205 research outputs found
Optical Synoptic Telescopes: New Science Frontiers
Over the past decade, sky surveys such as the Sloan Digital Sky Survey have
proven the power of large data sets for answering fundamental astrophysical
questions. This observational progress, based on a synergy of advances in
telescope construction, detectors, and information technology, has had a
dramatic impact on nearly all fields of astronomy, and areas of fundamental
physics. The next-generation instruments, and the surveys that will be made
with them, will maintain this revolutionary progress. The hardware and
computational technical challenges and the exciting science opportunities are
attracting scientists and engineers from astronomy, optics, low-light-level
detectors, high-energy physics, statistics, and computer science. The history
of astronomy has taught us repeatedly that there are surprises whenever we view
the sky in a new way. This will be particularly true of discoveries emerging
from a new generation of sky surveys. Imaging data from large ground-based
active optics telescopes with sufficient etendue can address many scientific
missions simultaneously. These new investigations will rely on the statistical
precision obtainable with billions of objects. For the first time, the full sky
will be surveyed deep and fast, opening a new window on a universe of faint
moving and distant exploding objects as well as unraveling the mystery of dark
energy.Comment: 12 pages, 7 figure
The Mass distribution of the Cluster 0957+561 from Gravitational Lensing
Multiply gravitationally lensed objects with known time delays can lead to
direct determinations of H independent of the distance ladder if the mass
distribution of the lens is known. Currently, the double QSO 0957+561 is the
only lensed object with a precisely known time delay. The largest remaining
source of systematic error in the H determination results from uncertainty
in the mass distribution of the lens which is comprised of a massive galaxy
(G1) and the cluster in which it resides.
We have obtained V-band CCD images from CFHT in order to measure the mass
distribution in the cluster from its gravitional distorting effect on the
appearance of background galaxes. We use this data to constuct a
two-dimensional mass map of the field. A mass peak is detected at the
level, offset from, but consistent with, the position of G1. Simple
tests reveal no significant substructure and the mass distribution is
consistent with a spherical cluster. The peak in the number density map of
bright galaxies is offset from G1 similarly to the mass peak.
We constructed an azimuthally averaged mass profile centered on G1 out to 2
\arcmin ( kpc). It is consistent with an isothermal mass
distribution with a small core (r_c \approx 5 \arcsec = 17 h^{-1} kpc). The
inferred mass within 1 Mpc is consistent with the dynamical mass estimate but
higher than the upper limits from a ROSAT X-ray study.
We discuss implications for H in a future paper.Comment: LaTeX, aas version 4 macros. Calibration error in original led to
overestimate of cluster mass. Seven out of twelve figures included. Complete
paper is available at: http://www.astro.lsa.umich.edu:80/users/philf
A Catalog of Digital Images of 113 Nearby Galaxies
We present a digital catalog of images of 113 galaxies in this paper. These
galaxies are all nearby, bright, large and well resolved. All images were
recorded with charge coupled devices (CCDs) at the Palomar Observatory with the
1.5 meter telescope and at the Lowell Observatory with the 1.1 meter telescope.
At Palomar we used the Thuan--Gunn g, r and i photometric bands to take 3
images each of 31 spiral galaxies; at Lowell we used the B_J and R bands (2
images per galaxy) of the photometric system by Gullixson et al. (1995) to
observe 82 spirals and ellipticals. The galaxies were selected to span the
Hubble classification classes. All data are photometrically calibrated with
foreground stars removed. Important data on these galaxies published in the
"Third Reference Catalog of Bright Galaxies" (RC3) are recorded in the FITS
file headers. All files are available through anonymous FTP from
ftp://astro.princeton.edu/, through WWW at
http://astro.princeton.edu/~frei/galaxy_catalog.html, and Princeton University
Press will soon publish the data on CD-ROM.Comment: uuencoded compressed tar archive of postscript files (paper + 2
tables + 7 figures) Accepted for publication in the Astronomical Journa
Precision Studies of Dark Energy with LSST
Starting around 2013, data from the Large Synoptic Survey Telescope (LSST)
will be analyzed for a wide range of phenomena. By separately tracing the
development of mass structure and rate of expansion of the universe, these data
will address the physics of dark matter and dark energy, the possible existence
of modified gravity on large scales, large extra dimensions, the neutrino mass,
and possible self interaction of dark matter particles.Comment: 9 pages, 3 figures, Talk given at CIPANP 2006, 9th Conference on the
Intersections of Particle and Nuclear Physics, May 30-June 3, 2006, Rio
Grande, Puerto Ric
The Mass distribution of the Most Luminous X-ray Cluster RXJ1347.5-1145 from Gravitational Lensing
Galaxy cluster mass distribution are potentially useful probes of
and the nature of the dark matter. Large clusters will distort the observed
shapes of background galaxies through gravitational lensing allowing the
measurement of the cluster mass distributions. In this paper we describe weak
statistical lensing measurements of the most luminous X-ray cluster known,
RXJ1347.5-1145 at z=0.45. We detect a shear signal in the background galaxies
at a signal-to-noise ratio of 7.5 in the radial range kpc. A mass map of the cluster reveals an 11 peak in the
cluster mass distribution consistent with the position of the central dominant
galaxy and 3 evidence for the presence of a subcluster at a projected
radius of 1.3 - 1.7 h^{-1} Mpc from the cluster center. In the range kpc mass traces light, and the azimuthally averaged cluster
mass and light profiles are consistent with singular isothermal spheres with
M(r<1 Mpc) = . Assuming an isotropic
velocity distribution function, the implied velocity dispersion is . The rest-frame mass-to-light ratio is . The lensing mass estimate is almost twice as high as
a previously determined X-ray mass estimate.Comment: 21 Pages LaTeX, AASTEX version 4 macros, Accepted for publication in
the AJ. 8 of 12 figures included, full paper at
http://www.astro.lsa.umich.edu:80/users/philf/www/papers/list.htm
Large Synoptic Survey Telescope: Overview
A large wide-field telescope and camera with optical throughput over 200 m^2
deg^2 -- a factor of 50 beyond what we currently have -- would enable the
detection of faint moving or bursting optical objects: from Earth threatening
asteroids to energetic events at the edge of the optical universe. An optimized
design for LSST is a 8.4 m telescope with a 3 degree field of view and an
optical throughput of 260 m^2 deg^2. With its large throughput and dedicated
all-sky monitoring mode, the LSST will reach 24th magnitude in a single 10
second exposure, opening unexplored regions of astronomical parameter space.
The heart of the 2.3 Gpixel camera will be an array of imager modules with 10
micron pixels. Once each month LSST will survey up to 14,000 deg^2 of the sky
with many ~10 second exposures. Over time LSST will survey 30,000 deg^2 deeply
in multiple bandpasses, enabling innovative investigations ranging from
galactic structure to cosmology. This is a shift in paradigm for optical
astronomy: from "survey follow-up" to "survey direct science." The resulting
real-time data products and fifteen petabyte time-tagged imaging database and
photometric catalog will provide a unique resource. A collaboration of ~80
engineers and scientists is gearing up to confront this exciting challenge
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