RADIATIVE TRANSFER IN A CLUMPY UNIVERSE. IV. NEW SYNTHESIS MODELS OF THE COSMIC UV/X-RAY BACKGROUND

We present improved synthesis models of the evolving spectrum of the UV/X-ray diffuse background, updating and extending our previous results. Five new main components are added to our radiative transfer code CUBA: (1) the sawtooth modulation of the background intensity from resonant line absorption in the Lyman series of cosmic hydrogen and helium; (2) the X-ray emission from the obscured and unobscured quasars that gives origin to the X-ray background; (3) a piecewise parameterization of the distribution in redshift and column density of intergalactic absorbers that fits recent measurements of the mean free path of 1 ryd photons; (4) an accurate treatment of the photoionization structure of absorbers, which enters in the calculation of the helium continuum opacity and recombination emissivity; and (5) the UV emission from star-forming galaxies at all redshifts. We provide tables of the predicted H I and He II photoionization and photoheating rates for use, e.g., in cosmological hydrodynamics simulations of the Lyα forest and a new metallicity-dependent calibration to the UV luminosity density-star formation rate density relation. A "minimal cosmic reionization model" is also presented in which the galaxy UV emissivity traces recent determinations of the cosmic history of star formation, the luminosity-weighted escape fraction of hydrogen-ionizing radiation increases rapidly with look-back time, the clumping factor of the high-redshift intergalactic medium evolves following the results of hydrodynamic simulations, and Population III stars and miniquasars make a negligible contribution to the metagalactic flux. The model provides a good fit to the hydrogen-ionization rates inferred from flux decrement and proximity effect measurements, predicts that cosmological H II (He III) regions overlap at redshift 6.7 (2.8), and yields an optical depth to Thomson scattering, τes = 0.084 that is in agreement with Wilkinson Microwave Anisotropy Probe results. Our new background intensities and spectra are sensitive to a number of poorly determined input parameters and suffer from various degeneracies. Their predictive power should be constantly tested against new observations. We are therefore making our redshift-dependent UV/X emissivities and CUBA outputs freely available for public use at http://www.ucolick.org/~pmadau/CUBA.

[1]  J. Schaye.  Model-independent Insights into the Nature of the Lyα Forest and the Distribution of Matter in the Universe , 2001, astro-ph/0104272.

[2]  The Evolution of Optical Depth in the Lyα Forest: Evidence Against Reionization at z~6* , 2006, astro-ph/0607633.

[3]  L. Trouille,et al.  MEASURING THE SOURCES OF THE INTERGALACTIC IONIZING FLUX , 2008, 0811.1042.

[4]  G. Richards,et al.  An Observational Determination of the Bolometric Quasar Luminosity Function , 2006, astro-ph/0605678.

[5]  W. Sargent,et al.  ACCEPTED FOR PUBLICATION IN THE ASTROPHYSICAL JOURNAL Preprint typeset using LATEX style emulateapj v. 4/9/03 METALLICITY OF THE INTERGALACTIC MEDIUM USING PIXEL STATISTICS. II. THE DISTRIBUTION OF METALS AS TRACED BY CIV 1 , 2003 .

[6]  A. Kinney,et al.  The Dust Content and Opacity of Actively Star-forming Galaxies , 1999, astro-ph/9911459.

[7]  D. Shupe,et al.  High-Redshift QSOs in the SWIRE Survey and the z~3 QSO Luminosity Function , 2007, 0711.0211.

[8]  J. Prochaska,et al.  The Keck+Magellan Survey for Lyman Limit Absorption. I. The Frequency Distribution of Super Lyman Limit Systems , 2006, astro-ph/0610726.

[9]  P. Hopkins,et al.  He ii REIONIZATION AND ITS EFFECT ON THE INTERGALACTIC MEDIUM , 2008, 0807.2799.

[10]  C. Steidel,et al.  A STEEP FAINT-END SLOPE OF THE UV LUMINOSITY FUNCTION AT z ∼ 2–3: IMPLICATIONS FOR THE GLOBAL STELLAR MASS DENSITY AND STAR FORMATION IN LOW-MASS HALOS , 2008, 0810.2788.

[11]  Martin J. Rees,et al.  Radiative Transfer in a Clumpy Universe. III. The Nature of Cosmological Ionizing Sources , 1998, astro-ph/9809058.

[12]  Max Pettini,et al.  The Direct Detection of Lyman Continuum Emission from Star-forming Galaxies at z~3 , 2006, astro-ph/0606635.

[13]  N. Gnedin.  Cosmological Reionization by Stellar Sources , 1999, astro-ph/9909383.

[14]  Early reionization by miniquasars , 2003, astro-ph/0310223.

[15]  D. Turnshek,et al.  Damped Lyα Systems at z < 1.65: The Expanded Sloan Digital Sky Survey Hubble Space Telescope Sample , 2006 .

