6 research outputs found
Galaxy orbits and the intracluster gas temperature in clusters
In this paper we examine how well galaxies and intra-cluster gas trace the
gravitational potential of clusters. Utilizing mass profiles derived from
gravitational lensing and X-ray observations, coupled with measured galaxy
velocities, we solve for the velocity anisotropy parameter using the
anisotropic Jeans equation. This is done for five clusters, three at low
redshift: A2199, A496 and A576 and two at high redshifts: A2390 and MS1358.
With X-ray temperature profiles obtained from Chandra and ASCA/ROSAT data, we
estimate the ratio of energy in the galaxies compared to the X-ray gas. We find
that none of these clusters is strictly in hydro-static equilibrium. We compare
the properties of our sample with clusters that form in high-resolution
cosmological N-body simulations that include baryonic physics. Simulations and
data show considerable scatter both these profiles. We demonstrate the future
feasibility and potential for directly comparing the orbital structure of
clusters inferred from multi-wavelength observations with high resolution
simulated clusters.Comment: 9 pages, 6 figures, accepted for publication in MNRA
CfA3: 185 Type Ia Supernova Light Curves from the CfA
We present multi-band photometry of 185 type-Ia supernovae (SN Ia), with over
11500 observations. These were acquired between 2001 and 2008 at the F. L.
Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics (CfA).
This sample contains the largest number of homogeneously-observed and reduced
nearby SN Ia (z < 0.08) published to date. It more than doubles the nearby
sample, bringing SN Ia cosmology to the point where systematic uncertainties
dominate. Our natural system photometry has a precision of 0.02 mag or better
in BVRIr'i' and roughly 0.04 mag in U for points brighter than 17.5 mag. We
also estimate a systematic uncertainty of 0.03 mag in our SN Ia standard system
BVRIr'i' photometry and 0.07 mag for U. Comparisons of our standard system
photometry with published SN Ia light curves and comparison stars, where
available for the same SN, reveal agreement at the level of a few hundredths
mag in most cases. We find that 1991bg-like SN Ia are sufficiently distinct
from other SN Ia in their color and light-curve-shape/luminosity relation that
they should be treated separately in light-curve/distance fitter training
samples. The CfA3 sample will contribute to the development of better
light-curve/distance fitters, particularly in the few dozen cases where
near-infrared photometry has been obtained and, together, can help disentangle
host-galaxy reddening from intrinsic supernova color, reducing the systematic
uncertainty in SN Ia distances due to dust.Comment: Accepted to the Astrophysical Journal. Minor changes from last
version. Light curves, comparison star photometry, and passband tables are
available at http://www.cfa.harvard.edu/supernova/CfA3
HeCS-red: An MMT/Hectospec Survey of redMaPPer-selected Clusters
<p>Galaxy Clusters Accros Cosmic Times : oral presentation</p