Dust in starburst nuclei and ULIRGs: SED models for observers

TL;DR

This paper introduces a library of 7000 spectral energy distributions (SEDs) for starburst and ULIRG nuclei, enabling quick parameter estimation and flux prediction across wavelengths using radiative transfer models with spherical symmetry.

Contribution

It provides a comprehensive SED library and demonstrates its effectiveness in fitting observed galaxy data, including well-studied cases like M82 and Arp220, with a simple matching procedure.

Findings

Library successfully fits observed SEDs of key galaxies.

Model parameters align with detailed galaxy studies.

Approach is validated against other SED computation methods.

Abstract

We provide a library of some 7000 SEDs (available at www.eso.org/~rsiebenm) for the nuclei of starburst and ultra luminous galaxies. Its purpose is to quickly obtain estimates of the basic parameters, such as luminosity, size and dust or gas mass and to predict the flux at yet unobserved wavelengths. The procedure is simple and consists of finding an element in the library that matches the observations. The objects may be in the local universe or at high z. We calculate the radiative transfer in spherical symmetry for a stellar cluster permeated by an interstellar medium with standard (Milky Way) dust properties. The cluster contains two stellar populations: old bulge stars and OB stars. Because the latter are young, a certain fraction of them will be embedded in compact clouds which constitute hot spots that determine the MIR fluxes. We present SEDs for a broad range of luminosities, sizes and obscurations. We argue that the assumption of spherical symmetry and the neglect of clumpiness of the medium are not severe shortcomings for computing the dust emission. The validity of the approach is demonstrated by matching the SED of seven of the best studied galaxies, including M82 and Arp220, by library elements. In all cases, one finds an element which fits the observed SED very well, and the parameters defining the element are in full accord with what is known about the galaxy from detailed studies. We also compare our method of computing SEDs with other techniques described in the literature.