scispace - formally typeset
Search or ask a question
Author

Hector Flores

Other affiliations: PSL Research University
Bio: Hector Flores is an academic researcher from Paris Diderot University. The author has contributed to research in topics: Galaxy & Gamma-ray burst. The author has an hindex of 48, co-authored 118 publications receiving 6692 citations. Previous affiliations of Hector Flores include PSL Research University.


Papers
More filters
Journal ArticleDOI
TL;DR: In this article, a catalog of 78 15 μm sources with both radio and optical identifications was generated using the Canada-France Redshift Survey 1452+52 field, which includes all strong and heavily extincted starbursts up to z=1.
Abstract: The Canada-France Redshift Survey 1452+52 field has been deeply imaged with the Infrared Space Observatory using ISOCAM through the LW3 filter (12-18 μm). Careful data analysis and comparison with deep optical and radio data have allowed us to generate a catalog of 78 15 μm sources with both radio and optical identifications. They are redder and lie at higher redshift than I-band-selected galaxies, with most of them being star-forming galaxies. We have considered the galaxies detected at radio and 15 μm wavelengths, which potentially include all strong and heavily extincted starbursts, up to z=1. Spectral energy distributions (SEDs) for each of the sources have been derived using deep radio, mid-IR, near-IR, optical, and UV photometry. The sources were then spectrally classified by comparing with SEDs of well-known nearby galaxies. By deriving their far-IR luminosities by interpolation, we can estimate their star formation rate (SFR) in a way that does not depend sensitively on the extinction. Between 35% and 85% of the star formation at z≤1 is related to IR emission, and the global extinction is in the range AV=0.5-0.85. While heavily extincted starbursts with SFRs in excess of 100 M☉ yr-1 constitute less than 1% of all galaxies, they contribute about 18% of the SFR density out to z=1. Their morphologies range from S0 to Sab, and more than a third are interacting systems. The SFR derived by far-IR fluxes is likely to be ~2.9 times higher than those previously estimated from UV fluxes. The derived stellar mass formed since the redshift of 1 could be too high when compared with the present-day stellar mass density. This might be due to an initial mass function in distant star-forming galaxies different from the solar neighborhood one or an underestimate of the local stellar mass density.

347 citations

Journal ArticleDOI
TL;DR: In this article, a carefully selected sub-sample of Swift Long Gamma-ray Bursts (GRBs) that is complete in redshift was constructed by considering only bursts with favorable observing conditions for ground-based follow-up searches, that are bright in the 15-150 keV Swift/BAT band, with 1-s peak photon fluxes in excess to 2.6 ph s^-1 cm^-2.
Abstract: We present a carefully selected sub-sample of Swift Long Gamma-ray Bursts (GRBs), that is complete in redshift. The sample is constructed by considering only bursts with favorable observing conditions for ground-based follow-up searches, that are bright in the 15-150 keV Swift/BAT band, i.e. with 1-s peak photon fluxes in excess to 2.6 ph s^-1 cm^-2. The sample is composed by 58 bursts, 52 of them with redshift for a completeness level of 90%, while another two have a redshift constraint, reaching a completeness level of 95%. For only three bursts we have no constraint on the redshift. The high level of redshift completeness allows us for the first time to constrain the GRB luminosity function and its evolution with cosmic times in a unbiased way. We find that strong evolution in luminosity (d_l=2.3\pm 0.6) or in density (d_d=1.7\pm 0.5) is required in order to account for the observations. The derived redshift distribution in the two scenarios are consistent with each other, in spite of their different intrinsic redshift distribution. This calls for other indicators to distinguish among different evolution models. Complete samples are at the base of any population studies. In future works we will use this unique sample of Swift bright GRBs to study the properties of the population of long GRBs.

