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Mid-IR selection of Ultra-Luminous Far-IR Galaxies Starburst and AGN tracers in z~2 ULIRGs

Mid-IR selection of Ultra-Luminous Far-IR Galaxies Starburst and AGN tracers in z~2 ULIRGs continuum & CO mm emission, radio and PAH Alain Omont (IAP, CNRS and Université Paris 6). OUTLINE Mid-IR luminous Ultra-Luminous Far-IR Galaxies.

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Mid-IR selection of Ultra-Luminous Far-IR Galaxies Starburst and AGN tracers in z~2 ULIRGs

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  1. Mid-IR selection of Ultra-Luminous Far-IR Galaxies Starburst and AGN tracers in z~2 ULIRGs continuum & CO mm emission, radio and PAH Alain Omont (IAP, CNRS and Université Paris 6)

  2. OUTLINE Mid-IR luminous Ultra-Luminous Far-IR Galaxies • Submillimeter galaxies: high-z Ultra-Luminous Far-IR Galaxies • 24µm bright z~2 ULIRGs: AGN vs PAHs/starburst • Mm continuum emission. Far-IR luminosity, star formation rate • Radio emission: starburst/AGN • CO mm emission. Molecular gas, structure and dynamics • Stellar mass • Sructure (HST, radio, CO): merger/outflow • Prospects (Herschel, ALMA, JWST) Collaborators: C. Lonsdale, M. Polletta, N. Fiolet, A. Beelen, A. Baker, F. Owen, S. Berta L. Yan, L. Tacconi, D. Lutz, A. Sajina , G. Lagache, D. Shupe J. Huang, J. Younger, G. Fazio, etc.

  3. Reminder SMGs: strongest starbursts in the Universe Essential steps of star formation in massive galaxies at z >~ 2 • Revealed by SCUBA surveys at 850µm (+ MAMBO at 1.2mm  AzTEC, LABOCA, BOLOCAM) Easy detection of dust FIR emission through « inverse K-correction », same flux at ~1mmfrom z ~ 0.5 to 10 • At least ULIRGs 1012 Lo  Numerous ~0.1-0.3 per arcmin2  Star Formation Rate SFR > 100 Mo/yr • Account for a significant fraction of submm background • Most exceptional HLIRGs 1013 Lo, 1000 Mo/yr nothing equivalent in the local Universe • Giant starbursts at the peak of star formation, z ~ 2-3  1-4, in massive proto-elliptical galaxies

  4. 24µm bright z~2 ULIRGs: AGN vs PAHs/starburst Optically faint, 24µm bright Spitzer sources  high z sources Large Spitzer surveys (SWIRE, FLS, etc.) with sensitivity S24µm~250-300µJy (1mJy at z~2  nLn ~ 1012Lo) Large programs with IRS/Spitzer spectrometer ~15-35µm  ~5-12µm rest Houck et al. 2005, Yan et al. 2005;2007,etc., Weedman et al. 2006, Farrah et al. 2008, Huang et al. 2008, etc. - Most of 1mJy sources are AGN dominated: hot dust close to the BH, emitting at ~8µm - Many have strong silicate 9.7µm absorption -Some have strong PAH features at 6.2, 7.7, 8.6, 11.3µm, or are composite PAH/AGN Such PAH emission is known to trace strong starbursts (PDR regions)

  5. PAH dominated spectra Yan et al. 2007 Composite AGN-PAH spectra

  6. Yan et al. 2007 Starburst vs AGN PAH spectrum Starbust Composite AGN-starburst

  7. Stacked spectrum for10 z~1.9, Spitzer selected starburst ULIRGs Huang et al. 2008

  8. Mid-IR properties of SMGs (for comparison) • Large range of 24µm fluxes Average flux rather low: • Pope et al. 2005 (HDFN) <S24µm> ~ 240µJy • Ivison et al. 2007 (SHADES) <S24µm> ~ 340µJy • IRS spectra • Only for strongest sources: • Pope et al. 2006 <S24µm> ~ 380 µJy • Valiante et al. 2007 <S24µm> ~ 500 µJy • Strong PAH features • Hints of AGN

  9. Selection of z~2 starbursts from Spitzer IRAC & 24µm photometry IRAC bands allow discrimination between AGN and starburst (PAH) dominated sources AGN (and many composites) have more or less power law IRAC SED Starbursts display a ‘stellar bump’ (1.6µm rest) in IRAC bands Maximum at 5.8µm (4.5µm) band mostly selects sources at z~1.8-2.0 (1.5-1.7) Lonsdale et al. 2008, Fiolet et al. in prep.

