Surveys with OmegaCAM / VST
KIDS
Koen Kuijken, Leiden
• ESO public survey proposal– Accepted as core survey (May)
• 1700 square degrees• ~ 400 nights• Sloan band survey, median redshift 0.8• Goals:
– Halo structure (weak lensing)– Dark energy (w via ang. power spec; wk lensing)– Galaxy evolution vs. environment– Cluster searches– Higher-redshift quasars than SDSS– White dwarf samples
KIDS: Kilo-Degree Survey
• Overlaps:– UKIDSS– SDSS– 2dFGRS– CFHLS– COSMOS
• 960 sq deg.
2dFGRSSDSS DR2
CFHLS
KIDS(Leiden, Groningen, Munchen, Bonn, Paris, Naples, Imperial, Edinburgh, Cambridge)
• Overlaps:– 2dFGRS– VISTA!
• 720 sq deg.
• Perfect for VLT and AAT, APEX, ALMA
2dFGRS
KIDS(Leiden, Groningen, Munchen, Bonn, Paris, Naples, Imperial, Edinburgh, Cambridge)
Post-PSP field layout
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Integration times, sensitivities
• Use all moon phases, best 80% of seeing
<0.7”
(40%)
0.7-0.85”
(20%)
0.85-1.1”
(20%)
Dark (50%) r’ g’ u’
Grey (15%) i’ i’ i’
Bright (35%) z’ z’ z’
filter Exp time (s)
Medn seeing
(“)
5- 2” AB
u’ 900 1.0 24.8
g’ 900 0.75 25.4
r’ 1800 0.6 25.2
i’ 1080 0.75 24.2
z’ 2520 0.75 23.2
TOT 7200
Optimize for weak lensing
Wide-i
VISTA
KIDS vs. SDSS
Galaxy-galaxy lensing45 sq. deg from RCS survey (Hoekstra, Yee, Gladders 2004)
Galaxy-mass correlation
Halo radii
Halo shapes
KIDS:
7x smaller errors (#pairs)
Good photo-z’s (b/g), spectroscopic z’s (lenses)
Study effect by galaxy type
‘w’ (weak lensing)
• Weak lensing constraints– Lensing effect depends on relative distances
of source and lens
– Measure lensing strength as function of redshift
– Deduce distance as function of redshift– Geometrical test of expansion history: w (5%)– Needs well-controlled photo-z’s!
‘w’ (wiggles)• Use scale of power
spectrum wiggles as standard candle
• Spec redshift surveys: need few 100,000 gals for detection– Photometric redshift
surveys: wash out z information, but many more galaxies!
• KIDS: 67,000,000 gals with r<23.5 (20- fluxes)
• Photo-z accurate to 0.03(1+z) (ugrizYJHK)
– w(z=0) to <15% from KIDS– w(z=1) to better accuracy
z=0.6 z=1.0 z=1.4
Angular waveno. (deg-1)
Photo-z from KIDS/UKIDSS
r<23.5 r<24 r<25 0<z<6 0<z<1.5
Typical SED’s (r~24, redshift~1)
• KIDS ugriz
• UKIDS YJHK
z>6.4 QSOs
• Combine with IR (UKIDSS, VISTA)• Look for IR objects faint in i or z• Find brown dwarfs and high-z QSOs• Expect ~7 @ z>6.4• Many fainter z~5-6
The challenges
• Distributed dataprocessing (ASTRO-WISE!)– Work in a KIDS context
– Central monitoring of calibration
– Quality control is the key:• Some overlaps between teams intercompare• Version control of the procedures, parameters, etc.• Advanced QC tools, incl lensing and photo-z
– Integration with ‘static’ IR surveys (VISTA, UKIDSS)• Image and catalogue level
The challenges II
• Lensing measurements with shapelets
• Photo-z : matched-PSF and matched-aperture photometry for colors
• Shapelets session at 3pm.
SUMMARY
• 1700 sq.deg.:– Equatorial strip = UKIDSS / 2dFGRS area– South Galactic Pole = 2dFGRS field VISTA!!
• 5-band u’g’r’i’z’• Integration time 2hrs per field 440 nts• Use range of seeing conditions, moon phase
• Optimized for weak lensing survey– Other applications: large-scale structure, cluster
evolution, galaxy evolution, …