Crafoord Symposium, Sept 2005 1
Quasars and Galaxies at the
Highest RedshiftsRichard McMahon
Institute of Astronomy
University of Cambridge, UK
Crafoord Symposium, Stockholm, Sep 2005
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Some Background Information• Main motivation is that objects at high redshift are ‘young’ due to the light travel time.
e.g. we can ‘see’ objects that existed in the Universe before the Earth formed.
• Quasars are the most luminous members of the Active Galactic Nuclei (AGN) family. – MB< -23 ; AGN light exceeds energy from host galaxy stellar light.
• Quasars are intrinsically luminous bright beacons that are easier to observe that ‘normal’ galaxies like the Milky Way. Also ‘illuminate’ intervening material. i.e. IGM
• Energy source is accretion of matter onto a super-massive black hole (107 to 109 Msol ) – Rees, 1984, ARA&A, 22, 471, ‘Black Hole Models for Active Galactic Nuclei’
• Recent observations have shown that most massive galaxies in the local Universe host super-massive black holes. The BH mass is correlated with the stellar bulge mass implies that the formation and evolution of BH and the stellar component in galaxies related (Magorrian et al, 1998; Ferrarese & Merrit, 2000; Gebhardt etal, 2000)
– Rees, 1989, RvMA, 2, 1, ‘Is There a Massive Black Hole in Every Galaxy?’
• Radiative feedback from quasars may play a major role in formation and evolution of galaxies.
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Formation of Solar System: ~5 Billion year ago (5Gyr)
Look Back Time
Redshift
Look back Time
(Gyr)
Age of Universe
0 0.0 13.5 Gyr
0.5 5.0 8.5
1.0 7.7 5.7 Gyr
3.0 11.4 2.1 Gyr
6.0 12.5 915 Myr
8.0 12.8 630 Myr
10 13.0 460Myr
30 13.4 97 Myr
100 13.45 16 Myr
1000 13.46 0.42 Myr
matter, , H0 = 0.3, 0.7, 70
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Highest Redshift History
Galaxies
Quasars
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Highest Redshift History
Galaxies
Quasars
“Gunn”
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The Observational Challenges in surveys for surveys for high redshift objects
• Experimentally difficult because:– Distant objects are very faint.– Rest frame UV radiation is red-shifted to regions of
observed sky spectrum where night-time sky is bright.– Foreground objects are much more numerous so the
experimental selection technique has to be very efficient.
– May be undetectable, in a ‘reasonable’ amount of time using current technology; i.e. may need to wait or develop the technological solution.
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Basic observational principles in optical surveys for higher redshift quasars and galaxies
• UV ‘drop-out’ due to:– Intrinsic or Intervening Neutral Hyrogen
‘Lyman limit’ at 912Å. – Intervening Lyman-a forest (<1216Å)
• Emission line searches based on Lyman-(rest=1216Å) emission from ionized Hydrogen.
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3C273 and z=3.62 comparison
Evolution of HI: 3C273 spectrum from HST/FOC z=0; z=3.6 QSO HIRES/Keck spectrum from M. Rauch
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z=4 Model Quasar +SDSS filter set
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z = 4.90, Schneider, Schmidt,Gunn, 1991, AJ, 98, 1951
z = 5.0, Fan with Guun, Luptonet al. 1999 (SDSS collaboration)
Quasars at z 5
Lyman- Forest
C,N,O,Si .
Lyman-(rest=1216Å)
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z=5 quasar with SDSS filters
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z=6 quasar with SDSS filter set
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SDSS Surveys for z>5 Quasars• Color selection of i-drop out
quasars
– At z>5.5, Lyα enters z-band quasars have red i-z colour
• Technical Challenges:– Rarest objects
• One z~6 quasar every 500 deg2
• Key: contaminant elimination
– Major contaminants are L and T type Brown Dwarfs additional IR photometry
Fan, et al.
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SDSS compilation z>5.7 quasars
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‘Edited’ Quasar compilation (pre-SDSS)
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?
Quasar compilation (now with SDSS)
DR3QSO
50, 000 quasars
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Higher Redshift Quasar Surveys
• Need to work in Infra-Red– Different detector technology
– Sky ‘brightness’ problem
• Two relevant projects– UK Infra Red Deep Sky Survey (UKIDSS)
• WFCAM on UKIRT
• Survey started in May 2005
• Pipeline Data processing centre(Cambridge+Edinburgh)
– VISTA (will be an ESO telescope) (Surveys will start in early 2007?)
