Re: Newtonian simulations of dark matter only sphere

From: ABINASH KUMAR SHAW <abinashkumarshaw_at_gmail.com>
Date: Thu, 10 Sep 2020 00:20:02 +0530

Dear Dr. McBride,

Thank you for the help and clarifications. I shall go through the
references and look into the choice of softening parameters more closely.

Sincerely,
Abinash Kumar Shaw

On Thu, Sep 10, 2020 at 12:10 AM Cameron McBride <cameron.mcbride_at_gmail.com>
wrote:

> My guess here is that you need to adapt your gravitational softening in
> Gadget-2. I've been out of actively following the literature for the last
> ~5ish years, but there was a host of papers that talk about cusp - core
> connection to gravitational softening that can change the cusp vs core.
> It's a little bit of a numerical quagmire, as you can tune softening to act
> differently (and there are tradeoffs even if you force a strict N^2
> calculation, which Gadget-2 typically doesn't). I also suggest you don't
> use grid, but tree only configurations.
>
> I think Zavala et al 2019 or Kuhlen et al 2012 might discuss aspects of
> this. There are some older articles, like Boylan-Kolchin et al 2005 that
> might also discuss some of it.
>
> Others might have more insight, but hopefully that might help you start
> digging deeper.
>
> Cameron
>
> On Wed, Sep 9, 2020 at 8:32 AM ABINASH KUMAR SHAW <
> abinashkumarshaw_at_gmail.com> wrote:
>
>> Hello,
>>
>> I am trying to study time evolution of the density profile of a single
>> dark matter only halo in Newtonian space (without boundary) using Gadget-2.
>> My initial condition file contains a spherical distribution of only the
>> cold dark matter particle which is written in gadget format. I am following
>> the example of the gassphere (provided with the code) to evolve the CDM
>> halo. I expect the density profile to show the cusp at the halo centre
>> whereas I am getting a core. I understand that a core forms when there are
>> baryons in addition to the CDM. There are no baryons here, however I expect
>> that somehow baryonic interaction is still taking place. So, do I need to
>> modify the code of my simulations; or am I doing something wrong?
>>
>> Thank you in advance.
>>
>> Sincerely,
>> Abinash Kumar Shaw
>>
>> *Senior Research Fellow*
>> *Department of Physics*
>> *Indian Institute of Technology Kharagpur*
>> *Kharagpur, India -- 721302.*
>>
>
Received on 2020-09-09 20:50:43