arXiv subjects

M. D. Gladders

Publications and source records attributed to M. D. Gladders.

95 records · Page 6Linked to original sources

arXiv2002

The EXPLORE Project I: A Deep Search for Transiting Extrasolar Planets

(Abridged) We discuss the design considerations of the EXPLORE (EXtra-solar PLanet Occultation REsearch) project, a series of transiting planet searches using 4-m-class telescopes to continuously monitor a single field of stars in the Galactic Plane in each ~2 week observing campaign. We discuss the general factors which determine the efficiency and the number of planets found by a transit search, including time sampling strategy and field selection. The primary goal is to select the most promising planet candidates for radial velocity follow-up observations. We show that with very high photometric precision light curves that have frequent time sampling and at least two detected transits, it is possible to uniquely solve for the main parameters of the eclipsing system (including planet radius) based on several important assumptions about the central star. Together with a measured spectral type for the star, this unique solution for orbital parameters provides a powerful method for ruling out most contaminants to transiting planet candidates. For the EXPLORE project, radial velocity follow-up observations for companion mass determination of the best candidates are done on 8-m-class telescopes within two or three months of the photometric campaigns. This same-season follow-up is made possible by the use of efficient pipelines to produce high quality light curves within weeks of the observations. We conclude by presenting early results from our first search, EXPLORE I, in which we reached <1% rms photometric precision (measured over a full night) on ~37,000 stars to I <= 18.2.

astro-ph↗

arXiv2002

The EXPLORE Project: A Deep Search for Transiting Extra-Solar Planets

Searching for transits provides a very promising technique for finding close-in extra-solar planets. Transiting planets present the advantage of allowing one to determine physical properties such as mass and radius unambiguously. The EXPLORE (EXtra-solar PLanet Occultation REsearch) project is a transit search project carried out using wide-field CCD imaging cameras on 4-m class telescopes, and 8-10m class telescopes for radial velocity verification of the photometric candidates. We describe some of the considerations that go into the design of the EXPLORE transit search to maximize the discovery rate and minimize contaminating objects that mimic transiting planets. We show that high precision photometry (2 to 10 millimag) and high time sampling (few minutes) are crucial for sifting out contaminating signatures, such as grazing binaries. We have completed two searches using the 8k MOSAIC camera at the CTIO4m and the CFH12k camera at CFHT, with runs covering 11 and 16 nights, respectively. We obtained preliminary light curves for approximately 47,000 stars with better than ~1% photometric precision. A number of light curves with flat-bottomed eclipses consistent with being produced by transiting planets has been discovered. Preliminary results from follow-up spectroscopic observations using the VLT UVES spectrograph and the Keck HIRES spectrograph obtained for a number of the candidates are presented. Data from four of these can be interpreted consistently as possible planet candidates, although further data are still required for definitive confirmations.

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arXiv2001

Optical Surveys for Galaxy Clusters

We present a brief review of the history of optical searches of galaxy clusters, starting from that of Abell. The traditional application of this survey method suffers from contamination due to projection of galaxies along the line of sight, which becomes increasingly more severe at higher redshift. The new generation of wide-field CCD imagers has provided a renewed impetus for optical surveys for clusters. We describe a new cluster finding technique using the red sequence of early-type galaxies in galaxy groups and clusters, which eliminates the projection problem by essentially producing a 3-D distribution of red galaxies using two-filter imaging data. The Red-Sequence Cluster Survey (RCS) is a 100 square degree optical survey, carried out using 4m class telescopes, which is optimally designed to search for clusters at $0.5<z<1.4$\ utilizing this technique. We present preliminary results which indicate that the RCS is extremely efficient in detecting galaxy clusters at these redshifts, including a number of clusters with multiple strong lensing arcs.

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arXiv1999

The Color-Magnitude Relation of Early-Type Galaxies: A Tool for Cluster Finding and Redshift Determination

The color-magnitude relation (CMR) of early-type galaxies in clusters provides a powerful tool for finding clusters and determining photometric redshifts for clusters using two-filter imaging data. We demonstrate the high accuracy of photometric redshifts attainable using the CMR by applying the technique to a sample of 45 Abell clusters with known redshifts. Furthermore, by using the red sequence of galaxies from the CMR, we have developed an extremely efficient technique for detecting clusters and groups of galaxies. We demonstrate this using both observed photometric catalogs with redshifts (from the CNOC2 Survey) and simulations.

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arXiv1998

The Slope of the Cluster Elliptical Red Sequence: A Probe of Cluster Evolution

The current formation models for cluster elliptical galaxies which incorporate a mechanism for the metallicity enhancement of massive ellipticals predict a change in the observed slope of the red sequence of ellipticals as a function of redshift. This change occurs primarily because the metal-rich galaxies become redder faster than the metal-poorer galaxies with increasing age. This effect is most pronounced within ~ 4 Gyr of formation. Observations of the change of the slope of the red sequence with redshift may thus be used to constrain the formation epoch for galaxy clusters. We examine the red sequence of cluster ellipticals using publicly available HST imaging data for a set of six 0.75>z>0.2 clusters, and a sample of 44 Abell clusters at z<0.15 imaged with the KPNO 0.9 m. We compare the derived slopes of the red sequences with a set of cluster-elliptical evolution models and find good agreement. We demonstrate that such a comparison provides a useful constraint on the formation epoch for clusters, which can be made independently from considerations of absolute color evolution and scatter in the red sequence. From our initial comparison of the observed and model slopes as a function of redshift, we conclude, conservatively, that most of the elliptical galaxies in the cores of clusters must form at z>2.0, and that these galaxies are coeval and passively evolving.

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