Slide 1

Deep far-IR surveys and source counts G. Lagache Institut dAstrophysique Spatiale Slide 2 Standard model of cosmological structure formation: Very successful in the description of the formation of LSS Small adiabatic perturbations amplified by self gravity Linear development of the density perturbations modeled by well-known physics Description of the non-linear phase: (of the baryonic component) More complicated Model the thermal balance (depends on the chemistry and hydrodynamics of the baryonic gas) Major numerical simulations (e.g. GalICS project, IAP) Main problems: overcooling problem => Observe small structures that are becoming non linear first Galaxy formation Slide 3 Observations relevant to the problem of star and galaxy formation at high z: Cosmic Infrared-submm Background (CIB) see Hauser & Dwek 2001 for a review Power spectra of the unresolved background in the far-IR Lagache & Puget 2000, Matsuhara et al. 2000, Miville-Deschnes et al. 2002 Deep number counts of IR galaxies from mid-IR to mm e.g. Dole et al. 2001, Serjeant et al. 2001, Elbaz et al. 2002, Scott et al. 2002, Papovich et al. 2004, Dole et al. 2004. Identifications and multi-wavelength observations of IR galaxies Status of IR-submm observations Slide 4 Find discrepancies with present theories of structure formation Plan future observations Empirical models Basic inputs of empirical models: Luminosity functions of a small number of populations of IR galaxies as a function of z Set of templates of SED e.g. Devriendt & Guiderdoni 2000, Wang & Biermann 2000, Chary & Elbaz 2001, Dole et al. 2001, Franceschini 2001, Lagache et al. 2003, Malkan & Stecker 2001, Pearson 2001, Rowan-Robinson 2001, Takeuchi et al. 2001, Xu et al. 2001, Wang 2002, Chapman et al. 2003, .. Investigate the basic capabilities of the future missions: Sensitivity Resolving power to beat confusion Capabilities to cover large enough areas to find rare distant sources Status of empirical models in the IR Slide 5 The Model Features Phenomenological (backward evolution) Valid in the range: 5 m to 2 mm Fast, Portable, Available (http://www.ias.fr/PPERSO/glagache/act/gal_model.html) No source clustering Convenient tool to plan further observations Lagache, Dole, Puget, 2003, MNRAS Lagache et al., 2004, APJSS Slide 6 Galaxy SEDs Lagache, Dole, Puget, 2002, MNRAS SEDs for Starburst Galaxies 10 10 L o 10 11 L o 5. 10 11 L o 3. 10 12 L o Comparison of SEDs: Starburst & Normal Galaxies 5. 10 11 L o Normal Starburst Only two populations Slide 7 IR luminosity function evolution Normal Starburst Total LF Local LF At high z, (U)LIRGs dominate the energy production Linked to the merger/ interaction phases Slide 8 The Model Features Phenomenological (backward evolution) Valid in the range: 5 m to 2 mm Fast, Portable, Available (http://www.ias.fr/PPERSO/glagache/act/gal_model.html) No source clustering Convenient tool to plan further observations Reproduces Source Counts, Galaxy redshift distributions, CIB SED CIB Fluctuation levels, SPITZER confusion levels (Dole et al. 2003) Lagache, Dole, Puget, 2003, MNRAS Lagache et al., 2004, APJSS Slide 9 15 m 850 m 24 m 170 m Slide 10 The Model Features Phenomenological (backward evolution) Valid in the range: 5 m to 2 mm Fast, Portable, Available (http://www.ias.fr/PPERSO/glagache/act/gal_model.html) No source clustering Convenient tool to plan further observations Reproduces Source Counts, Galaxy redshift distributions, CIB SED CIB Fluctuation levels, SPITZER confusion levels One exemple of cosmological implications: The PAHs features remain prominent in the redshift band 0.5-2 The IR energy output has to be dominated by ~2 10 11 Lo to ~3 10 12 Lo galaxies from z~0.5 to 2. Lagache, Dole, Puget, 2003, MNRAS Lagache et al., 2004, APJSS Slide 11 Predictions for Herschel and ALMA Slide 12 Surface ( m) Days 5 inst (mJy) S min (mJy) N sources %CIB 20 Sq. Deg.170887.0810.0732249 625 Sq. Arcmin110670.891.26195577 25 Sq. Arcmin75960.130.1819287 The Herschel/PACS cosmological surveys Designed surveys that could be done with PACS : 5 inst = S lim = Conf. limit Slide 13 Sq. deg 5 inst 5 conf 5 tot DaysN sources %CIB 400100 mJy28.2103.91847681 10015.322.427.1192334516.7 