THE PHOTON UNDERPRODUCTION CRISIS

We examine the statistics of the low-redshift Lyα forest from smoothed particle hydrodynamic simulations in light of recent improvements in the estimated evolution of the cosmic ultraviolet background (UVB) and recent observations from the Cosmic Origins Spectrograph (COS). We find that the value of the metagalactic photoionization rate (ΓHI) required by our simulations to match the observed properties of the low-redshift Lyα forest is a factor of five larger than the value predicted by state-of-the art models for the evolution of this quantity. This mismatch in ΓHI results in the mean flux decrement of the Lyα forest being overpredicted by at least a factor of two (a 10σ discrepancy with observations) and a column density distribution of Lyα forest absorbers systematically and significantly elevated compared to observations over nearly two decades in column density. We examine potential resolutions to this mismatch and find that either conventional sources of ionizing photons (galaxies and quasars) must contribute considerably more than current observational estimates or our theoretical understanding of the low-redshift universe is in need of substantial revision.

[1]  R. Cen,et al.  The Lyα Forest from Gravitational Collapse in the Cold Dark Matter + Λ Model , 1995, astro-ph/9511013.

[2]  Bruce A. Peterson,et al.  On the Density of Neutral Hydrogen in Intergalactic Space , 1965 .

[3]  C. Conselice,et al.  A SPECTROSCOPIC SEARCH FOR LEAKING LYMAN CONTINUUM AT z ∼ 0.7 , 2010, 1008.0004.

[4]  J. Kollmeier,et al.  Galactic Wind Effects on the Lyα Absorption in the Vicinity of Galaxies , 2005, astro-ph/0503674.

[5]  Juna A. Kollmeier,et al.  The intergalactic medium over the last 10 billion years – I. Lyα absorption and physical conditions , 2010, 1005.2421.

[6]  R. Cen,et al.  Gravitational collapse of small scale structure as the origin of the Lyman alpha forest , 1994, astro-ph/9409017.

[7]  B. Oppenheimer,et al.  Cosmological simulations of intergalactic medium enrichment from galactic outflows , 2006, astro-ph/0605651.

[8]  J. Ostriker,et al.  What Produces the Ionizing Background at Large Redshift , 1990 .

[9]  D. Weinberg,et al.  Pressure support versus thermal broadening in the Lyman α forest – II. Effects of the equation of state on transverse structure , 2009, 0910.0250.

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

[11]  M. Malkan,et al.  Integrated ultraviolet radiation field from QSOs , 1986 .

[12]  J. Bland-Hawthorn,et al.  WARM IONIZED GAS REVEALED IN THE MAGELLANIC BRIDGE TIDAL REMNANT: CONSTRAINING THE BARYON CONTENT AND THE ESCAPING IONIZING PHOTONS AROUND DWARF GALAXIES , 2013, 1305.4932.

[13]  C. Steidel,et al.  The Hubble Space Telescope quasar absorption line key project. v. redshift evolution of lyman limit absorption in the spectra of a large sample of quasars , 1995 .

[14]  T. Tripp,et al.  The Statistical and Physical Properties of the Low-Redshift Lyα Forest Observed with the Hubble Space Telescope/STIS , 2001, astro-ph/0101419.

[15]  R. Lynds.  The Absorption-Line Spectrum of 4c 05.34 , 1971 .

[16]  D. Weinberg,et al.  The Lyman-Alpha Forest in the Cold Dark Matter Model , 1995, astro-ph/9509105.

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

[18]  S. S. Institute,et al.  Physical Properties, Baryon Content, and Evolution of the Lyα Forest: New Insights from High-Resolution Observations at z ≲ 0.4 , 2006, astro-ph/0612275.

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

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

[21]  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 .

[22]  The Lyman-alpha Forest Power Spectrum from the Sloan Digital Sky Survey , 2004, astro-ph/0405013.

[23]  D. Weinberg,et al.  A Lower Bound on the Cosmic Baryon Density , 1997, astro-ph/9701012.

[24]  J. Bechtold,et al.  Accepted for publication in the Astrophysical Journal A Uniform Analysis of the Ly-α Forest at z = 0 − 5: V. The extragalactic ionizing background at low redshift , 2001 .

[25]  L. Hui,et al.  Equation of state of the photoionized intergalactic medium , 1996, astro-ph/9612232.

[26]  James S. Bolton,et al.  The observed ionization rate of the intergalactic medium and the ionizing emissivity at z≥ 5: evidence for a photon-starved and extended epoch of reionization , 2007 .

[27]  A. Broderick,et al.  THE COSMOLOGICAL IMPACT OF LUMINOUS TeV BLAZARS. I. IMPLICATIONS OF PLASMA INSTABILITIES FOR THE INTERGALACTIC MAGNETIC FIELD AND EXTRAGALACTIC GAMMA-RAY BACKGROUND , 2011, 1106.5494.

[28]  Phillip J. MacQueen,et al.  A NEW z = 0 METAGALACTIC ULTRAVIOLET BACKGROUND LIMIT , 2010, 1012.3188.

[29]  D. Weinberg,et al.  Cosmological Simulations with TreeSPH , 1995, astro-ph/9509107.

[30]  S. V. Penton,et al.  The Metagalactic Ionizing Radiation Field at Low Redshift , 1999, astro-ph/9907123.

[31]  L. Hernquist,et al.  The Opacity of the Lyα Forest and Implications for Ωb and the Ionizing Background , 1996, astro-ph/9612245.

[32]  J. Michael Shull,et al.  HST-COS OBSERVATIONS OF AGNs. I. ULTRAVIOLET COMPOSITE SPECTRA OF THE IONIZING CONTINUUM AND EMISSION LINES , 2012, 1204.3908.

[33]  Joseph Ribaudo,et al.  A HUBBLE SPACE TELESCOPE STUDY OF LYMAN LIMIT SYSTEMS: CENSUS AND EVOLUTION , 2011, 1105.0659.

[34]  D. Weinberg,et al.  Pressure support versus thermal broadening in the Lyman α forest - I. Effects of the equation of state on longitudinal structure , 2009, 0910.0256.

[35]  R. Davé,et al.  Lyman break galaxies and the Ly alpha forest , 2003 .

[36]  A Multispecies Model for Hydrogen and Helium Absorbers in Lyman-Alpha Forest Clouds , 1995, astro-ph/9508133.

[37]  A. Fontana,et al.  THE GREAT OBSERVATORIES ORIGINS DEEP SURVEY: CONSTRAINTS ON THE LYMAN CONTINUUM ESCAPE FRACTION DISTRIBUTION OF LYMAN-BREAK GALAXIES AT 3.4 < z < 4.5 , 2010, 1009.1140.

[38]  R. Davé,et al.  Lyman Break Galaxies and the Lyα Forest , 2002, astro-ph/0209563.

[39]  P. Madau,et al.  Radiative Transfer in a Clumpy Universe. II. The Ultraviolet Extragalactic Background , 1995, astro-ph/9509093.

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

[41]  V. Springel,et al.  The Lyman α forest in a blazar-heated Universe , 2011, 1107.3837.

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

[43]  V. Springel.  The Cosmological simulation code GADGET-2 , 2005, astro-ph/0505010.

[44]  B. Oppenheimer,et al.  Mass, metal, and energy feedback in cosmological simulations , 2007, 0712.1827.

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

[46]  Piero Madau,et al.  RADIATIVE TRANSFER IN A CLUMPY UNIVERSE. IV. NEW SYNTHESIS MODELS OF THE COSMIC UV/X-RAY BACKGROUND , 2011, 1105.2039.