Strongly lensed high redshift galaxies identified in Herschel wide surveys Prospects for ALMA observations
Alain Omont (IAP, CNRS and Université Paris 6)
On behalf of the H-ATLAS and HerMES Teams and the IRAM Team
Strongly lensed high redshift galaxies identified in Herschel wide surveys Prospects for ALMA observations
Using gravitational magnification for studying Ultra-Luminous InfraRed Galaxies (ULIRGs) at high redshift
• Introduction - (Local ULIRGs) - High-z ULIRGs and the magic of the submm window - Mm/submm continuum & line studies of high-z ULIRGs: the promise of ALMA - Herschel wide surveys multiply by 100 the number of high-z ULIRGs identified - Herschel lenses increase the sensitivity by ~10 for studying high-z ULIRGs
• Herschel high-z strong lenses- Early studies of Herschel lenses- Prospects and Current status
• Example: H2O mm/submm lines at high z in Herschel lensed galaxies
• Examples of ALMA programs possible with Herschel high-z lensed galaxies
Arp 220: prototype of ULIRGs • LIR = 1.4×1012 Lo • thought to be in the final stage of merging• radio & NIR imaging double nuclei projected separation ~300 pc• MH2 ~ 1010 Mo within central kpc in accord with simulations of galaxy mergers
M 82: prototype of LIRGs, • 3.2 1011 Lo• Strong mid-IR PAH emission, even in strong outflow• Most high-z ULIRGs seem to have IR SEDs similar to M 82
Arp 220 M 82
ULIRGs observed with the WFPC2 of the HSTat optical wavelengths. Many of these ULIRGs are merging galaxies
See Steve Lord’ s talk
SMGs: strongest starbursts in the UniverseImportant players of star formation at z >~ 2
ULIRGs are much more numerous at high redshift than locally factor close to 1000 at z=2
Revealed by SCUBA surveys at 850µm (+ MAMBO at 1.2mm AzTEC, LABOCA, BOLOCAM) « Sub-Millimeter Galaxies » (SMG)
Easy detection of dust FIR emission through « inverse K-correction », same flux observed at l ~ 1mm from z ~ 0.5 to 10
from Bertoldi, Voss, WalterLFIR(Lo) = 4x1012 S1.2mm(mJy)
FIR emission of cold dust (Td ~ 30-40 K) :
- steep submm spectrum - compensates for distance - Sn practically independent of z from z ~ 0.5 to 10
Effect often known as « negative K correction »
Redshift degeneracy
Dust detection: The Magic of the high-z submm window
SPIRE
ULIRGs and Star Formation at high-z• ULIRGs dominate star formation at z>~2• SMGs (and Herschel/SPIRE) sources are luminous ULIRGs They provide only a small fraction of total star formation
>ULIRGs > z=2 SMGs SPIRE sources
Lindner+ 2011 Le Floch+ 2005
1.2mm
Total
Spirals
LIRGsULIRGs
SMGs: strongest starbursts in the UniverseImportant players of star formation 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
Giant starbursts at the peak of elliptical formation z ~ 2-3 1-4
A few 1012Lo: at least ULIRGs ~1 per 3-5 arcmin2
Most exceptional HLIRGs 1013Lo ~1 per 50-100 arcmin2
nothing equivalent in the local Universe probably in most massive DM halos progenitors of BCG/cD galaxies of clusters?
