SPAMCART: A code for smoothed particle Monte Carlo radiative transfer

Abstract

We present a code for generating synthetic spectral energy distributions and intensity mapsfrom smoothed particle hydrodynamics simulation snapshots. The code is based on the LucyMonte Carlo radiative transfer method, i.e. it follows discrete luminosity packets as theypropagate through a density field, and then uses their trajectories to compute the radiativeequilibrium temperature of the ambient dust. The sources can be extended and/or embedded,and discrete and/or diffuse. The density is not mapped on to a grid, and therefore the calculationis performed at exactly the same resolution as the hydrodynamics. We present twoexample calculations using this method. First, we demonstrate that the code strictly adheresto Kirchhoff's law of radiation. Secondly, we present synthetic intensity maps and spectra ofan embedded protostellar multiple system. The algorithm uses data structures that are alreadyconstructed for other purposes in modern particle codes. It is therefore relatively simple toimplement.