Mass and Light distributions in Clusters of Galaxies - Henry A ...
Mass and Light distributions in Clusters of Galaxies - Henry A ...
Mass and Light distributions in Clusters of Galaxies - Henry A ...
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Weak Lens<strong>in</strong>g Dilution <strong>in</strong> A1689<br />
Note that the peak value is rather large, equivalent to M/L B ∼ 400h(M/L) ⊙<br />
<strong>in</strong> the restframe B-b<strong>and</strong> <strong>of</strong>ten used as a reference, but the mass <strong>of</strong> A1689<br />
is at the extreme end <strong>of</strong> the cluster population, M ∼ 2 × 10 15 hM ⊙ (Broadhurst<br />
et al. 2005b), <strong>and</strong> given the general tendency <strong>of</strong> M/L to <strong>in</strong>crease with<br />
<strong>in</strong>creas<strong>in</strong>g mass, from galaxies through groups to clusters, we may not be<br />
surprised to f<strong>in</strong>d the peak to somewhat exceed the typical range for clusters,<br />
150 − 300hM/L B ⊙<br />
(Carlberg et al. 2001). The general pr<strong>of</strong>ile <strong>of</strong> M/L is<br />
similar <strong>in</strong> form to that derived for CL 0152-1357 by Jee et al. (2005) based<br />
on a careful weak lens<strong>in</strong>g analysis <strong>of</strong> recent deep ACS images.<br />
We have also constructed a pr<strong>of</strong>ile <strong>of</strong> the total mass to stellar mass M/M ∗<br />
ratio (red curves <strong>in</strong> Fig. 2.18 <strong>and</strong> Fig.2.19). This is arguably a more physically<br />
useful <strong>in</strong>dicator <strong>of</strong> the relationship between dark <strong>and</strong> lum<strong>in</strong>ous matter<br />
compared to the ratio <strong>of</strong> M/L, because the starlight can be strongly <strong>in</strong>fluenced<br />
by the presence <strong>of</strong> relatively small numbers <strong>of</strong> lum<strong>in</strong>ous hot stars. To<br />
calculate M/M ∗ we make use <strong>of</strong> the color pr<strong>of</strong>ile derived <strong>in</strong> § 2.7, <strong>and</strong> an empirical<br />
relationship between color <strong>and</strong> the ratio M ∗ /L for stellar populations<br />
established for local galaxies <strong>in</strong> the the SDSS survey by Bell et al. (2003). The<br />
slope <strong>of</strong> the projected stellar mass pr<strong>of</strong>ile, d log(M ∗ )/d log(r) = −1.15 ± 0.13,<br />
derived this way is slightly steeper than the lum<strong>in</strong>osity pr<strong>of</strong>ile, as expected.<br />
The observed relation we derive this way is somewhat flatter than for M/L<br />
<strong>and</strong> the mean contribution by mass for stars is about 1.25% for this cluster<br />
<strong>and</strong> similar to a mean value <strong>of</strong> ∼ 2% derived from a carefully selected sample<br />
<strong>of</strong> local clusters by Biviano & Salucci (2006).<br />
2.10 Cluster mass pr<strong>of</strong>ile<br />
We use the comb<strong>in</strong>ed distortion <strong>in</strong>formation obta<strong>in</strong>ed from the ACS <strong>and</strong> Subaru<br />
imag<strong>in</strong>g, as described above (Fig. 2.6) <strong>and</strong> compare with models for the<br />
mass distribution. We have improved on our earlier distortion measurements<br />
made with Subaru, with the addition <strong>of</strong> the background blue galaxy population<br />
def<strong>in</strong>ed here, so that the significance <strong>of</strong> the distortion measurements<br />
is somewhat greater than our earlier work which was based only on the red<br />
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