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, …