Molecules in high redshift galaxies as probes of star formation and galaxy evolution

Alain Omont (IAP, CNRS and Université Paris 6)

OUTLINEMolecules in high redshift galaxies Molecules in high redshift galaxies

as probes of star formation and galaxy evolutionas probes of star formation and galaxy evolution

General Features - Molecules in the ISM of galaxies - Molecules at high redshift Millimeter emission of molecules at very high redshift (PdBI)

- CO and the structure of starbursts in SMGs

- Mm follow up of the Spitzer heritage

- CO in high z QSOs and the MBH/Mspheroid relation

PAHs as tracers of starbursts

H2 as tracer of shocks and cooling of warm gas

Prospects (ALMA, etc.)

Omont 2007, Rep. Prog. Phys. 70, 1-78 Solomon & Vanden Bout 2005 ARAA 43, 677

- Local ULIRGs (Yu Gao) - Molecular absorption lines (mm, radio, UV) at high z

- Lensing of high-z molecular lines

- * Special features of interstellar chemistry at high redshift Other molecules than CO (and H2 and PAHs)

- * Evolution of nucleo-synthesis through molecular isotopes - Host galaxies of the most distant QSOs (Ran Wang)

- * Molecular outflows and AGN feedback

- H2O mega-masers

- Possible variation of fundamental constants measured with molecular lines: me/Mp through UV H2 lines, through OH lines- Etc.

Important topics NOT to be addressed(* = still poorly documented)

Molecules are essential ingredient of the interstellar medium

• Normal molecular gas: cold (~10-100K) and dense (~103-105 cm-3)

Various steps of star formation:- Giant Molecular Clouds- Accretion disks- Molecular outflows- Photo-Dissociation Regions and Compact HII Regions- Supernova remnants

• Warm molecular gas: - Shocks - (+ UV or X fluorescence, stellar winds, etc.)

Molecules are essential ingredient of the interstellar medium

Rich molecular diagnosis

• VelocityVelocity fields in dense, obscured gas dynamicsdynamics: rotation, outflows (inflows), merging, shocks

• MassMass of molecular gas. Dynamical massDynamical mass of the galaxy

• TemperatureTemperature probe: Molecular ladder excitation through collisions (vs radiative processes): CO, NH3, etc.

Other excitation (shocksshocks, UV…) and coolingcooling processes

• ChemistryChemistry processes: formation/destruction: UV, Cosmic Rays, shocks, grains, X-rays, etc.

• Abundances Abundances of elements and isotopes

General Features at high redshift

• z > (0.5)-1 6…. (mostly ~2) - Cosmic times

• D2 distance fading: ~105 from nearby galaxies to local ULIRGs (z~1). Another factor ~200 to z=2

Rudimentary informationRudimentary information

• Exceptional Exceptional objects. Peak of starbursts and AGN

• Metallicity/UV: harshharsh for molecules

Millimeter CO lines are by far the best tracer of molecular gas

• H2 is hardly observable in cold gas

- IR lines are not excited and forbidden

- Absorption UV lines are too extincted

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J = 10 275 K

J = 9 250 K

J = 8 180 K

J = 7 140 K

J = 6 105 K

J = 5 75 K

J = 4 50 K

J = 3 30 K

J = 2 15 KJ = 1 5 KJ = 0 0 K

Rotational CO lines

1.3mm 230GHz 2.7mm 115GHz

520µm 576GHz

260µm 1152GHz

Redshifted lines =0 /(1+z)

Millimeter CO lines are by far the best tracer of molecular gas

• H2 is hardly observable in cold gas

- IR lines are not excited and forbidden - Absorption UV lines are too extincted

• CO millimeter lines are: - the strongest millimeter lines

- free from dust extinction

- observable with heterodyne high velocity resolution

- observable with high angular resolution with mm interferometers

- easy to excite in cold gas

- providing a good diagnostic of TK through multi-line studies

- roughly proportional to the mass of H2

- available in 3mm (1.3mm) atmospheric band at practically any redshift

- easy to observe at high z through an « inverse K-correction »

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J = 10 275 K

J = 9 250 K

J = 8 180 K

J = 7 140 K

J = 6 105 K

J = 5 75 K

J = 4 50 K

J = 3 30 K

J = 2 15 KJ = 1 5 KJ = 0 0 K

Rotational CO lines

1.3mm 230GHz 2.7mm 115GHz

520µm 576GHz

260µm 1152GHz

« Inverse K-correction » for CO lines 

Redshifted lines = 0 /(1+z)