87.522.423.66435337.8 The Herschel/SPIRE cosmological surveys Designed surveys that could be done with SPIRE (350 m): __ 400 Sq. deg. (x2) - - 100 Sq. deg z=1.0 z=0.7z=2.5 z=0.5 100 Sq. deg. Slide 14 Herschel will Give for the first time complete IR SEDs. Combined with SPITZER: from 3.6 to 550 microns. Fill the far-IR desert (between 160-850 microns) Resolve the peak of the CIB - NOT probe the CIB at long wavelengths Slide 15 Large area survey: GOAL: Find 3 10 11 L o galaxies at z~5 1 Deg 2, 5 = 0.1 mJy (50% of CIB) 138 days (30 000 sources) A deeper survey: GOAL: 80% of the CIB 10 arcmin 2, 5 =0.02 mJy 96 days (200 sources) A total of ~8 months (without including overheads) ALMA capabilities for surveys at 230 GHz Slide 16 So what? Future surveys: (SPITZER), Herschel, Planck For >150 m: confusion-limited - Resolved CIB: 8 months in the final config) Informations on the underlying population and constraints on the clustering of IR galaxies: => Studying the CIB fluctuations Slide 17 The CIB fluctuations: A tool for studying the source Clustering Probe the LSS at high z Slide 18 Same sources (shape of the counts) You probe the fluctuations = you probe the CIB P(D) analysis: number count distribution Statistical informations on the SEDs Clustering: On large angular scales: linear clustering bias of far-IR galaxies in dark matter halos On smaller angular scales: non-linear clustering within a dark matter halo Problem: detecting them! (Component separation) Detection of the shot noise at 60, 100, 170 m (Miville-Deschnes et al. 2003, Lagache &Puget 2000, Matsuhara et al. 2000) The CIB and its fluctuations ( >100 m) Slide 19 Cirrus/CIB power spectra at 550 m IR gal Poisson (S lim =103.9 mJy) Cirrus (NHI=1, 2, 3 10 20 at/cm 2 ) IR gal clustering Slide 20 FIRBACK 170 m: constraint on b b=3 Diamonds: FIRBACK observations b=0.6 Poissonian (from the model) - IR emissivities: j/j = b ( / ) dark matter - FIRBACK observations => b 0.6 (N. Fernandez et al.) (N. Fernandez et al.) Slide 21 Longer probe to higher z CIB fluctuation maps ( 100 m => 1 mm) IRAS (IRIS, Miville-Deschnes & Lagache, 2004), SPIRE, Planck/HFI Waveband decorrelation => Invert fluctuation maps / z Clustering in function of z Seems very easy!! Fluctuations of the CIB Slide 22 Slide 23 Slide 24 Slide 25 Slide 26 Slide 27 Longer probe to higher z CIB fluctuation maps ( 00 m => 1 mm) IRAS/IRIS, SPIRE, Planck/HFI Waveband decorrelation => Invert fluctuation maps / z Clustering in function of z Seems very easy!! Fluctuations of the CIB Slide 28 Exemple of decorrelation F(250) F(250) F(100) F(850) F(850) F(250) F(100) F(1380) F(1380) F(850) Slide 29 Panchromatic IR Sky MIPS 24 mMIPS 70 m MIPS 160 m Simulated sky: 5 squares degrees Dole, Lagache, Puget, 2003, ApJ Towards including the correlations Slide 30 Conclusions - Dust emission and extinction: Key processes at high-z => Large IR/submm/mm surveys - In the Far-IR/Submm: current and planned surveys are and will be confusion-limited - Except for ALMA (but need time) -Before ALMA: Study the clustering using the CIB anisotropies with Planck/HFI and Herschel/SPIRE Slide 31 Slide 32 Herschel follow-up observations PACS: no problem for source identification SPIRE: use band merging technique (as for SPITZER) when PACS data are available to extract sources In areas where we have only SPIRE data : Build an extreme source sample Use the same technique as for the SCUBA/MAMBO sources: interferometry Problem: about 3000 sources with z>3 (and about 9000 with z>2) Slide 33 Large area survey: (3 10 11 L o objects) 1 Deg 2, 5 = 0.21 mJy Need 4289 years !! => The L=3 10 11 L o objects will not be found at 350 microns (5 observation days for ONE source 3 10 11 L o at z~5) The 850 GHz is not suited for cosmological surveys ALMA capabilities for surveys at 850 GHz Slide 34 overcooling problem The fraction of the predicted baryonic mass that fragment and form stars is clearly larger than what is observed The mass distribution of galaxies should also contain more dwarf galaxies than it does The baryonic gas collapses to the center of the potential well loosing its angular momentum to the non dissipative dark mater component. Main unresolved problem in gal. formation