270 citations

Journal ArticleDOI
TL;DR: In this article, the authors present direct observational evidence supporting this finding from a long term, multi-wavelength study of 195 intermediate-mass galaxies, mostly selected from the Canada France Redshift Survey (CFRS), and show that recent and efficient star formation is revealed at IR wavelengths since ~15% of intermediate mass galaxies at are indeed luminous IR galaxies (LIRGs), a phenomenon far more common than in the local Universe.
Abstract: Studies of distant galaxies have shown that ellipticals and large spirals (Schade et al. [CITE], ApJ, 525, 31; Lilly et al. [CITE], ApJ, 500, 75) were already in place 8 Gyr ago, leading to a very modest recent star formation (Brinchmann & Ellis [CITE], ApJ, 536, L77) in intermediate mass galaxies ( ). This is challenged by a recent analysis (Heavens et al. [CITE], Nature, 428, 625) of the fossil record of the stellar populations of ~105 nearby galaxies, which shows that intermediate mass galaxies formed or assembled the bulk of their stars 4 to 8 Gyr ago. Here we present direct observational evidence supporting this findings from a long term, multi-wavelength study of 195 intermediate mass galaxies, mostly selected from the Canada France Redshift Survey (CFRS). We show that recent and efficient star formation is revealed at IR wavelengths since ~15% of intermediate mass galaxies at are indeed luminous IR galaxies (LIRGs), a phenomenon far more common than in the local Universe. The star formation in LIRGs is sufficient in itself to produce 38% of the total stellar mass of intermediate mass galaxies and then to account for most of the reported stellar mass formation since . Observations of distant galaxies have also the potential to resolve their star formation and mass assembly histories. The high occurrence of LIRGs is easily understood only if they correspond to episodic peaks of star formation, during which galaxies are reddened through short IREs (infrared episodes). We estimate that each galaxy should experience 4 to IREs from to , being the characteristic timescale. An efficient and episodic star formation is further supported by the luminosity-metallicity relation of emission line galaxies, which we find to be on average metal deficient by a factor of ~2 when compared to those of local spirals. We then examine how galaxy IREs can be related to the emergence at high redshift of the abundant population of galaxies with small size (but not with small mass), blue core and many irregularities. We show that recent merging and gas infall naturally explain both morphological changes and episodic star formation history in a hierarchical galaxy formation frame. We propose a simple scenario in which % of intermediate mass spirals have recently experienced their last major merger event, leading to a drastic reshaping of their bulges and disks during the last 8 Gyr. It links in a simple manner distant and local galaxies, and gives account of the simultaneous decreases during that period, of the cosmic star formation density, of the merger rate, and of the number densities of LIRGs, compact and irregular galaxies, while the densities of ellipticals and large spirals are essentially unaffected. It predicts that 42, 22 and 36% of the IR (episodic) star formation density is related to major mergers, minor mergers and gas infall, respectively.

259 citations

Journal ArticleDOI
TL;DR: The first public data release (DR1) of the Calar Alto Legacy Integral Field Area (CALIFA) survey is presented in this article, which consists of science-grade optical datacubes for the first 100 of eventually 600 nearby (0.005 < z < 0.03) galaxies, obtained with the integral field spectrograph PMAS/PPak mounted on the 3.5 m telescope at the Calal Alto observatory.
Abstract: We present the first public data release (DR1) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. It consists of science-grade optical datacubes for the first 100 of eventually 600 nearby (0.005 < z < 0.03) galaxies, obtained with the integral-field spectrograph PMAS/PPak mounted on the 3.5 m telescope at the Calar Alto observatory. The galaxies in DR1 already cover a wide range of properties in color-magnitude space, morphological type, stellar mass, and gas ionization conditions. This offers the potential to tackle a variety of open questions in galaxy evolution using spatially resolved spectroscopy. Two different spectral setups are available for each galaxy, (i) a low-resolution V500 setup covering the nominal wavelength range 3745-7500 angstrom with a spectral resolution of 6.0 angstrom (FWHM), and (ii) a medium-resolution V1200 setup covering the nominal wavelength range 3650-4840 angstrom with a spectral resolution of 2.3 angstrom (FWHM). We present the characteristics and data structure of the CALIFA datasets that should be taken into account for scientific exploitation of the data, in particular the effects of vignetting, bad pixels and spatially correlated noise. The data quality test for all 100 galaxies showed that we reach a median limiting continuum sensitivity of 1.0 x 10(-18) erg s(-1) cm(-2) angstrom(-1) arcsec(-2) at 5635 angstrom and 2.2 x 10(-18) erg s(-1) cm(-2) angstrom(-1) arcsec(-2) at 4500 angstrom for the V500 and V1200 setup respectively, which corresponds to limiting r and g band surface brightnesses of 23.6 mag arcsec(-2) and 23.4 mag arcsec(-2), or an unresolved emission-line flux detection limit of roughly 1 x 10(-17) erg s(-1) cm(-2) arcsec(-2) and 0.6 x 10(-17) erg s(-1) cm(-2) arcsec(-2), respectively. The median spatial resolution is 3 ''.7, and the absolute spectrophotometric calibration is better than 15% (1 sigma). We also describe the available interfaces and tools that allow easy access to this first public CALIFA data at http://califa.caha.es/DR1.

