Active galactic nucleus feedback in clusters of galaxies

Observations made during the last ten years with the Chandra X-ray Observatory have shed much light on the cooling gas in the centers of clusters of galaxies and the role of active galactic nucleus (AGN) heating. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes found in the nuclei of the dominant cluster galaxies leading to AGN outbursts which can reheat the gas, suppressing cooling and large amounts of star formation. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio lobes, and the dissipation of sound waves.Comment: Refereed review article published in Chandra's First Decade of Discovery Special Feature edition of the Proceedings of the National Academy of Science

Building Capacity for Continuous Improvement of Math and Science Education in Rural Schools

Schools in 47 high-poverty school districts located mostly along the Atlantic Coast of North Carolina, South Carolina, and Virginia may have a head start on new requirements of the No Child Left Behind (NCLB) Act of 2001, thanks to a $6 million grant from the National Science Foundation. Begun in April 2000, the five-year Coastal Rural Systemic Initiative (CRSI) is striving to stimulate sustainable systemic improvements in science and mathematics education in school districts with a long history of low student expectations, persistent poverty, low teacher pay, and high administrator turnover. The CRSI capacity-building model is designed to address issues in rural school districts that traditionally limit the capacity for creating sustainable improvements in math and science programs. A critical action step is that each school district must sign a cooperative agreement to establish Continuous Improvement Teams (CITs) at the district and school levels. These CITs represent a fundamental system capacity-building change in how decisions are made at the school and district levels—a change that is also fundamental to creating lasting improvements in math and science education programs

Ultraviolet images of the gravitationally lensed quadruple quasar Q2237+0305 with the HST

We analyze observations of the quadruple lensed quasar Q2237+0305, taken with the WFPC2 camera in the F336W and F300W bands. 25 exposures were performed within 15 hours real time on 3 November 1995. On a timescale of 3--4 hours, we observe no variation in component A of greater than 0.02 mag. The other components are constant over a period of 10 hours to within about 0.05 mag. In the final 5 hours there is some evidence (not conclusive) for variation of component D by about 0.1 mag. Component A was brighter than component B by about 0.3 mag. Components C and D were fainter than component A by about 1.3 and 1.4 mag. Any fifth (central) component was at least 6.5 mag fainter than component A. Using the PC chip, we measure the relative distances of the four components with high accuracy. Our values are systematically larger than other investigators' (by 0.1% to 2.0%). The F336W filter had been chosen for the observations because it could have allowed us to see extended Ly-alpha emission from the Broad-Line Region (BLR). However, the quasar components are consistent with a point source. We conclude that there cannot be a Ly-alpha feature in the image plane brighter than about 23.5 mag in F336W and further from the quasar core than 100 mas. According to a lensing model by Rix, Scheider & Bahcall (1992), this would preclude any such features in the source plane further than 20 mas (~ 100 h^{-1} pc, assuming q_0 = 0.5) from the quasar core and brighter than 25 mag before magnification.Comment: 16 pages, Latex, 9 figures, accepted by MNRAS, 3 tables adde