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A. Gil de Paz

Bio: A. Gil de Paz is an academic researcher from Complutense University of Madrid. The author has contributed to research in topics: Galaxy & Star formation. The author has an hindex of 56, co-authored 200 publications receiving 13290 citations. Previous affiliations of A. Gil de Paz include Carnegie Learning & Jet Propulsion Laboratory.


Papers
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Journal ArticleDOI
Sebastián F. Sánchez1, Robert C. Kennicutt2, A. Gil de Paz3, G. van de Ven4, José M. Vílchez1, Lutz Wisotzki5, C. J. Walcher5, D. Mast1, J. A. L. Aguerri6, J. A. L. Aguerri1, Sergio Albiol-Pérez7, Almudena Alonso-Herrero1, João Alves8, J. Bakos6, J. Bakos1, T. Bartakova9, Joss Bland-Hawthorn10, Alessandro Boselli11, D. J. Bomans12, África Castillo-Morales3, C. Cortijo-Ferrero1, A. de Lorenzo-Cáceres6, A. de Lorenzo-Cáceres1, A. del Olmo1, Ralf-Jürgen Dettmar12, Angeles I. Díaz13, Simon Ellis10, Simon Ellis14, Jesús Falcón-Barroso1, Jesús Falcón-Barroso6, Hector Flores15, Anna Gallazzi16, Begoña García-Lorenzo1, Begoña García-Lorenzo6, R. M. González Delgado1, Nicolas Gruel, Tim Haines17, C. Hao18, Bernd Husemann5, J. Iglesias-Páramo1, Knud Jahnke4, Benjamin D. Johnson19, Bruno Jungwiert20, Bruno Jungwiert21, Veselina Kalinova4, C. Kehrig5, D. Kupko5, Angel R. Lopez-Sanchez14, Angel R. Lopez-Sanchez22, Mariya Lyubenova4, R. A. Marino3, R. A. Marino1, E. Mármol-Queraltó3, E. Mármol-Queraltó1, I. Márquez1, J. Masegosa1, Sharon E. Meidt4, Jairo Méndez-Abreu1, Jairo Méndez-Abreu6, Ana Monreal-Ibero1, C. Montijo1, A. Mourao23, G. Palacios-Navarro7, Polychronis Papaderos24, Anna Pasquali25, Reynier Peletier, Enrique Pérez1, I. Pérez26, Andreas Quirrenbach, M. Relaño26, F. F. Rosales-Ortega13, F. F. Rosales-Ortega1, Martin Roth5, T. Ruiz-Lara26, Patricia Sanchez-Blazquez13, C. Sengupta1, R. Singh4, Vallery Stanishev23, Scott Trager27, Alexandre Vazdekis6, Alexandre Vazdekis1, Kerttu Viironen1, Vivienne Wild28, Stefano Zibetti16, Bodo L. Ziegler8 
TL;DR: The Calar Alto Legacy Integral Field Area (CALIFA) survey as discussed by the authors was designed to provide a first step in this direction by obtaining spatially resolved spectroscopic information of a diameter selected sample of similar to 600 galaxies in the Local Universe.
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.

1,143 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present images, integrated photometry, surface-brightness and color profiles for a total of 1034 nearby galaxies recently observed by the GALEX satellite in its far-ultraviolet (FUV; 1516A) and near-ult ultraviolet (NUV; 2267A) bands.
Abstract: We present images, integrated photometry, surface-brightness and color profiles for a total of 1034 nearby galaxies recently observed by the GALEX satellite in its far-ultraviolet (FUV; 1516A) and near-ultraviolet (NUV; 2267A) bands. (...) This data set has been complemented with archival optical, near-infrared, and far-infrared fluxes and colors. We find that the integrated (FUV-K) color provides robust discrimination between elliptical and spiral/irregular galaxies and also among spiral galaxies of different sub-types. Elliptical galaxies with brighter K-band luminosities (i.e. more massive) are redder in (NUV-K) color but bluer in (FUV-NUV) than less massive ellipticals. In the case of the spiral/irregular galaxies our analysis shows the presence of a relatively tight correlation between the (FUV-NUV) color and the total infrared-to-UV ratio. The correlation found between (FUV-NUV) color and K-band luminosity (with lower luminosity objects being bluer than more luminous ones) can be explained as due to an increase in the dust content with galaxy luminosity. The images in this Atlas along with the profiles and integrated properties are publicly available through a dedicated web page at this http URL

