Dara Norman)A Search for Galaxy Clusters in the Fields of Bright Quasars1
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Follow Up Observations of Transients in the Deep Lens Survey2
Dara Norman)
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Research Experiences for Undergraduates (REU)
January - March 2002 La Serena, Chile |
Abstract1:
We examine evidence for gravitational lensing of quasi-stellar objects due to an overdensity of foreground galaxy clusters.
Studies of bright quasars have shown correlation between these background sources and foreground galaxies (Norman and Impey 2001 and references within). This suggests that these quasars appear intrinsically brighter as a result of their location behind large mass structures. Further studies (Fort et. Al., 1995) have demonstrated that there exists weak lensing of distant galaxies in the fields of some quasars. In order to investigate this weak lensing generally, more information about the mass structures themselves is needed.
We examine several quasar fields, in which quasars have redshifts of 0.7 < z < 2.5, in 4 SDSS filters (ugri) with the 1.5m telescope at CTIO. We will determine the photometric redshifts of galaxies in these fields in order to look for associated foreground clusters. As photometric redshifts are much less time consuming to obtain than spectroscopic redshifts, they are a good alternate means for initial determination of the presence of structures and thus a good indicator as to whether or not more difficult to obtain spectroscopic data should be pursed.
Abstract2:
We propose to take photometric follow-up observations of the brighter (V < 23) newly discovered, stationary Deep Lens Survey (DLS) transient objects with the 1.5m telescope at CTIO.
The discovery of these transients is a ``by-product'' of this wide-field survey. Currently, there is no systematic effort made by the survey team to follow these discoveries in time intervals or with additional filters that might facilitate the
identification of these objects. Based on 2 years of past DLS observations, we expect 3-5 bright, stationary transients with stellar progenitors to be discovered each month during the 2001 DLS observing runs. These objects will be targeted for multicolor (BVRI) observations over an additional 2 nights during each month. This baseline will give us sensitivity to the multiple timescales over which we expect known astronomical objects to vary. This additional photometric data will enable us to classify these objects as cataclysmic variables ,orphan gamma ray burst afterglows and AGN. These classifications will be based on the observed colors and light curves of the targets. Further we hope that some of these observations might even lead to discoveries of entirely unanticipated objects. We intend to use this limited amount of data to define a project that can suitably be carried out by high school teachers and students as part of the Research Based Science Education program. Getting Started:
Initially all REU/PIA students were assigned an observing run consisting of 2 nights on the
0.9m telescope. In those 2 nights we were to obtain optical data for several projects in cooperation with various researchers.
Revised 26 November 2002
email: astrofizkid@yahoo.com