Characterization of the mid- and far-IR population detected by ISO, Spitzer... and HERSCHEL!!

High-z GT Programme Will address issues like: How? Investing 850hrs of SPIRE (Hermes) and 650hrs of PACS (PEP) GT Observing a Set of Blank Fields in Different Depths Observing a Sample of Rich Clusters (0.2 < z < 1.0) History of star formation and energy production Structure formation Cluster evolution CIRB fluctuations AGN-starburst connection After Guiderdoni et al. MNRAS 295, 877, ,00010, L ¤ Z = Flux density (mJy)  (  m) Herschel probes the rest-frame bolometric emission from galaxies as they formed most of their stars

Wedding Cake Survey GOODS-S 0.04 deg^2GOODS-N 0.04 deg^2 GOODS-S/Groth/ Lockman 0.25 deg^2 Cosmos/XMM 2 deg^2 ES1/EN1/EN2/XMM/ Lockman deg^2 will probe L bol over a wide redshift range XMM/CDFS/Lockman 10 deg^2 Clusters

Herschel Extragalactic GT Survey Wedding Cake Time : PACS (659) SPIRE (850) Harwit (10) (Spitzer Depths)

The case for a joint effort PACS strengths –Excellent spatial resolution –Capabilities for FIR spectroscopy of selected subsamples SPIRE strengths –Best exploitation of K-correction for high-z sources –Fast mapping speed Both are needed for characterizing FIR/sub-mm properties of large samples of high-z objects

Beam 350 micron / 9 mJy / 0.04 deg^2 Beam 110 micron / 3 mJy / 0.04 deg^2 PACS SPIRE Redshift distributions Favourable K-corr!! Better resolution!! Model by Franceschini 2008

the PACS Evolutionary Probe is a Herschel guaranteed time key programme survey of the extragalactic sky, aimed to study the restframe far-infrared emission of galaxies up to redshift ~3, as a function of environment. The survey will shed new light on the constituents of the cosmic IR background and their nature, as well as on the co-evolution of AGN and starbursts. PEP is coordinated with SPIRE GT observations of the same fields in the HerMES program. PEP

GT (PEP & HERMES) SCIENCE GOALS: Resolve the Cosmic Infrared Background and determine the nature of its constituents. Determine the cosmic evolution of dusty star formation and of the infrared luminosity function Elucidate the relation of far-infrared emission and environment, and determine clustering properties Determine the contribution of AGN

The integrated extragalactic background light in the far-infrared and sub-millimeter region of the spectrum is approximately equal to the integrated background light in the optical and UV part of the spectrum. To develop a complete understanding of galaxy formation, this background light must be resolved into galaxies and their properties must be characterized. The Cosmic IR Background Radiation Resolved Into Sources

The power of multiwavelength studies IRAC/SPITZER micron : passive & massive stellar dominated galaxies + star forming sources MIPS/SPITZER 24/70/160 micron: SF dominated galaxies, LIRGs, ULIRGS, emission dominated by dust reprocessed UV/optical photons HERSCHEL micron: detect the peak of the bolometric IR emission

Lagache, Puget & Dole 2005 (ARAA)

One of the most direct results of deep PACS surveys will be the resolution of the majority of the CIB into individual well detected sources, at wavelengths near the CIB peak which contains most of the energy and represents most of the cosmic star formation and metal production, modulo the contribution of AGN. We expect to resolve about 80%, 85% and 55% of the CIB due to galaxies at 75, 110, and 170 microns into individual 5-sigma detected sources for the blank field surveys. These fractions clearly depend on the faint number counts at these wavelengths that only PACS can measure. Lensing cluster observations and fluctuation analysis will increase these fractions further. Using the wealth of multi-wavelength data already existing in the chosen well-studied fields and techniques like SED fitting, as well as dedicated follow up projects, we will be able to determine the physical nature of these objects, for example redshifts, luminosities, morphologies, masses, star formation histories, and the role of AGN

We expect to resolve about 80%, 85% and 55% of the CIB due to galaxies at 75, 110, and 170 microns into individual 5-sigma detected sources for the blank field surveys. These fractions clearly depend on the faint number counts at these wavelengths that only PACS can measure. Using the wealth of multi-wavelength data already existing in the chosen well- studied fields and techniques like SED fitting, as well as dedicated follow up projects, we will be able to determine the physical nature of these objects, for example redshifts, luminosities, morphologies, masses, star formation histories, and the role of AGN.

How does the star formation rate density and galaxy luminosity function evolve? Luminosity of infrared galaxies detectable in the three PACS bands at different redshifts for a single star-forming SED galaxy

Our surveys will sample the critical far-infrared peak of star forming galaxy SEDs and will probe a large part of the infrared luminosity function, down to luminosities of ~1e11 Lsun at redshift 1 and <1e12 Lsun at redshift 2. This will enable a detailed study of the evolution of the infrared luminosity function with redshift, expanding on the results based on mid-infrared or submm surveys and suppressing the associated uncertainties due to extrapolation of the IR SEDs. The the multi-wavelength coverage of our fields will ensure a robust estimate of photometric stellar masses, hence extending studies of the evolution of the specific star formation rate to the currently missing obscured component of star formation.

