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Véronique Buat & Sebastien Heinis With the contribution of Laure Ciesla

Far-infrared properties of UV selected galaxies from z=4 to z=1.5: unveiling obscured star formation. Véronique Buat & Sebastien Heinis With the contribution of Laure Ciesla Based on HerMES /SPIRE data in the COSMOS field Heinis , Buat et al. 2013.

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Véronique Buat & Sebastien Heinis With the contribution of Laure Ciesla

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  1. Far-infraredproperties of UV selectedgalaxies from z=4 to z=1.5: unveilingobscured star formation Véronique Buat & SebastienHeinis With the contribution of Laure Ciesla Based on HerMES/SPIRE data in the COSMOS field Heinis, Buat et al. 2013 FromExoplanets to Distant Galaxies: SPICA’s New Window on the Cool Universe 18-21 june 2013-University of Tokyo, Japan

  2. Only 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. Weperform a UV rest-frameselectionin the COSMOS field @ z=1.5, 3 & 4 Based on photometricredshifts (Ilbert+13) Down to u, r, i ≈ 26 ABmag

  4. What do wefindwithinHerMES/ SPIRE images?Almostnothing……. Z = 1.5

  5. Stacking per bin of LFUV LIRmeasured by fitting Dale & Helou (2002) templates on SPIRE data AFUV = f(LIR/LFUV) (Buat+05) LIRGs and sub-LIRGs

  6. Stacking per bin of M*(again on the UV selection) Z=1.5 Z=3 Z=4

  7. Stacking per bin of (LFUV,M*) Dustattenuationincreaseswith M* for a given LFUV Dustattenuationdecreaseswith LFUV for a given M* The dispersion in dustattenuationdecreaseswith LFUV Seealso Burgarella+06, Buat+09,12

  8. A recipe to derive LIR/LFUV=IRXHeinis+13, very close to besubmittedIRX=log(LIR/LFUV)=IRX0(LFUV)+0.72*log(M*/1010.35)@z=1.5 & 3

  9. SFR versus M* : a welldefined ‘Main Sequence’ for star-forming galaxies (fromKennicutt, 98) SFR= SFR0 M*0.7 slope< 1 seealso Noeske+07, Oliver+10, Whitaker+12 slope~1 found by Elbaz+07, Daddi+07, Wuyts+11 Z=1.5 Z=3 Z=4

  10. Specific SFR (sSFR=SFR/M*) : very active galaxies at z =3 & 4, a challenge for the models sSFR(z,M*) highredshift galaxies (z~2.5-4) stayonlyaround 1 Gyr on the Main Sequence, this time increasingwithdecreasingredshift

  11. Whatcanwe do with SPICA? • Herschel wasunable to detectindividual galaxies selected in UV at z >= 1.5 (lessthan 1% of the galaxies directlydetected) Studiesbased on a stackingtechnics: average trends only, no or little dispersion measured • We must increase the number of individualdetections if wewant to discuss the variety of physicalproperties of individual galaxies

  12. Individualdetectionswith SPICA? α=2 α=1.5 Assuming 50 µJy @ 70 µm Dale & Helou 02 templates

  13. As a function of LFUV • How many galaxies in the COSMOS field? • z=1.5 9419 galaxies/deg2 • z=3 3162 galaxies/deg2 • Assuming a Dale & Heloutemplatewithα = 2

  14. As a function of M* • How many galaxies couldbedetected in the COSMOS field? • z=1.5 9731 galaxies/deg2 • z=3 3493 galaxies/deg2 • z=4 952 galaxies/deg2

  15. Whichtemplate to measure LIR? What do welearnfrom Herschel? Z=1.5 Z=0 Ciesla+13, in prep.

  16. The determination of LIRwith a single monochromaticmeasurementmightlead to large uncertainties Several bands mightbeveryuseful to constrain the SED Stillsomework to be made to refineSEDs…… Ciesla+13, in preparation

  17. Conclusions • To measure the dustemission of UV brighthighredshift galaxies ischallenging • HERSCHEL was not able to detectthemindividuallyat z ≥1.5 • Deepphotometric observations with SPICA @ λ≈70 μmwillallow direct detections of severalthousands of galaxies per deg2alsoobserved in optical (UV rest-frame) • Coordinateddeepsurveyswith SPICA instruments (SAFARI-MCS-FPF) wouldprovide full SEDs of these galaxies, allowingphysical analyses.

  18. Stacking per bin of M*(again on the UV selection)

  19. Stacking per bin of LFUV LIRmeasured by fitting Dale & Helou (2002) templates on SPIRE data AFUV = f(LIR/LFUV) (Buat+05) LIRGs and sub-LIRGs

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