mid-ir selection of ultra-luminous far-ir galaxies starburst and agn tracers in z~2 ulirgs
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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. BertaL. Yan, L. Tacconi, D. Lutz, A. Sajina , G. Lagache, D. ShupeJ. Huang, J. Younger, G. Fazio, etc.
Reminder
SMGs: strongest starbursts in the UniverseEssential 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 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 massiveproto-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 S24µm~250-300µJy
(1mJy at z~2 L ~ 1012Lo)
Large programs with IRS/Spitzer spectrometer ~15-35µm ~5-12µm restHouck 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. 2007
Composite AGN-PAH spectra
Yan et al. 2007 Starburst vs AGN PAH spectrum
Composite AGN-starburst
Starbust
Stacked spectrum for10 z~1.9, Spitzer selected starburst ULIRGsHuang et al. 2008
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 spectraOnly for strongest sources: Pope et al. 2006 <S24µm> ~ 380 µJy Valiante et al. 2007 <S24µm> ~ 500 µJy
Strong PAH featuresHints 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) bandmostly selects sources at z~1.8-2.0(1.5-1.7) 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 the1.2mm MAMBO study of Lutz et al. 2005
PAH dominated (starbursts) (andmany composite sources) havestrong/significant mm fluxes,as confirmed by our MAMBO1.2mm studies
MAMBO 1.2mm observations of Spitzer z~2 starbursts
PAH dominated (starbursts) (and many composite sources) havestrong/significant mm fluxes
Three samples
Lonsdale, Polletta, Omont et al. 2008 ApJ in press61 sources S24µm >~ 500 µJy <S24µm>=820µJy 5.8µm-peakers
16 3 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 3 detections < S1.2mm > = 1.54+/-0.14 mJy
Younger, Omont et al. 2008, submitted to MNRAS12 sources S24µm >~ 500 µJy <S24µm>=800µJy [3.6]-[4.5] vs [3.6]-[8.0] 9 3 detections < S1.2mm > = 1.6 +/- 0.1 mJy
Homogeneous samples, no sources S1.2mm >5mJy, very few >4mJy, many 2 ‘detections’Practically all are ULIRGs/SMGs (S1.2mm = 1.5mJy S850µm ~ 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 6090But more luminous, withoutlocal 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 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 µmTdust ~ 34 – 47 KLFIR ~ 2 – 10 x 1012 Lo
Or stack at 70-160µm 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 Tdust and LFIR
Younger et al. 2008
Radio Properties
StarburstsLFIR (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 of starbursts a ~ - 0.7
AGNAGN are known to be even stronger radio emitters
Radio loud, S1.4GHz >~ 300µJy at z~2Significant 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 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 havea 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?
LFIR inferred from radio/FIR relationLFIR ~ 2-6 1012Lo, SFR ~ 300 –1000 Mo/yrRather consistent with Tdust ~ 40K fromYounger et al.
CO Study of 24µm bright z~2 Spitzer ULIRGs
ReminderDissecting SMGs through mm CO lines at IRAM-PdBI
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 ~2Further 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 PdBICase of an unresolved ~1kpc rotating disk
(2008)
Examples of mapping CO in SMGs at PdBISpatial 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 > 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.
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 bandwidth1 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~1.8-2.0especially 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 9Tacconi 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
MIPS16144 – Integrated CO 3-2 Emission
‘PAH’ source, Mambo flux=2.930.56, z=2.1340 MHz spectral smoothing, rms=0.32 mJy/beamC-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 9Tacconi 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??
MIPS15949 – Integrated CO 3-2 Emission
AGN (+PAH) source, Mambo flux=1.240.51, z=2.1140 MHz spectral smoothing, rms=0.28 mJy/beamC-configurationCO43=148 CO65=222
PdBI Spring08 ROC4
MIPS8327 – Integrated CO 3-2 Emission
Absorbed source, Mambo flux=1.030.55, z=2.4440 Mhz spectral smoothing, rms=0.24 mJy/beamC-configurationCO54=167.52
PdBI Spring08 ROC4
MIPS8342 – Integrated CO 2-1 Emission
AGN (+‘PAH’) source, Mambo flux=0.980.55, z=1.5640 MHz spectral smoothing, rms=0.19 mJy/beamNote: this source was done in D-configurationCO32=
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 sourcesALMA for weak sources
HST ACS (Huang+08), NICMOS (Dasyra,Yan+08) : many sources extendedbut 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 giantsIRAC 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?
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)
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- 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
JWSTMIRI/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 intensitiesfor such galaxies and more distant ones