  10. Selection of Huang et al. 2008, from [3.6]-[4.5] vs [3.6]-[8.0], is practically equivalent to select z~2 starburst Blue Huang08+ Red Fiolet09+ Green Lonsdale08+

  11. How strong in FIR/submmare Spitzerz~2 starbursts? Although one expects some correlation between bright sources in mid-IR (24µm at z~2), FIR and mm/submmfluxes, the detailed correlation is not obvious Pure AGN (e.g. Type I QSOs) are known to have flat SEDs and rather weak mm fluxes This is confirmed for obscured 24µm-bright Spitzer AGN by the 1.2mm MAMBO study of Lutz et al. 2005 PAH dominated (starbursts) (and many composite sources) have strong/significant mm fluxes, as confirmed by our MAMBO 1.2mm studies

  12. MAMBO 1.2mm observations of Spitzerz~2 starbursts • PAH dominated (starbursts) (and many composite sources) have • strong/significant mm fluxes • Three samples • Lonsdale, Polletta, Omont et al. 2008 ApJ in press • 61 sources S24µm >~ 500 µJy <S24µm>=820µJy 5.8µm-peakers •  16 3s detections < S1.2mm > = 1.49+/-0.18 mJy • Fiolet, Omont et al. 2009 in prep. • 32 sources S24µm >~ 400 µJy <S24µm>=540µJy 5.8µm-peakers •  13 3s detections < S1.2mm > = 1.54+/-0.14 mJy • Younger, Omont et al. 2008, submitted to MNRAS • 12 sources S24µm >~ 500 µJy<S24µm>=800µJy[3.6]-[4.5] vs [3.6]-[8.0] • 9 3s detections < S1.2mm > = 1.6 +/- 0.1 mJy Homogeneous samples, no sources S1.2mm>5mJy, very few >4mJy, many 2s ‘detections’ Practically all are ULIRGs/SMGs (S1.2mm = 1.5mJy  S850µm ~ 4mJy)

  13. Large ratio PAH/FIR (1.2M/24µm) emission Ratio S(1.2mm)/S(24µm) much smaller than most SMGs whose typical SED is relatively cold, similar to Arp 220 SED rather similar to M 82 or NGC 6090 But more luminous, without local equivalent (Desai 07) (or compositeAGN IRAS19254) « Optimized »sample 350µm detections Unbiased sample x Literature sources

  14. Far-IR Luminosity and Star Formation Rate Waiting for Herschel and ALMA, measuring flux densities between 40µm and 700µm is still difficult, so that the flux at SED maximum and LFIR are often uncertain Spitzer has poor sensitivity at 70 and 160µm  Exceptionally deep 70-160µm data: Huang08+, Younger08+ Tdust and LFIR well constrained by data at 70, 160 and 1200 µm Tdust ~ 34 – 47 K LFIR ~ 2 – 10 x 1012 Lo  Or stack at 70-160µm of >~10 sources Lonsdale08+, Fiolet08+ Similar resultsbut more uncertain  Or/and measurement at 350µm (SHARC2/CSO) Kovacs+ in prep. The few observed sources yield similar values for Tdust and LFIR

  15. Younger et al. 2008

  16. Radio Properties • Starbursts • LFIR (and SFR) are known to be strongly correlated with radio • (synchrotron) emission in starbursts • LFIR/L1.4GHz about constant over several orders of magnitude: • from HII regions to ULIRGs • Spectral index na of starbursts a ~ - 0.7 • AGN AGN are known to be even stronger radio emitters Radio loud, S1.4GHz >~ 300µJy at z~2 Significant radio emission from the AGN even below this limit Various spectral index and spatial extension: Jets; flat spectrum; compact steep spectrum sources Deep radio surveys in many Spitzer fields

