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The CIGALE code and its application to Herschel surveys

Fitting the full SED ( from UV to far-IR ) of galaxies to put constraints on dust attenuation and star formation determinations , from z=0 to z=2. The CIGALE code and its application to Herschel surveys. Véronique Buat , Elodie Giovannoli , Médéric Boquien , Sébastien Heinis ,

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The CIGALE code and its application to Herschel surveys

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  1. Fitting the full SED (from UV to far-IR) of galaxies to put constraints ondustattenuation and star formation determinations, from z=0 to z=2 The CIGALE code and its application to Herschel surveys Véronique Buat, Elodie Giovannoli, Médéric Boquien, Sébastien Heinis, Denis Burgarella & the Herschel Reference Survey and GOODS-Herschel teams SED2011-Preston- sept-2011

  2. Outline • Description of the CIGALE code • Applications: -z=0 [Herschel Reference Survey]: integrated and spatiallyresolvedSEDs -1<z<2: [GOODS-Herschel]: evidence for a UV bump in the attenuationcurves of IR detected galaxies

  3. CIGALE : Code InvestigatingGALaxyEmission • P.I. D. Burgarella (Noll et al. 2009) http://www.oamp.fr/cigale/ A physically-motivated code: CIGALE combines a UV-optical SED & a dust IR emitting component: Energetic balance fully conserved between stellar and dust emission. • INPUT PARAMETERS: • Photometric data +errors • Star Formation Histories • Dustattenuationcurves • IR libraries • OUTPUT PARAMETERS : • All based on a Bayesian analysis • input parameters • Stellar Mass • Dustluminosity • Amount of obscuration • D4000 break, slope of the UV continuum….

  4. STELLAR COMPONENT • « Old » stellar population: SFR exponentiallydecreasing, age, e-folding rates are free parameters • «Young » stellar population: SFR exponentiallydecreasing or constant, age, e-folding rates are free parameters • Composite population: mass fraction due to the youngstellar population as free parameter • Populations synthesismodelsfrom: • Maraston 2005 • PEGASE (Fioc & Rocca-Volmerange)

  5. CIGALE: optimized to study dust attenuation curves different amount of dust attenuation (and same attenuation curve) for the young and the old stellar population Calzetti et al. (2000) UV bump power law Width Central wavelength Amplitude slope 5500 Å

  6. Variousmid and far-IRlibraries of star forming and starburst galaxies Dale & Helou (2002) 64 templates Chary & Elbaz (2001) 105 templates Siebenmorgen & Krügel (2007) ~7000 SEDs -Library of modifiedBlack bodies Now : β=1.5, Tdust varies severalβ and Tdust:collaboration with the Herschel Reference Survey Team, nearbyuniverse -Draine & Li (2007) library, work in progress

  7. AGN libraries Giovannoli, 2011, PhDthesis Current Baseline: 9 SED templates of AGNs 2 AGNs Siebenmorgen & Krugel (04) Mean AGN fromMullaney et al. (10) 6 AGNsfrom Fritz et al. (06) To go deeper in the AGN analysis 32 AGNsfrom Fritz et al. 2006

  8. Webuildmock catalogues to check the robustness of parameterestimates: • Run CIGALE a first time and take the best model for eachgalaxy • Create an artificialdatasetwith the best modelsintegrated in the photometric bands and add noise • Runagain CIGALE on the mock catalogue and compare « true » and estimatedparameters • (Giovannoli et al. 2011, Buat et al. 2011)

  9. SED fitting in the Herschel Reference Survey HRS (PI S. Eales): Volume limited, K-selectedsurvey of 323 galaxies observedat 250, 350, 500 µm 15 < D < 25 Mpc, b > 55°, AB< 0.2 K < 8.7 for E, S0, S0a and K < 12 for Sa-Im-BCD Boselli et al. 2010 all Early-types Late-types

