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Véronique Buat Laboratoire d’Astrophysique de Marseille

Herschel observations: contraints on dust attenuation and star formation histories at high redshift. Véronique Buat Laboratoire d’Astrophysique de Marseille. A few words about the physical link between UV and IR emissions. Visible. UV. Infrared. mm. dust.

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Véronique Buat Laboratoire d’Astrophysique de Marseille

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  1. Herschel observations: contraints on dustattenuation and star formation histories athighredshift Véronique Buat Laboratoire d’Astrophysique de Marseille

  2. A few words about the physicallink between UV and IR emissions Visible UV Infrared mm dust Both UV and IR are related to recent star formation They are anti-correlatedbecause of dustattenuation IR selectedobjectsare usuallyobscuredwith a lowresidualemission in UV Conversely: weexpecta UV selectionto bedominated by IR faint sources intensity wavelength Elbaz’s lectures (david.elbaz3.free.fr/coursJ1.html), adaptedfrom Devriendt+99

  3. SFR densitytraced by combining UV and IR surveys Takeuchi, Buat & Burgarella, 2005

  4. Two parts in this talk…. • Analysis of the full UV-to-IR Spectral Energy Distributions of galaxies, dustattenuation & star formation at z> 1 Véronique • UV and IR luminosityfunctions, evolution of global dustattenuation and star formation rate densitywithredshift up to z~4  Denis

  5. Outline of the first part • Fitting the full SED in a physicalway • The GOODS-Herschelproject: observedSEDs of distant galaxies • Dustattenuationcurve • Star formation rates and stellar mass determinations • The Herschel insight on IR spectral energy distributions of distant galaxies With Sébastien Heinis, Médéric Boquien, Denis Burgarella & the GOODS-Herschel team

  6. 1. Modeling the UV-to-IRSEDs: with or withoutenergy budgets Stellar emission Dustemission Muzzin+10 Stellar and dustemissionfittedseparately Da Cunha+08, Magphyscode

  7. Focusing on SED fittingwith conservation of the energybewteenUV-optical and IR Radiation transfer & multi-components: valid for local resolved galaxies Popescu+12 Simple recipes: dustattenuationcurves, IR libraries Valid for large samples of unresolved galaxies CIGALE code, Noll+09

  8. Stellarspectra and isochrones depend on Z Various SFH, one or several populations Minimum age free or fixed UsuallyStarburstlaw but not always Metallicityfixed or variable A set of templates

  9. CIGALE : Code InvestigatingGALaxyEmission • P.I. D. Burgarella (Noll+09) http://cigale.oamp.fr/

  10. OUTPUT PARAMETERS : • All based on a Bayesian analysis • input parameters • Stellar Mass • Dustluminosity • Amount of obscuration • D4000 break, slope of the UV continuum….

  11. 2. The GOODS-Herschel, PI D.Elbaz GOODS-N: 10’x15’ PACS+SPIRE, 100, 160, 250, 250, 500 µm 1 mJy @ 100 µm GOODS-S/CDFS: 10’x10’ PACS 100,160 µm down to the confusion limitat 100 µm ~0.7 mJy SPITZER data GOODS-Northfield SPIRE PACS HERSCHEL data

  12. A public website for Herschel extragalactic and cosmologicalsurveys: GOODS-Herschel, HerMES, HRS, VNGShttp://hedam.lam.fr/

  13. Building the multi-wavelengthsample for objects in the CDFS Z> 1 : to redshift the UV range in the visible optical (UV rest-frame) + IR thermal data 1<Z<3 CombiningGOODS-Herschel/PACS data and Subaru/MUSYC broad and intermediate band filters (Cardamone+10) +IRAC & MIPS data (Dickinson+03) 28 photometric bands: SNR > 5 in optical and NIR + SNR> 3 at 24 µm 236 galaxies 80 sources detectedwith PACS, upperlimits for the otherones GOODS-H-CDFS fieldat 24-100-160 µm Subaru Intermediate band filters

  14. Someexamples of SEDs, withtheir best fit obtainedwith CIGALE Buat+11 An absorption featureat 2175 A rest frameclearlyseen and modeled. The full UV-to-IR SED fitted. Physicalparametersderivedfrom the analysis of their PDF (not from the best SED)

  15. 3. Dustattenuationcurve in external galaxies at 1<z<2 Buat et al. 2011, 2012 __ MW ---- LMC ___SMC Calzetti 01 Extinction law ≠ Attenuationlaw starburst Calzetti et al. 94, 00:fromspectroscopic data no bump in attenuationcurve of local starburt galaxies, moderaterise in UV

