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 17
  • 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
    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
    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
    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
    Evolutionary paths among different red galaxy types at 0.3 < z < 1.5 and the late buildup of massive E-S0's through major mergers
    (Wiley, 2013-01) Prieto, Mercedes; Eliche Moral, María del Carmen; Balcells, Marc; Cristobal Hornillos, David; Erwin, Peter; Abreu, David; Domínguez Palmero, Lilian; Hempel, Ángela; López Sanjuan, Carlos; Guzmán, Rafael; Pérez González, Pablo Guillermo; Barro, Guillermo; Gallego Maestro, Jesús; Zamorano Calvo, Jaime
    Some recent observations seem to disagree with hierarchical theories of galaxy formation about the role played by major mergers in the late buildup of massive E-S0s. We re-address this question by analysing the morphology, structural distortion level and star formation enhancement of a sample of massive galaxies (M_* > 5x10^10M_⨀) lying on the Red Sequence and its surroundings at 0.3 < z < 1.5. We have used an initial sample of ∼1800 sources with K_s < 20.5 mag over an area ∼155 arcmin^2 on the Groth Strip, combining data from the Rainbow Extragalactic Database and the Galaxy Origins and Young Assembly survey. Red galaxy classes that can be directly associated with intermediate stages of major mergers and with their final products have been defined. We report observational evidence of the existence of a dominant evolutionary path among massive red galaxies at 0.6 < z < 1.5, consisting in the conversion of irregular discs into irregular spheroids, and of these ones into regular spheroids. This result implies: (1) the massive red regular galaxies at low redshifts derive from the irregular ones populating the Red Sequence and its neighbourhood at earlier epochs up to z ∼ 1.5; (2) the progenitors of the bulk of present-day massive red regular galaxies have been discs that seem to have migrated to the Red Sequence mostly through major mergers at 0.6 < z < 1.2 (these mergers thus starting at z ∼ 1.5) and (3) the formation of E-S0s that end up with M_* > 10^11 M_⨀ at z = 0 through gas-rich major mergers has frozen since z similar to 0.6. All these facts support that major mergers have played a dominant role in the definitive buildup of present-day E-S0s with M-* > 10(11) M-circle dot at 0.6 < z < 1.2, in good agreement with hierarchical scenarios of galaxy formation.
  • Publication
    The buildup of E–S0 galaxies at z < 2 from pure luminosity evolution models
    (Springer-Verlag Berlin, 2010) Eliche Moral, María del Carmen; Prieto, M.; Barro, Guillermo; Balcells, M.; Gallego Maestro, Jesús; Pérez González, Pablo Guillermo; Zamorano Calvo, Jaime; Cardiel López, Nicolás; Gil de Paz, Armando; Guzmán, R.; Pelló, R.; Villar, V.
    Considering that the recent history of E-S0’s can be approximated by Pure Luminosity Evolution (PLE), we have examined a set of PLE models in order to de-limit the epoch in which the majority of the red galaxy population moved away this simple evolution framework. The models assume that they were assembled and formed most of their stars at a given formation redshift (zf), and that they have evolved without merging or substantial dust obscuration since then. Comparing the model predictions with real data, we conclude that most of E-S0’s at low and inter-mediate luminosities must have been progressively built up at 1 < z < 2, being the bulk of formation at z ∼ 1.5, as recently claimed by several observational studies.
  • Publication
    Deconstructing the K-band number counts
    (Springer-Verlag Berlin, 2010) Barro, Guillermo; Gallego Maestro, Jesús; Pérez González, Pablo Guillermo; Eliche Moral, María del Carmen; Balcells, M.; Villar, V.; Cardiel López, Nicolás; Cristobal Hornillos, D.; Gil de Paz, Armando; Guzmán, R.; Pelló, R.; Prieto, M.; Zamorano Calvo, Jaime
    We present a study that links the NCs to the rest-frame luminosity functions (LFs) at the passbands probed by the observed K-band at different epochs. Making use of a large K-band selected sample in the Groth Field, HDFN and CDFS (∼0.27deg^(2)), we have derived highly reliable photometric redshift estimates that allow us to estimate LFs in the redshift range [0.25-1.25]. We find that the larger flattening in the slope of the K-band NCs is mostly a consequence of a prominent decrease in the characteristic density (φ∗) around z∼1, and an almost flat evolution of M∗.
