Novel Picture for Lyman Alpha Emitters
Ikkoh Shimizu
doctoral candidate

collaborator
Masayuki Umemura

1Standard biased galaxy formation
galaxyDensity peaks with an amplitude exceeding a minimum
threshold value δmin are identified as galaxies.
Biased galaxy formation2

Large-scale structure ofLyα emitters(LAEs)
LAEs(z=3.1)

LAEs(z=5.7)

LAEs are major population of high-z galaxyLAEs(z=4.8)

To study LAEs is important tounderstand galaxy evolution.

3

LAEs in SSA22 region at z=3.1
zThe correlation of observation is weaker thantheoretical expectation→ Spatial distribution of LAEs is difficult
to reproduce with standard biased galaxy formation

The biased galaxy formation model does notLAEs
are special objects???
contour of the consider
mean number density properties of LAEs.
observation
Theoretical expectation

Weak correlation

Hayashino et al.,(2004)

Kauffmann et al.,(1999)

4

Observational Properties of LAEs
Wave lengthLyαzstrong Lyα emission

Lyα

EWLyα＞20[Å]In this study,
zsmaller wesizes
develop a new galaxy formation model
than other classes of high-z galaxies
forLAEs
basedon their observational properties.
zmuch less dust
zfainter continuum than LBG

These suggests thatLAEs are very young objects and have shorter lifetimes.

5

Our modelLAEs

The growth time =lifetime of LAEs

CA
B

The fluctuations between δmin and δmax are
identified as LAEs
6

result•Simulation box：(32h70Mpc)3•particle number ：(256)3⇒1 particle mass：7.1×107Msun•Initial z：z=51•periodic boundary condition

Spatial distribution of halos

LAEs in SSA22 region
Halos to 6×107yr oldHalos from 5×108yr old
to 6×108yr old

Our model can reproduce
Biased galaxy formationmodel
the observed spatial distribution
well!!
ω(θ)

Mpc

Correlation function

Our modelMpc□：biased galaxy formation model＊：halos from 5×108yr old to 6×108yr old●：halos to 6×107yr old

Correlation length(Mpc)

7summary
We calculate cosmological N-body simulation
to explain observed LAEs spatial distribution.
We consider the lifetime of the LAEs,
which has not been hitherto considered in the standard
biased galaxy formation scenario.

zOur model can reproduce
observed spatial distribution of LAEs in SSA22 region.
zLAEs should be in the first phase of galaxy evolution.
zlifetime of LAEs is 6×107yr.

8Appendix

9Model and assumption
zthe dynamical evolution of baryonic matter follows that of dark matterzthe dark matter particles begins the star formation,
when they trapped in halo.
：dark matter particle：young particle trapped in halo：old particle trapped in halo

halo

evolution

halo

evolution

10timeCalculation method and condition
zCalculation method•N-body simulation(Particle-Particle-Particle-Mesh method+grape)•we independently consider star formation history
and chemical evolution of each substructure(particle) in galaxies
with evolutionary spectral synthesis code 'PEGASE'.
→ we can treat more realistic dynamical
and chemical evolution of galaxies.

zcalculation condition•ΛCDM(Ω0=0.27,ΩΛ=0.74,Ωb=0.02h-2,h=0.7,σ8=0.85)•Simulation box：(32h70Mpc)3•particle number ：(256)3⇒1 particle mass：7.1×107Msun•Initial z：z=51•periodic boundary condition

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Distribution of LAEs at high-z(z>3.1)
ｚ＝４ｚ＝５ｚ＝６There is no change to intrinsic number density
at ４～ｚ～８ｚ＝７ｚ＝８ｚ＝９12

Correlation function of LAEs at high-z(z>3.1)
ｚ＝４ｚ＝５ｚ＝６ｚ＝７ｚ＝８ｚ＝９z dependence

Place where LAEs reside
High-z → high-density peak
Low-z→
low-density peaktransition this like13

Large scale structure of galaxies
at high redshift(high-z)

Discovery of large scale structure such as Lyman break galaxies(LBGs)
and Lyα galaxies(LAEs) high-z
LBGs(z=4)

LAEs(z=5.7)

statisticalproperty
to understandfrom observation
Wepayattention
tospatialdistribution
galaxyThough the observation technique of LGBs and LAEs isofdifferent,
zspatialfunction)
bothdistribution(correlation
galaxiesin
arethisstar study
forminggalaxy.
zluminosity, number density(luminosity function)

Ouchi et al.,(2005)

Ouchi et al.,(2005)
Lyα

SED of high redshift galaxy
14
Steidel et al.,(1998)

spatial distribution of LBGs and LAEs
LAEs(z=5)
LBGs(z=4)

Ouchi et al.,(2001)

matches observation!

Ouchi et al.,(2003)

cannot reproduce observation!

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Hamana et al.,(2004)

result(Lyα luminosity)
Lyα luminosity(erg/s)

LAEs(A)

LAEs(B)

Intrinsic Lyα luminosity correspondthat of observed LAEs.
ただしLyα光子のEscape fractionに不定性あり

Age of halo16

correlation function and density fluctuation
zdensity fluctuation at x δ(x)zRelations with correlation function and density fluctuation

We draw out density fluctuation from correlation function!!! 17

Theoretical approach to LAEs
Mori & Umemura.,(2006a,b)← ultra high resolution simulation on
the dynamical and chemical evolution of galaxy

LAEs phasezmultiple supernova explosions at an early phase of < 3 × 108 yr resultin forming high density cooling shells, which emit so strong
Lyα as to account for the luminosity of LAE.
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