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The Night Sky Problem
Waveband Central Wavelength
(Angstroms)
‘Dark’ Sky
Brightness
Redshift Lyman- (1216Å)
B 4400 22.1 2.6
V 5500 21.3 3.5
R 6000 20.4 3.9
I 7500 19.0 5.2
Z 8900 18.0 6.4
Y 10,300 17.0 7.5
J 12,500 16.0 9.3
H 16,500 14.0 12.6
K 22,000 13.0 16.3
Broad band sky gets brighter as you go to redder wavelengths
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z=6 quasar (SDSS filter set)
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z=7 quasar (SDSS filter set)
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z=8 quasar (SDSS filter set)
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z=6 quasar (SDSS filter set + WFCAM)
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z=7 UKIDSS/VISTA Filters
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z=8 UKIDSS/VISTA Filters
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z=9 UKIDSS/VISTA Filters
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z=10 UKIDSS/VISTA Filters
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UK Infra Red Telescope (UKIRT) Wide Field Camera (WFCAM)
3.6m telescope
Mauna Kea, Hawaii
4x2048x2048 Hawaii II arrays
0.4 arcsec pixels
0.21 sq. degs / exposure
• Not contiguous
Filters:
• Z,Y,J,H,K,H2-S(1),Br-g
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UKIRT Wide Field Cameraon Telescope Simulator
Asembled WFCAM cryostat
WFCAM cryostat
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UKIDSS overview5 elements of UKIDSS(5-7 year duration)
Sub-Survey Bands Limit(K)
Area
deg2
nights
Large Area Survey LAS YJHK 18.4 4000 262
Deep Extragalactic Survey DXS JK 21.0 35 118
Ultra Deep Survey UDS JHK 23.0 0.77 296
Galactic Plane Survey GPS JHK 19.0 1800 186
Galactic Clusters Survey GCS JHK 18.7 1600 84
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UKIDSS Science goals
Cool Universe
- Y brown dwarfs
Obscured Universe
- Galactic plane
- reddened AGN, starbursts, EROs
High-redshift Universe
- 4000A break z>1; high redshift galaxy clusters
- Quasars at z>6.5
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Current Status of WFCAM+UKIDSS
• Instrument started commissioning on-sky phase in Nov, 2004
• Science Verification started in April 2005
• UKIDSS Survey started in May, 2005
• Instrument taken off telecope in June, 2005– As planned
• Survey restarted end of Aug, 2005
• Should have 100deg2 of data by end of 2005
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Visible and Infrared Survey Telescope for
Astronomy
• 4-m wide field survey telescope at European Southern Observatory (ESO) , Paranal near the VLT site.
• Initially Infra Red camera only. (i.e. an IR SDSS)
• 75% time for “large surveys”. (e.g. Southern SDSS)
• UK project (consortium of 18 Universities; funded in 1999)– Principal Investigator Jim Emerson (QMUL, London)
• Now part of UK ESO ‘late joining fee’. • Will become ESO facility on completion of construction and
commissioning in late 2006.
Crafoord Symposium, Sept 2005
The ‘Heart of VISTA’; the IR focal plane:• 16 IR arrays, each 2048 x 2048; sparse filled mosaic; • 0.60 deg2 covered by detectors• 0.34 arcsec/pix.
- 6 consecutive ‘offset’ pointings give a continuous region- 1.5deg by 1.0deg i.e. 1.5deg2
- every pixel covered by 2 pointings.
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Comparison of IR camera field sizes
Moon!
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Dome – May 05
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Summer 2005
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Highest Redshift Galaxies
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Searches for higher redshift quasars and galaxies
• UV ‘drop-out’ technique survey technique due to:– Intrinsic or Intervening ‘Lyman limit’ 912Å. – Intervening Lyman-a forest (<1216Å)
• Emission line searches based on Lyman- emission from ionized Hydrogen.
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Highest Redshift History
Galaxies
Quasars
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High Redshift Lyman- emission lines surveys:Astrophysical principles for Success
Partridge and Peebles, 1967, Are Young Galaxies visible?
