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Sagittarius B2 (Sgr B2) is a giant molecular cloud complex in the centralmolecular zone of our Galaxy hosting several sites of high-mass star formation.The two main centers of activity are Sgr B2(M) and Sgr B2(N), which contain 27and 20 continuum sources, respectively. Our analysis aims to be a comprehensivemodeling of each core spectrum, where we take the complex interaction betweenmolecular lines, dust attenuation, and free-free emission arising from HIIregions into account. In this work, we determine the dust and, if HII regionsare contained, the parameters of the free-free thermal emission of the ionizedgas for each core, and derive a self-consistent description of the continuumlevels of each core. Using the high sensitivity of ALMA, we characterize thephysical and chemical structure of these continuum sources and gain betterinsight into the star formation process within the cores. We used ALMA toperform an unbiased spectral line survey of all 47 sources in ALMA band 6 witha frequency coverage from 211 GHz to 275 GHz. In order to model the free-freecontinuum contribution of a specific core, we fit the contained recombinationlines (RRLs) to obtain the electron temperatures and the emission measures,where we use an extended XCLASS program to describe RRLs and free-freecontinuum simultaneously. In contrast to previous analyses, we derived thecorresponding parameters here not only for each core, but also for their localsurrounding envelope, and determined their physical properties. Thedistribution of RRLs we found in the core spectra closely fits the distributionof HII regions described in previous analyses. For the cores we determineaverage dust temperatures of around 236 K (Sgr B2(M)) and 225 K (Sgr B2(N)),while the electronic temperatures are located in a range between 3800 K and23800 K.

The physical and chemical structure of Sagittarius B2 VIIIa. Dust and ionized gas contributions to the full molecular line survey of 47 hot cores