The First Stars and Black Holes

1
The First Stars and Black Holes
2
Stars today

• Old and young populations (I and II)
• Different histories
• Different chemical makeup
• Initial material (sampled between galaxies)
  almost pure H/He
• No known stars so metal-poor
• So - where are the Old Ones?

3
Starbirth

• Interstellar gas/dust common
• Gas must cool to collapse
• Dust grains and heavy elements are important in
  this (coolants)
• Hydrogen/helium stars would be different

4
Pure H/He starbirth

• Only very massive stars could collapse
• Only minimal cooling from molecular H
• Likely 80-300 solar masses, maybe more
• One to a protogalaxy theyre fratricidal

5
(No Transcript)
6
They blew up real good

• Up to 10x energy of type Ia supernova
• Up to 40 of mass released in O,C
• Seeded future galaxies and gas between (which we
  now see is slightly enriched)
• Enough heavy elements for normal star formation
  to ensue
• But galaxy formation had to start twice!

7
Closest local analogs the most massive stars
8
Can we see them?

• Dont come in clusters
• Short-lived
• High-redshift (pure infrared targets)
• Dont blow their mass away in winds
• Their explosions bright enough to see and there
  should be one seen about every 8 seconds.
  Somewhere in the sky.

9
(No Transcript)
10
Have we already seen them?

• Gamma-ray bursts have finally been associated
  with asymmetric supernovae
• Some bright bursts have no optical/near-infrared
  afterglow
• Are these at still higher redshifts?

11
Digression Gamma-ray bursts

• Discovered by Vela satellites
• No pattern on sky
• Compton statistics indicate very distant
• BeppoSAXground fading afterglow in optical,
  high redshift, host galaxy
• Later bursts some have optical/X-ray signature
  of fading supernova
• Collapsar picture

12
(No Transcript)
13
Fading afterglow Of GRB 991216 (z1) Near-infrared
bands
14
Collapsar model

• Hot neutron star or black holes forms in center
  of explosion
• Temporary high-density surrounding disk
• Directs relativistic jets
• Gives stellar surface very rude surprise
• Boosted to gamma rays if we look along the jet
  (so there are many more of these than we see)

15
(No Transcript)
16
Finding Pop III (VMOs, SMOs)

• Look for their supernovae in IR (important in
  JWSTs survey strategy)
• Look for deep-IR-only GRB afterglows
• Early ionization input seen by WMAP??
• Understand chemical prehistory of stars
• Look for their remnant black holes
• Read Stephen Baxters Vacuum Diagrams

17
And speaking of black holes where did the first
massive ones come from?
18
The Problem(s)

• Most bright galaxies have a supermassive central
  black hole
• Only some of these are now accreting and easy to
  find
• Quasars are now known to redshift 6 (about t800
  million years)
• Which have black holes just as massive as we see
  later on. How did they do that?
• And have gas as metal-rich as we see later!

19
Nearby supermassive black holes
20
(No Transcript)
21
How could black holes jump-start?

• Direct formation from collapsing gas
• Primordial objects
• Dense relativistic star clusters
• More exotic objects collapsing?
• Are primordial stars even more massive than we
  thought?

22
Gas around quasars enriched!

• Spectra of quasars at all times show very similar
  metal abundances
• Most heavy metals come from supernovae
• Are all quasars in sites of intense and early
  starbirth (and stardeath)?
• Could the quasars have triggered this?
• Were starting to look earlier than the age of a
  type I supernova, should see iron decline

23
Composite of high-redshift quasars
24
H
N
Absorption by intergalactic gas
Si