Evolution in Lyman-alpha Evolution in Lyman-alpha Emitters and Lyman-break Emitters and Lyman-break

GalaxiesGalaxiesMasao Mori

Theoretical Astrophysics division,Center for Computational Sciences, University of

Tsukuba

Collaboration with

Masayuki UmemuraHidenobu Yajima

Presentation OutlinePresentation 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 LAECompact LAE and Extended LAE

Private communication with Hayashino, Mastuda,

Yamada et eal.

Extended LAECompact LAE

Matsuda et al. 2004

Observational properties Observational properties

Compact LAEs Extended LAEsCompact LAEs Extended LAEs Lya luminosity: 1042-43 1042-44 erg s-1 Size (Lya): a few kpc 10-100 kpc Morphology: UV: compact scattered Lya: extended very extended Stellar mass: 108-10 M ~1010-11 M

SFR: ~1―~10 M yr-1 ~10― ~100 M yr-1

Part IPart I

Three-dimensional Hydrodynamic Three-dimensional Hydrodynamic Model of Bright LAEsModel of Bright LAEs

Images of Bright Lyman Alpha Images of Bright Lyman Alpha EmittersEmitters (Lyman alpha (Lyman alpha blobs)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 6x1042 to 1044 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 Possible Models of Lyman Alpha EmissionEmission

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 10243 grid points, where SN remnants are resolved with sufficient accuracy.

• Three-dimensional hydrodynamics (AUSM-DV)• Gravity of dark matter halos• Radiative cooling (including H2 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 Three-dimensional Hydrodynamic Model of Bright Lyman-alpha Model of Bright Lyman-alpha EmittersEmitters

ParametersParameters

Total mass : 1011 M , Total gas mass: 1.3x1010 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 5x109 M and virialize at z=7.8. Star formation : Shmidt law　　 τcool < τff < τcros 　 d* / dt = C* g / ff

Local star formation efficiency: C*=0.1　　 Salpeter’s IMF Supernova feedback: ESN = 1051 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 resultSimulation result

Movie http://www.ccs.tsukuba.ac.jp/Astro/Members/mmori/nature/Mori.mpg

SED : Gas and StarsSED : 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 1043 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.

gasstar

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 observationComparison of simulation and observation

L Ly α < LUV LBG phase

LLy α > LUV LAE phase

Lyα+abs.Lyα

UV cont.

Evolution of LyEvolution of Lyαα emission and emission andstellar continuum emissionstellar continuum emissionEvolution of LyEvolution of Lyαα emission and emission andstellar continuum emissionstellar 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 Subsequent dynamical evolution with NN-body simulation containing million -body simulation containing million particlesparticles

The virializaion of the total system is almostcompleted 3 Gyrs. Stellar mass: 1.1×1010 M

Velocity dispersion: 133 km s-1

Effective radius: 3.97 kpc MB= -17.2, MV= -18.0, U-V=1.15, V-K=2.85

Surface brightness profile

Mori & Umemura 2006

Part IIPart II

Extended modelExtended model

Observational properties Observational properties

Compact LAEs Extended LAEsCompact LAEs Extended LAEs Lya luminosity: 1042-43 1042-44 erg s-1 Size (Lya): a few kpc 10-100 kpc Morphology: UV: compact scattered Lya: extended very extended Stellar mass: 108-10 M ~1010-11 M

SFR: ~1―~10 M yr-1 ~10― ~100 M yr-1

3D hydrodynamics model3D 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 : 108-12 M , Total gas mass: 1.3x107-

11 M

Dark Matter: NFW profile, Gas: Constant density Star formation : τcool < τff < τcros ρcrit=0.1 cm-3

d* / dt = C* g / ff , Salpeter’s IMF Supernova feedback: ESN = 1051 erg, Oxygen : 2.4

M

Evolution of mass and metallicityEvolution of mass and metallicity

Stellar mass Gas mass 　　　　　　 Gas metallicity

Lyman alpha emissionLyman alpha emission

1012

1011

1010 109

108

Gas cooling radiation Stellar origin (HII)

Llya , Case B = SFR / 9.1x10-43 (Kennicutt 1998)

Collisional ionization and excitation

Origin of Lyman alpha Origin of Lyman alpha photonsphotons

Red: cooling radiation (collisional ionization and excitation) Blue: Prediction by Kennicutt’s relation : SFR = 9.1x10-43 Llya (Kennicutt 1998)

1010 M 1011 M 1012 M

Spatial distribution of Spatial distribution of Lyman alpha emissionLyman alpha emission

M=109M z=8.1 M=1010M z=6.2 M=1012M 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.

SummarySummary

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.