Simulations of Lyα emission: fluorescence, cooling, galaxies Jordi Miralda Escudé ICREA University of Barcelona, Catalonia Berkeley, Collaborators: Juna Kollmeier, Zheng Zheng David Weinberg, Neal Katz, Romeel Dave Renyue Cen, Hy Trac Andy Gould Östlin et al Hα UV Lyα ESO 338–IG04

White et al Iye et al Tanvir et al Quasars Lyα galaxies fireball shots? Exploring reionization with the highest redshift objects Gamma-ray burst afterglow:

Can we observe the IGM in 3D? Santos et al cm, epoch of reionization. Extended Lyα emission? This can be done at lower redshift. Rauch et al. 2008

Possible origin of extended Lyα Star-forming galaxies: the ionizing photons from stars ionize the surrounding interstellar or intergalactic gas, which emits Lyα by recombinations. Radiative cooling: infalling gas is heated during dissipational galaxy formation, emitting Lyα after collisional ionization or line excitation. Fluorescence of the ionizing background: dense Lyman limit systems in the intergalactic medium are ionized by distant sources and recombine to emit Lyα. Scattering: Lyα forest systems scatter the continuum UV background radiation when it redshifts to the Lyα line.

Lyα blobs: large emission region outside of a star- forming galaxy Matsuda et al Yang et al. 2009

Physical properties and abundance of Ly α blobs Abundance: ~ 3·10 -6 Mpc -3, luminosity L > erg/s, size ~ 30 kpc. The luminosity implies recombinations/second. The minimum gas density required is 0.1 cm -3 ~ 10 4 ρ mean, for the size of 30 kpc and no clumping, with a total mass of M Sun. These atoms must be ionized every ~ 10 6 years to keep them emitting. The ionizing source should be a quasar with L UV > erg/s. When it is not seen, it is probably obscured and anisotropic. Cooling gaseous halos: better for blobs of L < erg/s (10 11 M Sun of gas emitting 10 Lyα photons over 3· 10 8 years).

Expected Lyα surface brightness from fluorescence of the ionizing background Measured intensity of the ionizing background: J ν ~ 3· erg/cm 2 /s/Hz/sr. Surface brightness of optically thick Lyman limit system: ~ 0.5 J ν ν HI /β Observed surface brightness: ~ erg/cm 2 /s/arcsec 2 / (1+z) 4 Hogan & Weymann 1987; Gould & Weinberg 1996

Lyα line H atom rest frame H laboratory frame ? surface brightness frequency change Lyα Radiative Transfer: how to compute a Lyα image from any distribution of gas and emission? a large number of scatterings frequency change after each scattering with Zheng Zheng

Monte Carlo Code for Lyα Radiative Transfer 1. Initialization of the photon 2. determine the spatial location of the scattering 3. choose the velocity of the atom that scatters the photon 4. scattering in the rest frame of the atom: new frequency and direction 5. repeat 2-5 until escape Zheng & Miralda-Escudé 2002 Lyα

The code can be applied to systems with arbitrary gas geometry gas emissivity distribution gas density distribution gas temperature distribution gas velocity distribution well suited for applying to cosmological simulation outputs The code outputs IFU-like data cube, which can be used to obtain Lyα image and 2D spectra. Image Courtesy: Stephen Todd & Douglas Pierce-Price x y λ Application: z~3 fluorescent Lyα emission from cosmic structure: Kollmeier et al. 2009

Fluorescence of the background in an SPH simulation Kollmeier et al. 2009

Spectra of the fluorescent emission

Fluorescence in the presence of a luminous quasar

The damped wing of the Gunn- Peterson trough indicates that a source is being seen behind atomic intergalactic medium We may observe this on the spectrum of a fireball shot. Only a fraction of the intergalactic medium should be neutral, and this fraction will vary widely among different lines of sight. Main challenge: separating the host galaxy damped Lyα system from the intergalactic absorption. Scattering of Lyα photons from star-forming galaxies and other luminous sources Absorption profile of a neutral medium in Hubble expansion.

Observation of the spectrum of GRB Totani et al The absorption is due to local hydrogen with column density N HI = cm -2

McQuinn et al Lyα emitting galaxies: the damped IGM absorption becomes a probe to the late stages of reionization. The clustering of Lyα emitters increases owing to a patchy reionization structure. An accurate radiative transfer calculation is required.

Lyman-alpha Radiative Transfer applied to galaxy sources placed in a simulation at z=5.7 (with Cen, Trac): example of one halo

Shift in the Ly α Line Peak

Intrinsic and Apparent Ly α Luminosity

Comparison with Observation Ly α Equivalent Width Distribution Ando et al deficit of UV bright, high Lyα EW sources dust extinction? age of stellar population? gas density? gas kinematics? Ouchi et al. 2008

Comparison with Observation Ly α Equivalent Width Distribution Observational effect of small survey volume decreasing UV LF towards high UV luminosity + decreasing EW distribution at fixed UV luminosity

Lyα Lyαluminosity Lyα Lyαline profile A Simple Model of LAEs Intrinsic Lyαemissi on Apparent Lyαemissi on spectra Lyα LyαEW LyαLF UV LF morphology clustering... Radiative Transfer neutral gas distribution ✦ radiative transfer as the single factor in transforming the intrinsic properties of Lyα emission to observed ones ✦ natural interpretation of observations ✦ high predictive power

Effect on clustering of Lyα emitters.

Correlation functions

Angular correlation function Large effects on the angular correlation function are induced by the special selection of Lyα emitters depending on the radiative transfer in their intergalactic environment.

Conclusions We expect the sky background to contain a detailed map of Lyα emission from the intergalactic medium. Detecting fluorescence from the ionizing background requires even greater depths than achieved so far. Fluorescence in the vicinity of quasars should more easily be detectable now. Lyα blobs likely are particular cases of high gas density near luminous quasars; we expect the lower luminosity ones to arise from cooling in galactic halos. The Lyα emission of star-forming galaxies is greatly affected by scattering in their surrounding medium. This can result in: –The wide distribution of equivalent widths in galaxies of different UV luminosity. –A greatly enhanced correlation function along the line of sight, and projected angular correlation function. These Lyα emitting galaxies may provide a powerful probe to the structure of the reionized intergalactic medium, but modelling the radiative transfer is fundamental.

Apparent Lyα Luminosity Function

Comparison with Observation Ly α Luminosity Function offset in Lyα luminosity ✴ SFR ✴ IMF ✴ intrinsic line width

Comparison with Observation UV Luminosity Function Broad distribution of apparent Lyα luminosity at fixed intrinsic (UV) luminosity