  17. Very deep radio data at 1400 and 610 MHz in a 0.25-0.5 deg2 field • ‘Lockman-Owen’ Field Fiolet et al. in prep. • MAMBO 1.2mm study of 32 5.8µm-peakers. High detection rate • Combination of radio + 1.2mm well discriminate AGN and starbursts • Most of our 24µm sources have • a radio 30µJy detection • Ratio 1.2mm/20cm in usual limits • (e.g. Chapman et al. 2005) • except 20-35% mm-faint 5 to 13 AGN? • A number are radioextended >~ 10kpc • AGN or extended starbursts? • LFIR inferred from radio/FIR relation • LFIR ~ 2-6 1012Lo, SFR ~ 300 –1000 Mo/yr • Rather consistent with Tdust ~ 40K from • Younger et al.

  18. CO Study of 24µm bright z~2 Spitzer ULIRGs Reminder Dissecting SMGs through mm CO lines at IRAM-PdBI

  19. Dissecting SMGs through mm CO lines at IRAM-PdBI • (Very) Large program at the IRAM Plateau de Bure millimeter interferometer (PdBI) (Genzel, Ivison, Neri, Tacconi, Smail, Chapman, Blain, Cox, Omont, Bertoldi, Greve et al.) • -30 SMGs with z~2-3 spectroscopic redshifts from radio positions (Chapman, et al.) • Detection and velocity profiles of CO(3-2) and (4-3) lines for 22 SMGs (Neri et al. 2003, Greve et al. 2005, Tacconi et al. 2006, Smail et al. in prep.). • Subarcsecond resolution imaging in progress (Tacconi et al. 2006, 2008, and in prep.) • Parallel programs for HST imaging and high resolution radio imaging with MERLIN • Key goals • - Physical properties and evolution of the SMG population • - How SMGs fit in general picture of galaxy evolution and formation

  20. The Plateau de Bure Interferometer In 2007 PdBI has increased sensitivity by >~2 and baseline by ~2 Further gain by 2009: larger bandwidth 4GHz and more bands (2mm+0.85mm).

  21. High angular resolution CO mapping at PdBI Example of mapping CO in an SMG at PdBI Case of an unresolved ~1kpc rotating disk (2008)

  22. Examples of mapping CO in SMGs at PdBI Spatial and Kinematic Evidence for Mergers Double or multiple knots, with complex, disturbed gas motions Tacconi et al. 2008

  23. Current conclusions of PdBI CO survey of SMGs • High CO detection rate, close to 100% with current PdBI sensitivity • Large fraction are resolved with subarcsecond resolution (2/3 are resolved in the radio with 0.3’’ MERLIN beam) • Mm lines of the molecular ISM, are unique to trace dynamical masses. (Also large stellar masses > 1011Mo) • SMGs are short-duration (~100 Myr) maximum starburst events in the evolution of a major gas-rich merger of massive galaxies. • Different combinations of ordered disk rotation and merger driven random motions and inflows • The high surface densities in SMGs are similar to compact quiescent galaxies in the same redshift range and much higher than in local spheroids.

  24. CO Study of 24µm bright z~2 Spitzer ULIRGs 1/2 with upgraded PdBI (in 2007 PdBI has increased sensitivity by >~2 and baseline by ~2) Needs accurate redshift for current PdBI limited bandwidth 1 GHz for full sensitivity ( 3000 km/s) ( 4 GHz in 2009) PAH determination of z not currently accurate enough ( 2009) Optical/NIR redshift measurement is difficult at z~1.8-2.0 especially for starbursts (‘redshift desert’) Only a dozen of IRS sources have accurate z (Sajina07+, Yan05+) We observed 10 with PdBI and detected CO in 9

  25. CO Study of 24µm bright z~2 Spitzer ULIRGs 2/2 • We observed 10 sources of Yan+07 with PdBI and detected CO in 9 • Tacconi et al. in prep., Fiolet et al. in prep. • PAH dominated sources strong CO signals; intensity and width comparable to SMGs;  MH2 Most of these sources are 5.8µm-peakers or similar sources