  • Publication
    Exploring the evolutionary paths of the most massive galaxies since z ~ 2
    (American Astronomical Society, 2008-11-01) Pérez González, Pablo Guillermo; Trujillo, Ignacio; Barro, Guillermo; Gallego Maestro, Jesús; Zamorano Calvo, Jaime; Conselice, Christopher J.
    We use Spitzer MIPS data from the FIDEL Legacy Project in the extended Groth strip to analyze the stellar mass assembly of massive (M > 1011 M_☉) galaxies at z < 2 as a function of structural parameters. We find 24 μm emission for more than 85% of the massive galaxies morphologically classified as disks, and for more than 57% of the massive systems morphologically classified as spheroids at any redshift, with about 8% of sources harboring a bright X-ray- and/or infrared-emitting AGN. More noticeably, ~60% of all compact massive galaxies at z = 1–2 are detected at 24 μm, even when rest-frame optical colors reveal that they are dead and evolving passively. For spheroid-like galaxies at a given stellar mass, the sizes of MIPS nondetections are smaller by a factor of ~1.2 in comparison with IR-bright sources. We find that disklike massive galaxies present specific SFRs ranging from 0.04 to 0.2 Gyr^−1 at z < 1 (SFRs ranging from 1 to 10 M_☉ yr^−1), typically a factor of 3-6 higher than massive spheroid-like objects in the same redshift range. At z > 1, and more pronouncedly at z > 1.3, the median specific SFRs of the disks and spheroids detected by MIPS are very similar, ranging from 0.1 to 1 Gyr^−1 (SFR = 10–200 M_☉ yr^−1). We estimate that massive spheroid-like galaxies may have doubled (at the most) their stellar mass from star-forming events at z < 2: less than 20% mass increase at 1.7 < z < 2.0, up to 40% more at 1.1 < z < 1.7, and less than 20% additional increase at z < 1. Disklike galaxies may have tripled (at the most) their stellar mass at z < 2 from star formation alone: up to ~40% mass increase at 1.7 < z < 2.0, and less than 180% additional increase below z = 1.7 occurred at a steady rate.
  • Publication
    SHARDS: stellar populations and star formation histories of a mass-selected sample of 0.65 < z < 1.1 galaxies
    (Wiley, 2013-09) Pérez González, Pablo Guillermo; Cardiel López, Nicolás; Cava, Antonio; Barro, Guillermo; Gallego Maestro, Jesús
    We report on results from the analysis of a stellar mass-selected (log (M-*/M-circle dot) >= 9.0) sample of 1644 galaxies at 0.65 < z < 1.1 with ultradeep (m(AB) < 26.5) optical medium-band (R similar to 50) photometry from the Survey for High-z Absorption Red and Dead Sources (SHARDS). The spectral resolution of SHARDS allows us to consistently measure the strength of the 4000 A spectral break [D-n(4000), an excellent age indicator for the stellar populations of quiescent galaxies] for all galaxies at z similar to 0.9 down to log (M-*/M-circle dot) similar to 9. The D-n(4000) index cannot be resolved from broad-band photometry, and measurements from optical spectroscopic surveys are typically limited to galaxies at least 10 times more massive. When combined with the rest-frame U - V colour, (U - V)(r), D-n(4000) provides a powerful diagnostic of the extinction affecting the stellar population that is relatively insensitive to degeneracies with age, metallicity or star formation history. We use this novel approach to estimate de-reddened colours and light-weighted stellar ages for individual sources. We explore the relationships linking stellar mass, (U - V)(r), and D-n(4000) for the sources in the sample, and compare them to those found in local galaxies. The main results are: (a) both D-n(4000) and (U - V)(r) correlate with M-*. The dispersion in D-n(4000) values at a given M-* increases with M-*, while the dispersion for (U - V)(r) decreases due to the higher average extinction prevalent in massive star-forming galaxies. (b) For massive galaxies, we find a smooth transition between the blue cloud and red sequence in the intrinsic U - V colour, in contrast with other recent results. (c) At a fixed stellar age, we find a positive correlation between extinction and stellar mass. (d) The fraction of sources with declining or halted star formation increases steeply with the stellar mass, from similar to 5 per cent at log (M-*/M-circle dot) = 9.0-9.5 to similar to 80 per cent at log (M-*/M-circle dot) > 11, in agreement with downsizing scenarios.