Chemical and Physical Structures of Massive Star Forming Regions Hideko Nomura, Tom Millar (UMIST) ABSTRUCT We have made self-consistent models of the density and temperature profiles, and then investigated the hot core chemistry after grain mantle evaporation due to heating by an embedded luminous object, taking into account the different binding energies of the mantle molecules. We find that the resulting column densities are consistent with most of those observed toward G at a time around 10 4 yrs after the central star formation. We have also investigated the dependence of the density profile on the chemical structures which suggests an observational possibility of constraining density profiles of hot cores from determination of the source sizes of line emission from desorbed molecules. INTRODUCTION Physical & Chemical Properties of Hot Cores Size < 0.1pc, T ~ K, n H ~ 10 7 cm -3 IR source, Outflow, Inflow Massive Star Formation X(M, hot core)~ X(M, dark cloud) M: NH 3, H 2 S, CH 3 OH, (CH 3 ) 2 O etc. Origin of Abundant Molecules in Hot Cores evaporation of icy mantle + subsequent gas-phase reaction -> complex molecules prestellarstar-formationprotostellar freeze out & grain surface reaction evaporation of icy mantle Density Profile SED & Radial Profile of Radiation Flux V ~1pc G31.41 Core + Envelope Model n H (r) = n 0 /(1+r/r core ) -1.5 N H =10 25 cm -2 (Hatchell et al. 2000) Dust Temperature Heating Source: Central Star Local Radiative Equilibrium Reemission = Absorption Radiative Transfer Eq. Gas Temperature Thermal Equilibrium  +L-  = 0 -> T gas (r)  : photoelectric heating on dust by FUV L : heating & cooling by collision between gas and dust particles  cooling by line excitations Obs. of G34.3 MODEL FOR G Central Star: L=5×10 5 L s r core =0.05pc Density & Temperature Profiles Obs. from Macdonald et al. ’ 96, Hatchell et al. ’ 00, Ikeda et al. ’ 01 Calculation (3× ×10 5 yr) Molecular Column Densities Time Evolution Comparison with Obs. Consistent with obs. of SED for r core = 0.05pc Destruction of parent mol. & creation of daughter t ~ yr Consistent with obs. of most mol. around t ~10 4 yr GENERAL MODELS - Dependence of Density Profile - Density profiles Temperature profiles cf.  ,  r -p ->T ∝ r -(p+1)/(4- n) Density & Temperature Profiles Radial Profiles of Molecular Abundances -> Obs. of dramatic changes in mol. abundance due to dust evaporation possibility constrain density profiles of hot cores OUTFLOW REGION Outflow (v~10km/s, N H =10 24 cm -2 ) Hot core (t =10 4 yr, N H =10 25 cm -2 ) Destruction of some molecules in inner hot region Advection of molecules to outer region SUMMARY Chemical and Physical Structure of Hot Core G Radiative transfer calculation -> dust & gas temperature + Chemical calculation (inc. temp. dependent dust evap.) Calculated N mol : consistent with ~10 4 yrs after the star formation. Dependence of Density Profile on Chemical Structure -> observational possibility of constraining density profiles of hot cores from source sizes of line emission Chemical Model for Outflow Region -> PHYSICAL MODEL CHEMICAL MODEL Chemical Network 211 species, 2190 reactions Initial Condition (evaporation of mantle molecules) ★ YSO R i =ν i exp(-E i /T d ), τ i ~1/ R i ~10 3 yr ->T d,i (from Hasegawa & Herbst 1993) (Kean 2000 ) t ~10 4 yr NH 3, CO 2 H 2 O, CH 3 OH H2SH2S CH 4, CO