Spitzer-IRAC GLIMPSE of high mass protostellar objects II - SED modelling of a bonafide sample

TL;DR

This study models the spectral energy distributions of high-mass protostellar objects using radiative transfer models to derive their physical properties, revealing insights into their masses, ages, and accretion processes.

Contribution

It provides a comprehensive SED fitting analysis of a large sample of HMPOs using an online radiative transfer model, offering new estimates of their physical parameters.

Findings

Median mass of 10 solar masses and age of 10,000 years.

High envelope accretion rates with a power-law dependence on mass.

Most sources are consistent with being proto-B stars, some potentially evolving into O stars.

Abstract

We aim to estimate and analyse the physical properties of the infrared counterparts of HMPOs by comparing their spectral energy distributions (SED) with those predicted by radiative transfer accretion models of YSOs. The SED of 68 IRCs are extended beyond the GLIMPSE photometry to the possible limits, from the near-infrared to the millimetre wavelengths by using the 2MASS, GLIMPSE version 2.0 catalogs, MSX, IRAS and some single dish (and interferometric) (sub)mm data. An online SED fitting tool that uses 2D radiative transfer accretion models of YSOs is employed to fit the observed SED to obtain various physical parameters. The SED of IRCs were fitted by models of massive protostars with a range of masses between 5-42 Msun and ages between 10^3 and 10^6 years. The median mass and age are 10 Msun and 10^4 yrs. The envelopes are large with a mean size of ~ 0.2-0.3 pc and show a distribution that is very similar to the distribution of the sizes of 8 micron nebulae discussed in Paper I. The estimated envelope accretion rates are high with a mean value of 10^(-3) Msun/yr and show a power law dependence to mass with an exponent of 2, suggesting spherical accretion at those scales. Disks are found to exist in most of the sources with a mean mass of 10^(-1.4+-0.7) Msun. The observed infrared-millimetre SED of the infrared counterparts of HMPOs are successfully explained with an YSO accretion model. The modelled sources mostly represent proto-B stars although some of them could become O stars in future. We demonstrate that many of these results may represent a realistic picture of massive star formation, despite some of the results which may be an effect of the assumptions within the models.