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  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.

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 ~1mm from z ~ 0.5 to 10  At least ULIRGs Lo  Numerous ~ per arcmin 2  Star Formation Rate SFR > 100 Mo/yr  Account for a significant fraction of submm background  Most exceptional HLIRGs 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

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 S 24µm ~ µJy (1mJy at z~2  L ~ Lo) 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)

PAH dominated spectra Yan et al Composite AGN-PAH spectra

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

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

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

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~ ( ) Lonsdale et al. 2008, Fiolet et al. in prep.

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

How strong in FIR/submm are Spitzer z~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 PAH dominated (starbursts) (and many composite sources) have strong/significant mm fluxes, as confirmed by our MAMBO 1.2mm studies

MAMBO 1.2mm observations of Spitzer z~2 starbursts PAH dominated (starbursts) (and many composite sources) have strong/significant mm fluxes Three samples  Lonsdale, Polletta, Omont et al ApJ in press 61 sources S 24µm >~ 500 µJy =820µJy 5.8µm-peakers  16 3  detections = 1.49+/-0.18 mJy  Fiolet, Omont et al in prep. 32 sources S 24µm >~ 400 µJy =540µJy 5.8µm-peakers  13 3  detections = 1.54+/-0.14 mJy  Younger, Omont et al. 2008, submitted to MNRAS 12 sources S 24µm >~ 500 µJy =800µJy [3.6]-[4.5] vs [3.6]-[8.0]  9 3  detections = 1.6 +/- 0.1 mJy Homogeneous samples, no sources S 1.2mm >5mJy, very few >4mJy, many 2  ‘detections’ Practically all are ULIRGs/SMGs ( S 1.2mm = 1.5mJy  S 850µm ~ 4mJy)

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 composite AGN IRAS19254) « Optimized »sample 350µm detections Unbiased sample x Literature sources

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 L FIR are often uncertain Spitzer has poor sensitivity at 70 and 160µm  Exceptionally deep µm data: Huang08+, Younger08+ T dust and L FIR well constrained by data at 70, 160 and 1200 µm T dust ~ 34 – 47 K L FIR ~ 2 – 10 x Lo  Or stack at µm of >~10 sources Lonsdale08+, Fiolet08+ Similar results but more uncertain  Or/and measurement at 350µm (SHARC2/CSO) Kovacs+ in prep. The few observed sources yield similar values for T dust and L FIR

Younger et al. 2008

Radio Properties  Starbursts L FIR (and SFR) are known to be strongly correlated with radio (synchrotron) emission in starbursts L FIR/ L 1.4GHz about constant over several orders of magnitude: from HII regions to ULIRGs Spectral index  of starbursts a ~  AGN AGN are known to be even stronger radio emitters Radio loud, S 1.4GHz >~ 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

Very deep radio data at 1400 and 610 MHz in a deg2 field ‘Lockman-Owen’ FieldFiolet et al. in prep. MAMBO 1.2mm study of µm-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 radio extended >~ 10kpc AGN or extended starbursts?  L FIR inferred from radio/FIR relation L FIR ~ Lo, SFR ~ 300 –1000 Mo/yr Rather consistent with T dust ~ 40K from Younger et al.

CO Study of 24µm bright z~2 Spitzer ULIRGs Reminder 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

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).

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

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

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 > Mo) 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. Current conclusions of PdBI CO survey of SMGs

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~ 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

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;  M H2 Most of these sources are 5.8µm-peakers or similar sources

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

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;  M H2  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??

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

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

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

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

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

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 (>~10 11 Mo) (Berta+07  Lonsdale+08, Fiolet+08, Huang-Younger 08) Maybe slightly larger than SMGs?

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 T dust (mean ~40K instead ~34K)

Herschel  Too small collecting area vs ALMA (/500!) for high-z molecules  But will detect 10 4 ’s of SMGs in wide surveys with full SEDs, L FIR and SFR  For follow up at PdBI and ALMA  Will need multi- 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 Prospects Herschel bands and SMG SEDs

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