Romeel Dave’s talk

Today we had a speaker, Romeel Dave who talked about galactic outflow model based on their hydrodynamic simulation. Dark matter mass functions from theory follows power law, but galaxy luminosity or mass function not only shows the negative offset in overall but also shows suppressed feature in faint end and bright end.
The question is what mechanisms make currently observed luminosity or mass function revealed by luminous matter. For very faint end, the UV background radiation from nearby galaxies is candidate to ionize neutral gas, which leads to the suppressed star formation. For bright end, AGN is considered as the suppression mechanism. For intermediate regime, galactic outflows(or sometimes called as a wind)is believed to be a important mechanism to blow out gas and to suppress the star formation.
To explain many observations about ISM/IGM/Galaxy(especially not too faint or bright galaxy, which is a dominant population)connection, it’s important to understand the wind mechanism.

Recent observation tells us that the wind velocity is proportional to the circular velocity of a galaxy. Motivated by this observation, a momentum driven wind(MDW)has been proposed by him. In this model, energetic photons from star forming region transport their momentum to ISM, then this momemtum driven wind takes baryons out to IGM. His simulation successfully reproduces some of key observations(e.g. metal enrichment of IGM, mass-metalicity relation). But still there is a question: what’s the physical reason for MDW? Is it really what’s happening in a galaxy? What about other galaxies with different star formation mechanism(eg. merger driven star formation)?

As usual, the truth may not be simple, some galaxies might have MDW or not. The physic behind the wind needs to be known from the observation.


~ by ilsangyoon on September 25, 2008.

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