Are Pop III Stars Finally Detected in I Zw 18?

[Chronos]

This paper; http://arxiv.org/abs/1504.02742, Population III Stars in I Zw 18, claims potentially conclusive evidence of detection of pop III stars.

 

[e.bar.goum]

Thanks for sharing, Chronos! I'm looking forward to hearing more about this.

 

[marcus]

That's interesting. These are, perhaps, the first stars formed.
They are distinguished by very low "metal" (absence of elements heavier than H and He)

The authors found stars so hot that their light contained the recombination UV from doubly ionized Helium.
Takes very high temperature to get both electrons off a helium atom.

And apparently these very hot bright massive stars did not show evidence of WIND.
Stellar wind is caused by radiation pressure of star's light on heavier elements ("metals") like Oxygen and Carbon.

So these stars were so young that they had not made metals, and they were so early that the galaxy they formed in did not have metals made by earlier stars. These were pristine first-type stars. So-called PopIII

The windlessness seems to have been the clincher---the fact that here were these extremely hot intense stars whose ATMOSPHERES apparently contained only H and He.

Really interesting paper! Thanks for sharing.

 

[e.bar.goum]

That's interesting. These are, perhaps, the first stars formed.
They are distinguished by very low "metal" (absence of elements heavier than H and He)

The same kind of stars that were the first stars formed, surely. My understanding of Zw 18 is that it's still a very active star forming galaxy, and in any case, the first pop III stars will be long gone, even in a galaxy 18 Mpc away.

But hey, a good analogy is fantastic.

 

[marcus]

Good point 18 x 3.26 is only 59 million LY. This is relatively near, these stars are practically our contemporaries . But they are the same TYPE as the first stars----analogous to them as you say.

 

[e.bar.goum]

Good point 18 x 3.26 is only 59 million LY. This is relatively near, these stars are practically our contemporaries . But they are the same TYPE as the first stars----analogous to them as you say.

Right! And being basically on our doorstep, they are good candidates for investigation too!