Only ~1000 SMGs provided by SCUBA/MAMBOASTEC/BOLOCAM surveys ( <~ 1-2 deg2)
Herschel surveys are detecting several 105 SMGs
IRAM-PdBI
Mm/submm studies of high-z ULIRGs
- High extinction makes optical/NIR studies of high-z ULIRGs hardly feasible- Extinction is practically negligible in mm
In addition to continuum, molecular mm lines are key tool for high-z ULIRG studies
CO lines are the strongest and most important (but C+):They give the mass of molecular gas MH2
(Rotation) velocity profileSpatial extension of molecular gas dynamical massRotation line ladder (SLED) TK + nH2 multi-TK gas
AGN excitation of high-J lines HCN is the best tracer of dense gas and star formation
H2O traces warm, dense gas and very strong IR
C+ (very strong, very high freq.) traces diffuse, (partially) ionized gas
IRAM-PdBIIn addition to continuum, molecular mm lines are key tool for high-z ULIRG studies
CO lines are the strongest and most important (but C+):They give the mass of molecular gas MH2
(Rotation) velocity profileSpatial extension of molecular gas dynamical massRotation line ladder (SLED) TK + nH2 multi-TK gas
AGN excitation of high-J lines HCN is the best tracer of dense gas and star formation H2O traces warm, dense gas and very strong IR C+ (very strong, very high freq.) traces diffuse, (partially) ionized gas
ALMA
PdBI CO high-resolution study of SMGSTacconi et al. 2008
Compact post-merger Resolved pre-merger
HERSCHELSee Steve Lord’ s talk
Space Observatory, ESA (+NASA)
3.5m dish
3 instruments:5
• Camera-photometer, FTS- SPIRE 250-500µm wide surveys 1000 deg2
~4 x 105 high-z ULIRGs- PACS 70-160µm
• Heterodyne- HIFI
May 2009 January-March 2013
Herschel high-z extragalactic wide surveys
H-ATLAS 550 deg2
HerMES 70 deg2 deeper + 270 deg2 shallow
Both mostly SPIRE (250, 350, 500µm) close to confusion limit
Plus • PACS surveys: smaller areas, deeper• HLS: lensing clusters,• 100 deg2 overlap with SPT (South Pole Telescope)• AKARI/NEP ?• etc.
H-ATLASPIs Eales & Dunne
550deg2
The HerMES surveySPIRE Guaranteed Time; PIs Seb Oliver & Jamie Bock
~900h (Multi-level Deep fields ~5 deg2 )
Wide fields
• ~70 deg2 Practically all Spitzer wide fields: SWIRE (Lockman, ELAIS-N1, ELAIS-N2, XMM-LSS, CFDS, ELAIS-S1) + FLS, Bootes, AKARI-ADFS
• practically all observed • mostly SPIRE (250, 350, 500µm) practically at the confusion limit
• somewhat deeper than H-ATLAS multi-l ancillary data
+ HeLMS 270 deg2 shallow, equatorial, RA ~ 0
without optical IDs with optical IDsHerschel surveys revolutionize
the field of high-z submm galaxies
Several 105s high-z sources
Half H-ATLAS sources have z>1(inverse K-correction)
All high-z sources are ULIRGswith SFR > 300 Mo/yr
and LFIR > 1012 Lo
Some Herschel/SPIRE sources are warmer than SMGs and not detected at ~1mm
Some cold SMGs not detected by Herschel
Lapi et al. 2011
Lapi et al. 2011
Herschel lenses increase the sensitivity by ~10 for studying high-z ULIRGs
The power of gravitational lensing
Since 20 years lenses mark the frontier of mm radioastronomy
Gravitational lensing
« Einstein Cross » Einstein ring QSO (radiogalaxy) Cloverleaf QSO
X-Ray optical
Unlensed SMGS Neri+ 2003
Lensed Cloverleaf
Thanks to magnification factor µ ~11- CO lines are more intense by ~10 than in unlensed SMGs- High S/N HCN & HCO+ lines are detectedwhile they are out of reach in unlensed SMGs with current PdBI sensitivity
The power of gravitational lensing
Cloverleaf
The power of gravitational lensingSince 20 years lenses mark the frontier of mm radioastronomyRowan-Robinson’s galaxy
FIRAS10214 Swinbank’s Eyelash SMMJ2135
APM08279+5255
Herschel lenses increase the sensitivity by ~10 for studying high-z ULIRGs
Herschel high-z strong lenses
Early studies of Herschel lenses
Prospects and Current status
Negrello et al. 2010
Submm wide surveys are ideal for finding high-z lenses
- High-z submm sources are very strong (‘inverse K-correction’)
- Very steep unlensed counts
Almost half of the strongestSPIRE sources are high-zlenses
Very easy to identifyfrom local galaxies (+ blazars)
radio
unlensed
lensed
Local galaxies
(faint)
Early studies of Herschel high-z strong lenses
1. H-ATLAS SDP Field Negrello et al. Science 2010
~14.4 deg2 7000 sources
Brightest 500µm sources:11 sources with S500μm > 100 mJy4 nearby galaxies (z<0.05), + 1 blazar, 1 galactic blob
5 high z candidates confirmed redshifts z = 1.5 – 3.4
SED of lens candidates in H-ATLAS S DP fieldclear cases of double-source SEDs
z~0.2-0.8 elliptical galaxy + high-z ULIRG
Negrello+2010
ID15.141
Submm photometric redshiftsRatios S250/S350 & S350/S500
plus a template such as Arp220 submm z-phot
