Star formation

From: Fabrice DURIER <>
Date: Sat, 12 Nov 2005 12:50:58 +0100

Dear all,

  Presently, I'm trying to introduce a mechanism to form stars on
Gadget1 (unfortunately Gadget2 does not work yet on our Alpha machine:
it compiles with mpich1.2.6 but crashes after a few steps without any
particular error message, just p0_882848: p4_error: interrupt SIGFPE: 8...)

  Anyway, I have already put a cooling function (Katz, Weinberg &
Hernquist, 96) in the energy equation for gas particles. I select
particles which satisfy specific conditions (in the usual way: Jeans
instability, density threshold...). I then switch these particles from
type 0 to type 4.

  As I have seen previous messages here on this subject, I wanted to
follow Volker's advice: to insert a "rearrange_particle" routine just
before the domain decomposition, but the code crashes immediately after.
Without this routine, the code continue with the following warning
sometimes appearing after the "birth" of a star:

    Warning. No convergence in `findSplitPoint' achieved.
    Balance: 0.469157 Iterations: 128 Task: 0
    xmaxleftofguess=14535.1 xminrightofguess=14856.6 xleft=14856.6

  I found the function findSplitPoint() in the file domain.c, but does
anyone know what it means?

  My main problem however concern the feedback model. During the star
formation process, I need to "temporarily" remove some of the particles
(they must reappear later) of the simulation. I know Eugene Kurbatov
tried to introduce a negative type, but this seems too complicated to me
(I don't know how to modify the tree structure...). As a result, I put
Mass=0 for these gas particles (in the hope of later regaining mass),
but I'm not sure if the simulation treats them as "invisible". For the
moment I can't work out how to make them reappear!

Does anyone know how to do this? Any advice or idea would be appreciated!

 Fabrice Durier
 Observatoire de la Côte d'Azur
 Département CASSIOPEE
 B.P. 4229
 06304 NICE Cedex 04
 T: (+33)
 E-mail: <>
Received on 2005-11-12 13:00:35

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