The Dark Ages of the Universe

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The Dark Ages of the Universe

NTU/ASIAA Joint Colloquium May 13, 2014

Naoki Yoshida

Physics / Kavli IPMU University of Tokyo

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C ^ONTENTS

✦

From the big bang to the first stars

!

✦

First light

!

✦

Early blackholes and supernovae

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

A missing piece in cosmic history

!

The mass of the first stars

!

Setting the scene for galaxy formation

!

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γ-ray burst

0 10 20 30 40 [sec]

Photon count by Swift sat. X-ray image

Afterglow

•

Every few days

•

From all directions on the sky

(=extragalactic)

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The record redshift of z=9.4!

~ 13.5 billion light yrs

Relativistic jet from the central

black hole

Death of a massive star

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A Y OUNG BUT B IG ! B LACKHOLE

2 billion times heavier than the sun

13 billion light years away

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Light in various wavelengths

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Stellar relics in the Milky Way

A forbidden star

Low-mass (<1M^sun),

extremely metal-poor (not only iron-poor) Metallicity below 4.5 x 10^-5 that of the sun.

Caﬀau et al. 2012, Nature

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No spectral features

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.

Sun

wavelength

Fe

Sun

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Seemingly different phenomena

•

Prompt emission of high-energy photons

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Emergence of a super-massive blackhole

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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.

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T ^HE C ^OSMIC H ^ISTORY

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The Dark Ages

•

^dsf

Has not been observed by any wavelength

2-300 million years

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In the beginning,

there was a sea of light elements and dark matter…

!

and tiny ripples left over from the Big Bang

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Compare with present-day star formation

Turbulence Cosmic rays

Supernovae

Stellar winds Radiation

Magnetic ﬁeld

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Early universe

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STANDARD COSMOLOGICAL MODEL

!

THEORY OF STAR FORMATION molecular cloud protostar

star

4%

22%

74%

inflation

dark matter

early structure

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F ^IRST S ^TAR N ^URSERIES

Web-like structure in the early universe.

Yellow spots are

clumps of dark matter.

First star nurseries are 1000 times

heavier than the sun.

Strongly clustered.

Matter distribution

T_age = 300 million years

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P RIMORDIAL G AS C LOUD

H ^He

Gravity

Radiative cooling

H2 (0.01%)

Simple picture

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!

Resolving planetary scale structures in a cosmological

volume!

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A complete picture of how a protostar is formed from tiny density fluctuations.

!

From primeval ripples

to a protostar

Minihalo

Molecular cloud

New-born protostar

NY, Omukai, Hernquist 2008 25 solar-radii

5pc

300pc 10⁶ M! sun

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Physics is hard

adiabatic contraction

H2 formation line cooling

(NLTE)

loitering

(~LTE)

3-body reaction

Heat release

opaque to molecular

line collision induced emission

T [K]

10⁴

10³

10²

number density

opaque to continuum

and

dissociation A proto-star

(hydrostatic core) The PhysicsThermal evolution (EoS)

NY, Hosokawa, Omukai, PTEP 2012

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Hyper-accreting protostar

hydrostatic core

outer envelope

The central protostar!

accretes the surrounding!

gas at a very large rate:!

!

A classic picture

dM/dt ∝ T^1.5/G

= 0.01-0.1 Msun/yr

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The mass and the fate of a star

mass lifetime fate

1 solar 10 billion years white dwarf

!

10 10 million years supernova

!

200 2 million years energetic > 1 million times brighter

than the sun

supernova

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Theorists said....

2000 2002 2004 2006 2008 2010 2012

10 100 1000

!

Msun ohkubo

ny johnson

mckee

tan hosokawa

clark omukai

bromm abel

jeans mass accretion time

protostar evolution

1D

HD PopIII.2

Disk evap.

core evolution

Disk fragment protostar

feedback

mass

“evolution”

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Protostars grow through gas accretion, mergers, plus, protostellar feedback

over 100,000 years

gas cloud protostar star

The Key Question How and when

does a ﬁrst star stop growing ?

