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
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Now showing 1 - 10 of 48
  • Publication
    The minor role of gas-rich major mergers in the rise of intermediate-mass early types at z ≤ 1
    (American Astronomical Society, 2010-02-20) López Sanjuan, Carlos; Balcells, Marc; Pérez González, Pablo Guillermo; Barro, Guillermo; García Dabó, César Enrique; Gallego Maestro, Jesús; Zamorano Calvo, Jaime
    We study the evolution of galaxy structure since z ~ 1 to the present. From a Great Observatories Origins Deep Survey South (GOODS-S) multi-band catalog, we define (blue) luminosity- and mass-weighted samples, limited by MB ≤ –20 and M sstarf ≥ 1010 M ☉, comprising 1122 and 987 galaxies, respectively. We extract early-type (ET; E/S0/Sa) and late-type (LT; Sb-Irr) subsamples by their position in the concentration-asymmetry plane, in which galaxies exhibit a clear bimodality. We find that the ET fraction, f ET, rises with cosmic time, with a corresponding decrease in the LT fraction, f LT, in both luminosity- and mass-selected samples. However, the evolution of the comoving number density is very different: the decrease in the total number density of MB ≤ –20 galaxies since z = 1 is due to the decrease in the LT population, which accounts for ~75% of the total star formation rate in the range under study, while the increase in the total number density of M sstarf ≥ 1010 M ☉ galaxies in the same redshift range is due to the evolution of ETs. This suggests that we need a structural transformation between LT galaxies that form stars actively and ET galaxies in which the stellar mass is located. Comparing the observed evolution with the gas-rich major merger rate in GOODS-S, we infer that only ~20% of the new ET galaxies with M sstarf ≥ 1010 M ☉ appeared since z ~ 1 can be explained by this kind of mergers, suggesting that minor mergers and secular processes may be the driving mechanisms of the structural evolution of intermediate-mass (M sstarf ~ 4 × 1010 M ☉) galaxies since z ~ 1.
  • Publication
    Formation of S0 galaxies through mergers. V - Antitruncated stellar discs resulting from major mergers
    (EDP Sciencies, 2014-10) Borlaff, Alejandro; Eliche Moral, María del Carmen; Rodríguez Pérez, Cristina; Querejeta, Miguel; Tapia, Trinidad; Pérez González, Pablo Guillermo; Zamorano Calvo, Jaime; Gallego Maestro, Jesús; Beckman, John
    Context. Lenticular galaxies (S0s) are more likely to host antitruncated (Type III) stellar discs than galaxies of later Hubble types. Major mergers are popularly considered too violent to make these breaks. Aims. We have investigated whether major mergers can result into S0-like remnants with realistic antitruncated stellar discs or not. Methods. We have analysed 67 relaxed S0 and E/S0 remnants resulting from dissipative N-body simulations of major mergers from the GalMer database. We have simulated realistic R-band surface brightness profiles of the remnants to identify those with antitruncated stellar discs. Their inner and outer discs and the breaks have been quantitatively characterized to compare with real data. Results. Nearly 70% of our S0-like remnants are antitruncated, meaning that major mergers that result in S0s have a high probability of producing Type III stellar discs. Our remnants lie on top of the extrapolations of the observational trends (towards brighter magnitudes and higher break radii) in several photometric diagrams, because of the higher luminosities and sizes of the simulations compared to observational samples. In scale-free photometric diagrams, simulations and observations overlap and the remnants reproduce the observational trends, so the physical mechanism after antitruncations is highly scalable. We have found novel photometric scaling relations between the characteristic parameters of the antitruncations in real S0s, which are also reproduced by our simulations. We show that the trends in all the photometric planes can be derived from three basic scaling relations that real and simulated Type III S0s fulfill: h_i ∝ R_brkIII, h_o ∝ R_brkIII, and μ_brkIII ∝ R_brkIII, where h_i and h_o are the scalelengths of the inner and outer discs, and μ_brkIII and R_brkIII are the surface brightness and radius of the breaks. Bars and antitruncations in real S0s are structurally unrelated phenomena according to the studied photometric planes. Conclusions. Major mergers provide a feasible mechanism to form realistic antitruncated S0 galaxies.