Good agreement with zCO
for 6 sources with zCO
A good value of z-phot is important for searching zCO
with a limited bandwidthAdding 1.2mm MAMBO flux helps: S1.2mm=10-40mJyDannerbauer+
Measuring zCO at z>~4 is difficult with Zspec, impossible with Zpectrometer PdBI, EMIR or CARMA blind searche.g. ID15.141
Zspec Lupu et al. to be submitted to ApJ
Redshifts have been confirmed with PdBI or CARMA interferometers
Best, highest-z H-ATLAS SDP lenses
Sub-Millimeter Array images at 870µmExtended images: gravitational arcs on top of the lens galaxy
Red 870µm contours on top of I Keck image
Extended images: gravitational arcs on top of the lens galaxy
from Negrello ESLAB2010
Idealized gravitational arcs
S. Serjeant
(faint)
Early studies of Herschel high-z strong lenses
2. H-ATLAS prominent z=4 lens ID15.141 Cox et al. 2011
Z = 4.24
(faint)
Early studies of Herschel high-z strong lenses
3. HerMES SDP exceptional lens
HerMES Lockman-01 = HLSW-01Very wide image
Riechers et al. 2011 PdBI, SMA & CARMA mapsK. Scott et al. 2011 Z-Spec spectroscopyGavazzi et al. 2011 lensing modeling
HerMES Lockman-01 = HLSW-01 PdBI + SMA Riechers+ 2011
Prospects for studies of Herschel high-z strong lenses
• A simple extrapolation of 5 lenses in 15 deg2 H-ATLAS SDP yields ~200-300 similar lenses in total in ~1000 deg2 Herschel surveys
• This number may be much increased by lowering the flux limits, e.g. by a factor >~5 for S(350µm) > 80 mJy
• Work is in progress for extensions of lens identifications:- larger areas- lower flux limits- use of additional data, e.g. NIR surveys for identifying the
deflectors
• One may thus expect thousands of Herschel high z lenses,including ~50-100 lensed sources in which the magnification is > 10
Prospects for studies of Herschel high-z strong lenses
The two main applications of Herschel lenses should be:
1. Deep studies of high-z lensed sources (see below e.g. for H2O, ALMA )
2. Studying the evolution of dark matter halo of the deflectors - Most deflectors are massive spheroids with a few spirals and groups
- Redshifts of the deflectors are found mostly between z = 0.2 and 1, with a significant fraction at z>1. This is much higher than for the deflectors of optical lenses
- A major goal is thus to check the evolution of dark-matter halos at z~ 1
In addition Herschel wide surveys are important tools for cosmological studies, through map fluctuation studies, etc. (see e.g. Cooray+ 2010)
Work in progress on Herschel high-z strong lenses
Enormous amount of work for identifying and following up hundreds of Herschel lenses
2/3 of observations carried on; half of them well processed
Several hundreds: identified candidates planned HST snapshots
Several tens: 1mm observations PdBI next Winter CO redshifts PdBI next Winter Identifications of deflector candidate with z-phot
About 10: High-resolution mm/submm images PdBI next Winter High-resolution optical/NIR (HST, Keck-AO…)
Spectroscopic redshifts of deflectorLens models
About 5: Other lines than CO (and CI): H2O, C+ PdBI next Winter
Multi-line CO SLED IRAM-30m next Winter
H2O mm/submm lines at high z
- Strong H2O emission in the nuclei of local ULIRGs
- H2O in high-z lensed QSOs
- H2O in Herschel lenses
- Prospects
H2O is one of the most abundant molecules in the ISM
- In cold clouds practically all in ice on grainsabundance up to ~10-4, 1/3 of total oxygen
- Desorbed into the gas in hot cores
No confirmed detection of H2O at high z prior to 2011
H2O in local ULIRGs (Mrk 231)
H2O is one of the most abundant molecules in the ISM
- In cold clouds practically all in ice on grains abundance up to ~10-4, 1/3 of total oxygen - Desorbed into the gas in hot cores
But it is very difficult to observe in the gas:
- Needs to be desorbed from the grains - At low z: H2O lines are completely absorbed by water in the Earth atmosphere space - At high z: H2O lines are very weak without lensing amplification
No confirmed detection of H2O at high z prior to 2011
Strong H2O emission in the nuclei of local ULIRGsCompact single- double-nuclei (+AGN) of major mergers
see talks by D. Sanders and others
Prominent FIR H2O absorption lines in local ULIRGs (+AGN) such as Arp220 , Mrk231… (ISO; Herschel Gonzalez-Alfonso +2011)
Evidence for high H2O abundance from H218O , and high 18O/16O ratio
(Gonzalez-Alfonso+2011, Martin+2011)
Herschel/SPIRE: spectacular submm emission linese.g. Mrk231 (obscured QSO) (van der Werf+ 2010) - Several H2O lines up to Eexc~600K- Strong lines comparable to CO (very different from M82 and PDR)- Plus high-J CO (strong), [CI], H2O+, OH+, HF, CH+, [NII], etc.