  10. Full integrated IR SEDs (cf L. Ciesla poster) • IndividualSEDs: Dale & Helou (02) give good fits, Draine & Li (07) betterreproduce the data • MeanSEDs per morphological type: Dale & Helou (02), Chary & Elbaz (01), Elbaz et al. (11) wellreproducemeanSEDs of late types. Dale & Helou 2002 MeanSEDs HRS SEDs by morphological type Chary & Elbaz 2001 MeanSEDs Draine & Li 2007 M99

  11. SpatiallyresolvedSEDs on large galaxies (M. Boquien et al. In prep.) Subset of ~30 late-type galaxies and pixel to pixel analysisat the resolution of the 350 microns frame All the data are convolved and regridded to the samereference frame (at 350 microns) and a pixel-to-pixelanalysis of the emissionisperformed by fitting the SED of each pixel with CIGALE u FUV NUV r g i HRS102-M99 H z 70 µm 250 µm 350 µm 350 µm FUV

  12. A(FUV) LIR

  13. Dustattenuationcurve in external galaxies: Evidence for a UV bump in galaxies detected in IR at 1<z<2 Buat et al. 2011, A&A, in press Calzetti 01 Wild et al. Wild et al. 11 FUV NUV u In local galaxies: GALEX UV bands and u(SDSS) wellsuited to test the presence of the bump Calzetti et al. 94, 00:fromspectroscopic data no bump in local starburt galaxies, moderaterise in UV

  14. Atlow z: someevidence for a bump in local star forming galaxies frombroad band analyses MW LMC FUV-NUV 0.4 0.6 0.8 1.0 1.2 1.4 Burgarella et al. 05- SED-fittingIRAS-GALEX data NUV-u Conroy et al. 2010, broad band coloursand model (SDSS) Similar conclusion by Wild et al 11 but seealsoWijesinghe et al. 2010, Johnson et al. 2007

  15. Athigh z: Ilbert et al. 2009- Cosmos field-30 photometric bands from UV to NIR: « A broad absorption excessat 2175 A seemsnecessary to explain the UV flux of somestarburst galaxies » Composite spectrum 1.5<z<2.5: evidence for a bump for 30% of the sources Noll et al. 2009 But no evidence for a bump in Lyman Break Galaxies at z≈2 (Vijh et al. 03, Reddy et al. 08)

  16. Weworkathigh z to redshift the UV range in the visible • We combine optical (UV rest-frame) and far-IR data: strongconstraint on SFR and dustattenuation • We use intermediate band filters in optical to tightlysample the UV rest frame Working in the CDFScombiningHerschel/PACS (GOODS-Herschelproject, PI: D Elbaz) and Subaru/MUSYC broad and intermediate band filters (Cardamone et al. 2010) +IRAC & MIPS data (Dickinson et al. 2003) 30 sources (28 withspec-z) in the GOODS-S fieldwith1<z<2 and high SNR in 30 photometric bands: SNR > 5 in optical, NIR, mid-IR and at 100 µm, SNR > 3 at 160 µm: Selection of the sources with 1<z<2 to sample the region of the UV bump GOODS-H- CDFS fieldat 24-100-160 µm Subaru Intermediate band filters

  17. Evidence for a UV bump on the observedSEDs • Intermediate band photometryverypowerful for SED analyses • Very good fits for the wholesample: a bumpisalwaysfound.

  18. General shape of the averageattenuationcurve consistent withthat of Charlot & Fall and (marginally) withthat of Calzetti et al. on top of whichthereis a bumpat 2175 A whose amplitude is 35% (76%) that of the MW (LMC2) one . Width of the feature: 356 Å (437 Å for the MW) Charlot & Fall 00, cst SFR over3 108yrs BUMP Calzetti et al. 00

  19. Conclusions • We have developped a physically-motivated code of SED fitting, wellsuited for the analysis of dustattenuation and star formation • The code has been appliedbothatlow and highredshift, in the framework of Herschel surveys • HRS: analysis of bothintegrated and spatiallyresolvedSEDs • GOODS-Herschel: dustattenuationcurvederived for galaxies at 1<z<2 and with a UV bumpwhose amplitude is 35% that of the MW • PEP/HerMES/COSMOS : work in progress

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