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Evolution in Lyman-alpha Emitters and Lyman-break Galaxies

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.

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Evolution in Lyman-alpha Emitters and Lyman-break Galaxies

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  1. 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

  2. Presentation Outline • Three-dimensional Hydrodynamic Model of Bright Lyman Alpha Emitters 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)

  3. Part IThree-dimensional Hydrodynamic Model of Bright LAEs

  4. Extended LAEs LAEs Images of Bright Lyman Alpha Emitters 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.

  5. 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)

  6. Three-dimensional Hydrodynamic Model of Bright Lyman-alpha Emitters • 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)

  7. Parameters • Total mass : 1011M , Total gas mass: 1.3x1010M (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 5x109M 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

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

  9. gas star 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 1043 erg/s . This completely matches the observed Lyα luminosities of Lyαemitters. After 300 Myr, the luminosity declines to less than the observed level. Then, the SED becomes dominated by stellar continuum emission.

  10. Comparison of simulation and observation 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) Smoothed image Matsuda et al. 2004

  11. Lyα+abs. Lyα UV cont. Evolution of Lyα emission andstellar continuum emission LLy α> LUV LAE phase LLy α<LUV LBG phase 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.

  12. Subsequent dynamical evolution with N-body simulation containing million particles Surface brightness profile The virializaion of the total system is almost completed 3 Gyrs. Stellar mass: 1.1×1010M 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

  13. Part IIExtended model

  14. Observational properties Compact LAEs Extended LAEs • Lya luminosity: 1042-43 1042-44 erg s-1 • Size (Lya): a few kpc 10-100 kpc • Morphology: Lya: extended very extended UV: compact scattered • Stellar mass: 108-10 M ~1010-11 M • SFR: ~1―~10 Myr-1~10― ~100 M yr-1

  15. 3D hydrodynamics model • We consider a forming galaxy undergoing multitudinoussupernova explosions as a possible model ofLymanα emitters. • Three-dimensional hydrodynamics • Gravity of dark matter halos (fixed potential) • Radiative cooling (metals dependent) • Star formation and supernova • Total mass : 108-12M , Total gas mass: 1.3x107-11M • Dark Matter: NFW profile, Gas: Constant density • Star formation : τcool < τff < τcrosρcrit=0.1 cm-3 • d* / dt = C*g / ff , Salpeter’s IMF • Supernova feedback: ESN = 1051 erg, Oxygen : 2.4 M

  16. Evolution of mass and metallicity Stellar mass Gas mass Gas metallicity

  17. Lyman alpha emission Gas cooling radiation Stellar origin (HII) 1012 1011 108 1010 109 Llya, Case B = SFR / 9.1x10-43 (Kennicutt 1998) Collisional ionization and excitation

  18. Origin of Lyman alpha photons 1010 M 1011 M 1012 M Red: cooling radiation (collisional ionization and excitation) Blue: Prediction by Kennicutt’s relation : SFR = 9.1x10-43Llya(Kennicutt 1998)

  19. Spatial distribution of Lyman 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.

  20. Discussion Private communication with Hayashino, Mastuda, Yamada et eal. NB497 NB-BV(Lya) V03 U BV R

  21. 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 LyαemittersandLyman 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.

  22. Real vs Virtual

  23. Extended LAEs LAEs Lyα emitters and Lyα blobs Matsuda et al., AJ, 128, 569 (2004) Ouchi. et al. ApJS, 176, 3010 (2008)

  24. Filling factor Metal free Z > 0.001 Z Z > Z Z > 0.1 Z

  25. log n 0.351 Gyr 0.548 Gyr 0.723 Gyr 0.936 Gyr log T [O/H] • Mtotal=1012M , zcol=2.98

  26. log n 6.2 Myr 16.4 Myr 35.9 Myr 59.8 Myr log T [O/H] • Mtotal=108M , zcol=10.3

  27. log n 0.238 Gyr 0.396 Gyr 0.580 Gyr 1.21 Gyr log T [O/H] • Mtotal=1011M , zcol=6.23

  28. Kennicutt’s law dstar/dt = C*gas/dyn C*=1.0 C*=0.1 Spiral galaxies dstar /dt (M yr-1 kpc-2) Starburst galaxies gas (M pc-2) gas (M pc-2) dstar/dt = 2.5×10-4 gas1.4 Kennicutt 1998

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