  16. Somepreviousevidence for the presence of bumpsathigh z Composite spectrum 1.5<z<2.5: evidence for a bump for 30% of the sources Noll+09 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 » But no evidence for a bump in Lyman Break Galaxies at z≈2 (Vijh+03, Reddy+08)

  17. 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

  18. Eb= 1.6 +/- 0.4 δ = -0.27 +/- 0.17 20% of the galaxies (47% of thosedetected in IR) have a confirmedbump (2 σlevel) 20% of the galaxies (43% of thosedetected in IR) have a dustattenuationsteeperthan the Calzettilaw (2 σlevel)

  19. Derivation of a meandustattenuationcurvewith a UV bump in the CDFS galaxies with 1<z<2 SMC LMC SMC LMC C00 C00 MW C00: Starburstlaw, Calzetti.00 General shape of the averageattenuationcurve consistent with an increase in UV similar to that of the LMC supershellextinction curve (steeperthan the Calzetticurve on top of whichthereis a bumpat 2175 A) whose amplitude issimilar to thatfound in the LMC supershell, (45% that of the MW one) . Large dispersions among galaxies

  20. 3. Stellar mass and Star Formation Rate derivation for 1<z<3 galaxies Buat+13, (A&A, underrevision) • Impact of Different Star Formation Histories: • exp(-t/τ), age free, decl. τ model  1 stellar pop. • exp(t/τ), agefixed (zf ≈ 8), rising. τ model  1 stellar pop. • An old (age free or fixed) decl. τ pop. + a young, age free pop with a constant SFR  2 st. pop. 0.12 dex 0.17 dex Base line model: 2 pop, bothage free • When IR data are includedSFRs are welldetermined and are non dependent on the SFHs • Uncertaintiesremainlarger for Mstarestimates

  21. Stellar mass and Star formation rate derivation (cont’d) Buat+13 Impact of including or not IR data W/o IR-with IR w/o IR with IR Fitswithout IR data (MIPS and PACS data omitted): the SFR are poorlymeasured, stellar masses remainunchanged due to uncertainties on dustattenuation

  22. Consequences on the measure of the Specific Star Formation Rate: SSFR = SFR/Mstar AdoptedLimit for Starburst galaxies Elbaz+11 Sargent+12 Dispersion of the Main Sequence of Galaxies definedwith IR data or accuratemeasures of dustattenuation (Noeske+07, Rodighiero+11, Salmi+12) log(SSFR-withoutIR)-log(SSFR-with IR))

  23. 4. IR SEDs: new insights from Herschel Dale & Helou (2002) 64 semi-empiricaltemplates -Draine & Li (2007) models (Draine+07): veryusefulwith Herschel data Dale+12 Chary & Elbaz (2001) 105 empiricaltemplates

  24. Templatesfor the distant universedependent on the SFR activity ,Elbaz+11 « normal galaxies » Starbursting galaxies • Main Sequence: on average SFR-M* relation, even if veryluminous, PAH are prominent • Starburst galaxies: SFR/M* higherthan for Main Sequence, less PAH, warmerdust DIFFERENT FROM LOCAL TEMPLATES OF SIMILAR LUMINOSITY: The contribution of PAHs for high-zluminous galaxies islargerthan in nearby galaxies of same IR luminosity

  25. Whenusing local templates of CE01, Lircalculatedwith 24 µm isoverestimatedat z=2, (Nordon+12) « exact » log(LIR) @ z=2  8 μmrest frame, PAH dominated

  26. Original CE01 templates With the New Main Sequencetemplate LIRfrommonochromatic flux/LIR (total-allMIPS-Herschel data)

  27. With Herschel, the situation remainscomplex…. Ciesla+13, in prep.

  28. To beoptimistic: Lirestimates do not stronglydepend on the adoptedtemplatewhenseveral bands are available Ciesla, 12, PhDthesis Herschel ReferenceSample, SPITZER+ SPIRE data Casey 12

  29. Conclusions • Fitting the full SED from the UV to the IR with a conservation of the enery balanceisverypowerful to constraindustattenuation and consequentlySFRs • The attenuationcurve of galaxies with 1<z<2 issteeperthan the law for local starburstsand isfound to exhibita bumpat 2175 A with an amplitude similar to that of the LMC2 extinction curve, • Without IR data, SFRscanbe over or underestimated by factorslargerthan 2 • inducing a similaruncertainty for the SSFRs. • Stellar masses derivations are more sensitive to the adopted star formation historythanSFRs. • IR SEDsat all z are constrainedwith Herschel data, modifying the local templates, but more workisneeded to buildreliable, detailedSEDs • All these analyses are based on data from the CDFS obtained in the framework of the GOODS, GOODS-Herschel and MUSYC projects Thank You!

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