!

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Bi-polar HII regions vs

accretion flow.

!

Self-regulation mechanism.

temp.

density

outﬂow hot

cold

Pressure-driven outﬂow around a protostar

McKee-Tan08; Hosokawa+11; Stacey+12

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Final mass of a ﬁrst star

Accretion rate onto the protostar

Photo-dissociation Cloud evaporation

Final mass

Hosokawa, Omukai, NY, Yorke, 2011, Science

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A long standing puzzle … resolved.

Iwamoto et al. 2005 Abundance pattern from a 25 Msun Hypernova model

Observed elemental abundances

SN models of 20-40 Msun

progenitor

Metal-poor stars were formed from a gas cloud enriched by the first supernova explosions

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100 First Stars

Hirano, NY+ 2014, ApJ

Cosmological hydro simulation

+

radiation-hydro calculation of

protostellar evolution

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100 star forming

clouds located in the cosmological volume.

!

Characteristic mass of the first stars

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Toward Primordial IMF

Imagine this enormous eﬀort...

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The result : ﬁnal masses

Collapse to BH

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3 evolutionary paths

stellar mass

stellar radius

main sequence

dM/dt =

By Hirano & Hosokawa

KH contract.

accreting protostar

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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

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Distant supernova

Type IIn at z=2.4

Cooke et al. 2009, 2012, Nature

brightness variation

11 billion light years away

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Powered by shock- interaction with

dense gas cloud

Bright in ultra-violet Death of a very

massive star (> 50 Msun?)

They will be visible to very high-z.

Teﬀ = 12000 K

Super-luminous

supernovae

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Super-Luminous SN

Powered by shock- interaction with

dense CSM.

Bright in rest-UV Death of a very

massive star (> 50 Msun?)

They will be visible to very high-z.

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Monte-Carlo Simulation

!

Distinguished from low-z SN

example Model Spectra

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SN occurance rate SED evolution

Locally calibrated SN occurance rate

Tanaka, Moriya, NY, Nomoto 2012

Light curve

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Subaru-HSC ^2014-

Number

color selection

Tanaka, Moriya, NY, Nomoto, 2012

3.5 deg²

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Probing stellar mass

Salpeter

100 deg² 1-4 μm

SLSN progenitors are the high-mass end of the population

How many massive stars

are formed.

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Future surveys

Tanaka, Moriya, NY 2013

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Personal goal

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First blackholes

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Blackhole mass

Marziani+11

(super-)

Eddington mild evolution ?

BigBang 1Gyr

2Gyr

← time 10⁹

10⁷ 10¹¹ 10¹⁰

10⁸

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Blackhole seeds: Rees diagram

Volonteri 2012, Science

PopIII remnant

via a super-massive star

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Blackhole growth

t=0.2 0.5 0.8 Gyr 10⁹

10⁵

10²

M

BH

popiii remnant

direct collapse

smbh

observed

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Direct collapse model

Strong radiation

Latif+13, A&A

See also Regan & Haehnelt 2011; Choi+2013

dM/dt

~ T^1.5/G

1Msun/year

Super Massive

Star

10⁵ Msun

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Supergiant star

stellar mass

stellar radius

main sequence

dM/dt > 0.06 Msun/yr

Hosokawa, Yorke, Inayoshi, Omukai, NY 2013, ApJ

KH contract.

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100,000 M ^sun star

Low effective Temp

→ no UV feedback

1 10 100 1000 10⁴ 10⁵ Radius

mass

L M, R M

1/2

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James Webb

Space Telescope

By T. Hosokawa

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Gravitational stability

General relativistic

instability

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Blackhole growth

z=30 20 15 10 7 10⁹

10⁵

10²

M

BH

popiii

dc

smbh

Large gap

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Summary

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Formation of massive primordial stars as origin of objects in the early universe

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Supernova explosions might be visible to the most distant places

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Rapid growth of a primordial star makes a supermassive star and possibly a BH

The Dark Ages of the Universe