The Population III ConnectionJonathan Devor

Outline

• GRBs as Cosmological Probes: Why is this interesting?

• Population III – A brief historical overview• The primordial IMF• Stars: Then and now• Supernovae• What can we hope to see?• The road ahead

GRBs as Cosmological Probes: Why is this interesting?

• Cosmological model

• Big bang nucleosynthesis

• First stars (population III)

• Galactic formation

• Reionization epoch

• Early IGM metallicity enhancement

Population III – A brief historical overview

• (Baade 1944) – star populations:Pop. I: Sun-like (1 - 2% metals by mass)Pop. II: Globular cluster-like (0.01 – 0.1%)Pop. III: No metals (actually < 0.001%)

• (Schwarzschild et al. 1953):First model for pop. III stars(far less complex than type I stars in a modern environment)

Ongoing work

• 1980’s: Cosmological consequences-- Effects on CMB (SZ effect)- “Primordial” abundances of Helium - “Pregalactic metal enrichment”- Reionization epoch- Effects on early galactic formation

• 1990’s: clump/star formation• 2000’s: WMAP, Swift, JWST

Space Missions…

• BATSE (1991-2000) = Burst and Transient Source Experiment [5-1,500 keV ]

• WMAP (2003-) =Wilkinson Microwave Anisotropy Probe [22-90 GHz]

• Swift (2004-)• JWST (2011-) = James Webb Space Telescope• EXIST =Energetic X-ray Imaging Survey Telescope

5-100 KeV: x10-20 better than Swift

100-600 KeV: x300 better than HEAO-A3 survey

CDM at z=17

Taken from (Yoshida 2003)Taken from Swift website

Primordial gas

Taken from (Bromm 2002)

Adiabatic H2 cooling

Stable point Gravitycompression

Lingers at: T~200K3410~ cmn

Jean’s instability criterion

2/1

34

2/3

3

2

3

10200700

)22.1()(

)(:

cm

n

K

TMM

mRnRMM

Gn

kT

G

kTR

R

RGkTUnstable

solJ

pJJJ

J

Protostellar collapse

• No dust, no metal – need H2 as coolent- Free electron catalyzer (feedback from UV)

- 3-body channel Clump breakup

• Radiation pressure dominated (very low opacity- electron scatter)

• Halo breakup Nstar ~ 1-5 (if N=1, problem getting rid of the angular momentum)

HHH 23)10( 38 cmn

cGM

LEdd

4

eHHHHeH 2

Clump evolution

Taken from (Omukai 1998)

Growth of protostar

The accretion is effectively shut off at some critical value because of the dramatic increase in radius

Taken from(Omukai 2003)

Pop. III supernovae

< 140 M Type II SNe

(core collapse)

Low yield

140-260 M Pair-instability supernova (PISN)

No remnant High yield ½M metals

> 260 M Massive black hole (MBH)

High accretion No yield (quasar?)

ergE 5310

•Life time: yearsL

cM

Edd

62

* 103007.0

ergE 5110

Pop. III star – remnant

ergEyearst 536 10;10

400 pc

fragmentation

metals

Taken from(Bromm 2003)

SPH simulation

Reionization

HI 13.6 eV

HeI 24.6 eV

HeII 54.4 eV

Though comparable in brightness, GRB afterglows release less energy than quasars into the IGM (ionizes M of hydrogen). So they have a negligible effect on their environment (with the exception of dwarf galaxies )

1010~510~

Taken from (Wyithe 2003)

What can we see?

All GRBsSwiftBATSE

Taken from (Bromm 2002)

With Swift, 10-25% of GRB afterglows will come from z > 5

That is, about a dozen a year!

Taken from (Lamb 2002)

The road ahead – open questions

• Do pop. III stars exist?

Need observations!!! (Swift?)• Do their supernovae make GRBs? (quenching?) • Primordial environment• Primordial IMF / star formation history (GRB redshift distribution)

• Early cosmological formation (filaments, galaxies)

• “Extreme physics” (SNe, MBH)

Some references

• Historical:- Schwarzschild M., ”Inhomogeneous Stellar Models. III. Models with Partially

Degenerate Isothermal Cores.”, 1953, Astrophysical Journal, vol. 118, p.326

• Survey papers:- Bromm V. and Larson R., “The First Stars”, 2003, astro-ph/0311019- Bromm V., “The First Sources of Light‘, asyro-ph/0211292- Lamb D., “Gamma-Ray Bursts as a Probe of Cosmology”, 2002, astro-

ph/0210434- Loeb A. and Barkana R.,”The reionization of the Universe by the First stars and

Quasars”, Annu. Rev. Astron. Astrophys., 2001, 39:19-66- Loeb A., “Observing the First Stars, One Star a Time”, 2003, astro-ph/0307231

The Swift SongWe know that gamma ray explosions happen randomly all over the sky (It's like a lottery: a

ticket for each square degree) You see a FLASH! and then there's not another till about a day has gone by (But that depends

upon detector sensitivity) In just a moment they spew energy worth (That's pretty fast) A value we can't even fathom on

Earth (It's really vast!) But just what's giving rise to gamma ray sparked skies? Is it the death cry of a massive star or

black hole birth? (Or both, or both? or both!)

Chorus: Swiftly swirling, gravity twirling Neutron stars about to collide Off in a galaxy so far away Catastrophic interplay A roller coaster gamma ray ride Superbright explosion then Never to repeat again How are we supposed to know? How about a telescope rotation Swiftly onto the location Of its panchromatic afterglow?