LIghtcone observer coordinates

From: Robin Booth <>
Date: Mon, 11 Oct 2021 11:49:42 +0000

Hi Volker

One of the things we would like to do in a future GADGET-4 run is to generate multiple lightcone realisations from the same simulation box by repositioning the observer in the box for each of the realisations, e.g. at each of the 8 vertices of the simulation box (q.v. DiRAC RAC 14, project 3.5). The GADGET-4 code paper (Springel et al 2020) implies that this feature exists in the code:

Section 7.5 : "An arbitrary coordinate within the simulation box can be selected as an observer position.
One or several lightcone geometries can then be defined through their starting redshift zstart,
their ending redshift zend (which can be zero as in the sketch of Fig. 41,"

but if that is the case, it does not seem to be documented and from a cursory examination of the code in, it does not appear that the code handles the reading of observer coordinates as a parameter option.

I would be grateful if you could comment on whether this was a planned feature that has not yet been implemented, or perhaps I am missing something in the code?


Received on 2021-10-11 13:50:03

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