Star Formation Dark Matter and Baryons Gravity (DM) defines large - - PowerPoint PPT Presentation

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Star Formation Dark Matter and Baryons Gravity (DM) defines large - - PowerPoint PPT Presentation

Oct 22, 2022 137 likes •474 views

Star Formation Dark Matter and Baryons Gravity (DM) defines large scale structure of the Universe Baryons are mostly hitchhiking a ride Yet, their physical interactions are far richer Gastrophysics How are stars

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Star Formation

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KAS16/MT Lecture1II - Star Formation

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Dark Matter and Baryons

★Gravity (DM) defines

large scale structure of the Universe

★Baryons are mostly

hitchhiking a ride

★Yet, their physical

interactions are far richer

★“Gastrophysics” ★How are stars formed?

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★ Gas in the Interstellar Medium is not dense enough

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Radiative cooling

★How do you expect cooling to depend

  • n metallicity of gas?
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Radiative cooling and “metals”

★ Simple atoms and molecules are inefficient at

radiative cooling

★ Metal-free gas (Z<10-3.5ZSun) hard to cool ★ The more “metals” the more efficient the cooling:

many energy levels available

★What is your expectation for the Jeans mass in

first gas clouds?

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Log{Cooling efficiency}

★ But cooling

efficiency grows with temperature

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Log{Cooling efficiency}

★ But cooling

efficiency grows with temperature

★ WHY?

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DM halos and cooling of gas

★ Temperature of gas in DM halos depends on halo

mass and redshift

★There is a minimum halo mass for which cooling is

efficient (cooling time less than Hubble time)

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Minimum halo for cooling

Trenti & Stiavelli (2009)

z Mcool Tvir=1e4K minimum halo mass for cooling

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Gas cloud starts to contract

It gets smaller and denser And smaller...

Denser, Hotter until H-fusion begins: A star is born!

The simple picture

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30 Smith et al. (2009) n [cm-3] T [K]

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