May 19-22, 2014Bologna 3. Radiative transfer models for infrared galaxies Michael Rowan-Robinson Imperial College, London Early work on radiative transfer models for ir sources Radiative transfer models Physical assumptions 1-D, 2-D and 3-D radiative transfer Infrared templates, applications

May 19-22, 2014Bologna Early work on radiative transfer models for ir sources 1960s models: assume density, temperature have power-law dependence on r, optically thin, no scattering (ie sum Q  B  (T) ) Leung 1975: detailed grain properties, radiative transfer solution of moment equations including anisotropic scattering, temperature by radiative balance Yorke and Krugel 1977: dynamical evolution of HII region, interaction between gas and dust RR 1980: need full calculation of I (  ), find sideways beaming at inner edge of cloud, back radiation onto star

May 19-22, 2014Bologna ingredients for models for seds of infrared sources model for interstellar grains [ Mathis et al 1977, Draine and Lee 1984, Desert et al 1990, Rowan-Robinson 1992, Siebenmorgen and Krugel 1992, Dwek 1998] assumed density distribution for dust [  ~r - , HII region physics (Yorke 1977, Efstathiou et al 2000)] dust geometry [ spherically symmetric, axisymmetric (Efstathiou and RR 1990, 1991, 1995, Pier and Krolik 1992, Granato et al 1994, 1997, Silva et al 1998), clumpy [Rowan-Robinson 1995, Hoenig et al 2006] radiative transfer code [Rowan-Robinson 1980, Efstathiou and RR 1990, Pier and Krolik 1992, Krugel and Siebenmorgen 1994, Granato et al 1997, Silva et al 1998, Popescu et al 2000, Hoenig et al 2006]

May 19-22, 2014Bologna Physical assumptions Molecular cloud evolution: T-Tauri and OB star formation. Spherical symmetric phase, blister phase. Late stages of HII region evolution, supernova evolution. Dust grain properties, amorphous v. crystalline, very small grains and PAHs. Importance of A V > 1. Patchiness of A V in galaxies. Impact of multiple star-forming clouds in ultraluminous mergers like Arp 220 (need 3-D treatment).

Bologna HI-GAL image of MW: the complexity of dust in galaxies wonderful filamentary lattice of denser gas, with protostellar cores reminiscent of ‘cosmic web’ of intergalactic gas May 19-22, 2014

SAG3 - Gould Belt survey N E 80’’ Bologna May 19-22, 2014

Bologna the radiative transfer equation The intensity of radiation I (r,  ) satisfies the equation dI /ds = - n(r) C,ext I + n(r) C  abs B [T(r)] + n(r)   C,sc (  ’) I (  ’) d  where C  abs =  a 2 Q  abs C,sc =  a 2 Q,sc  (  ’) C,ext = C  abs +   C,sc (  ’) d 

May 19-22, 2014Bologna equation of radiative balance Radiative balance:  Q  abs J  (r) d =  Q  abs B  {T(r)} d where J  (r) =   I d  Energy absorbed by a dust grain is balanced by the energy it emits. Can be shown to be equivalent to conservation of flux through the dust cloud.

May 19-22, 2014Bologna Radiative transfer models for infrared sources spherically symmetric dust clouds - first accurate code 1980 (R-R, ApJS 234, 111) - circumstellar dust shells (R-R & Harris ) - starbursts and ULIRGs (RRE, 1993, MN 263, 675; ERRS, 2000) - cirrus galaxies (RR 1992; ERR 2003) axially symmetric dust clouds - first accurate code 1990 (Efstathiou and R-R, MN 245, 275) - protostars AGN dust tori 1995

May 19-22, 2014Bologna Spherically symmetric radiative transfer models for starbursts - RR and Crawford 1989, RR and Efstathiou Krugel and Siebenmorgen Silva et al 1998, axisymm interstellar dust, OB stars in hot spots - Efstathiou, RR, Siebenmorgen 2000, model molecular cloud, HII region and supernova evolution - Takagi et al 2003, distributed stars and dust satisfy King law - Dopita et al 2005, 2006ab, Groves et al 2008, detailed HII region physics - Siebenmorgen and Krugel 2007, large library of parameterized models

May 19-22, 2014Bologna Eftstathiou, Rowan-Robinson, Seibenmorgen, 2000, MN 313, 734 embedded phase, t < 10 7 yrs expanding neutral shell, t = years at 10 8 yrs, indistinguishable from cirrus can we detect starbursts of different ages ? Models for starburst galaxies

May 19-22, 2014Bologna 2-D, axially symmetric, radiative transfer models for ir sources - protostars Eftstathiou and RR, 1991 Whitney et al 2003, AGN dust tori Pier and Krolik 1992 Granato and Danese 1994 Efstathiou and RR 1995

May 19-22, 2014Bologna 3-D radiative transfer models for clumpy AGN dust tori - Rowan-Robinson 1995, slab model for clumpy torus in QSOs - Nenkova et al 2002, 2008, 5-10 clump model for NGC1068 (slab model) - Dullemond and van Bemmel 2005, Monte Carlo - Shartmann et al 2005, 2008, Monte Carlo - Honig et al 2006, Monte Carlo R-R 95

May 19-22, 2014Bologna 3-D radiative transfer codes (Steinacker 2013)

May 19-22, 2014Bologna 3-D radiative transfer Examples of spatial grids used currently for 3-D radiative transfer (Saftley et al 2013). Left: assumed density distribution [top: double exponential disk wiht 3-arm spiral, centre: clumpy AGN dust torus, bottom: late-type disk galaxy model from N-body calculation]. Centre and right: two different spacial grids.

