Evolution in Lyman-alpha Emitters and Lyman-break Galaxies Masao Mori Theoretical Astrophysics division, Center for Computational Sciences, University of Tsukuba Collaboration with Masayuki Umemura Hidenobu Yajima

Presentation Outline Three-dimensional Hydrodynamic Model of Bright Lyman Alpha Emitters (Lyman Alpha Blobs) Mori & Umemura, Nature, 440, 644 (2006) Evolutionally sequence among bright Lyman alpha emitters, Lyman break galaxies, and elliptical galaxies Application to Faint Lyman Alpha Emitters Mori, Yajima & Umemura in prep.  Star formation histories of LAEs with different masses  Dynamical and chemical evolution of LAEs  Emission process of Lyman alpha photons (photo ionization vs collisional ionization)

Compact LAE and Extended LAE Private communication with Hayashino, Mastuda, Yamada et eal. Extended LAE Compact LAE Matsuda et al. 2004

Observational properties Compact LAEs Extended LAEs Lya luminosity: erg s -1 Size (Lya): a few kpc kpc Morphology: UV: compact scattered Lya: extended very extended Stellar mass: M  ~ M  SFR: ~1―~10 M  yr -1 ~10― ~100 M  yr -1

Part I Three-dimensional Hydrodynamic Model of Bright LAEs

Images of Bright Lyman Alpha Emitters (Lyman alpha blobs) (Lyman alpha blobs) 190 kpc at z = 3.1 Matsuda et al., AJ, 128, 569 (2004) observed the 35 extended Lyα emitters in and around the SSA22a field at z=3.09. The luminosity range of Lyα emission is 6 x to erg s -1. They have bubble-like features, and filamentary and clumpy structures. One third of them are apparently not associated with UV continuum sources that are bright enough to produce Lyα emission. Extended LAEs LAEs

Possible Models of Lyman Alpha Emission Photo-ionization by obscured UV sources like an AGN or starburst Chapman et al. ApJ, 606, 85 (2004) Cooling radiation from gravitationally heated gas in collapsed halos Haiman, Spaans & Quataert, ApJ, 537, L5 (2000) Fardal et al., ApJ, 562, 605 (2001) Shock heating by supernova driven galactic outflows Taniguchi & Shioya, ApJ, 532, L13 (2000) Mori, Umemura & Ferrara, ApJ, 613, L97 (2004) Mori & Umemura, Nature, 440, 644 (2006)

We consider a forming galaxy undergoing multitudinous SN explosions as a possible model of bright extended LAEs. To verify this model, an ultra-high-resolution hydrodynamic simulation is performed using grid points, where SN remnants are resolved with sufficient accuracy. Three-dimensional hydrodynamics (AUSM-DV) Gravity of dark matter halos Radiative cooling (including H 2 molecule and metals) Star formation Supernova feedback (thermal energy and metals) Stellar emission: population synthesis model by Fioc 1997 (PÉGASE) Gas emission: Optically thin and collisional ionization equilibrium Sutherland & Dopita 1993 (MAPPING III) Three-dimensional Hydrodynamic Model of Bright Lyman-alpha Emitters

Parameters Total mass : M , Total gas mass: 1.3x10 10 M  (  M =0.3,   =0.7, h=0.7, z=7.8,  b =0.024 h -2 ) Sub-galactic system: N-body dynamics (20 bodies ) According to the general picture of bottom-up scenarios for galaxy formation, we model a proto-galaxy as an assemblage of numerous sub-galactic condensations building up the total mass of a galaxy. This sub-galactic unit has a mass of 5x10 9 M  and virialize at z=7.8. Star formation : Shmidt law τ cool < τ ff < τ cros d  * / dt = C *  g /  ff Local star formation efficiency: C * =0.1 Salpeter’s IMF Supernova feedback: E SN = erg / SN (thermal energy) Oxygen : 2.4 M  / SN

. These bubbly structures (middle panels in right fig.) suggest that supernova events could be closely related to observed LAEs. So we think these complexes of various super-bubbles driven by multiple supernovae are an attractive explanation for LAEs. Simulation result Movie

