GESE: a small UV space telescope to conduct a large spectroscopic survey of z∼1 Galaxies

One of the key goals of NASA’s astrophysics program is to answer the question: How did galaxies evolve into the spirals and elliptical galaxies that we see today? We describe a space mission concept called Galaxy Evolution Spectroscopic Explorer (GESE) to address this question by making a large spectroscopic survey of galaxies at a redshift, z～1 (look-back time of ～8 billion years). GESE is a 1.5-m space telescope with an ultraviolet (UV) multi-object slit spectrograph that can obtain spectra of hundreds of galaxies per exposure. The spectrograph covers the spectral range, 0.2–0.4 μm at a spectral resolving power, R～500. This observed spectral range corresponds to 0.1–0.2 μm as emitted by a galaxy at a redshift, z=1. The mission concept takes advantage of two new technological advances: (1) light-weighted, wide-field telescope mirrors, and (2) the Next-Generation MicroShutter Array (NG-MSA) to be used as a slit generator in the multi-object slit spectrograph.     

Gas Flows and Star Formation in the Ringed Galaxy NGC 4736

We present high-resolution (∼5″) BIMA CO observations of the ringed galaxy NGC 4736, along with previously published VLA HI data (Braun, 1995). Strong CO emission is detected from the star-forming ring at r=45″ and in the central region, where a molecular bar is apparent. The azimuthally averaged gas surface density is still much less than the Toomre critical density within r=60″, despite the starburst conditions in the ring (gas depletion time ≲1Gyr). Both CO and HI velocity fields show strong departures from a circular rotating disc model. The velocity residuals are consistent with inflowing gas near the ends of the central bar, outflowing gas between the bar and the ring, and inflowing gas outside the ring. We propose that the high star formation efficiency in the ring results from gas being driven out towards the OLR of the bar and in towards the ILR of the larger oval distortion. However, the strong signature of inflow outside the ring is probably due in part to gas motion in elliptical orbits. This revised version was published online in July 2006 with corrections to the Cover Date.     

Using Points of Presence to Measure Accessibility to the Commercial Internet

As the Internet continues to grow, questions of accessibility and infrastructure equity persist. In the increasingly competitive telecommunications industry, profit-seeking firms continue to upgrade infrastructure in select market areas creating an uneven spatial distribution of access opportunities. This article utilizes a longitudinal database of Internet infrastructure development, highlighting fiber-optic backbone points of presence (POP) established by commercial Internet service providers to examine city accessibility to the commercial Internet. Results indicate that many larger metropolitan areas maintain dominant shares of telecom infrastructure, but several midsized metros are emerging as important centers for telecommunication interconnection.     

Resolving the kinematic distance ambiguity of southern massive young stellar object candidates

We investigate the use of H  i data to resolve the near/far ambiguity in kinematic distances of massive young stellar object (MYSO) candidates. Kinematic distances were obtained from ¹³CO 1-0 (and N₂H⁺) spectral-line observations with the Mopra Telescope towards 94 candidates selected from the Red MSX Source (RMS) survey in the fourth Galactic quadrant  (282° < l < 350°)  . H  i data from the Southern Galactic Plane Survey (SGPS) were used in conjunction with the H  i self-absorption (SA) technique to determine the near or far distance. We resolved the kinematic distance ambiguity to 70 per cent of the sources. We can also simultaneously solve for any multiple line-of-sight component sources. We discuss the advantages and disadvantages of this technique in comparison with other methods, and also perform confidence checks on the reliability of using the H  i SA technique.
We examined the projected location of these sources in both the Galactic plane and longitude–velocity ( l – v ) diagrams to ascertain any recognizable spiral arm pattern. Although no obvious spiral pattern was found when compared to that proposed by Cordes and Lazio, far distance sources tended to lie on or near spiral arm loci. Near distance sources, however, had peculiar velocity uncertainties consistent with the separation between the spiral arms themselves. The l – v plot shows a more consistent picture, with tangent points of the spiral arm loci easily seen.
We conclude that using the H  i SA technique to determine kinematic distance ambiguities is a quick and reliable method in most cases, with an 80 per cent success rate in determining the correct designation of whether an object is at the near or far distance.     

Fisheries: Hope or despair?

Recent work suggesting that fisheries depletions have turned the corner is misplaced because analysis was based largely on fisheries from better-managed developed-world fisheries. Some indicators of status show improvements in the minority of fisheries subjected to formal assessment. Other indicators, such as trophic level and catch time series, have been controversial. Nevertheless, several deeper analyses of the status of the majority of world fisheries confirm the previous dismal picture: serious depletions are the norm world-wide, management quality is poor, catch per effort is still declining. The performance of stock assessment itself may stand challenged by random environmental shifts and by the need to accommodate ecosystem-level effects. The global picture for further fisheries species extinctions, the degradation of ecosystem food webs and seafood security is indeed alarming. Moreover, marine ecosystems and their embedded fisheries are challenged in parallel by climate change, acidification, metabolic disruptors and other pollutants. Attempts to remedy the situation need to be urgent, focused, innovative and global.     

Environmental recovery in Sydney Harbour,Nova Scotia: Evidence of natural and anthropogenic sediment capping

Contaminants were assessed in Sydney Harbour during baseline and three years of remediation of a former coking and steel facility. Concentrations of PAHs; PCBs; and lead measured in surface sediments indicate overall spatial distribution patterns of historical contaminants remains unchanged, although at much lower concentrations than previously reported due to natural sediment recovery. Recovery rates were in broad agreement with predicted concentrations; or in some cases lower, despite remediation at the Sydney Tar Ponds (STP) site. Contaminants showed little temporal variability, except for detection of significant increases in PAH concentrations during onset of remediation compared to baseline which represented a short term interruption in the overall long term natural recovery of sediments in Sydney Harbour. Recovery (via “capping”) was enhanced following recent harbour dredging activities where less contaminated outer harbour sediments were discharged into a confined disposal facility (CDF) required for a new container in the inner harbour.