Line J ~ 1+z redshifted into the 3 mm best atmospheric band

Line luminosity proportional to J3

strong increase of the 3mm line, almost compensating for the distance2 decrease

Millimeter CO lines are by far the best tracer of molecular gas

• H2 is hardly observable in cold gas - IR lines are not excited and forbidden - Absorption UV lines are too extincted

• CO millimeter lines are: - the strongest millimeter lines

- free from dust extinction- observable with heterodyne high velocity resolution- observable with high angular resolution with mm interferometers

- easy to excite in cold gas - providing a good diagnostic of TK through multi-line studies - roughly proportional to the mass of H2

- available in 3mm (1.3mm) atmospheric band at practically any redshift- easy to observe at high z through an « inverse K-correction »

• However,

- complex CO line formation uncertain MH2

- limited angular resolution uncertain Mdyn

- limited current sensitivity massive objects = Submm Galaxies (SMGs)

Molecular gas in Sub-Millimeter Galaxies (SMG)

From the heritage of SCUBA

To updated IRAM-PdBI

Waiting for ALMA

5

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

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

(Greve et al. 2005; Neri et al. 2004)

Detection with low angular resolutionHigh angular resolution: Tacconi+

22 radio-detected submm galaxies with known optical/near-IR redshift detected in CO (March 2008)

1<z<3.5

Variety of profiles: 500-1000 km/s

SFR 500 - >1000 Msun/yr

MH2 ~ 3x1010 Msun

Mdyn ~ 1011 Msun

SMM J02396-0134 SMM J02399-0136 SMM J04431+0210

SMM J09431+4700 SMM J13120+4242 SMM J14011+0252

SMM J16368+4057 SMM J16359+6612 SMM J16366+4105

SMM J16371+4053 ERO J16450+4626 SMM J22174+0015

CO Survey of submm Galaxies

(from P. Cox)

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

The Spitzer Heritage for Molecules in Galaxies

Routine detection of PAHs at z~2 PAHs are universal (in starbursts) at high z

24µm bright SMGs and CO detection

Massive detection of H2 rotational lines

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PAHs at highy redshift as tracers of starbursts

PAHs are known to be an important component of the ISM

Polycyclic Aromatic Hydrocarbons and related species are nano-particles from ~50 to a few 102 atoms, intermediate between conventional dust and molecules

They are not individually identified, but display characteristic IR vibration features from C-H bonds and 2D C-lattice

Orion

PAHs at highy redshift as tracers of starbursts

PAHs are known to be an important component of the ISM

Polycyclic Aromatic Hydrocarbons and related species are nano-particles from ~50 to a few 102 atoms, intermediate between conventional dust and molecules

They are not individually identified, but display characteristic IR vibration features from C-H bonds and 2D C-lattice

It is known from ISO that their bands dominate the mid-IR spectrum of galaxies. They are excited from UV fluorescence, and are thus interesting tracers of star formation

The sensitivity of Spitzer InfraRed Spectrometer (IRS) at ~20-30µm allows routine detection of PAHs in 24µm-bright ULIRGs: z~1-2.5, in redshifted 6 to 11µm bands, especially 7.7µm

PAH features are known to be relatively weaker in AGN, compared to hot dust continuum. PAHs are thus a good discriminant between starburst and AGN in high-z ULIRGs

Yan et al. 2007 Starburst vs AGN PAH spectrum

Composite AGN-starburst

Starbust

mJy

Highest z, z=3.01 Huang+07

St

24µm bright z~2 starbursts Yan et al. 2007

PAHs are universal in starbursts at high z

Several 10^2 Spitzer/IRS spectra of 24µm sources

PAHs are universal in starbursts at high z

Several tens of SMGs at z~2

SCUBA-MAMBO SMGsValiante et al. 2007

Spitzer selected

SMGs

Average obs. spectra

(and templates)

Huang+ in prep.

