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

SummarySummary  General Perspective  Past: ISOCAM Surveys  Present: from ISOCAM to Spitzer : What can we learn from the comparison between 15- and 24-  m?  Future: from ISOCAM and Spitzer to Herschel and ALMA  General Perspective  Past: ISOCAM Surveys  Present: from ISOCAM to Spitzer : What can we learn from the comparison between 15- and 24-  m?  Future: from ISOCAM and Spitzer to Herschel and ALMA

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

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

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

 Source counts exhibit a strong excess of sources below S 15 ~2 mJy. of sources below S 15 ~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  m is: EBL models (15  m) ~ 3.3 nW m -2 sr -1  ISOCAM resolves ~73 % of EBL  Source counts exhibit a strong excess of sources below S 15 ~2 mJy. of sources below S 15 ~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  m is: EBL models (15  m) ~ 3.3 nW m -2 sr -1  ISOCAM resolves ~73 % of EBL

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) : La Franca, Gruppioni et al. ’04) : ~ L , ~ 0.2 ~ L , ~ 0.2  from Deep Surveys (i.e. IGTES; Elbaz et al. ’99,’01) : ~ L ,  0.8 al. ’99,’01) : ~ L ,  0.8  LIG is an important phase in galaxy life: a galaxy might experience several bursts of intense SF 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) : La Franca, Gruppioni et al. ’04) : ~ L , ~ 0.2 ~ L , ~ 0.2  from Deep Surveys (i.e. IGTES; Elbaz et al. ’99,’01) : ~ L ,  0.8 al. ’99,’01) : ~ L ,  0.8  LIG is an important phase in galaxy life: a galaxy might experience several bursts of intense SF = 0.2 = 0.2 ELAIS-S1 ELAIS-S1 = 0.8 = 0.8HDFN

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 Gruppioni, Oliver et al. ‘04 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 Gruppioni, Oliver et al. ‘04

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  m The major output of these models was to show that LIGs/ULIGs were much more common in the past than they are today (i.e. Chary & Elbaz ’01: comoving IR luminosity due to LIGs ~ 70 times larger at z~1 than today) All use a combination of luminosity and density evolution as a function of z of the IR luminosity function at 15 or 60  m The major output of these models was to show that LIGs/ULIGs were much more common in the past than they are today (i.e. Chary & Elbaz ’01: comoving IR luminosity due 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.

1)Data ELAIS: larger OT ISO survey,  12 deg 2 ELAIS: larger OT ISO survey,  12 deg 2 (PI: M. Rowan-Robinson) (PI: M. Rowan-Robinson) ELAIS-S1 : field (  4 sq.deg) completely analysed ELAIS-S1 : field (  4 sq.deg) completely analysed Bologna + Roma Bologna + Roma 15  m : 406 sources (‘Lari method’, Lari et al. ‘01) 15  m : 406 sources (‘Lari method’, Lari et al. ‘01) R-band : 81% (330/406) of the 15 µm R-band : 81% (330/406) of the 15 µm sources optically identified R  23 sources optically identified R  23 Spectra: 72% (293/406) of the 15  m Spectra: 72% (293/406) of the 15  m source spectroscopically classified source spectroscopically classified R=23 at ESO+2dF (La Franca et al ‘04) R=23 at ESO+2dF (La Franca et al ‘04) 1)Data ELAIS: larger OT ISO survey,  12 deg 2 ELAIS: larger OT ISO survey,  12 deg 2 (PI: M. Rowan-Robinson) (PI: M. Rowan-Robinson) ELAIS-S1 : field (  4 sq.deg) completely analysed ELAIS-S1 : field (  4 sq.deg) completely analysed Bologna + Roma Bologna + Roma 15  m : 406 sources (‘Lari method’, Lari et al. ‘01) 15  m : 406 sources (‘Lari method’, Lari et al. ‘01) R-band : 81% (330/406) of the 15 µm R-band : 81% (330/406) of the 15 µm sources optically identified R  23 sources optically identified R  23 Spectra: 72% (293/406) of the 15  m Spectra: 72% (293/406) of the 15  m source spectroscopically classified source spectroscopically classified R=23 at ESO+2dF (La Franca et al ‘04) R=23 at ESO+2dF (La Franca et al ‘04) The Pozzi et al. (‘04) 15  m model (a)

Relation L 15 /L_opt of versus L 15 More luminous IR galaxy having larger L 15 /L opt More luminous IR galaxy having larger L 15 /L opt M51 M82 Arp220 Starbursts Spirals (Pozzi et al. 04)