251 citations

Journal ArticleDOI
TL;DR: In this paper, a carefully selected sub-sample of Swift long gamma-ray bursts (GRBs) that is complete in redshift was constructed by considering only bursts with favorable observing conditions for ground-based follow-up searches, which are bright in the 15-150 keV Swift/BAT band, i.e., with 1-s peak photon fluxes in excess to 2.6 photons s{sup −1} cm{sup -2}.
Abstract: We present a carefully selected sub-sample of Swift long gamma-ray bursts (GRBs) that is complete in redshift. The sample is constructed by considering only bursts with favorable observing conditions for ground-based follow-up searches, which are bright in the 15-150 keV Swift/BAT band, i.e., with 1-s peak photon fluxes in excess to 2.6 photons s{sup -1} cm{sup -2}. The sample is composed of 58 bursts, 52 of them with redshift for a completeness level of 90%, while another two have a redshift constraint, reaching a completeness level of 95%. For only three bursts we have no constraint on the redshift. The high level of redshift completeness allows us for the first time to constrain the GRB luminosity function and its evolution with cosmic times in an unbiased way. We find that strong evolution in luminosity ({delta}{sub l} = 2.3 {+-} 0.6) or in density ({delta}{sub d} = 1.7 {+-} 0.5) is required in order to account for the observations. The derived redshift distributions in the two scenarios are consistent with each other, in spite of their different intrinsic redshift distributions. This calls for other indicators to distinguish among different evolution models. Complete samples are at the base of any population studies.more » In future works we will use this unique sample of Swift bright GRBs to study the properties of the population of long GRBs.« less

247 citations


Cited by
More filters
Journal ArticleDOI
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 article, the authors review the range of complementary techniques and theoretical tools that allow astronomers to map the cosmic history of star formation, heavy element production, and reionization of the Universe from the cosmic "dark ages" to the present epoch.
Abstract: Over the past two decades, an avalanche of data from multiwavelength imaging and spectroscopic surveys has revolutionized our view of galaxy formation and evolution. Here we review the range of complementary techniques and theoretical tools that allow astronomers to map the cosmic history of star formation, heavy element production, and reionization of the Universe from the cosmic "dark ages" to the present epoch. A consistent picture is emerging, whereby the star-formation rate density peaked approximately 3.5 Gyr after the Big Bang, at z~1.9, and declined exponentially at later times, with an e-folding timescale of 3.9 Gyr. Half of the stellar mass observed today was formed before a redshift z = 1.3. About 25% formed before the peak of the cosmic star-formation rate density, and another 25% formed after z = 0.7. Less than ~1% of today's stars formed during the epoch of reionization. Under the assumption of a universal initial mass function, the global stellar mass density inferred at any epoch matches reasonably well the time integral of all the preceding star-formation activity. The comoving rates of star formation and central black hole accretion follow a similar rise and fall, offering evidence for co-evolution of black holes and their host galaxies. The rise of the mean metallicity of the Universe to about 0.001 solar by z = 6, one Gyr after the Big Bang, appears to have been accompanied by the production of fewer than ten hydrogen Lyman-continuum photons per baryon, a rather tight budget for cosmological reionization.

