The First Stars and Black Holes :The First Stars and Black Holes


Stars today :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?


Starbirth :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


Pure H/He starbirth :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 – they’re fratricidal


They blew up real good :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!


Closest local analogs – the most massive stars :Closest local analogs – the most massive stars


Can we see them? :Can we see them? Don’t come in clusters Short-lived High-redshift (pure infrared targets) Don’t 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.


Have we already seen them? :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?


Digression – Gamma-ray bursts :Digression – Gamma-ray bursts Discovered by Vela satellites No pattern on sky Compton: statistics indicate very distant BeppoSAX+ground: fading afterglow in optical, high redshift, host galaxy Later bursts: some have optical/X-ray signature of fading supernova Collapsar picture


Slide 13:Fading afterglow Of GRB 991216 (z=1) Near-infrared bands


Collapsar model :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)


Finding Pop III (VMOs, SMOs) :Finding Pop III (VMOs, SMOs) Look for their supernovae in IR (important in JWST’s 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 Baxter’s Vacuum Diagrams…


And speaking of black holes – where did the first massive ones come from? :And speaking of black holes – where did the first massive ones come from?


The Problem(s) :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 t=800 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!


Nearby supermassive black holes :Nearby supermassive black holes


How could black holes jump-start? :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?


Gas around quasars – enriched! :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? We’re starting to look earlier than the age of a type I supernova, should see iron decline


Slide 23:Composite of high-redshift quasars


Slide 24:Absorption by intergalactic gas H N Si