[16]  Destruction of Molecular Hydrogen during Cosmological Reionization , 1996, astro-ph/9608130.

[17]  M. Dijkstra.  CONTINUUM EMISSION BY COOLING CLOUDS , 2007, 0711.2698.

[18]  Takamitsu Miyaji,et al.  Cosmological Evolution of the Hard X-Ray Active Galactic Nucleus Luminosity Function and the Origin of the Hard X-Ray Background , 2003, astro-ph/0308140.

[19]  A. F. Davidsen,et al.  The Rest-Frame Extreme-Ultraviolet Spectral Properties of Quasi-stellar Objects , 2001, astro-ph/0109531.

[20]  Britton D. Smith,et al.  HST/COS OBSERVATIONS OF THE QUASAR HE 2347 − 4342: PROBING THE EPOCH OF He ii PATCHY REIONIZATION AT REDSHIFTS z = 2.4–2.9 , 2010, 1008.2957.

[21]  James L. Matteson,et al.  Diffuse Cosmic Gamma Radiation Measured by HEAO 1 , 1997 .

[22]  J. Matteson,et al.  The Spectrum of Diffuse Cosmic Hard X-Rays Measured with HEAO 1 , 1999, astro-ph/9903492.

[23]  G. Williger,et al.  STIS Observations of He II Gunn-Peterson Absorption toward Q0302–003 , 1998, astro-ph/9812429.

[24]  Spectral Analysis of the Lyα Forest in a Cold Dark Matter Cosmology , 1996, astro-ph/9609194.

[25]  G. Zamorani,et al.  A LOW ESCAPE FRACTION OF IONIZING PHOTONS OF L > L* LYMAN BREAK GALAXIES AT z = 3.3 , 2011, 1104.5237.

[26]  M. Franx,et al.  ULTRAVIOLET LUMINOSITY FUNCTIONS FROM 132 z ∼ 7 AND z ∼ 8 LYMAN-BREAK GALAXIES IN THE ULTRA-DEEP HUDF09 AND WIDE-AREA EARLY RELEASE SCIENCE WFC3/IR OBSERVATIONS , 2010, 1006.4360.

[27]  J. Gunn,et al.  THE ASTROPHYSICAL JOURNAL Preprint typeset using LATEX style emulateapj v. 10/09/06 THE PROPAGATION OF UNCERTAINTIES IN STELLAR POPULATION SYNTHESIS MODELING I: THE RELEVANCE OF UNCERTAIN ASPECTS OF STELLAR EVOLUTION AND THE IMF TO THE DERIVED PHYSICAL PR , 2022 .

[28]  D. Osterbrock,et al.  Astrophysics of Gaseous Nebulae and Active Galactic Nuclei , 1989 .

[29]  D. Weinberg,et al.  Voigt-Profile Analysis of the Lyα Forest in a Cold Dark Matter Universe , 1996, astro-ph/9609115.

[30]  de Jong,et al.  Island Universes: Structure and Evolution of Disk Galaxies , 2006 .

[31]  S. Borgani,et al.  First Results from the X-Ray and Optical Survey of the Chandra Deep Field South , 2000, astro-ph/0007240.

[32]  J. Prochaska,et al.  ON THE (NON)EVOLUTION OF H i GAS IN GALAXIES OVER COSMIC TIME , 2008, 0811.2003.

[33]  OH S.Peng,et al.  Reionization by Hard Photons. I. X-Rays from the First Star Clusters , 2000, astro-ph/0005262.

[34]  L. Pozzetti,et al.  The Star Formation History of Field Galaxies , 1997, astro-ph/9708220.

[35]  M. Zaldarriaga,et al.  Evolution of the Intergalactic Opacity: Implications for the Ionizing Background, Cosmic Star Formation, and Quasar Activity , 2008, 0807.4177.

[36]  J. Prochaska,et al.  A DEFINITIVE SURVEY FOR LYMAN LIMIT SYSTEMS AT z ∼ 3.5 WITH THE SLOAN DIGITAL SKY SURVEY , 2009, 0912.0292.

[37]  H. Tananbaum,et al.  The Luminosity Function of X-Ray-selected Active Galactic Nuclei: Evolution of Supermassive Black Holes at High Redshift , 2007, 0710.2461.

[38]  A Direct Precision Measurement of the Intergalactic Lyα Opacity at 2 ≤ z ≤ 4.2* ** , 2007, 0709.2382.

[39]  Hsiao-Wen Chen,et al.  Escape of Ionizing Radiation from High-Redshift Galaxies , 2007, 0707.0879.

[40]  M. Zaldarriaga,et al.  Submitted to ApJ Preprint typeset using L ATEX style emulateapj v. 10/09/06 A NEW CALCULATION OF THE IONIZING BACKGROUND SPECTRUM AND THE EFFECTS OF HEII REIONIZATION , 2022 .