  26. MIPS16144 – Integrated CO 3-2 Emission strong PAHs strong MAMBO 1.2m flux (2.9mJy)  strong CO L. Tacconi in prep. ‘PAH’ source, Mambo flux=2.930.56, z=2.13 40 MHz spectral smoothing, rms=0.32 mJy/beam C-configuration

  27. CO Study of 24µm bright z~2 Spitzer ULIRGs 2/2 • We observed 10 sources of Yan+07 with PdBI and detected CO in 9 • Tacconi et al. in prep., Fiolet et al. in prep. • PAH dominated sources strong CO signals; intensity and width comparable to SMGs;  MH2 • AGN dominated and composite sources weaker (narrower) CO lines but most are detected • CO is detectable with current PdBI sensitivity in practically all z~2 ULIRGs • High resolution maps in one sources in Winter 2009? • Multi-line CO observations in 2mm (1.3mm) bands?? • Search in large sample with PAH redshift with 4 GHz bandwidth??

  28. MIPS15949 – Integrated CO 3-2 Emission PdBI Spring08 ROC4 AGN (+PAH) source, Mambo flux=1.240.51, z=2.11 40 MHz spectral smoothing, rms=0.28 mJy/beam C-configuration CO43=148 CO65=222

  29. MIPS8327 – Integrated CO 3-2 Emission PdBI Spring08 ROC4 Absorbed source, Mambo flux=1.030.55, z=2.44 40 Mhz spectral smoothing, rms=0.24 mJy/beam C-configuration CO54=167.52

  30. MIPS8342 – Integrated CO 2-1 Emission PdBI Spring08 ROC4 AGN (+‘PAH’) source, Mambo flux=0.980.55, z=1.56 40 MHz spectral smoothing, rms=0.19 mJy/beam Note: this source was done in D-configuration CO32=

  31. Fiolet et al. in prep. Weak 1.2mm MAMBO Srong 10µm silicate absorption Broad CO line Narrow CO line, radio loud

  32. Spatial Extension • Crucial: a significant extension could explain stronger PAHs (merger, • outflow?) • While most SMGs and AGN are rather compact (+strong silicate • absorption) • But difficult, subarcsec • Best: CO (+1.2mm continuum) maps at PdBI of strong sources • ALMA for weak sources HST ACS (Huang+08), NICMOS (Dasyra,Yan+08) : many sources extended but difficult interpretation Radio: many large extensions (Owen; Fiolet in prep.) but could be AGN jets or merger starbursts

  33. Stellar Masses • Stellar mass well traced by NIR emission (1.6µm bump) of red giants • IRAC bands at z~2 But risk of contamination by young massive TP-AGBs Large mass (>~1011Mo) (Berta+07 Lonsdale+08, Fiolet+08, Huang-Younger 08) Maybe slightly larger than SMGs?

  34. Conclusions. Comparaison with classical SMGs • PAH luminous z~2 sources are strong starbursts and belong to the • SMG family  special subclass, probably extended starburst • (from late major mergers) • Compared to the bulk of the SMGs, they have: • Comparable mm/submm fluxes and CO intensities • Significantly larger 24µm/1.2mm flux ratio • Probably slightly larger Tdust (mean ~40K instead ~34K)

  35. Prospects • Herschel • Too small collecting area vs ALMA (/500!) for high-z molecules • But will detect 104’s of SMGs in wide surveys with full SEDs, LFIR and SFR • For follow up at PdBI and ALMA • Will need multi-l data to beat confusion • SPIRE GTO high-z ‘HERMES’: 900h mapping most Spitzer survey fields • GO key project ATLAS: ~500h, ~500 deg2  shallow observations : nearby and rare (lensed) objects • GO key project 300h on ~50 lensing clusters Herschel bands and SMG SEDs

  36. Prospects ALMA ALMA will provide exquisite CO images, and multi-line intensities for such galaxies and more distant ones JWST MIRI/JWST will have orders of magnitude improvements in sensitivity, spatial and/or spectral resolution compared with Spitzer  synergy with ALMA

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