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Cloudy u Accurate simulation of physical processes at the atomic & molecular level –“universal fitting formulae” to atomic processes fail when used outside.

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Presentation on theme: "Cloudy u Accurate simulation of physical processes at the atomic & molecular level –“universal fitting formulae” to atomic processes fail when used outside."— Presentation transcript:

1 Cloudy u Accurate simulation of physical processes at the atomic & molecular level –“universal fitting formulae” to atomic processes fail when used outside realm of validity, and are not used u Assumptions: –energy is conserved –(usually) atomic processes have reached steady state u Limits: –Kinetic temperature 2.7 K < T < K –No limits to density (low density limit, LTE, STE) –Radiation field 10 m to 100 MeV

2 Simultaneous solution of u Gas ionization –From ionization balance equations u Chemistry –Large network based on UMIST u Gas kinetic temperature –Heating and cooling u Grain physics –Charging, CX, photoejection, quantum heating u The observed spectrum –Radiative transport

3 Cloudy and its physics u Osterbrock & Ferland 2006, Astrophysics of Gaseous Nebulae and Active Galactic Nuclei, 2 nd edition (AGN3) u Ferland+2013, Rev Mex 49, 137, The 2013 Release of Cloudy u Ferland 2003, ARA&A, 41, 517, Quantitative Spectroscopy of Photoionized Clouds

4 Some applications to astronomy u Hamann & Ferland, ARA&A, 37, 487, Elemental Abundances in Quasistellar Objects: Star Formation and Galactic Nuclear Evolution at High Redshifts u Ferland 2001, PASP, 113, 41, Physical Conditions in the Orion H II Region u And the ~200 papers that cite its documentation each year

5 2012 Cloudy workshop

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7 Open source since 1978 u All versions, all data, on svn at nublado.org u You are most welcome to help!

8 https://www.nublado.org/

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10 2012 Cloudy workshop

11 https://www.nublado.org/

12 Where to go for help u https://groups.yahoo.com/neo/groups/cloud y_simulations/info

13 2012 Cloudy workshop

14 Documentation u Quick start guide u Hazy 1, all commands u Hazy 2, description of output, comparison with observations u Hazy 3, not compiled, badly out of date, some physics is described there

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18 The test suite u Fully tests the code after any changes –“Monitors” allow automatic comparison of current with previous results u Provides examples of how to use Cloudy –But may include extraneous commands for testing u Useful examples of how to set up a simulation

19 Running cloudy u “run” file contains path-to-cloudy.exe -r $ u If file “model.in” contains input, then u run model & u Produces output “model.out”

20 Minimum to run Cloudy u Must specify –SED – shape of the radiation field –Flux of photons per unit area –Gas density u May specify –Gas composition, grains (grain-free solar by default) –Gas equation of state (often constant density) –Stopping criterion, often physical thickness

21 Parameters – the SED u Quick start guide Chapter 5 u Hazy 1, Chapters 4, 6 u Can be specified as a fundamental shape such as a blackbody u Generally entered as table of points

22 SED brightness – the intensity case  Specify  (H) – photons per unit area –The “intensity case” –predicts emission per unit area –Inner radius of cloud does not need to be specified

23 SED brightness – the luminosity case u Specify Q (H) – photon luminosity –Inner radius of cloud must be specified, since  (H) = Q(H) / 4  r 2 –predicts emission line luminosities

24 The “main output” u The *.out file created when code is executed –QSG 7.1 & Hazy 2 Chapter 1 u Gas & grain composition u Physical conditions in first and last zone u Emission line spectrum u Mean quantities u Cloudy is designed to be autonomous and self aware u Will generate notes, cautions, or warnings, is conditions are not appropriate.

25 “Save” output u Requested with various “save” commands –Hazy 1 Section16.35 and later u The main way the code reports its results

26 The Orion H II Region u Based on Baldwin, Ferland, Martin+91 model u Layer in hydrostatic equilibrium u Only the H II region (so faster) u Cloudy / tsuite / auto / orion_hii_open.in 2012 Cloudy workshop

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34 Minimum to run Cloudy u Must specify –SED – shape of the radiation field –Flux of photons per unit area –Gas density u May specify –Gas composition, grains (solar by default) –Gas equation of state –Stopping criterion

35 Parameters – the SED u Quick start guide Chapter 5 u Hazy 1, Chapters 4, 6 u Can be specified as a fundamental shape such as a blackbody u Generally entered as table of points

36 SED brightness – the intensity case  Specify  (H) – photons per unit area –The “intensity case” –predicts emission per unit area –Inner radius of cloud does not need to be specified

37 SED brightness – the luminosity case u Specify Q (H) – photon luminosity –Inner radius of cloud must be specified, since  (H) = Q(H) / 4  r 2 –predicts emission line luminosities

38 Cloud density u “hden” command u Constant density by default u Other equations of state possible

39 Composition u Solar, no grains, by default u Other standard mixes possible

40 Open vs closed geometry Hazy Cloudy workshop

41 Covering and filling factors u Covering factor –AGN3 … u Filling factor, how to do clumps –AGN3, hazy Cloudy workshop

42 Strömgren length 2014 Cloudy workshop

43 Strömgren length u Number of ionizing photons entering layer is balance by number of recombinations along it 2014 Cloudy workshop

44 Matter vs radiation bounded u SL is for radiation bounded, there is an I front u Show Abell sphere – matter bounded, u So phi(H) > SL equation u Show pics, give section in AGN3

45 Beyond the H + layer 2014 Cloudy workshop u Little H + ionizing radiation gets past the H + layer u Deeper regions are atomic or molecular u Also cold and produce little visible light u Large extinction due to dust

46 Clumping u Filling factors, when clumps smaller than photon scale length –Osterbrock & Flather 1957 u Add together distinct clouds, when clumps larger than photon scale length –Balwin ApJ 455, L119+

47 Volume elements in larger structures


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