  • Publication
    Characterization of active galactic nuclei and their hosts in the extended groth strip: a multiwavelength analysis
    (IOP Publishing ltd, 2009-01) Ramos Almeida, C.; Rodríguez Espinosa, J. M.; Barro, Guillermo; Gallego Maestro, Jesús; Pérez González, Pablo Guillermo
    We have employed a reliable technique of classification of active galactic nuclei (AGNs) based on the fit of well sampled spectral energy distributions (SEDs) with a complete set of AGN and starburst galaxy templates. We have compiled UV, optical, and IR data for a sample of 116 AGNs originally selected for their X-ray and mid-IR emissions (96 with single detections and 20 with double optical counterparts). This is the most complete compilation of multiwavelength data for such a large sample of AGN in the Extended Groth Strip. Through these SEDs, we are able to obtain highly reliable photometric redshifts and to distinguish between pure and host-dominated AGNs. For the objects with unique detection we find that they can be separated into five main groups, namely: Starburst-dominated AGNs (24% of the sample), Starburst-contaminated AGNs (7%), Type-1 AGNs (21%), Type-2 AGNs (24%), and Normal galaxy hosting AGN (24%). We find these groups concentrated at different redshifts: Type-2 AGNs and Normal galaxy hosting AGNs are concentrated at low redshifts, whereas Starburst-dominated AGNs and Type-1 AGNs show a larger span. Correlations between hard/soft X-ray and UV, optical and IR luminosities are reported for the first time for such a sample of AGNs spanning a wide range of redshifts. For the 20 objects with double detection, the percentage of Starburst-dominated AGNs increases up to 48%.
  • Publication
    Constraints on the evolutionary mechanisms of massive galaxies since z ∼ 1 from their velocity dispersions
    (Wiley, 2015-10-11) Peralta de Arriba, L.; Balcells, M.; Trujillo, I.; Falcón Barroso, J.; Tapia, T.; Cardiel López, Nicolás; Gallego Maestro, Jesús; Guzmán, R.; Hempel, A.; Martín Navarro, I.; Pérez González, Pablo Guillermo; Sánchez Blázquez, P.
    Several authors have reported that the dynamical masses of massive compact galaxies (M_⋆ ≳ 10^11 M_⊙, r_e ∼ 1 kpc), computed as M_dyn=5.0 σ_e^2r_e/GMdyn=5.0 σe2re/G, are lower than their stellar masses M_⋆. In a previous study from our group, the discrepancy is interpreted as a breakdown of the assumption of homology that underlie the M_dyn determinations. Here, we present new spectroscopy of six redshift z ≈ 1.0 massive compact ellipticals from the Extended Groth Strip, obtained with the 10.4 m Gran Telescopio Canarias. We obtain velocity dispersions in the range 161–340 km s^−1. As found by previous studies of massive compact galaxies, our velocity dispersions are lower than the virial expectation, and all of our galaxies show M_dyn < M_⋆ (assuming a Salpeter initial mass function). Adding data from the literature, we build a sample covering a range of stellar masses and compactness in a narrow redshift range z ≈ 1.0. This allows us to exclude systematic effects on the data and evolutionary effects on the galaxy population, which could have affected previous studies. We confirm that mass discrepancy scales with galaxy compactness. We use the stellar mass plane (M_⋆, σ_e, r_e) populated by our sample to constrain a generic evolution mechanism. We find that the simulations of the growth of massive ellipticals due to mergers agree with our constraints and discard the assumption of homology.