3,104 citations

Journal ArticleDOI
Norman A. Grogin1, Dale D. Kocevski2, Sandra M. Faber2, Henry C. Ferguson1, Anton M. Koekemoer1, Adam G. Riess3, Viviana Acquaviva4, David M. Alexander5, Omar Almaini6, Matthew L. N. Ashby7, Marco Barden8, Eric F. Bell9, Frédéric Bournaud10, Thomas M. Brown1, Karina Caputi11, Stefano Casertano1, Paolo Cassata12, Marco Castellano, Peter Challis7, Ranga-Ram Chary13, Edmond Cheung2, Michele Cirasuolo14, Christopher J. Conselice6, Asantha Cooray15, Darren J. Croton16, Emanuele Daddi10, Tomas Dahlen1, Romeel Davé17, Duilia F. de Mello18, Duilia F. de Mello19, Avishai Dekel20, Mark Dickinson, Timothy Dolch3, Jennifer L. Donley1, James Dunlop11, Aaron A. Dutton21, David Elbaz10, Giovanni G. Fazio7, Alexei V. Filippenko22, Steven L. Finkelstein23, Adriano Fontana, Jonathan P. Gardner19, Peter M. Garnavich24, Eric Gawiser4, Mauro Giavalisco12, Andrea Grazian, Yicheng Guo12, Nimish P. Hathi25, Boris Häussler6, Philip F. Hopkins22, Jiasheng Huang26, Kuang-Han Huang3, Kuang-Han Huang1, Saurabh Jha4, Jeyhan S. Kartaltepe, Robert P. Kirshner7, David C. Koo2, Kamson Lai2, Kyoung-Soo Lee27, Weidong Li22, Jennifer M. Lotz1, Ray A. Lucas1, Piero Madau2, Patrick J. McCarthy25, Elizabeth J. McGrath2, Daniel H. McIntosh28, Ross J. McLure11, Bahram Mobasher29, Leonidas A. Moustakas13, Mark Mozena2, Kirpal Nandra30, Jeffrey A. Newman31, Sami Niemi1, Kai G. Noeske1, Casey Papovich23, Laura Pentericci, Alexandra Pope12, Joel R. Primack2, Abhijith Rajan1, Swara Ravindranath32, Naveen A. Reddy29, Alvio Renzini, Hans-Walter Rix30, Aday R. Robaina33, Steven A. Rodney3, David J. Rosario30, Piero Rosati34, S. Salimbeni12, Claudia Scarlata35, Brian Siana29, Luc Simard36, Joseph Smidt15, Rachel S. Somerville4, Hyron Spinrad22, Amber Straughn19, Louis-Gregory Strolger37, Olivia Telford31, Harry I. Teplitz13, Jonathan R. Trump2, Arjen van der Wel30, Carolin Villforth1, Risa H. Wechsler38, Benjamin J. Weiner17, Tommy Wiklind39, Vivienne Wild11, Grant W. Wilson12, Stijn Wuyts30, Hao Jing Yan40, Min S. Yun12 
TL;DR: The Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) as discussed by the authors was designed to document the first third of galactic evolution, from z approx. 8 - 1.5 to test their accuracy as standard candles for cosmology.
Abstract: The Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) is designed to document the first third of galactic evolution, from z approx. 8 - 1.5. It will image > 250,000 distant galaxies using three separate cameras on the Hubble Space Tele8cope, from the mid-UV to near-IR, and will find and measure Type Ia supernovae beyond z > 1.5 to test their accuracy as standard candles for cosmology. Five premier multi-wavelength sky regions are selected, each with extensive ancillary data. The use of five widely separated fields mitigates cosmic variance and yields statistically robust and complete samples of galaxies down to a stellar mass of 10(exp 9) solar mass to z approx. 2, reaching the knee of the UV luminosity function of galaxies to z approx. 8. The survey covers approximately 800 square arc minutes and is divided into two parts. The CANDELS/Deep survey (5(sigma) point-source limit H =27.7mag) covers approx. 125 square arcminutes within GOODS-N and GOODS-S. The CANDELS/Wide survey includes GOODS and three additional fields (EGS, COSMOS, and UDS) and covers the full area to a 50(sigma) point-source limit of H ? or approx. = 27.0 mag. Together with the Hubble Ultradeep Fields, the strategy creates a three-tiered "wedding cake" approach that has proven efficient for extragalactic surveys. Data from the survey are non-proprietary and are useful for a wide variety of science investigations. In this paper, we describe the basic motivations for the survey, the CANDELS team science goals and the resulting observational requirements, the field selection and geometry, and the observing design.

