Open AccessInfrared observations of gravitational lensing in Abell 2219 with CIRSI
Author(s) -
Gray Meghan E.,
Ellis Richard S.,
Refregier Alexandre,
Bézecourt Jocelyn,
McMahon Richard G.,
Beckett Martin G.,
Mackay Craig D.,
Hoenig Michael D.
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03750.x
Subject(s) - physics , astrophysics , gravitational lens , einstein radius , velocity dispersion , redshift , galaxy , halo , astronomy , william herschel telescope , weak gravitational lensing , spectrograph , spectral line
We present the first detection of a gravitational depletion signal at near‐infrared wavelengths, based on deep panoramic images of the cluster Abell 2219 ( z =0.22) taken with the Cambridge Infrared Survey Instrument (CIRSI) at the prime focus of the 4.2‐m William Herschel Telescope. Infrared studies of gravitational depletion offer a number of advantages over similar techniques applied at optical wavelengths, and can provide reliable total masses for intermediate‐redshift clusters. Using the maximum‐likelihood technique developed by Schneider, King & Erben, we detect the gravitational depletion at the 3 σ confidence level. By modelling the mass distribution as a singular isothermal sphere and ignoring the uncertainty in the unlensed number counts, we find an Einstein radius of (66 per cent confidence limit). This corresponds to a projected velocity dispersion of σ v ∼800 km s −1 , in agreement with constraints from strongly lensed features. For a Navarro, Frenk & White mass model, the radial dependence observed indicates a best‐fitting halo scalelength of 125 h −1 kpc. We investigate the uncertainties arising from the observed fluctuations in the unlensed number counts, and show that clustering is the dominant source of error. We extend the maximum‐likelihood method to include the effect of incompleteness, and discuss the prospects of further systematic studies of lensing in the near‐infrared band.