SED : Gas and Stars The red (blue) lines indicate the emission from gas (stellar) component. In the first 300 Myr, the resultant Lyα luminosity from gas component is more than erg/s. This completely matches the observed Lyα luminosities of Bright Lyα emitters. After 300 Myr, the luminosity declines to less than the observed level. Then, the SED becomes dominated by stellar continuum emission. gas star

Matsuda et al. 2004Smoothed image Upper: Projected distribution of Lyα emission derived by numerical results. Lower left: Simulation result smoothed with a Gaussian kernel with a FWHM of 1.0” Lower right: Lyα image of the LABs observed by Matsuda et al. (2004) Comparison of simulation and observation

L Ly α < L UV LBG phase  L Ly α > L UV LAE phase Lyα+abs. Lyα UV cont. Evolution of Lyα emission and stellar continuum emission The results of our simulation indicate the possible link among LAEs and LBGs. The simulated post-starburst galaxy with the age of 1 Gyr can correspond to LBGs. It is implied that LBGs are the subsequent phase of LAEs.

Subsequent dynamical evolution with N-body simulation containing million particles The virializaion of the total system is almost completed 3 Gyrs. Stellar mass: 1.1×10 10 M  Velocity dispersion: 133 km s -1 Effective radius: 3.97 kpc M B = -17.2, M V = -18.0, U-V=1.15, V-K=2.85 Surface brightness profile Mori & Umemura 2006

Part II Extended model

Observational properties Compact LAEs Extended LAEs Lya luminosity: erg s -1 Size (Lya): a few kpc kpc Morphology: UV: compact scattered Lya: extended very extended Stellar mass: M  ~ M  SFR: ~1―~10 M  yr -1 ~10― ~100 M  yr -1

3D hydrodynamics model We consider a forming galaxy undergoing multitudinous supernova explosions as a possible model of Lymanα emitters. Three-dimensional hydrodynamics Gravity of DM halos (fixed potential in each halo) Radiative cooling (metals dependent) Star formation and supernova Total mass : M , Total gas mass: 1.3x M  Dark Matter: NFW profile, Gas: Constant density Star formation : τ cool < τ ff < τ cros ρ crit =0.1 cm -3 d  * / dt = C *  g /  ff, Salpeter’s IMF Supernova feedback: E SN = erg, Oxygen : 2.4 M 

Evolution of mass and metallicity Stellar mass Gas mass Gas metallicity

Lyman alpha emission Gas cooling radiation Stellar origin (HII) L lya, Case B = SFR / 9.1x (Kennicutt 1998) Collisional ionization and excitation

Origin of Lyman alpha photons Red: cooling radiation (collisional ionization and excitation) Blue: Prediction by Kennicutt’s relation : SFR = 9.1x L lya (Kennicutt 1998) M  M  M 

Spatial distribution of Lyman alpha emission M=10 9 M  z=8.1 M=10 10 M  z=6.2 M=10 12 M  z=3.0 1 arcsec=4.8 kpc 5.6 kpc 7.7 kpc Theoretical Lyα emission comes mainly from high density regions. The filamentary structures are produced by the galaxy merger and multiple SN explosions. At the lower redshift, these galaxies with the complicated structures are observed as Lyman alpha blobs. But the higher redshift, most of structures become unclear due to the limited resolution.

Summary We have suggested that Lyα emitters can be identified with primordial galaxies catched in a supernova-dominated phase. The bubbly structures produced by multiple SN explosions are quite similar to the observed features in Lyα surface brightness of Lyα emitters. The resultant Lyα luminosity can account for the observed luminosity of Lyα emitters. After 1 Gyr the simulated galaxy is dominated by stellar continuum radiation and looks like the Lyman break galaxies. At this stage, the metal abundance reaches already the level of solar abundance. As a result of purely dynamical evolution over 13 billion years, the properties of this galaxy match those of present-day elliptical galaxies well. The results of our simulation indicates the possible link between Lyα emitters and Lyman break galaxies. The major episode of star formation and chemical enrichment in elliptical galaxies is almost completed in the evolutionary path from bright Lyα emitters to Lyman break galaxies.