús; Zamorano Calvo, Jaime; Gil de Paz, Armando
    We present Johnson B surface photometry for the UCM Survey galaxies. One-dimensional bulge-disk decomposition is attempted, discussing on fitting functions and computational procedures. The results from this decomposition, jointly with concentration indices and an asymmetry coefficient, are employed to study the morphological properties of these galaxies. We also compare our results with the previous morphological classification established using Gunn r imaging data and with other samples of galaxies. No major statistical differences in morphology are found between red and blue data, although some characteristics such as size and luminosity concentration vary. We find a correlation between luminosity and size. Several parameters are used to segregate the objects according to their morphological type.
  • Publication
    Optical photometry of the UCM lists I and II - I. The data
    (EDP Sciences, 2000-02) Pérez González, Pablo Guillermo; Zamorano Calvo, Jaime; Gallego Maestro, Jesús; Gil de Paz, Armando
    We present Johnson B CCD photometry for the whole sample of galaxies of the Universidad Complutense de Madrid (UCM) Survey Lists I and II. They constitute a well-defined and complete sample of galaxies in the Local Universe with active star formation. The data refer to 191 SO to Irr galaxies at an averaged redshift of 0.027, and complement the already published Gunn r, J and K photometries. In this paper the observational and reduction features are discussed in detail, and the new colour information is combined to search for clues on thee properties of the galaxies, mainly by comparing our sample with other surveys.