31 research outputs found
A preliminary investigation of the influence of pre-school musical experiences on a selected group of fifth grade students
The Sloan Bright Arcs Survey : Six Strongly Lensed Galaxies at z=0.4-1.4
We present new results of our program to systematically search for strongly
lensed galaxies in the Sloan Digital Sky Survey (SDSS) imaging data. In this
study six strong lens systems are presented which we have confirmed with
follow-up spectroscopy and imaging using the 3.5m telescope at the Apache Point
Observatory. Preliminary mass models indicate that the lenses are group-scale
systems with velocity dispersions ranging from 466-878 km s^{-1} at z=0.17-0.45
which are strongly lensing source galaxies at z=0.4-1.4. Galaxy groups are a
relatively new mass scale just beginning to be probed with strong lensing. Our
sample of lenses roughly doubles the confirmed number of group-scale lenses in
the SDSS and complements ongoing strong lens searches in other imaging surveys
such as the CFHTLS (Cabanac et al 2007). As our arcs were discovered in the
SDSS imaging data they are all bright (), making them ideally
suited for detailed follow-up studies.Comment: 13 pages, 3 figures, submitted to ApJL, the Sloan Bright Arcs page is
located here: http://home.fnal.gov/~kubo/brightarcs.htm
Measuring the flatness of focal plane for very large mosaic CCD camera
Large mosaic multiCCD camera is the key instrument for modern digital sky
survey. DECam is an extremely red sensitive 520 Megapixel camera designed for
the incoming Dark Energy Survey (DES). It is consist of sixty two 4k2k
and twelve 2k x 2k 250-micron thick fully-depleted CCDs, with a focal plane of
44 cm in diameter and a field of view of 2.2 square degree. It will be attached
to the Blanco 4-meter telescope at CTIO. The DES will cover 5000 square-degrees
of the southern galactic cap in 5 color bands (g, r, i, z, Y) in 5 years
starting from 2011.
To achieve the science goal of constraining the Dark Energy evolution,
stringent requirements are laid down for the design of DECam. Among them, the
flatness of the focal plane needs to be controlled within a 60-micron envelope
in order to achieve the specified PSF variation limit. It is very challenging
to measure the flatness of the focal plane to such precision when it is placed
in a high vacuum dewar at 173 K. We developed two image based techniques to
measure the flatness of the focal plane. By imaging a regular grid of dots on
the focal plane, the CCD offset along the optical axis is converted to the
variation the grid spacings at different positions on the focal plane. After
extracting the patterns and comparing the change in spacings, we can measure
the flatness to high precision. In method 1, the regular dots are kept in high
sub micron precision and cover the whole focal plane. In method 2, no high
precision for the grid is required. Instead, we use a precise XY stage moves
the pattern across the whole focal plane and comparing the variations of the
spacing when it is imaged by different CCDs. Simulation and real measurements
show that the two methods work very well for our purpose, and are in good
agreement with the direct optical measurements.Comment: Presented at SPIE Conference,Ground-based and Airborne
Instrumentation for Astronomy III, San Diego, 201
The Sloan Bright Arcs Survey: Four Strongly Lensed Galaxies with Redshift >2
We report the discovery of four very bright, strongly-lensed galaxies found
via systematic searches for arcs in Sloan Digital Sky Survey Data Release 5 and
6. These were followed-up with spectroscopy and imaging data from the
Astrophysical Research Consortium 3.5m telescope at Apache Point Observatory
and found to have redshift . With isophotal magnitudes
and 3\arcsec-diameter magnitudes , these systems are some of
the brightest and highest surface brightness lensed galaxies known in this
redshift range. In addition to the magnitudes and redshifts, we present
estimates of the Einstein radii, which range from 5.0 \arcsec to 12.7
\arcsec, and use those to derive the enclosed masses of the lensing galaxies
Discovery of A Very Bright, Strongly-Lensed z=2 Galaxy in the SDSS DR5
We report on the discovery of a very bright z = 2.00 star-forming galaxy that
is strongly lensed by a foreground z=0.422 luminous red galaxy (LRG). This
system was found in a systematic search for bright arcs lensed by LRGs and
brightest cluster galaxies in the Sloan Digital Sky Survey Data Release 5
sample. Follow-up observations on the Subaru 8.2m telescope on Mauna Kea and
the Astrophysical Research Consortium 3.5m telescope at Apache Point
Observatory confirmed the lensing nature of this system. A simple lens model
for the system, assuming a singular isothermal ellipsoid mass distribution,
yields an Einstein radius of 3.82 +/- 0.03 arcsec or 14.8 +/- 0.1 kpc/h at the
lens redshift. The total projected mass enclosed within the Einstein radius is
2.10 +/- 0.03 x 10^12 M_sun/h, and the magnification factor for the source
galaxy is 27 +/- 1. Combining the lens model with our gVriz photometry, we find
an (unlensed) star formation rate for the source galaxy of 32 M_sun/h / yr,
adopting a fiducial constant star formation rate model with an age of 100 Myr
and E(B-V) = 0.25. With an apparent magnitude of r = 19.9, this system is among
the very brightest lensed z >= 2 galaxies, and provides an excellent
opportunity to pursue detailed studies of the physical properties of an
individual high-redshift star-forming galaxy.Comment: 31 pages, 12 figures, 4 tables, submitted to Ap
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