Mid-IR spectral features (PAHs and silicates) are detected up to z=3

Hundreds of high-z spectra:

• PAHs emission bands mostly in starbursts

• Silicates in absorption 10µm (+18µm) in compact sources: AGN (+ starbursts)

• Composite spectra are frequent

• PAH features are weaker in AGN, but frequent, including classical bright high-z QSOs (Lutz et al. 2008)

Yan et al. 2007

Questions--------------

Spitzer data are still very incomplete, many unpublished; their analysis is thus begining

PAH fraction and diagnostic

Modelling observed spectra (in relation with gas properties):

In starbursts: various types; environment

In AGN:Central regionsAbsorption/emission of the host galaxy

Winds: AGN/starbursts

Spitzer 24µm-bright SMGs

Only ~500 SMGs provided by SCUBA/MAMBO surveys( <~ 0.5-1 deg2) AzTEC

Waiting for SCUBA2, Herschel, much larger (x>10) samples already exist in Spitzer wide field surveys, but difficult to identify

However, easy identification of a special subclass of z~2 SMGs, - large PAH/FIR ratio (strong 24µm) - large stellar mass (1.6µm-rest bump in SED not AGN-dominated) - ~50deg-2, in particular in SWIRE survey: 50 deg2

With MAMBO/IRAM we have confirmed they are SMGs by detecting

~50-60 SWIRE z~2 starburst ULIRGs/HLIRGs at 1.2mm (Lonsdale+ 2008, Fiolet+ in prep.

Younger+ in prep.)

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CO detection in Spitzer 24µm-bright high-z ULIRGs

• Spitzer 24µm-bright SMGs are obvious targets for CO search, andcomparison with classical SMGs

• However, because of limited mm bandwidth, need for optical spectroscopic redshifts: difficult in ‘redshift desert’ z~1.7-2.0: only a few redshifts determined

• CO search in IRS sources of Yan et al. in progress at PdBI (Tacconi+ in prep., Fiolet+ in prep. + Yan, Lutz, Fiolet, Cox, Sajina, Omont et al. )

Easy detection 8/8 observed sources: - not only on PAH-dominated sources - but on ‘composite’ AGN/starbursts, and even pure silicate- absorption spectra (including radio loud ones)

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.

Srong 10µm silicate absorption

Narrow CO line, radio loud

Fiolet et al. in prep.

Weak 1.2mm MAMBO

Broad CO line

CO in high z QSOs

and

the MBH/Mspheroid relation

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CO in high z QSOs and the MBH/Mspheroid relation

• High continuum 1.2mm detection rate of high-z luminous QSOs (55/200) Omont +.1996, Carilli + 2001, Omont+ 2001, Omont + 2003, Bertoldi+ 2003, Beelen 2004, Wang+ 2007,2008

strong starburst in their host galaxies (practically all the ‘SMGs’ identified at z>4) • CO has been detected in at least 18 high-zQSOs with IRAM-PdBI

• CO linewidth provides Mdyn x sin i

• MBH may be estimated from broad optical lines, or Lbol

• Coppin et al 2008 almost doubled the number of high-z QSOs with CO and MBH

CO(3-2) in J1409+5628

IRAM-30m + MAMBO camera

Beelen+ 2004

Six z~2 QSOs (i=20°) Coppin et al. 2008 Nine z~2-6 QSOs Shields et al. 2006

The ratio MBH/Msph of bright QSOs at z>~2 is larger than the local relation by an order of magnitude

H2 at high redshift

H2 UV absorption lines in damped Lyman-α systems of quasars

Emission of H2 mid-IR rotation lines from warm molecular gas of various origin

Breakthrough of (ISO and) Spitzer on H2 emission in local sources (up to z~0.3)Verma+ 2005, Rigopoulou+ 2002, Valentin & van der Werf 1999, Haas+ 2005: Various ISO resultsRoussel et al. (2007) SINGS nearby galaxiesHigdon et al. (2006) Local ULIRGsOgle et al. ( 2006) Local radio galaxiesJohnstone et al. (2007) Cooling-flow clustersAppleton et al. (2006) Galaxy-size shock in Stephan’s QuintetEgami et al. (2006) IR-luminous brightest galaxy of Zwicky cluster 3146 (z=0.3) Many more unpublished results

However, no H2 rotation line has yet been confirmed at high z

H2 at high z is a major target for future space missions: JWST, SPICA, H2EX, etc.