May 19-22, 2014Bologna 3-D radiative transfer Illustration of adaptive grid of rays for integration of radiative transfer equation

May 19-22, 2014Bologna 3-D radiative transfer Monte Carlo methods: Top: simple Monte Carlo. Bottom: weighted Monte Carlo. In each case the fate of 5 photons is followed.

May 19-22, 2014Bologna 3-D radiative transfer State of art 3-D models: Top: NGC891 (Schectman-Rook et al 2012) 2 nd : NGC4565 (de Looze et al 2012a) 3 rd : Sombrero (de Looze et al 2012b) Bottom: UGC7321 (Matthews & Wood 2001) observed model

May 19-22, 2014Bologna Radiative transfer models for (quiescent) disk galaxies (cirrus) - Rowan-Robinson 1992, Efstathiou and RR Silva et al Popescu et al 2000, 2011, Misiratis et al 2001, Tuffs et al Dale et al Piovani et al 2006

May 19-22, 2014Bologna Cirrus models for local galaxies assume optically thin ism, extinction A V (not >> 1) Bruzual & Charlot starburst models, age t *, exponential decay time  characterise galaxies by single mean intensity,  = bolometric intensity/solar neighbourhood intensity (R-R 1992) for local galaxies, t * = 0.25 Gyr,  = 5-11 Gyr (Efstathiou and Rowan-Robinson 2003)

May 19-22, 2014Bologna local galaxies A V = 0.9,  =

May 19-22, 2014Bologna Cirrus models for SCUBA galaxies Efstathiou and RR (2003) also found that cirrus models, with slightly higher A V and  ( ~ 2-3 times higher) can also fit high-z galaxies from SCUBA blank-field surveys restricted analysis to SCUBA sources: (a) which have been confirmed by submm interferometry, or (b) sources from 8 mJy survey which have radio associations, - found 70% of sources (16/23) successfully modeled by cirrus model. Efstathiou and Siebenmorgen (2009) model 12 submm galaxies which have IRS spectroscopy. - 3 fitted with pure cirrus, rest with cirrus+starburst.

May 19-22, 2014Bologna Cirrus models for SCUBA galaxies

May 19-22, 2014Bologna Infrared templates Starbursts, as function of A V (init) and age. [can we recognize young and old starbursts?] Cirrus, as function of  (+SED of radiation field?). [what is very cold dust seen by Herschel and Planck?] AGN dust tori, as function of inclination and torus geometry. [can we recognize Compton-thick (N(H)>10 23, A V >100) dust tori?]

May 19-22, 2014Bologna Infrared templates (Rowan- Robinson 2001)

May 19-22, 2014Bologna Eftstathiou, R-R, Seibenmorgen, 2000, MN 313, 734 embedded phase, t < 10 7 yrs expanding neutral shell, t = years at 10 8 yrs, indistinguishable from cirrus Models for starburst galaxies

May 19-22, 2014Bologna

May 19-22, 2014Bologna galaxy sed model fits from GRASIL (Silva et al 1998)

May 19-22, 2014Bologna IRAS - AGN dust tori Miley et al, 1984, ApJ 278, L79: a 25  m component in 3C390.3

May 19-22, 2014Bologna Hyperluminous infrared galaxies Rowan-Robinson, 2000, MN 316, 885 starburst dominated IRAS F10214, z=2.3 galaxy Teplitz et al 2006

May 19-22, 2014Bologna dust torus dominated

May 19-22, 2014Bologna SPITZER-IRS spectra of ELAIS sources IRS spectra for 70 ELAIS- N1 and -N2 sources with S15> 1mJy validate the template fits most are ULIRGs, with z =1-3 Filled circles: optical, ISO, SWIRE ( and MAMBO) data Solid curves: model seds Red curve: calibrated IRS data (Hernan-Caballero et al 2006 )

May 19-22, 2014Bologna what powers ultraluminous infrared galaxies ? Genzel et al, 1998, ApJ 498, 579

May 19-22, 2014Bologna what powers ultraluminous infrared galaxies ? Spoon et al, 2007, astro-ph/

Spoon IRS diagnostic diagram 9.7  m silicate depth v. 6.2  m PAH EW (Spoon et al 2007) models for starbursts, cirrus, AGN by Efstathiou and RR Rowan-Robinson and Efstathiou, (2009) May 19-22, 2014Bologna

Validity of  B  (T) fits ? May 19-22, 2014Bologna Huge numbers of papers in the literature ignore the large number of published radiative transfer models and fit mid and far infrared spectra with  B  (T) fits. The MAGPHYS code uses several such components to fit mid and far ir, and submm. These fits do not have any physical validity. For no known dust component does Q,abs ~ . For optically thin cirrus, predicted spectrum for real dust is quite different, especially on short wavelength side of peak. Each dust species and radius has its own (non-blackbody) SED. For optically thick star-forming clouds have range of temperatures from K. Single temperature makes no sense. Empirically, on long wavelength side of peak such fits can agree quite well with data. The meaning of this colour ‘temperature’ is the mass-weighted average temperature of the dust (R-R 1992).