The PEP surveys will sample the critical far-infrared peak of star forming galaxy SEDs and will probe a large part of the infrared luminosity function, down to luminosities of ~1e11 Lsun at redshift 1 and <1e12 Lsun at redshift 2. This will enable a detailed study of the evolution of the infrared luminosity function with redshift, expanding on the results based on mid-infrared or submm surveys and suppressing the associated uncertainties due to extrapolation of the IR SEDs.

The Padova IR evolutionary model (Franceschini et al. 2008, in prep.)  The 2001 phenomenological model (Franceschini et al. 2001) was rather successful in explaining & “exploring” ISO results  Spitzer & SCUBA data (re)-analyses, however, called for a revamp  Through a simple backward evolution approach, FR08 describes available observables (number counts, z-distributions, L-functions, integrated CIRB levels…) in terms of number and luminosity evolution of four populations slowly or non-evolving disk galaxies [blue dotted lines] type-1 AGNs evolving as shown by UV and X-ray selected Quasars & Seyferts [green long-short dashed lines] moderate-luminosity starbursts with peak emission at z ~ 1 [cyan dot- dashed lines] ultra-luminous starbursts with peak evolution between z = 2 and z = 4 [red long dashed lines]

Modeling Benchmarks

Spitzer MIPS Counts & redshift distribution : 24  m Most stringent constraint provided by Spitzer to date Vaccari et al 2008, Rodighiero et al 2008 in prep

Far-IR & Sub-mm source counts Vaccari et al in prep., Franceschini et al. in prep SWIRE+GTO SWIRE+FLS SHADES/SCUBA CSO

Z=  m Luminosity Functions GOODS-S + GOODS-N + SWIRE-VVDS Fields (Rodighiero et al in prep) ~ 2000 sources with some of the best spec info available The determination of redshift-dependent Luminosity Functions require large corrections which depend to a large extent on the adopted SED templates, and particularly so for IR Bolometric (  m) Luminosity Functions

Constraining Bolometric Luminosity Herschel bands will be crucial in constraining the bolometric luminosity of galaxies. This will help untangle the contribution of AGN and star-formation cool/warm dust and thus constrain the star-formation history. Herschel bands at z=1 vs model spectra

What is the role of AGN and how do they co-evolve with galaxies? 1.4°x1.4° XMM COSMOS (Hasinger et al.) Recent combined X-ray and Spitzer surveys have revised our view of the history of accretion onto AGN, in particular with respect to the detection of high redshift z~2 obscured AGN activity (e.g. Daddi 2007, Fiore 2007 via stacking analysis).

The close relation in the local universe between black hole mass and bulge properties calls for studies of how AGN and galaxies co-evolve. According to recent models, feedback by AGN is also central to terminating star formation in massive galaxies (Croton et al. 2006). Both locally and at high redshift, many infrared galaxies host both star formation and an active nucleus (e.g. Genzel et al. 1998, Alexander et al. 2003, 2005, Valiante et al. 2007). The PEP survey will shed new light on this relation, as a function of redshift and of galaxy properties, by studying for significant AGN samples the rest frame far- infrared emission and its relation to the AGN properties. Recent X-ray and optical surveys have revised our view of the history of accretion onto AGN, in particular with respect to the surprising role of moderate redshift z~0.5-1 obscured AGN (e.g. Hasinger 2003, Brandt & Hasinger 2005). PEP will also probe the far-infrared emission of fully obscured AGN not detected in X-ray surveys. Recent Spitzer mid-IR surveys detected a significant population of obscured AGNs, not accounted for by traditional optical or X-ray selections (e.g. Donley et al. 2005, Lutz et al. 2005, Martinez-Sansigre et al. 2005). In combination with SPIRE, and Spitzer 24 microns data, PEP/PACS will determine the overall SEDs of active galaxies, including AGN mid-IR emission. Hence PEP will quantify the total energetics of the obscured phases in black-hole evolution, as well as of the associated star formation.

PEP will also probe the far-infrared emission of fully obscured AGN not detected in X-ray surveys. Recent Spitzer mid-IR surveys detected a significant population of obscured AGNs, not accounted for by traditional optical or X-ray selections (e.g. Donley et al. 2005, Lutz et al. 2005, Martinez-Sansigre et al. 2005). In combination with SPIRE, and Spitzer 24 microns data, PEP/PACS will determine the overall SEDs of active galaxies, including AGN mid-IR emission. Hence PEP will quantify the total energetics of the obscured phases in black-hole evolution, as well as of the associated star formation.

The power of multiwavelength studies ARP220 MKN231

Selection of massive high-z obscured AGN and starburst galaxies Rodighiero et al. 2007

Extragalactic Confusion ChannelPACS1PACS2PACS3SPIRE1SPIRE2SPIRE3 mmmm Beam FWHM 4.74” 6.96”10.76”17.1”24.4”34.6” 3  [mJy]  [mJy]  [mJy] bps [mJy] bps [mJy] bps [mJy] bps [mJy] bps [mJy] Due to the different slope in counts, the  vs bps is not a one-to-one relation,  values being generally & consistently worse than bps ones for SPIRE with respect to PACS

A Pre-Launch Consensus View on Herschel EG Confusion Limits MEAN +- RMS of various models 4  values above are arguably best pre-launch indication