H2 cooling is fundamental for the formation of the first galaxies from primordial gas H2 (and HD) chemistry in primordial collapses is included in every model of formation of first galaxies

The promises of upgraded IRAM-PdBI (in 2007 PdBI has increased sensitivity by >~2 and baseline by ~2)

Further gain by 2009: larger bandwidth and more bands.

Sensitivity gain in continuum vs 2006 ~4-7 (20-50 in time!)

(+ multi-line, uncertain redshifts, extended baseline…)

Ambitious goals in high-z galaxies in pre-ALMA area:

- Several large programs on SMGs, Spitzer galaxies, AGN, radio sources, etc.

- More exploration of weaker sources: LBGs, BzKs, AGN, etc.

- Multi-line studies

- Deep and ultra-deep fields. Identification of z>5 SMGs

- Systematic follow-up of Herschel (and SCUBA2 sources)

- Etc.

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The promises of upgraded IRAM-PdBI (in 2007 PdBI has increased sensitivity by >~2 and baseline by ~2)

Further gain by 2009: larger bandwidth and more bands. Sensitivity gain in continuum vs 2006 ~4-7 (20-50 in time!) (+ multi-line, uncertain redshifts, extended baseline…)

Ambitious goals in pre-ALMA area: - Several large programs on SMGs, Spitzer galaxies, AGN, radio sources, etc. - More exploration of weaker sources: LBGs, BzKs, AGN, etc. - Multi-line studies - Deep and ultra-deep fields. Identification of z>5 SMGs - Systematic follow-up of Herschel (and SCUBA2 sources) - Etc.

Longer termLonger term::

Further bandwidth increase, up to 16 GHz (correlator)

Multi-beam receivers?

Double the number of antennas?

Ultimate goal:

Make the IRAM Interferometer the leading instrument on the northern hemisphere with 30-50% ALMA sensitivity in the mm range

ALMA50 12m-antennas 6 times the current PdBI collecting areaExcellent site, full submm capabilities (compact array) breakthrough

Comprehensive studies of high-z dusty starbursts in ALMA ultra-deep fields

Earliest starbursts in the Universe with deep fields, ‘gravitational telescopes’ and ALMA-JWST combined projects

Mapping all kinds of star-forming galaxies at all z: dust and mainly CO, C+ and CI lines structure and physical conditions

Blind z determination from CO. Multi-line detections in strong sources

Interstellar chemistry at all redshifts, including isotopomers,

Absorption lines with thousands of background sources ISM in standardgalaxies

Etc.

First ALMA Science in 2010!

JWST MIRI/JWST will have orders of magnitude improvements in sensitivity, spatial and/or spectral resolution compared with Spitzer synergy with ALMA

PAHs and H2 in various types of high z galaxies

SKA (when high bands are implemented)

Will be complementary to ALMA for studying the cold gas, detecting OH and H2O mega-masers and z>2 low-J lines of CO and other molecules

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

Prospects

Herschel bands and SMG SEDs

• Galaxy evolution

- Major evolution steps of the structure and star formation of massive galaxies -The first ULIRGs/HLIRGs at z >5-7- Physics of the most extreme starbursts- Physics of massive galaxy mergers- What is the importance of very cold molecular gas- Special features of interstellar chemistry at high redshift- Evolution of nucleo-synthesis through molecular isotopes- Early galaxy clustering at z>2- Galactic outflows in SMGs- Galaxy size shocks: accretion shocks; cooling flows; galaxy and cluster collisons, - Cooling of primordial gas in first (proto-)galaxies through H2 and HD

• AGN-galaxy connection and BH growth - Parallel evolution of AGN and starbursts. Host galaxies of obscured AGN.- Molecular outflows and AGN feedback. Molecules associated with jets of radio galaxies- Origin of the MBH- relation. Evolution with redshift - Host galaxies of the first super massive black holes - Physics of the central ISM in AGN host galaxies; molecular torus and accretion disk: H2O mega-masers, etc.

