NTU/ASIAA Joint Colloquium May 13, 2014 The Dark Ages of the Universe Naoki Yoshida Physics / Kavli IPMU University of Tokyo
C ONTENTS ✦ From the big bang to the first stars A missing piece in cosmic history � ✦ First light � The mass of the first stars � ✦ Early blackholes and supernovae � Setting the scene for galaxy formation References: Hosokawa, Omukai, NY, Yorke, 2011, Science � Bromm, NY, 2011, ARAA Hosokawa, Yorke, Omukai, Inayoshi, NY, 2013, ApJ Tanaka, Moriya, NY, 2013, MN Hirano et al. 2014, ApJ
γ-ray burst 0 10 20 30 40 [sec] X-ray image Afterglow Relativistic jet from the central black hole Death of a massive star Photon count by Swift sat. • Every few days • From all directions on the sky (=extragalactic) • The record redshift of z=9.4! ~ 13.5 billion light yrs
A Y OUNG BUT B IG ! B LACKHOLE � 2 billion times heavier 13 billion light years away than the sun � (130 ������ � � Light in various wavelengths �
Stellar relics in the Milky Way A “forbidden” star extremely metal-poor (not only iron-poor) Caffau et al. 2012, Nature Low-mass (<1 M sun ), Metallicity below 4.5 x 10 -5 that of the sun.
No spectral features Sun Fe Sun Ordinary stars like the sun contains a few percent (in mass) of heavy elements → many lines in the spectrum � There are many stars in Galaxy that contain less amount of heavey elements � A few of them contain almost no elements other than hydrogen and helium. wavelength
Seemingly different phenomena • Prompt emission of high-energy photons • Emergence of a super-massive blackhole • A nearby star with very low metal content They may have the same origin, which is also related, ultimately, to the beginning of our own existence.
T HE C OSMIC H ISTORY
The Dark Ages ~2-300 million years Has not been observed by any wavelength • dsf
In the beginning, there was a sea of light elements and dark matter… and tiny ripples left over from the Big Bang �
Turbulence Cosmic rays Supernovae Stellar winds Radiation Magnetic field Compare with present-day star formation
Early universe
� STANDARD COSMOLOGICAL MODEL THEORY OF STAR FORMATION 4% 22% 74% molecular cloud protostar star dark matter early structure inflation
F IRST S TAR N URSERIES Web-like structure Matter distribution in the early universe. Yellow spots are clumps of dark matter. First star nurseries are 1000 times heavier than the sun. Strongly clustered. T age = 300 million years �
P RIMORDIAL G AS C LOUD H He Gravity Radiative cooling H 2 (0.01%) Simple picture
From primeval ripples to a protostar Minihalo 300pc � � Resolving planetary 10 6 M sun scale structures in a cosmological volume! Molecular cloud � A complete picture of how a protostar is formed from tiny New-born protostar density fluctuations. 5pc � � 25 solar-radii NY, Omukai, Hernquist 2008
Physics is hard Thermal evolution (EoS) NY, Hosokawa, Omukai, PTEP 2012 A proto-star (hydrostatic core) The Physics 10 4 collision H 2 formation induced line cooling emission T [K] 3-body � (NLTE) reaction opaque to 10 3 continuum loitering and (~LTE) opaque to dissociation Heat molecular adiabatic release line contraction 10 2 number density
Hyper-accreting protostar A “classic” picture The central protostar � accretes the surrounding � gas at a very large rate: � hydrostatic � core dM/dt ∝ T 1.5 /G � = 0.01-0.1 M sun /yr outer envelope
mass lifetime fate 1 solar ~ 10 billion years white dwarf 10 ~ 10 million years supernova 200 ~ 2 million years energetic supernova The mass and the fate of a star � � > 1 million times brighter than the sun
Theorists said.... mass “evolution” omukai core 1000 evolution protostar � evolution � ohkubo 1D M sun Disk evap. mckee jeans mass 100 tan accretion time hosokawa protostar bromm HD feedback abel PopIII.2 ny clark Disk johnson 10 fragment 2000 2002 2004 2006 2008 2010 2012
Protostars grow through gas accretion, mergers, plus, protostellar feedback over ~ 100,000 years The Key Question How and when does a first star stop growing ? gas cloud protostar star
density temp. outflow hot cold Pressure-driven outflow around a protostar McKee-Tan08; Hosokawa+11; Stacey+12 Bi-polar H II regions vs accretion flow. � Self-regulation mechanism.