  • Publication
    UV-to-fir analysis of spitzer/irac sources in the extended groth strip. II. Photometric redshifts, stellar masses, and star formation rates
    (University Chicago Press, 2011-04) Barro, Guillermo; Pérez González, Pablo Guillermo; Gallego Maestro, Jesús; Ashby, M. L. N.; Kajisawa, M.; Miyazaki, S.; Villar, V.; Yamada, T.; Zamorano Calvo, Jaime
    Based on the ultraviolet to far-infrared photometry already compiled and presented in a companion paper (Paper I), we present a detailed spectral energy distribution (SED) analysis of nearly 80,000 IRAC 3.6 + 4.5 μ m selected galaxies in the Extended Groth Strip. We estimate photometric redshifts, stellar masses, and star formation rates (SFRs) separately for each galaxy in this large sample. The catalog includes 76,936 sources with [3.6] ≤ 23.75 (85% completeness level of the IRAC survey) over 0.48 deg^2. The typical photometric redshift accuracy is ∆z/(1 + z) = 0.034, with a catastrophic outlier fraction of just 2%. We quantify the systematics introduced by the use of different stellar population synthesis libraries and initial mass functions in the calculation of stellar masses. We find systematic offsets ranging from 0.1 to 0.4 dex, with a typical scatter of 0.3 dex. We also provide UV- and IR-based SFRs for all sample galaxies, based on several sets of dust emission templates and SFR indicators. We evaluate the systematic differences and goodness of the different SFR estimations using the deep FIDEL 70 μ m data available in the Extended Groth Strip. Typical random uncertainties of the IR-bases SFRs are a factor of two, with non-negligible systematic effects at z ≳1.5 observed when only MIPS 24 μ m data are available. All data products (SEDs, postage stamps from imaging data, and different estimations of the photometric redshifts, stellar masses, and SFRs of each galaxy) described in this and the companion paper are publicly available, and they can be accessed through our the Web interface utility Rainbow-navigator.
  • Publication
    Radial distribution of dust properties in nearby galaxies
    (Springer-Verlag Berlin, 2010) Muñoz Mateos, J.C.; Gil de Paz, Armando; Zamorano Calvo, Jaime; Pérez González, Pablo Guillermo; Gallego Maestro, Jesús
    We present a detailed analysis of the radial distribution of dust properties (extinction, PAH abundance and dust-to-gas ratio) in 57 galaxies in the SINGS sample, performed on a multi-wavelength set of UV, IR and radio surface brightness profiles, combined with published molecular gas profiles and metallicity gradients.
  • 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
    MEGARA, the new intermediate-resolution optical IFU and MOS for GTC: getting ready for the telescope
    (SPIE-Int Soc Optical Engineering, 2016) Gil de Paz, Armando; Gallego Maestro, Jesús; Cardiel López, Nicolás; Castillo Morales, África; Cruz García, Jesús Manuel de la; Esteban San Román, Segundo; López Orozco, José Antonio; Pascual, S.; Picazo, P.; Sánchez-Penim, A.; Zamorano Calvo, Jaime; Pérez González, Pablo Guillermo; otros, ...
    MEGARA (Multi-Espectrografo en GTC de Alta Resolucion para Astronomia) is an optical Integral-Field Unit (IFU) and Multi-Object Spectrograph (MOS) designed for the GTC 10.4m telescope in La Palma that is being built by a Consortium led by UCM (Spain) that also includes INAOE (Mexico), IAA-CSIC (Spain), and UPM (Spain). The instrument is currently finishing AIV and will be sent to GTC on November 2016 for its on-sky commissioning on April 2017. The MEGARA IFU fiber bundle (LCB) covers 12.5x11.3 arcsec(2) with a spaxel size of 0.62 arcsec while the MEGARA MOS mode allows observing up to 92 objects in a region of 3.5x3.5 arcmin(2) around the IFU. The IFU and MOS modes of MEGARA will provide identical intermediate-to-high spectral resolutions (R-FWHM similar to 6,000, 12,000 and 18,700, respectively for the low-, mid-and high-resolution Volume Phase Holographic gratings) in the range 3700-9800 angstrom angstrom. An x-y mechanism placed at the pseudo-slit position allows (1) exchanging between the two observing modes and (2) focusing the spectrograph for each VPH setup. The spectrograph is a collimator-camera system that has a total of 11 VPHs simultaneously available (out of the 18 VPHs designed and being built) that are placed in the pupil by means of a wheel and an insertion mechanism. The custom-made cryostat hosts a 4kx4k 15-mu m CCD. The unique characteristics of MEGARA in terms of throughput and versatility and the unsurpassed collecting are of GTC make of this instrument the most efficient tool to date to analyze astrophysical objects at intermediate spectral resolutions. In these proceedings we present a summary of the instrument characteristics and the results from the AIV phase. All subsystems have been successfully integrated and the system-level AIV phase is progressing as expected.
  • 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.