2,088 citations

15 Mar 1979
TL;DR: In this article, the experimental estimation of parameters for models can be solved through use of the likelihood ratio test, with particular attention to photon counting experiments, and procedures presented solve a greater range of problems than those currently in use, yet are no more difficult to apply.
Abstract: Many problems in the experimental estimation of parameters for models can be solved through use of the likelihood ratio test. Applications of the likelihood ratio, with particular attention to photon counting experiments, are discussed. The procedures presented solve a greater range of problems than those currently in use, yet are no more difficult to apply. The procedures are proved analytically, and examples from current problems in astronomy are discussed.

1,748 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the relationship between the local environment of galaxies and their star formation rate (SFR) in the Great Observatories Origins Deep Survey, GOODS, at z∼1.
Abstract: Aims We study the relationship between the local environment of galaxies and their star formation rate (SFR) in the Great Observatories Origins Deep Survey, GOODS, at z∼1 Methods We use ultradeep imaging at 24� m with the MIPS camera onboard Spitzer to determine the contribution of obscured light to the SFR of galaxies over the redshift range 08≤ z ≤12 Accurate galaxy densities are measured thanks to the large sample of ∼1200 spectroscopic redshifts with high (∼70 %) spectroscopic completeness Morphology and stellar masses are derived from deep HST-ACS imaging, supplemented by ground based imaging programs and photometry from the IRAC camera onboard Spitzer Results We show that the star formation‐density relation observed locally was reversed at z∼ 1: the average SFR of an individual galaxy increased with local galaxy density when the universe was less than half its present age Hierarchical galaxy for mation models (simulated lightcones from the Millennium model) predicted such a reversal to occur only at earlier epochs (z>2) and at a lower level We present a remarkable structure at z∼ 1016, containing X-ray traced galaxy concentrations, which will eventually merge into a Virgo-like cluster This structure illustrates how the ind ividual SFR of galaxies increases with density and shows that it is the∼1‐2 Mpc scale that affects most the star formation in galaxies at z∼ 1 The SFR of z∼ 1 galaxies is found to correlate with stellar mass suggesting that mass plays a role in the observed star formation‐density trend However the specific SFR ( =SFR/M⋆) decreases with stellar mass while it increases with galaxy density, which i mplies that the environment does directly affect the star formation activity of galaxies Major mergers do not appear to be the unique or even major cause for this effect since nearly half (46 %) of the luminous infrared galaxies (LIRGs) at z∼ 1 present the HST-ACS morphology of spirals, while only a third present a clear signature of major mergers The remaining galaxies are divided into compact (9 %) and irregular (14 %) galaxies Moreover, the specific SFR o f major mergers is only marginally stronger than that of spirals Conclusions These findings constrain the influence of the growth of large- scale structures on the star formation history of galaxies Reproducing the SFR‐density relation at z∼ 1 is a new challenge for models, requiring a correct balance between mass assembly through mergers and in-situ star formation at early epochs

1,696 citations