The Interplay of Cluster and Galaxy Evolution

We review here the interplay of cluster and galaxy evolution. As a case study, we consider the Butcher-Oemler effect and propose that it is the result of the changing rate of cluster merger events in a hierarchical universe. This case study highlights the need for new catalogs of clusters and groups that possess quantified morphologies. We present such a sample here, namely the Sloan Digital Sky Survey (SDSS) C4 Catalog, which has been objectively-selected from the SDSS spectroscopic galaxy sample. We outline here the C4algorithm and present first results based on the SDSS Early Data Release, including an X-ray luminosity-velocity dispersion (L_x-σ_v) scaling relationship (as a function of cluster morphology) and the density-SFR relation of galaxies within C4 clusters (Gomez et al., 2003). We also discuss the merger of Coma and the NGC4839 group and its effect on the galaxy populations in these systems. We finish with a brief discussion of a new sample ofHΔ-selected galaxies (i.e., k+a, post-starburst galaxies) obtained from the SDSS spectroscopic survey. This revised version was published online in July 2006 with corrections to the Cover Date.     

A conceptual hydrologic model for a forested Carolina bay depressional wetland on the Coastal Plain of South Carolina,USA

This paper describes how climate influences the hydrology of an ephemeral depressional wetland. Surface water and groundwater elevation data were collected for 7 years in a Coastal Plain watershed in South Carolina USA containing depressional wetlands, known as Carolina bays. Rainfall and temperature data were compared with water‐table well and piezometer data in and around one wetland. Using these data a conceptual model was created that describes the hydrology of the system under wet, dry, and drought conditions. The data suggest this wetland operates as a focal point for groundwater recharge under most climate conditions. During years of below‐normal to normal rainfall the hydraulic gradient indicated the potential for groundwater recharge from the depression, whereas during years of above‐normal rainfall, the hydraulic gradient between the adjacent upland, the wetland margin, and the wetland centre showed the potential for groundwater discharge into the wetland. Using high‐resolution water‐level measurements, this groundwater discharge condition was found to hold true even during individual rainfall events, especially under wet antecedent soil conditions. The dynamic nature of the hydrology in this Carolina bay clearly indicates it is not an isolated system as previously believed, and our groundwater data expand upon previous hydrologic investigations at similar sites which do not account for the role of groundwater in estimating the water budget of such systems. Copyright © 2007 John Wiley & Sons, Ltd.     

Toxicity of 17alpha-ethynylestradiol and norethindrone,constituents of an oral contraceptive pill to the swimming and reproduction of cladoceran Daphnia magna,with special reference to their synergetic effect

Toxicity of 17alpha-ethynylestradiol (EE2) and norethindrone (NOR), constituents of low dosage oral contraceptives, was assessed for the freshwater cladoceran Daphnia magna. Acute toxicity tests showed that 5 ppm of EE2, the highest concentration in this study, never inhibited swimming, whereas NOR inhibited swimming at >3 ppm: 48 h EC(50) for NOR was 6.41 ppm. Chronic toxicity tests were carried out for 25 days by measuring the number of offspring, moltings and sex ratios of neonates at 20, 100 and 500 ppb. EE2>100 ppb significantly decreased the number of offspring to 75% of the control; however, no effect was observed in molting and sex ratios at <500 ppb. NOR did not affect reproduction and sex ratios at <500 ppb. Mixture of EE2 (5.88 ppb) and NOR (94.12 ppb) also significantly decreased the number of offspring to 57% of the control. This result indicates the importance of examining synergetic effects of chemicals in the context of natural environments which face exposure to myriad chemicals.     

Climatic and environmental changes at southeastern coast of Lake Biwa over past 3000 years, inferred from borehole temperature data

In order to infer past climatic change in central Japan, we measured temperatures in a borehole at the Karasuma site, on the southeastern coast of Lake Biwa, and reconstructed sediment surface temperature history during the last 3000 years. The reconstructed temperature history shows apparent Medieval Warm Period, Little Ice Age, and contemporary temperature warming. However, the large amplitude of the temperature changes up to 4-5 K cannot be explained by past climatic change only, suggesting that there was some other cause of the larger amplitude temperature changes. The onsets of temperature decrease in the late 12th century a.d. and temperature increase in the mid 17th century a.d. appear to coincide with occurrences of two destructive earthquakes (1185 and 1662 a.d.) that caused water level changes of Lake Biwa. It suggests that the reconstructed sediment surface temperature history reflects the environmental change due to tectonically induced water level changes of the lake. If the annual mean of the ground surface temperature was higher than that of the bottom water temperature in a shallow part of the lake, which is consistent with the present-day data, the large amplitude of the sediment surface temperature change may be attributed to a combined effect of past climatic and environmental changes. Thus, we suggest that the borehole temperature at the Karasuma site preserves information not only on past climate changes but also on environmental changes due to tectonically induced water level changes.     

