A) Summary ISO, Spitzer & SCUBA counts are used to constrain models of extragalactic populations

1. (See C) for Legenda) Rodighiero et al. 2006 (MNRAS, 371) showed that using conventional deconvolution techniques one can use IRAC 3.6 m positions to detect MIPS 24 m sources down to 3  ~ 10 bps levels, thus “extrapolating” by nearly a decade in , as in e.g. MIPS 24 m vs SPIRE 250 m MIPS 24 m MIPS 70 m MIPS 160 m …fitting additional observables into modeling picture and applying techniques to other instruments, e.g. Akari & Planck & SPICA & FIRM. Public web page is also in the works! Confusion sets in at a flux determined by the Beam FWHM line (right) and the 10 bps line (below) z-distribution MIPS 24 m SCUBA 850 m Integral Counts PACS 70 PACS 170 SPIRE 350 (See C) for Legenda) What extragalactic OT KP surveys can we ask of Herschel? From a confusion point of view, rich opportunities exist to extend GT KP mid- & large-area planned surveys (~ 1 deg2 or larger) to deeper levels, and particularly so on the PACS side 3  ~ 10 bps 20 bps Opp. Area 10 bps Opp. Area 3  ~ 20 bps An Herschel Survey of Surveys (SOS) www.mattiavaccari.net/herschel/sos Mattia Vaccari mattia@mattiavaccari.net www.mattiavaccari.net • A) Summary • ISO, Spitzer & SCUBA counts are used to constrain models of extragalactic populations • Extragalactic confusion in Herschel bands is estimated using 2 complementary criteria • The two approaches respectively measure cell-to-cell fluctuations due to unresolved sources and set a maximum number density for resolved sources • These two methods provide results which are in good agreement for all Herschel bands • Currently envisaged sensitivities for Herschel KP surveys are compared with our predictions and opportunities for Herschel OT extragalactic KP surveys are outlined • B) Confusion at Long Wavelengths with Herschel • Confusion sets a major limit to the sensitivity of long- extragalactic surveys • As IRAS first dramatically showed, the FIR/sub-mm sky is very densely populated • ISO & Spitzer & SCUBA confirmed this view providing a wealth of additional data • Great care must be taken in taking stock of current knowledge in order to predict Herschel confusion limits and thus allow a timely planning of GT & OT KP observations • D) Measuring Confusion through “Fluctuations” & “Counts” • “Fluctuations” measure fluctuations in the background due to unresolved sources [Franceschini et al. 1989 (ApJ, 344) ] and set “confusion” at the 3  fluctuation level • “Counts” measure source counts and set “confusion” where a maximum number of sources per beam, or rather a minimum number of beams per source (bps), is reached [Franceschini et al. 2001 (A&A, 378)] • Roughly speaking, while “Fluctuations” follow the trend of counts fainter than the confusion limit, “Counts” follow the trend at brighter fluxes than that. The degree of consistency between the two depends on the slope of counts at and near this flux limit. • C) Modelling ISO, Spitzer & SCUBA Observations • Models by Franceschini et al. 2001 (A&A, 378) were updated to account for intervened reanalyses of ISO 15 m data and results from Spitzer MIPS and SCUBA observations • Models describe available observables (number counts, z-distributions, L-functions, integrated CIRB levels…), in terms 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] Extragalactic Confusion Limitsin Herschel Key ProgramsMattia Vaccari & Alberto Franceschini & Giulia Rodighiero & Stefano Berta Department of Astronomy - University of Padova • E) “Fluctuations” vs. “Counts” Confusion Limits • 3  “Fluctuations” are very close to “Counts” 10 bps for PACS but nearer to 20 bps for SPIRE, due to different count slopes at and fainter than 10/20 bps levels • The availability of multi- data (e.g. MIPS 24 m for PACS, PACS & SCUBA2 for SPIRE, etc) will be invaluable in linking various wavelength regimes and accurately pin-pointing sources in order to reach down to 10 bps levels in all Herschel bands. • See posters by Franceschini on H-COSMOS and by Dunne & Dunlop on H-SCLS Herschel Extragalactic GT Survey Wedding Cake • F) Recommendations for Herschel GT & OT KP Planning • From a confusion point of view, target sensitivities envisaged in Herschel GT KP surveys appear to be realistic when modeling ISO & Spitzer & SCUBA results. • Opportunities exist to go deeper (see posters by Franceschini on H-COSMOS and by Dunne & Dunlop on H-SCLS) and wider (see posters by De Zotti on SPIRE LAS and by Serjeant on H-SASSy) over medium- and large-size areas. • In particular, judging from Spitzer results, reaching the 3  ~ 10 bps levels in all PACS & SPIRE bands over larger areas than planned in GT KP surveys appears to be feasible and thus somehow mandatory in order to fulfill Herschel’s potential for extragalactic surveys. Such deep OT KP surveys should be undertaken over sky areas where deep Spitzer MIPS 24 m and/or SCUBA2 coverage is or will soon be available, e.g. within the most popular “Cosmic Windows”. • Survey-like ultra-deep exploratory efforts should be undertaken at a relatively early time during Herschel operations in order to determine actual confusion levels and test deconvolution techniques in a timely manner, thus ensuring to make the most of Herschel’s 3-year life span. Time (hr) : PACS (659)SPIRE (850) Harwit (10)(Spitzer Depths)