The Allen Telescope Array Twenty-centimeter Survey -- A 700-Square-Degree, Multi-Epoch Radio Dataset -- II: Individual Epoch Transient Statistics

We present our second paper on the Allen Telescope Array Twenty-centimeter Survey (ATATS), a multi-epoch, ~700 sq. deg. radio image and catalog at 1.4 GHz. The survey is designed to detect rare, bright transients as well as to commission the ATA's wide-field survey capabilities. ATATS explores the challenges of multi-epoch transient and variable source surveys in the domain of dynamic range limits and changing (u,v) coverage. Here we present images made using data from the individual epochs, as well as a revised image combining data from all ATATS epochs. The combined image has RMS noise 3.96 mJy / beam, with a circular beam of 150 arcsec FWHM. The catalog, generated using a false detection rate algorithm, contains 4984 sources, and is >90% complete to 37.9 mJy. The catalogs generated from snapshot images of the individual epochs contain between 1170 and 2019 sources over the 564 sq. deg. area in common to all epochs. The 90% completeness limits of the single epoch catalogs range from 98.6 to 232 mJy. We compare the catalog generated from the combined image to those from individual epochs, and from the NRAO VLA Sky Survey (NVSS), a legacy survey at the same frequency. We are able to place new constraints on the transient population: fewer than 6e-4 transients / sq. deg., for transients brighter than 350 mJy with characteristic timescales of minutes to days. This strongly rules out an astronomical origin for the ~1 Jy sources reported by Matsumura et al. (2009), based on their stated rate of 3.1e-3 / sq. deg.Comment: 28 pages, 12 figures, ApJ accepte

Spatial Distribution And Geomorphic Factors Of Lead Contamination On Floodplains Affected By Historical Mining, Big Rover, S.E. Missouri

Historical mining in the Old Lead Belt resulted in lead (Pb) contamination of floodplain soils for over 170 km along the Big River in southeastern Missouri. The overall pattern of contamination are understood. However, Pb distribution across floodplain surfaces has not been investigated at the scale needed for site-level remediation planning. The goal of this project is to examine spatial distribution of Pb with more detail and identify the role of geomorphic processes. Predictive models are needed to evaluate factors affecting Pb distribution such as elevation, distance from the channel, and geochemistry. This study evaluates Pb distribution at three ~1km sites on the Big River with varying floodplain conditions: (1) human-altered topography, (2) narrow valley and, (3) wide valley. Surface soil samples were collected to quantify Pb, geomorphic maps were created using LiDAR, and spatial patterns were analyzed using regression models. Results show that Pb levels at the three sites pose an ecological problem. The most effective predictive model was created at the narrow floodplain site using distance from the channel, elevation, and Fe as independent variables. Less sensitive models were created at the two other sites which had more complicated geomorphological characteristics and less variability in Pb. Using landform/soil series associations and examining the influence of watershed-scale factors such as valley width and proximity to source are likely more effective approaches for understanding Pb distribution on Big River floodplains

Catalog of Galaxy Morphology in Four Rich Clusters: Luminosity Evolution of Disk Galaxies at 0.33<z<0.83

Hubble Space Telescope (HST) imaging of four rich, X-ray luminous, galaxy clusters (0.33<z<0.83) is used to produce quantitative morphological measurements for galaxies in their fields. Catalogs of these measurements are presented for 1642 galaxies brighter than F814W(AB)=23.0 . Galaxy luminosity profiles are fitted with three models: exponential disk, de Vaucouleurs bulge, and a disk-plus-bulge hybrid model. The best fit is selected and produces a quantitative assessment of the morphology of each galaxy: the principal parameters derived being B/T, the ratio of bulge to total luminosity, the scale lengths and half-light radii, axial ratios, position angles and surface brightnesses of each component. Cluster membership is determined using a statistical correction for field galaxy contamination, and a mass normalization factor (mass within boundaries of the observed fields) is derived for each cluster. In the present paper, this catalog of measurements is used to investigate the luminosity evolution of disk galaxies in the rich-cluster environment. Examination of the relations between disk scale-length and central surface brightness suggests, under the assumption that these clusters represent a family who share a common evolutionary history and are simply observed at different ages, that there is a dramatic change in the properties of the small disks (h < 2 kpc). This change is best characterized as a change in surface brightness by about 1.5 magnitude between z=0.3 and z=0.8 with brighter disks at higher redshifts.Comment: 53 pages, including 13 figures and 7 tables. Accepted for publication in the Astrophysical Journal Supplement Serie

The EIU Student Life Survey: Explanations for Involvement

The research reported in this paper was designed to assist the EIU General Education Assessment Committee to understand the ways in which undergraduate students made use of their time on campus, both in-class and out-of-class. The results provided stakeholders with information to support student activities and student involvement. The survey instrument used for data collection is also attached