Van der Werf et al. 2010
GHz
Gonzalez-Alfonso+ 2010
SPIRE van der Werf+ 2010
CO J 15 14 13 12 11 10 9 8 7
Strong H2O emission in the nuclei of Mrk 231
Prominent FIR H2O absorption lines in local ULIRGs (+AGN):Arp220, Mrk231 Evidence for high H2O abundance from H2
18O , and high 18O/16O ratio
Herschel /SPIRE: spectacular submm emission linese.g. Mrk231 (van der Werf+ 2010) - Several H2O lines up to Eexc~500K, - Strong lines comparable to CO (very different from M82)- Plus high-J CO, [CI], H2O+, OH+, HF, CH+, [NII], etc.
Implications (Gonzalez-Alfonso+ 2010):- Lower levels may be excited by warm dense gas (~100K, ~106cm-3), with high H2O abundance (>~10-6)
- Higher levels imply intense FIR excitation in few 100s pc- Possible role of shocks, AGN (XDR), CR excitation, but unclear
High z: Many objects similar to MrK231 are expected, but very few detections of H2O are reported up to now Herschel lenses
H2O lines must be easily detectable in many Herschel lenses
• Herschel SPIRE 250/350/500 µm surveys (~1000deg2) are ideal to find rare, high-z strongly lensed SMGs Negrello+2010 • Only 1-2 deg2 observed by ‘traditional’ SCUBA/MAMBO/ASTEC surveys practically no strong lens
• Breakthrough by Herschel surveys hundreds of strong high-z lenses (while only ~6 found before Herschel)
• Unique opportunity for deep studies of high-z mm/submm linesAs performed with classical mmlenses, e.g. the Cloverleaf
• H2O line intensities are a significant fraction of that of CO lines in Mrk 231. They should be easily detectable in strongly lensed similar high-z ULIRGs
Negrello+ 2010
PdBI detection of H2O in H-ATLAS SPD-17b z = 2.305
ZSpec H2O tentative detectionLupu et al. 2011
H-ATLAS SPD-17 identified as lensed ULIRG by Negrello+ 2010Complex HST image (Negrello+ in prep.)Rich spectrum: high-J CO z=2.308 Lapp~4 1013LoPossible H2O 202-111 at 299GHz: seems very strong but noisy (2.6s)
PdBI detection of SPD-17b at 299GHz z=2.3Omont et al. 2011 A&A 530, L3
GHz
km/s
Compact D-conf.
Continuum 32+/-2 mJy
(+ extended A,B Confs.not yet fully processed)
Detection of H2O in H-ATLAS G12-29 z= 3.3One of the strongest Herschel lensed sources: S500µm = 285 mJy, even detected by Planck
Z-Spec/APEX spectrum (Lupu+ in prep.) impressive high-J CO lines up J=10-9 (11-10?) z~3.254 Confirmed with Zpectrometer 3.2588±0.0012
Strong line at 273.3GHz H2O 321-312
needed to be confirmed
273 GHz is not currently observable with PdBI, but another strong H2O line is expected at 231.96 GHz (in a bad ZSpec channel)
(H2O is also tentatively detected at 257.7GHz)
PdBI Detection of H2O 202-111Preliminary results (R. Neri)
• C-conf., 6 antennas• Very robust detection
• I ~ 5 +/-0.55 Jy.km/s ~ I(SPD.17b) / 2 ~same luminosity
• 231.96 GHz z = 3.260• Width 680 km/s
Lensed images of G12-29
Multi-galaxy deflector
The K image is very different from ~1mm images
Keck K-band SMA 870µm PdBI 1.3mm continuum + H2O
5 other detections of H2O in high-z sources(at IRAM 2011, except Cloverleaf)
• Multi-line detection in the lensed QSO APM08279+5255 z = 3.9 van der Werf et al. 2011, plus Lis et al. 2011, Bradford et al. 2011
• Zspec tentative detection in the lensed QSO Cloverleaf z= 2.56 Bradford et al. 2009
• Plus recent detections of two other Herschel sources and one QSO
Inferred conclusions for H2O in high-z ULIRGs
The detection of H2O implies special excitation conditions in an intense IR field and a warm dense gas, similar to Mrk 231 with higher luminosity
The high H2O/CO ratio makes it unlikely that the H2O emission originates in classical PDRs
But all the evidence suggests that SDP.17b, G12-29 and Mrk 231 have similar properties, with warm, dense gas and strong IR field ( plus possibly shocks, XDR, CR).
