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Understand Galaxy Evolution with IR Surveys:

Understand Galaxy Evolution with IR Surveys: Comparison between ISOCAM 15- m m and Spitzer 24- m m Source Counts as a Tool. Carlotta Gruppioni – INAF OAB. La Thuile 08/03/05. Summary. General Perspective Past: ISOCAM Surveys

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Understand Galaxy Evolution with IR Surveys:

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  1. Understand Galaxy Evolution with IR Surveys: Comparison between ISOCAM 15-mm and Spitzer 24-mm Source Counts as a Tool Carlotta Gruppioni – INAF OAB La Thuile 08/03/05

  2. Summary • General Perspective • Past: ISOCAM Surveys • Present: from ISOCAM to Spitzer : What can we learn from the comparison between 15- and 24-mm? • Future: from ISOCAM and Spitzer to Herschel and ALMA

  3. General Perspective • Locally stars form in giant molecular clouds, where optical and UV light is strongly absorbed byDUST • Thanks to IRAS we know that galaxies forming stars at > 20 M/yr radiate the bulk of their luminosity above 5 mm: LIGS: 11  log(LIR/L)  12 ULIGS: 12  log(LIR/L) 13

  4. In the Past, when galaxies were more gaseous and formed the bulk of their present-day stars, it would be logical to expect to detect a large population of LIGs/ULIGs. • ISO observations showed that Galaxy Formation could not be understood without accounting for dust extinction as a major ingredient

  5. ISO SURVEYS • Mid-IR: ISOCAM (at 15 mm a LIG is visible up to z~1.3) - Several Surveys were performed in Garanteed Time (IGTES: 0.1 < S < 0.5 mJy; Elbaz et al. 1999) and Open Time (ELAIS: 0.5 < S < 150 mJy; Oliver et al. 2000; Rowan-Robinson et al. 2004)

  6.  Source counts exhibit a strong excess of sources below S15~2 mJy. Galaxies above this flux density do fall within the “no-evolution region”(ELAIS counts: Gruppioni et al. ’02) The predicted Extragalactic Background Light at 15 mm is: EBLmodels(15 mm) ~ 3.3 nW m-2 sr-1  ISOCAM resolves ~73 % of EBL

  7. Nature of ISOCAM galaxies Most are star-forming galaxies, often in small groups and showing irregular/merging morphologies. • from Shallow Surveys (i.e. ELAIS; • La Franca, Gruppioni et al. ’04) : • <L15> ~ 1010 L , <z> ~ 0.2 • from Deep Surveys (i.e. IGTES; Elbaz et al. ’99,’01) : <L15> ~ 1011 L , <z>  0.8 •  LIG is an important phase in galaxy life: a galaxy might experience several bursts of intense SF < z > = 0.8 HDFN < z > = 0.2 ELAIS-S1

  8. Cosmic Evolution Several authors have produced backwards evolution models to reproduce source counts and redshift distributions of ISOCAM galaxies (and IR galaxies): i.e. Devriendt & Guiderdoni ’00; Dole et al. ’00; Chary & Elbaz ’01; Pearson ’01, ’05; Franceschini et al. ’01, ’03; Malkan & Stecker ’01; Xu et al. ’01, ’03;King & Rowan-Robinson ’03; Lagache, Dole & Puget ’03;Pozzi, Gruppioni, Oliver et al. ‘04

  9. Cosmic Evolution All use a combination of luminosity and density evolution as a function of z of the IR luminosity function at 15 or 60 mm The major output of these models was to showthat LIGs/ULIGs were much more commonin the pastthan they aretoday (i.e.Chary & Elbaz ’01:comoving IR luminositydue to LIGs ~ 70 times larger at z~1 than today) Pozzi et al. ‘04 Lagache et al.’04 Pearson et al. ’01 Franceschini ’01 Franceschini upd.

  10. The Pozzi et al. (‘04) 15 m model (a) • Data • ELAIS:larger OT ISO survey, 12 deg2 • (PI: M. Rowan-Robinson) • ELAIS-S1 :field (4 sq.deg) completely analysed • Bologna + Roma • 15 m :406 sources (‘Lari method’, Lari et al. ‘01) • R-band :81% (330/406) of the 15 µm • sources optically identified R23 • Spectra:72% (293/406) of the 15 m • source spectroscopically classified • R=23 at ESO+2dF (La Franca et al ‘04)

  11. Relation L15/L_opt of versus L15 More luminous IR galaxy having larger L15/Lopt Starbursts Arp220 M82 M51 Spirals (Pozzi et al. 04)

