AGN Feedback: deeper study of hot accretion mode


Research Project started from Mar. 2018 @ SHAO

Email from Prof. Ostriker (18.03.13)
Thank you for the query. In fact, it comes at exactly the right time. Yesterday
Zhaoming and I had a long session going over his test runs in which we examined
the exact fashion by which one should limit star formation to regions where it
may actually occur. First, let me give you the conclusion and then I will give
you the evidence and qualifications:
$T < 4 \times 10^{4}$ K to be required for star formation to occur.
Now to some of the background discussion. We tried various different temperature
limits from $10^{5}$ K down to $1.5\times10^{4}$ K. As background, the peak of the cooling
curve is near $10^{5}$ K. Star formation in the outer parts of the galaxy is killed for
all models with $T \ll 10^{6}$ K. But if the limiter is put far below $10^{5}$ K it begins to
be killed in the inner 100 pc as well. If we had higher spatial resolution and included
molecular cooling, then we could go lower and we also could implement an
additional criterion for Jeans’ instability and/or short collapse time in the cell in
question. But, given our current resolution it is not possible to further improve
the criterion to explicitly include a gravitational instability criterion.

When the limiter given above is adopted star formation occurs in bursts only (as is
the case for real elliptical galaxies) and seems limited to roughly the amount that
actually occurs in the E+A phenomenon. Also, with this limiter the Xray luminosities
are in the range allowed by Xray observations. Thus we are happy for you to begin
your experimentation with this new star formation limiter in place.