Final mass of a first star Photo-dissociation Final mass Hosokawa, Omukai, NY, Yorke, 2011, Science Accretion rate onto the protostar Cloud evaporation
A long standing puzzle … resolved. Observed elemental abundances SN models of 20-40 M sun progenitor Metal-poor stars were formed from a gas cloud enriched by the first supernova explosions Abundance pattern from a 25 Msun Hypernova model ����������� Iwamoto et al. 2005
100 First Stars Hirano, NY+ 2014, ApJ Cosmological hydro simulation + radiation-hydro calculation of protostellar evolution � 100 star forming clouds located in the cosmological volume. � Characteristic mass of the first stars
Toward Primordial IMF Imagine this enormous effort...
The result : final masses Collapse to BH
3 evolutionary paths stellar mass By Hirano & Hosokawa accreting protostar stellar radius dM/dt = KH contract. e c n e u q e s n i a m
Hunting for the first supernova explosions Tanaka, Moriya, NY, Nomoto 2012, MNRAS, 422, 2675 Moriya et al. 2013, MNRAS, 428, 1020 Tanaka, Moriya, NY, arxiv 1306.3743
Distant supernova Type IIn at z=2.4 Cooke et al. 2009, 2012, Nature brightness variation 11 billion light years away
Super-luminous T eff = 12000 K supernovae Powered by shock- interaction with dense gas cloud Bright in ultra-violet Death of a very massive star They will be visible (> 50 Msun?) to very high-z.
Super-Luminous SN Powered by shock- interaction with dense CSM. Bright in rest-UV Death of a very massive star They will be visible (> 50 Msun?) to very high-z.
Monte-Carlo Simulation Distinguished from low-z SN example Model Spectra + SN occurance rate Tanaka, Moriya, NY, Nomoto 2012 SED evolution Locally calibrated SN occurance rate Light curve �
Subaru-HSC 2014- Tanaka, Moriya, NY, Nomoto, 2012 3.5 deg 2 Number color selection
Probing stellar mass Salpeter 100 deg 2 1-4 μm How many massive stars are formed. SLSN progenitors are the high-mass end of the population
Future surveys Tanaka, Moriya, NY 2013
Personal goal
First blackholes
Blackhole mass Marziani+11 (super-) Eddington mild evolution ? BigBang 1Gyr 2Gyr ← time 10 9 10 7 10 11 10 10 10 8
Blackhole seeds: Rees diagram PopIII remnant via a super-massive star Volonteri 2012, Science
Blackhole growth t=0.2 0.5 0.8 Gyr 10 9 10 5 10 2 M BH popiii remnant direct collapse smbh “ o b s e r v e d ”
Direct collapse model Latif+13, A&A ~ 1M sun /year Super Massive Star ~ 10 5 M sun Strong radiation d M /d t ~ T 1.5 /G See also Regan & Haehnelt 2011; Choi+2013
Supergiant star stellar mass stellar radius Hosokawa, Yorke, Inayoshi, Omukai, NY 2013, ApJ dM/dt > 0.06 M sun /yr KH contract. e c n e u q e s n i a m
mass 100,000 M sun star M 1/2 Low effective Temp R ∝ → no UV feedback , M L ∝ Radius 1 10 100 1000 10 4 10 5
James Webb Space Telescope By T. Hosokawa
Gravitational stability General relativistic instability
Blackhole growth z=30 20 15 10 7 10 9 10 5 10 2 M BH popiii dc smbh Large gap
Summary origin of objects in the early universe the most distant places a supermassive star and possibly a BH • Formation of massive primordial stars as • Supernova explosions might be visible to • Rapid growth of a primordial star makes
Recommend
More recommend