  12. The Pozzi et al. (2004)15 m model (b) 2) Luminosity Function Method Quantitative estimators: Maximum likelihood (Marshall et al.’83) + 1/Vmax formalism (Schmidt ‘68) 4 Populations: Spiral (M51), Starburst (M82), AGN1 (Elvis et al. ‘94) & AGN2 (Circinus) Evolution:Starburst : density & luminosity Normal Spiral : no evolution Agn1 & AGN2 : luminosity NEW !!!! L_15/L_opt to divide starburst/spiral

  13. ISOCAM extragalactic counts at 15m Pop. kl kd zb ------------------------- Spiral 0 0 0 Starb 3.5 3.8 1 Agn1 2.6 0 2 Agn2 2-2.6 0 2 (NGC1068 or Circinus) Starbursts evolve in luminosity [as (1+z)3.5] and density [(1+z)3.8] up to z=1

  14. Luminosity Function z-distribution

  15. From ISOCAMto Spitzer... Spitzer Telescope is now providing new insight into the IR population contributing to the CIB In particular with the MIPS 24-mmband, which is starting to detect the high-z (z~1.5-3.0) analogs of the 15-mm galaxies

  16. FLS Extragalactic Source Counts at 24 mm:comparison with some existing models Galaxy evolution models: Franceschini et al. (2001) & Rodighiero et al. (2004): non-evolving normal pop, fast-evolving type-II AGNs & starbursts, evolving type-I AGNs Lagache, Dole & Puget (2003):non-evolving normal spirals and starbursts with L density evolving with redshift IRAS data points (transformed to 24 μm) (Hacking & Soifer 1991; Sanders et al. 2003) No-evolution model normalized to IRAS counts Marleau, Fadda, Storrie-Lombardi, et al. 2004

  17. Spitzer 24 m FLS compared to 15 mm source counts(Marleau et al. ‘04) Shaded region: 24 mm counts • Confirm existence of rapidly evolving population discovered by ISOCAM • Question: how to compare with previous ISOCAM 15m counts? • ONLY one ratio assumed to convert 15 mto 24 m(S24/S151.2) ? ELAIS range empty symbol: 15 mcounts Gruppioni et al.’02

  18. Ratio for different IR prototype populations Considering M82 (dominant population): ratio strongly dependent on z(because of PAHs) S24/S152-2.5 z 0 S24/S151.2 z 1 S24/S15> 5 2<z< 3 The ratio assumed by FLS team is fine for objects at z1 but NOT for ELAIS sources or higher z ones

  19. Model predictions S24/S15as a function of z, S24 S > 2-3 mJy dominated by objects with S24/S152-2.5 S  0.3 mJy dominated by objects with S24/S15 1.5 S < 0.2-0.3 mJy dominated by objects with S24/S15 > 2-3 -> NEW POPULATION !

  20. Contributionsfrom different z While galaxies with z<1.3 dominate up to S0.3 mJy, at lower fluxes the new high-z population starts contributing for a significant fraction: Anyway, 70 % background qt z < 1.5 Spitzer deep counts resolve75 % background

  21. A bit of criticism ... After some months… Swire team (Shupeet al. 2005, in preparation) First published 24 m data FLS team (Marleau et al. ‘04)

  22. Our Model fit to other Spitzer Bands

  23. From ISOCAMto the longer l’s of Spitzer and to HERSCHEL • For the longer l’s  Fundamental Ingredient: Galaxy SEDs (FIR BUMP) !!! • For starburst galaxies we need “colder” SEDs than the prototypical M82 to fit the observed 70 and 160 mmsource counts • Use the phenomenological evolution model to make predictions also in the Herschel bands (PACS:75, 110, 170 mm; SPIRE: 250, 350, 500 mm)

  24. Strength of our Model • The evolution parameters are determined with a Maximum Likelihood fit of the 15-mm LF, source counts and redshift distributions • Thestarburst/normal galaxy separation is based on a physical property of galaxies (L15/Lopt ratio) instead of being an arbitrary variable

  25. Weakness of our Model • Is based on 15-mm data only: Extend the ML fit to all the MIR/FIR observables (i.e. source counts and redshift distributions)  find the best-fitting multi-l solution • Use a single SED for each galaxy population: • Better using a SED library, with SEDs changing (i.e. becoming “colder”) as function ofLIRorz (mainly for starbursts)

  26. Separation between evolving and non-evolving population is sharp: • Better considering a smoother variation (i.e. different evolutions for different intervals of L15/Lopt)  MUCH WORK TBD SPITZER WILL HELP !!!

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