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Astronomy Observational, not experimental Photos of objects Spectrum A non-equilibrium gas Gas emitting spectrum has a very low density, exposed to a range of radiation fields and particles Populations of levels, ionization, spectrum, determined by many micro-physical processes Not characterized by a single temperature H, He rich, some O, C, N, Fe etc 30 Atomic Number 25 20 15 10 5 0 1 1000 106 n(Z) / n(Si) 109 1012 Solar corona Collisional kT equilibrium ~ iP Fe XII 102 Stellar SED Flux F 101 H0 He0 T = 40,000 K * 100 10-1 10-2 500 1000 Wavelength (A) 1500 2000 Photoionization Equilibrium energetic radiation interacts with surrounding gas – photoionization photoelectrons heat free electrons electrons excite heavy elements – collisionally excited line cooling free electrons recombine – recombination lines Cloudy Follows the detailed microphysics, with most processes treated at elementary level All stages of ionization of the lightest 30 elements, 100+ molecules 2.7 K ≤ T ≤ 1010 K 10-10 ≤ n ≤ 1015 cm-3 Continuously maintained Fully open source, at www.nublado.org - log fractional ionization Temperature 10000 1000 100 0 1 C+2 He0 H+ He 2 + C0 H0 molecular fractional 100 CO 10-1 H2 H2O 10-2 CH 10-3 OH 10-4 H2O 1.5e+17 1.6e+17 1.7e+17 1.8e+17 Depth (cm) Ferland, G.J., 2003, ARA&A, 41, 517 1.9e+17 2.0e+17 1000 L 100 [O III] [O II] H [S III] [O III] [O III] [Ne II] [C II] 10 [N II] Br -2 -1 F (erg cm s ) P 1 0.1 0.01 0.001 0.1 1 10 Wavelength (microns) 100 1000 Cloudy on the web www.nublado.org Some databases Originally home-grown internal database, hardwired into code – Moving to all data external to code Collisional ionization, Voronov 97, Dere 09 RR & DR, Badnell web site, our data Chemistry largely based on UMIST H2 internal structure, lines, Meudon databases Heavy molecules, internal structure, lines, Leiden LAMDA database Collisional radiative cooling – Fe VII Astronomy Observational, not experimental Photos of objects Spectrum