Hubble Space Telescope Far-ultraviolet Observations of Brightest Cluster Galaxies: The Role of Star Formation in Cooling Flows and BCG Evolution

Quillen et al. and O'Dea et al. carried out a Spitzer study of a sample of 62 brightest cluster galaxies (BCGs) from the ROSAT brightest cluster sample, which were chosen based on their elevated Hα flux. We present Hubble Space Telescope Advanced Camera for Surveys far-ultraviolet (FUV) images of the Lyα and continuum emission of the luminous emission-line nebulae in seven BCGs found to have an infrared (IR) excess. We confirm that the BCGs are actively forming stars which suggests that the IR excess seen in these BCGs is indeed associated with star formation. Our observations are consistent with a scenario in which gas that cools from the intracluster medium fuels the star formation. The FUV continuum emission extends over a region ~7-28 kpc (largest linear size) and even larger in Lyα. The young stellar population required by the FUV observations would produce a significant fraction of the ionizing photons required to power the emission-line nebulae. Star formation rates estimated from the FUV continuum range from ~3 to ~14 times lower than those estimated from the IR, however, both the Balmer decrements in the central few arcseconds and detection of CO in most of these galaxies imply that there are regions of high extinction that could have absorbed much of the FUV continuum. Analysis of archival Very Large Array observations reveals compact radio sources in all seven BCGs and kpc scale jets in A-1835 and RXJ 2129+00. The four galaxies with archival deep Chandra observations exhibit asymmetric X-ray emission, the peaks of which are offset from the center of the BCG by ~10 kpc on average. A low feedback state for the active galactic nucleus could allow increased condensation of the hot gas into the center of the galaxy and the feeding of star formation

Synchronous opening of the Rio Grande rift along its entire length at 25–10 Ma supported by apatite (U-Th)/He and fission-track thermochronology, and evaluation of possible driving mechanisms

152 new apatite (U-Th)/He (AHe) dates are presented from 34 sample locations along the flanks of the Rio Grande rift in New Mexico and Colorado. These data are combined with apatite fission-track (AFT) analyses of the same rocks and modeled together to create well constrained cooling histories for Rio Grande rift flank uplifts. The data indicate rapid cooling from ~28 Ma to Recent in the Sawatch Range and the Sangre de Cristo Mountains, ~21 to 5 Ma in the Albuquerque basin, and ~17 to 8 Ma in the southern Rio Grande rift in southern New Mexico. Rapid cooling of rift flanks followed the Oligocene ignimbrite flare-up and the northern section of the Rio Grande rift in Colorado exhibits semi-continuous cooling since the Oligocene. Overall, however, rift flank cooling along the length of the rift was out of phase with high volume magmatism and hence is inferred to have been driven mainly by exhumation due to faulting. Although each location preserves a unique cooling history, when combined with existing AHe data from the Gore Range in northern Colorado and the Sandia Mountains in New Mexico together these data indicate ~ synchronous extension and rift flank uplift along \u3e850 km of the length of the Rio Grande rift from ~20-10 Ma. These time-space constraints provide an important new dataset to develop geodynamic models for initiation and evolution of continental rifting. Models involving northward unzipping and Colorado Plateau rotation are not favored as primary mechanisms driving extension. Instead, a geodynamic model is proposed that involves upper mantle dynamics during multi-stage foundering and rollback of a segment of the Farallon plate near the Laramide hinge region that extended between the Wyoming and SE New Mexico high velocity mantle domains. First stage delamination accompanied and followed ~40-20 Ma volcanism in the San Juan and Mogollon-Datil ignimbrite centers. A second stage involved a ~30-20 Ma detachment of the remaining part of the Farallon slab. This produced renewed uplift of the Alvarado Ridge topographic high, enhanced surface uplift of rift flanks, developed a central graben with increased fault- related high strain rates, and resulted in maximum sediment accumulation in the Rio Grande rift. Our geodynamic model thus involves Oligocene removal of parts of the Farallon slab beneath the ignimbrite centers followed by a major Oligocene-Miocene slab break that instigated the discrete N-S Rio Grande rift, continuing upper mantle convection, and differential uplift of the southern Rocky Mountain - Rio Grande rift region

Patient Participation in Research in the Managed Care Environment: Key Perceptions of Members in an HMO

This study's objective was to elicit the views of research among enrollees in an HMO. A questionnaire was mailed to 207 adult enrollees, 55% had been exposed to research and 45% had not. Ninety-four percent of respondents supported research within the HMO, and 87% thought using information from medical records for research was acceptable. Sixty-three percent thought participation in research increased patient understanding of health care. Significantly more prior research participants thought that participation in research improves care. More patients would participate if written information were provided (67%), if feedback of results was provided (72%), and if their clinician invited them (67%). Only a modest percentage (20%) of patients would participate in a randomized trial