Mass and Light distributions in Clusters of Galaxies - Henry A ...

Abstract
Clusters of galaxies are the most massive bound objects in the Universe.
Their deep potential wells deflect the light of background galaxies creating
lensed galactic images. Gravitational lensing can be used as a diagnostic tool
to determine the mass profiles of clusters. In the weak lensing regime, the
measurement of the cluster mass can be badly compromised by the presence
of unlensed foreground and cluster members which dilute the true lensing
signal. In this thesis, I study galaxy clusters mass and light properties via
weak lensing observations. In the first part, I show the importance of carefully
isolating background galaxies from foreground and cluster galaxies for a clean
weak lensing measurement, avoiding dilution of the signal. The dilution is
in turn used to determine the light properties of the clusters. The second
focus of the work shows the use of the detailed measurements to determine
the increment of the weak lensing signal with redshift, which is an important
cosmological probe.
Following an introduction to the field of galaxy clusters and gravitational
lensing in Chapter 1, I demonstrate my methods and results for four massive
galaxy clusters in Chapters 2 and 3. In Chapter 2 I study cluster A1689
(z = 0.183) with deep Subaru imaging in the V and i ′ bands, using the
color-magnitude diagram and the weak lensing signal to derive the luminous
properties of cluster galaxies. The tangential distortion of galaxies bluer
than the E/S0 sequence falls rapidly toward the cluster center relative to the
lensing signal of the background galaxies redder than the sequence. I use
this dilution effect to derive the cluster light profile and luminosity function
to large radius, with the advantage that no subtraction of far-field background
counts is required. The light profile has a constant declining slope
, d log(L)/d log(r) = −1.12 ± 0.06 to the limit of the data, r < 2 h −1 Mpc,
whereas the mass profile steepens continuously with radius, such that M/L
peaks at an intermediate radius, r ∼ 100 h −1 kpc. The cluster luminosity
function has a flat faint-end slope, α = −1.05 ± 0.05, independent of radius
and with no faint upturn to M i ′ < −12. I show that the bluest objects are
V