773 citations

Journal ArticleDOI
TL;DR: The Local Volume Legacy (LVL) survey as discussed by the authors is a collection of low-luminosity galaxies with a large spread in mid-infrared colors, likely due to the conspicuous deficiency of 8 μm polycyclic aromatic hydrocarbon emission from low-metallicity, low-lightosity galaxies, exploiting the highest extragalactic spatial resolution achievable with Spitzer.
Abstract: The survey description and the near-, mid-, and far-infrared flux properties are presented for the 258 galaxies in the Local Volume Legacy (LVL). LVL is a Spitzer Space Telescope legacy program that surveys the local universe out to 11 Mpc, built upon a foundation of ultraviolet, Hα, and Hubble Space Telescope imaging from 11HUGS (11 Mpc Hα and Ultraviolet Galaxy Survey) and ANGST (ACS Nearby Galaxy Survey Treasury). LVL covers an unbiased, representative, and statistically robust sample of nearby star-forming galaxies, exploiting the highest extragalactic spatial resolution achievable with Spitzer. As a result of its approximately volume-limited nature, LVL augments previous Spitzer observations of present-day galaxies with improved sampling of the low-luminosity galaxy population. The collection of LVL galaxies shows a large spread in mid-infrared colors, likely due to the conspicuous deficiency of 8 μm polycyclic aromatic hydrocarbon emission from low-metallicity, low-luminosity galaxies. Conversely, the far-infrared emission tightly tracks the total infrared emission, with a dispersion in their flux ratio of only 0.1 dex. In terms of the relation between the infrared-to-ultraviolet ratio and the ultraviolet spectral slope, the LVL sample shows redder colors and/or lower infrared-to-ultraviolet ratios than starburst galaxies, suggesting that reprocessing by dust is less important in the lower mass systems that dominate the LVL sample. Comparisons with theoretical models suggest that the amplitude of deviations from the relation found for starburst galaxies correlates with the age of the stellar populations that dominate the ultraviolet/optical luminosities.

525 citations

Journal ArticleDOI
TL;DR: In this paper, the most widely used empirical oxygen calibrations, O3N2 and N2, by using new direct abundance measurements are reviewed, and the expected uncertainty of these calibrations as a function of the index value or abundance derived is analyzed.
Abstract: The use of integral field spectroscopy is since recently allowing to measure the emission line fluxes of an increasingly large number of star-forming galaxies, both locally and at high redshift. Many studies have used these fluxes to derive the gas-phase metallicity of the galaxies by applying the so-called strong-line methods. However, the metallicity indicators that these datasets use were empirically calibrated using few direct abundance data points (T_e-based measurements). Furthermore, a precise determination of the prediction intervals of these indicators is commonly lacking in these calibrations. Such limitations might lead to systematic errors in determining the gas-phase metallicity, especially at high redshift, which might have a strong impact on our understanding of the chemical evolution of the Universe. The main goal of this study is to review the most widely used empirical oxygen calibrations, O3N2 and N2, by using new direct abundance measurements. We pay special attention to (1) the expected uncertainty of these calibrations as a function of the index value or abundance derived and (2) the presence of possible systematic offsets. This is possible thanks to the analysis of the most ambitious compilation of T_e-based H II regions to date. This new dataset compiles the Te-based abundances of 603 H II regions extracted from the literature but also includes new measurements from the CALIFA survey. Besides providing new and improved empirical calibrations for the gas abundance, we also present a comparison between our revisited calibrations with a total of 3423 additional CALIFA H II complexes with abundances derived using the ONS calibration from the literature. The combined analysis of T_e-based and ONS abundances allows us to derive their most accurate calibration to date for both the O3N2 and N2 single-ratio indicators, in terms of all statistical significance, quality, and coverage of the parameters space. In particular, we infer that these indicators show shallower abundance dependencies and statistically significant offsets compared to others'. The O3N2 and N2 indicators can be empirically applied to derive oxygen abundances calibrations from either direct abundance determinations with random errors of 0.18 and 0.16, respectively, or from indirect ones (but based on a large amount of data), reaching an average precision of 0.08 and 0.09 dex (random) and 0.02 and 0.08 dex (systematic; compared to the direct estimations), respectively.