Quantitative estimators: Maximum likelihood (Marshall et al.’83) + 1/V max 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 NEW !!!! L_15/L_opt to divide starburst/spiral Quantitative estimators: Maximum likelihood (Marshall et al.’83) + 1/V max 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 NEW !!!! L_15/L_opt to divide starburst/spiral The Pozzi et al. (2004)15  m model (b) The Pozzi et al. (2004) 15  m model (b) 2) Luminosity Function Method

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

Luminosity Function z-distributionz-distribution

From ISOCAM to Spitzer... Spitzer Telescope is now providing new insight into the IR population contributing to the CIB Spitzer Telescope is now providing new insight into the IR population contributing to the CIB In particular with the MIPS 24-  m band, which is starting to detect the high-z (z~ ) analogs of the 15-  m galaxies In particular with the MIPS 24-  m band, which is starting to detect the high-z (z~ ) analogs of the 15-  m galaxies

FLS Extragalactic Source Counts at 24  m: comparison with some existing models FLS Extragalactic Source Counts at 24  m: comparison with some existing models Franceschini et al. (2001) & Rodighiero et al. (2004): non-evolving normal pop, fast-evolving type-II AGNs & starbursts, evolving type-I AGNs 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 No-evolution model normalized to IRAS counts Galaxy evolution models: IRAS data points (transformed to 24 μ m) (Hacking & Soifer 1991; Sanders et al. 2003) Marleau, Fadda, Storrie-Lombardi, et al. 2004

Spitzer 24  m FLS compared to 15  m source counts (Marleau et al. ‘04) Spitzer 24  m FLS compared to 15  m source counts (Marleau et al. ‘04) Shaded region: 24  m counts empty symbol empty symbol: 15  mcounts 15  m counts ? ELAISrange  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  m to 24  m (S 24 /S 15  1.2)  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  m to 24  m (S 24 /S 15  1.2) Gruppioni et al.’02

Considering M82 (dominant population): ratio strongly dependent on z (because of PAHs) S 24 /S 15  z  0 S 24 /S 15  1.2 z  1 S 24 /S 15 > 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 Considering M82 (dominant population): ratio strongly dependent on z (because of PAHs) S 24 /S 15  z  0 S 24 /S 15  1.2 z  1 S 24 /S 15 > 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 Ratio for different IR prototype populations

Model predictions S 24 /S 15 as a function of z, S 24 S > 2-3 mJy dominated by objects with S 24 /S 15  objects with S 24 /S 15  S  0.3 mJy dominated by objects with S 24 /S 15  1.5 objects with S 24 /S 15  1.5 S 2-3 -> NEW POPULATION ! -> NEW POPULATION ! S > 2-3 mJy dominated by objects with S 24 /S 15  objects with S 24 /S 15  S  0.3 mJy dominated by objects with S 24 /S 15  1.5 objects with S 24 /S 15  1.5 S 2-3 -> NEW POPULATION ! -> NEW POPULATION !

Contributions from 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 qt z < 1.5 Spitzer deep counts resolve  75 % background 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 qt z < 1.5 Spitzer deep counts resolve  75 % background

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

Our Model fit to other Spitzer Bands

From ISOCAM to the longer ’s of Spitzer and to HERSCHEL Spitzer and to HERSCHEL From ISOCAM to the longer ’s of Spitzer and to HERSCHEL Spitzer and to HERSCHEL  For the longer ’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  m source counts  Use the phenomenological evolution model to make predictions also in the Herschel bands (PACS:75, 110, 170  m; SPIRE: 250, 350, 500  m)  For the longer ’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  m source counts  Use the phenomenological evolution model to make predictions also in the Herschel bands (PACS:75, 110, 170  m; SPIRE: 250, 350, 500  m)

Strength of our Model  The evolution parameters are determined with a Maximum Likelihood fit of the 15-  m LF, source counts and redshift distributions  The starburst/normal galaxy separation is based on a physical property of galaxies (L 15 /L opt ratio) instead of being an arbitrary variable  The evolution parameters are determined with a Maximum Likelihood fit of the 15-  m LF, source counts and redshift distributions  The starburst/normal galaxy separation is based on a physical property of galaxies (L 15 /L opt ratio) instead of being an arbitrary variable

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

 Separation between evolving and non- evolving population is sharp:  Better considering a smoother variation (i.e. different evolutions for different intervals of L 15 /L opt )  MUCH WORK TBD SPITZER WILL HELP !!!  Separation between evolving and non- evolving population is sharp:  Better considering a smoother variation (i.e. different evolutions for different intervals of L 15 /L opt )  MUCH WORK TBD SPITZER WILL HELP !!!