UKIDSS SciVer Products E. A. Gonzalez-Solares (IoA, Cambridge) (+CASU) UKIDSS SV Meeting – 18/08/05 RoE

Topics 1.Data summary 2.Completeness & reliability 3.Astrometry accuracy from overlaps 4.Flux accuracy from overlaps 5.Stacking 6.Colour-colour diagrams using other surveys

Data Summary: coverage Using DXS data J and K band MSB: 25 dithers of 2x2 interleaved frames of 5 s exposure each, i.e., 500 s total exp time. High repeatability: up to 20 MSBs of the same pointing Lockman and EN1 fields well covered at other wavelengths

Seeing* *(as measured from the stacked interleaved frames)

Seeing J bandK band Chip 1Chip 2 Chip 3 Chip 4 Chip 1Chip 2 Chip 3 Chip 4

Magnitude limit* (500 s) *(this is the 5  detection limit in an aperture of 2” radius) Chip 1Chip 2 Chip 3 Chip 4

Completeness & Reliability Simulations performed using ARTDATA in IRAF 1000 stars in chip 1 – simulation repeated until good stats Stacked superframe interleaved 2x2 (i.e. pixel of 0.2 arcsec) Exposure time 500 s. Seeing ~ 1” Aperture magnitudes in 2” diameter

Simulations performed using ARTDATA in IRAF 1000 stars in chip 1 – simulation repeated until good stats Stacked superframe interleaved 2x2 (i.e. pixel of 0.2 arcsec) Exposure time 500s. Seeing ~ 1” Aperture magnitudes in 2” diameter Completeness & Reliability

K band stacked superframe (interleaved) K band stacked (non interleaved) Without interleaving -> completeness ~0.3 mags deeper

Completeness & Reliability Reliability J bandReliability K band Completeness measure the fraction of objects found but does not tell us about their measured properties. Reliability tell us the fraction of objects with correct fluxes in each bin (taking into account flux errors).

Simulation of a high density field with stars Expect lower level of completeness and reliability Completeness & Reliability

Star/Galaxy separation How good we can classify the objects… Selected only objects with class_star=-1

Astrometric accuracy Astrometric comparison between overlapping MSBs Magnitudes K<17 Overall astrometry accuracy better than 0.04 arcsec

Flux accuracy Comparison of fluxes of same objects measured in different MSBs Only bright (K<17) objects, point-like and extended (from catalogue class) (poor observing conditions)

Magnitudes good within 3%

Stacking Stacking of 80 min of J data and 2 hours of K data Magnitude limits J=21.7, K=20.8 DXS aim is K=21 and J=22.5.

Colour Magnitude Diagram Blue: point-like Red: Extended (from catalogue classification)

Colour Magnitude Diagram

Datasets useful to correlate with Optical: –WFS: U, g, r, i, Z – EN01 –Subaru: I – EN01 –KPNO: U, g, r, i – Lockman –Several deeper imaging over small regions (including HST). Spitzer: 3.5, 4.6,5.8, 8.0, 24, 70, 160 µm

Colours* : K-[3.6] vs J-K *SED models by Polleta et al 2005 (in prep)

Colours : K-[3.6] vs [3.6]-[4.5]