479 citations

Journal ArticleDOI
TL;DR: In this paper, the authors presented the largest and most homogeneous catalog of H ii regions and associations compiled so far, consisting of more than 7000 ionized regions, extracted from 306 galaxies observed by the CALIFA survey.
Abstract: We present the largest and most homogeneous catalog of H ii regions and associations compiled so far The catalog comprises more than 7000 ionized regions, extracted from 306 galaxies observed by the CALIFA survey We describe the procedures used to detect, select, and analyze the spectroscopic properties of these ionized regions In the current study we focus on characterizing of the radial gradient of the oxygen abundance in the ionized gas, based on the study of the deprojecteddistribution of H ii regions We found that all galaxies without clear evidence of an interaction present a common gradient in the oxygen abundance, with a characteristic slope of α_O/H = −01 dex/r_e between 03 and 2 disk effective radii (r_e), and a scatter compatible with random fluctuations around this value, when the gradient is normalized to the disk effective radius The slope is independent of morphology, the incidence of bars, absolute magnitude, or mass Only those galaxies with evidence of interactions and/or clear merging systems present a significantly shallower gradient, consistent with previous results The majority of the 94 galaxies with H ii regions detected beyond two disk effective radii present a flattening in the oxygen abundance The flattening is statistically significant We cannot provide a conclusive answer regarding the origin of this flattening However, our results indicate that its origin is most probably related to the secular evolution of galaxies Finally, we find a drop/truncation of the oxygen abundance in the inner regions for 26 of the galaxies All of them are non-interacting, mostly unbarred Sb/Sbc galaxies This feature is associated with a central star-forming ring, which suggests that both features are produced by radial gas flows induced by resonance processes Our result suggests that galaxy disks grow inside-out, with metal enrichment driven by the local star formation history and with a small variation galaxy-by-galaxy At a certain galactocentric distance, the oxygen abundance seems to be correlated well with the stellar mass density and total stellar mass of the galaxies, independently of other properties of the galaxies Other processes, such as radial mixing and inflows/outflows seem to have a limited effect on shaping of the radial distribution of oxygen abundances, although they are not ruled out

474 citations


Cited by
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TL;DR: In this article, the authors present a comprehensive study of the physical properties of ∼ 10 5 galaxies with measurable star formation in the Sloan Digital Sky Survey (SDSS) by comparing physical information extracted from the emission lines with continuum properties, and build up a picture of the nature of star-forming galaxies at z < 0.2.
Abstract: We present a comprehensive study of the physical properties of ∼ 10 5 galaxies with measurable star formation in the Sloan Digital Sky Survey (SDSS). By comparing physical information extracted from the emission lines with continuum properties, we build up a picture of the nature of star-forming galaxies at z < 0.2. We develop a method for aperture correction using resolved imaging and show that our method takes out essentially all aperture bias in the star formation rate (SFR) estimates, allowing an accurate estimate of the total SFRs in galaxies. We determine the SFR density to be 1.915 +0.02 −0.01 (random) +0.14

3,262 citations

Journal ArticleDOI
TL;DR: In this paper, the authors review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies.
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.