Minimum Flux limit• Previous surveysin the early 1990’s were based on the simple paradigm of a
monolithic collapse. – expected star formation rates of 50-500 Msol yr-1
– i.e. the SCUBA/FIR Population?• Assume SFR detection limits more appropriate to a slowly forming disc or
sub-galactic units in a halo– i.e. 1-3 Msol yr-1
1.0-2.0 10-17erg s-1 cm-2 at z=4
Minimum Volume • search a comoving volume within which you expect to find the progenitors of
around 10 L* galaxies. (.i.e.~ Milky Way mass)– Local density 1.4±0.2 10-2 h50 Mpc-3 (e.g. Loveday etal, 1992)
minimum is 1000 Mpc3
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Potential Narrow band filter locationsPotential Narrow band filter locations
5.7 6.6 6.9
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z=5.7 for Lyman- z=6.6 for Lyman-
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Basic experimental principle
• Basic principle is to survey regions where the sky sky spectrum is darkest in between the intense airglow. – “Gaps in the OH airglow picket fence”
• Lyman-alpha redshifts of gaps in “Optical-Silicon” CCD regime– 7400 Å; z=5.3– 8120 Å; z=5.7; used extensively– 9200 Å; z=6.6; used extensively– 9600 Å; z=6.9; no results yet
• CCDs have poor QE and sky relatively bright
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Summary of known spectroscopically confirmed z>6.0 galaxies
Narrow Band Surveys• z>6.0; n=13
– from Hu et al. 2002(1), Kodeira et al. 2003(2), Rhoads et al 2004(1), Taniguchi et al. 2005(9)
– z(max)=6.6
Other Surveys• 2 other z>6 emission line selected galaxies
– Kurk et al, 2004(1); Stern etal, 2005(1)
• Ellis etal, lensed search z=7 candidate (no line emission; photo-z) • i-drops Nagao et al, 2004(1); Stanway etal, 2004(1)• Quasars; SDSS n=5 (6.0< z<6.5)
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(observed; Lyman-)=9190Å(rest; Lyman-)=1216ÅRedshift=6.558
Hu, etal, 2002
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z=6.597 galaxy (Taniguchi et al, PASJ, 2005)
9235Ang
redshift 6.597
zAB 26.49
i-z >1.72
Survey:• Subaru 8.2m• Suprimecam 34’ x 27’; 0.2”/pixel• 132Å filter centred at 9196Å • Exposure time; 54,000 secs (15hrs)
Results• 58 candidates• 9 spectroscpoically confirmed with z=6.6
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Composite spectrum of z=5.7 candidate galaxies
z=5.7; note asymmetry
z=1.2; note resolved doublet
z=0.6; unresolved and 4959 line[OIII]4959
Lyman-(1216Å)
[OII](3727Å)
[OIII](5007Å)
n=18 galaxies
Hu, Cowie, Capak, McMahon, Hayashino, Komiyama, 2004, AJ, 127, 563
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z~5.7 Lyman-(1216Å) emitters
Observed wavelength (Angstroms)
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z~1.2 [OII]3727 doublet emitters
Observed wavelength (Angstroms)
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The Night Sky Problem
Waveband Central Wavelength
(Angstroms)
‘Dark’ Sky
Brightness
Redshift Lyman- (1216Å)
B 4400 22.1 2.6
V 5500 21.3 3.5
R 6000 20.4 3.9
I 7500 19.0 5.2
Z 9000 18.0 6.4
J 12,500 16.0 9.3
H 16,500 14.0 12.6
K 21,000 13.0 16.3
Broad band sky gets brighter as you go to redder wavelengths
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Narrow band searches in the near Infrared
• OH lines contribute 95% of sky background in 1.0-1.7m range;– i.e. 20 times the continuum emission.
• Filters need to have widths of 10Å or 0.1% to avoid OH lines.– c.f. 100Å in the optical
• NB. Narrower band means you solve a smaller redshift range i.e. volume so wide field is needed.
Some of the technical issues– Filter design and manufacture– Field angle shift of central wavelength– Out of band blocking;
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Infrared OH Sky Observations: Mahaira etal, 1993, PASP
GOOD NEWS
The 1.0 to 1.8 micron IR sky is very dark between the OH lines which contain 95% of broad band background.
THE NOT SO GOOD NEWS
The narrowest gaps are narrower than in the optical; filter widths of 0.1 per cent are needed compared with 1% filters in optical.
THIS IS A TECHNICAL CHALLENGE WE HAVE SOLVED; see Ian Parry’s talk
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Sky emission and absorption spectrum around 1.06 and 1.33 microns showing DAZLE filter pairs for Lyman at z=7.7, 9.9; other gaps are at 8.8, 9.2
DAZLE – Dark Age Z Lyman ExplorerDAZLE – Dark Age Z Lyman Explorer
McMahon, Parry, Bland-Hawthorn(AAO), Horton et alMcMahon, Parry, Bland-Hawthorn(AAO), Horton et al
IR narrow band imager with OH discrimination at R=1000 i.e. 0.1% filter
FOV 6.9 6.9 arcmin 2048 Rockwell Hawaii-II 0.2”/pixel
Sensitivity: 2. 10-18 erg cm-2 sec-1(5), 10hrs on VLT i.e. ~1 M yr-1 at z=8;
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DAZLE: Digital state
• 3D CAD drawing of DAZLE Final Design on VLT UT3(Melipal) Visitor Focus Nasmyth Platform.
• UT3 optical axis is 2.5m above the platform floor
• grey shading shows the DAZLE cold room(-40C)which is 2.5m(l) x 1.75m(w) x 3m(h).
• Blue Dewar at top contains the 2048 x 2048 pixel IR detector
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Dazle in Cambridge Laboratory(Aug 2005)
Refridgeration ‘Box’
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Highest Redshift History
Galaxies
Quasars
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?
Quasar compilation (now with SDSS)
DR3QSO
50, 000 quasars
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Some Future ground based surveys for higher redshift Galaxies and Quasars
z>7 galaxies• Dark Ages ‘Z’ Lyman- Explorer (DAZLE) on the VLT (to start Jan
2006)
z>7 quasars
• UKIDSS: UK Intra-Red Deep Sky Survey (started May 2005; 5 year survey project)– UKIRT (Hawaii) + WFCAM – ESO members; Public Access from late 2005); Worldwide +18month
• VISTA Surveys (to start early 2007)
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FINAL SLIDE