The physical and chemical structure of Sagittarius B2

The giant molecular cloud Sagittarius B2 (hereafter SgrB2) is the most massive region with ongoing high-mass star formation in Galaxy. Two ultra-compact HII (UCHII) regions were identified SgrB2's central hot cores, SgrB2(M) and SgrB2(N). Our aim to characterize properties of entire SgrB2 cloud. Comparing dust we depict evolutionary stages different parts SgrB2. We use Very Large Array its A, CnB, D configurations, frequency band C (~6 GHz) observe whole complex. Using ancillary VLA data at 22.4 GHz ALMA 96 GHz, calculated physical parameters UCHII their dense gas environment. identify 54 6 image, 39 which are also detected GHz. Eight newly discovered. have radii between $0.006 {\rm pc}$ $0.04 pc}$, emission measure $10^{6} pc\,cm^{-6}}$ $10^{9} pc\,cm^{-6}}$. ionized by stars types from B0.5 O6. found a typical density $\sim10^6-10^9 cm^{-3}}$ around regions. pressure surrounding them comparable. expansion timescale these determined be $\sim10^4-10^5 yr}$. percentage cores that associated 33%, 73%, 4%, 1% for SgrB2(N), SgrB2(M), SgrB2(S), SgrB2(DS), respectively. Two-thirds SgrB2(DS) outflows. electron densities agreement regions, while smaller than those SgrB2(N) more evolved but younger SgrB2(M).