2,525 citations

Journal ArticleDOI
TL;DR: Galaxy Evolution Explorer (GALEX) as mentioned in this paper performed the first space UV sky survey, including imaging and grism surveys in two bands (1350-1750 and 1750-2750?).
Abstract: We give an overview of the Galaxy Evolution Explorer (GALEX), a NASA Explorer Mission launched on 2003 April 28. GALEX is performing the first space UV sky survey, including imaging and grism surveys in two bands (1350-1750 and 1750-2750 ?). The surveys include an all-sky imaging survey (mAB 20.5), a medium imaging survey of 1000 deg2 (mAB 23), a deep imaging survey of 100 deg2 (mAB 25), and a nearby galaxy survey. Spectroscopic (slitless) grism surveys (R = 100-200) are underway with various depths and sky coverage. Many targets overlap existing or planned surveys in other bands. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the relationship of the UV and global star formation rate in local galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the redshift range 0 < z < 2 and probe the physical drivers of star formation in galaxies. The GALEX mission includes a guest investigator program, supporting the wide variety of programs made possible by the first UV sky survey.

2,410 citations

Journal ArticleDOI
TL;DR: In this paper, the authors calculated IR emission spectra for dust heated by starlight, for mixtures of amorphous silicate and graphitic grains, including varying amounts of PAH particles.
Abstract: IR emission spectra are calculated for dust heated by starlight, for mixtures of amorphous silicate and graphitic grains, including varying amounts of PAH particles. The models are constrained to reproduce the average Milky Way extinction curve. The calculations include the effects of single-photon heating. Updated IR absorption properties for the PAHs are presented that are consistent with observed emission spectra, including those newly obtained by Spitzer. We find a size distribution for the PAHs giving emission band ratios consistent with the observed spectra of the Milky Way and other galaxies. Emission spectra are presented for a wide range of starlight intensities. We calculate how the efficiency of emission into different IR bands depends on PAH size; the strong 7.7 μm emission feature is produced mainly by PAH particles containing Umin. We present graphical procedures using Spitzer IRAC and MIPS photometry to estimate the parameters qPAH, Umin, and γ, the fraction fPDR of the dust luminosity coming from photodissociation regions with U > 100, and the total dust mass Mdust.

2,102 citations

Journal ArticleDOI
TL;DR: In this article, the authors review the theoretical underpinning, techniques, and results of efforts to estimate the CO-to-H2 conversion factor in different environments, and recommend a conversion factor XCO = 2×10 20 cm −2 (K km s −1 ) −1 with ±30% uncertainty.
Abstract: CO line emission represents the most accessible and widely used tracer of the molecular interstellar medium. This renders the translation of observed CO intensity into total H2 gas mass critical to understand star formation and the interstellar medium in our Galaxy and beyond. We review the theoretical underpinning, techniques, and results of efforts to estimate this CO-to-H2 “conversion factor,” XCO, in different environments. In the Milky Way disk, we recommend a conversion factor XCO = 2×10 20 cm −2 (K km s −1 ) −1 with ±30% uncertainty. Studies of other “normal galaxies” return similar values in Milky Way-like disks, but with greater scatter and systematic uncertainty. Departures from this Galactic conversion factor are both observed and expected. Dust-based determinations, theoretical arguments, and scaling relations all suggest that XCO increases with decreasing metallicity, turning up sharply below metallicity ≈ 1/3–1/2 solar in a manner consistent with model predictions that identify shielding as a key parameter. Based on spectral line modeling and dust observations, XCO appears to drop in the central, bright regions of some but not all galaxies, often coincident with regions of bright CO emission and high stellar surface density. This lower XCO is also present in the overwhelmingly molecular interstellar medium of starburst galaxies, where several lines of evidence point to a lower CO-to-H2 conversion factor. At high redshift, direct evidence regarding the conversion factor remains scarce; we review what is known based on dynamical modeling and other arguments. Subject headings: ISM: general — ISM: molecules — galaxies: ISM — radio lines: ISM

2,004 citations