• Fundamental physics and cosmology- Possible variation of fundamental constants measured with molecular lines: me/Mp through UV H2 lines, through OH lines- H0 determination from H2O mega-masers- Angular narrow-band correlations in CMB

• Interstellar dust and nano-particules- PAH properties in various galactic environments and redshifts- (Origin of Diffusse Interstellar Bands)

20 Questions to be addressed by observations of molecules in galaxies (at high z)

z Dphot (Gpc)

1000

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20

12

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z= 6

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z=2 -------------------

z=0.5 --------------------

z=0

~ 300 million

~ 3.5 billion

z >~ 20-30Dark agesNo stars, no galaxies

z ~ 6 – 15 ?Reionization - First galaxies - First QSOs

z ~ 4 – 7 :Current frontier- Galaxy and Black-Hole early assembly- End of reionization

z ~ 1.5 -4: - Peak of star formationin massive elliptical galaxies- Peak of QSO activity

z ~ 0.5-1.5 : Final phase of active SF peak in spiral galaxies

Cosmic Times

Molecules are essential ingredient of the interstellar medium

Cooling through molecular lines

- Cold molecular gas: CO

- Warm: H2, H2O, CO primordial gas: H2, HD

- (Heating through PAH photo-ionization)

Molecular masers:

OH, H2O Mega-masers

Connection with interstellar grains building molecular complexity

- H2 formation on grains

- Other chemical processes on grains. Accretion/desorption

- Polycyclic Aromatic Hydrocarbons (PAH) and related species

- Building molecular complexity pre-biotic molecules?

Distance fading

Flux proportional to 1/DL2 (DL = Luminosity Distance)

very large factor

“nearby” “local” high-zgalaxies ULIRGs, QSOs SMGs, QSOs

Redshift 0.001 0.1 2DL

2(Gpc2) 2 10-4 0.2 40

[But additional factor when observing at fixed frequency emission at 0 = (1+z)]

General features at high z

Prospects: SMGs in wide Herschel surveys

Full SEDs, LFIR and Star Formation Rate

Detection of tens of thousands SMGswith full SEDs at maximum of FIR emission

LFIR (and Tdust) Star formation rate Stacking analysis with Spitzer, radio, etc.

Star formation @ z = 2.5

▪ Submm bright Galaxy Population MSB ?

▪ Single or merging LIRGs ?

Greve et al. 2005Greve et al. 2005

Tacconi et al. 2007

(from P. Cox)

Gain in Sensitivity / TimeGain in Sensitivity / Time

FrequencyFrequency 110 GHz110 GHz 140 GHz140 GHz 230 GHz230 GHz 345 GHz345 GHz

LineLine 1.7 / 31.7 / 3 2.7 / 72.7 / 7

Cont 2 GHzCont 2 GHz 2.3 / 52.3 / 5 3.7 / 143.7 / 14

Cont 4 GHzCont 4 GHz 4.5 / 204.5 / 20 7.1 / 507.1 / 50

2008

2008

2007

2007

The ‘dream’

Courtesy K. Schuster

2007 2008 2009 2010 2011 2012 =>

NG-PdB 3

NG-PdB 4

4GHz corr

4GHz corr

NG-PV NG-PV

HEMT-PV HEMT-PV

HERA xer HERA xer

3mm Arr 3mm Arr 3mm Arr

Bolo Bolo Bolo Bolo

SHERA SHERA SHERA SHERA

2SB/8GHz

2SB/8GHz 2SB/8GHz 2SB/8GHz

16Ghz corr 16GHz corr

16GHz corr

50ch FX 50ch FX

The Current 5-year Plan

Early CO detections ….. and their improvements

CO has been detected at high z since 15 yearsFIRAS 10214, Cloverleaf, BR1202-0725, APM 08279+5255, etc.

Significative improvements especially with new capabilities of PdBI

E.g.

- New map of CO(5-4) in BR1202-0725 this rules out lensing andconfirms 2 HLIRGs at ~30-50kpc

- Multiple CO Lines

1.2mm dust map CO(5-4) 3mm spectra

Absorption/emission

- Emission (lines) is affected by factor 1/DL2 exceptional objects

but strength of absorption lines independent of DL “normal” galaxies

- Absorption in many mm lines in a very few systems provide a glimpse at

molecular gas in « ordinary » galaxies at z ~0.2-0.9 (Wiklind & Combes)

Gravitational Lensing Amplification allows gain up to 50

General features

(Kneib et al.) z=2.5 J=3-2 (30K)

APM 08279+5255 (z=3.9) : very hot CO SMM J16359 + 6612 : weak galaxy, multi-image

(Weiss et al.)

J=11-10 (300K)