However, this needs to be confirmed by higher excitation lines of H2O ALMA
Prospects for H2O studies in Herschel lenses (with ALMA)
(Full) ALMA will easily detect H2O multi-lines in hundreds of Herschel high-z lenses (filler in ALMA Cycle 0 for 3 sources, and search for H2O in 8 additional H-ATLAS lenses is scheduled at 18 PdBI next Winter)
Together with high-J CO lines, H2O lines will provide rich information about the conditions in the dense warm ISM of the compact merger nucleiof SMGs, and their strong FIR, plus shocks, X Rays, Cosmic Rays, etc.
The full ALMA sensitivity will also allow detection of weaker lines or details of H2O lines such as:
- Absorption lines - Outflows - Isotopologues H2
18O, H217O (possibly HDO, D2O?)
- Other molecules detected in Mrk 231: OH+, H2O+ (related to H2O and allowing diagnostic of XDR chemistry), HF, etc. - And many other molecules allowing, together with H2O, further checks of the ISM of merger nuclei for their physical conditions, chemistry, dynamics, AGN influence, etc.
ALMA
50 x 12m dishes+ ACA array 7m dishes
Prospects, strategy and questions for ALMA• There will be 100’s of strongly lensed sources available for ALMA - Object selection in function of goals
- Systematic studies of specific classes if populated enough
- Muli-l studies: EVLA, JWST, HST, etc.
This would allow in particular to populate rare classes of objects for comprehensive ALMA studies, e.g.
- highest redshifts, z>4 even z>5 - strong AGN of various types - radio loud - LIR> 1013Lo, LIR<1012Lo - H2O mega-masers - cluster lensing - extremely strong amplification, etc.
• Studies of the lensing galaxies through ALMA observations will have important cosmological applications
But detailed lensing models are needed for inferring properties of lensed SMGs
• Anyway, ALMA will have a fantastic time with such sources!
Examples of ALMA programs possible with Herschel lenses
• Blind CO redshift determination and the highest redshifts - Finding redshifts for 100’s sources remain a major issue
- Searching for z~>~6 objects (lensed or not) is specially important
• ALMA high-resolution imaging of strong lenses - ALMA can do that in the continuum, CO lines & C+line (+H2O lines, etc.)
- Structure of the ISM and SF; AGN molecular torus - Dynamics: rotation, Mdyn, mergers, outflows, etc.
• High sensitivity molecular (and atomic) spectroscopy - H2O, HCN...: diagnostic
- etc.: chemistry, isotopologues
• Golden objects with two background sources lensed by the same galaxy, making possible cosmological tests that are independent of the mass of the lens.
ALMA Cycle 0 Projectson Herschel high-z strongly lensed galaxies
Accepted (top 10%)
- 0.53’’ resolution snapshot mapping at 870µm of30 HerMES lenses (Riechers et al.)
- Comprehensive study of a z=1 H-ATLAS lens (Orellana et al.)
Fillers- Multi-line H2O study in the three high-z H2Osources visible from ALMA (van der Werf et al.)- Dense gas tracers (HCN,HCO+ …) in H-ATLAS SDP sources (Lupu et al.)- High-resolution mapping of a cluster-lensed high-z source(Egami et al.)
Summary
• Herschel surveys will observe ~1000 deg2
• First lens identifications and intensive follow-up confirm that one may expect hundreds of lensed SMGs with magnification ~5-10
Unique legacy for mm/submm studies of molecular gas in high-z major starbursts (ULIRGs even below the confusion limit)
• Effective sensitivity increase by ~10 for ALMA, IRAM/NOEMA etc. for studies of high-z ULIRGs
• H2O is an important tracer of compact, dense warm, strong-IR nuclei of SMGs, especially obscured AGN
• New step in studying high-z lensing and their dark matter structures at higher deflector redshift up to z >~ 1
• But needs much follow-up and high-quality lensing modeling