Long-term monitoring of the temperature profile in a deep borehole: Temperature variations associated with water injection experiments and natural groundwater discharge

Long-term temperature monitoring was carried out in a borehole drilled for investigation of the Nojima fault, an active fault in SW Japan, using the distributed optical fiber temperature sensing (DTS) technique. Temperatures in the borehole had been measured every 1 m along an optical fiber cable with a resolution of about 0.1 K over a period of 6 years. Water injection experiments were conducted in this borehole in 1997, 2000 and 2003. Monitoring of the temperature profile was started after the first injection experiment, and the temperature profile remained very stable until the start of the second injection experiment. During the second and third experiments, the temperatures in the borehole dropped due to cooling by the injected water but no appreciable temperature change was observed below about 580 m. It clearly shows that the water leaked out of the hole around this point and the leaking depth is estimated to be about 540 m based on the shape of the temperature profile. After the injection was stopped, the recovery of the temperature to the undisturbed profile was exceptionally slow around the leaking point, resulting in a local temperature anomaly, probably because the water leaking out of the hole had cooled the surrounding formations extensively. A very similar temperature anomaly was observed at the beginning of temperature monitoring, which suggests that water leaked out at the same depth in the first injection experiment as well. Between the second and third injection experiments, the top of the borehole was kept open to allow groundwater discharge for about 1 month in 2000 and 2003. In both periods, groundwater flowed out continuously and the shapes of the observed temperature profiles indicate that the groundwater entered in the hole at the same depth as the leaking point during the injection experiments. The temperature records also show that the rate of discharge had been nearly constant through the two test periods. The water discharge appears to have been little affected by the water injection. These results demonstrate that the optical fiber temperature monitoring system is a very effective tool for hydrological experiments.     

Radial and 2D colour properties of E+A galaxies

We investigated the radial colour gradient and two-dimensional (2D) colour properties of 22 E+A galaxies with  5.5 < Hδ equivalent width(EW) < 8.5 Å  and 49 normal early-type galaxies as a control sample at a redshift of <0.2 in the Second Data Release of the Sloan Digital Sky Survey. We found that a substantial number of E+A galaxies exhibit positive slopes of radial colour gradient (bluer gradients toward the centre) which are seldom seen in normal early-type galaxies. We found irregular 'colour morphologies'– asymmetrical and clumpy patterns – at the centre of g − r and r − i 2D colour maps of E+A galaxies with positive slopes of colour gradient. Kolomogorov–Smirnov two-sample tests show that g − r and r − i colour gradient distributions of E+A galaxies differ from those of early-type galaxies with a more than 99.99 per cent significance level. We also found a tight correlation between radial colour gradients and colours, and between radial colour gradients and the 4000-Å break in the E+A sample; E+A galaxies which exhibit bluer colour or weaker D ₄₀₀₀ tend to have positive slopes of radial colour gradient. We compared the GISSEL model and E+A observational quantities,  Hδ EW, D ₄₀₀₀  and u − g colour, and found that almost all our E+A galaxies are situated along a single evolutionary track. Therefore, these results are interpreted as E+A galaxies evolving from  Hδ EW ∼ 8 Å  to  Hδ EW ∼ 5 Å  , with colour gradients changing from positive to negative, and with the irregular 2D colour map becoming smoother, during a time-scale of ∼300 Myr. Our results favour the hypothesis that E+A galaxies are post-starburst galaxies caused by merger/interaction, having undergone a centralized violent starburst.     

Post-seismic Effects of an M 7.2 Earthquake and Microseismicity in an Abandoned, Flooded, Deep Mine

—?An M 7.2 earthquake took place 67?km southeast of an abandoned mine containing flooded, vertical ore veins at depth of 1?km. Multidisciplinary monitoring of the unweathered country rock within the mine was carried out for a distance of about one kilometer. The M 7.2 earthquake was followed by significant post-seismic changes in strain and tilt of ～10^?6, with a self-potential of ～10?mV, and an increase in the water level in the mine of about 10?cm/day. These phenomena continued for several months before returning to pre-earthquake levels. Coseismic elastic deformations were too small to account for the observed post-seismic changes, and have different senses in strain and tilt from the observed post-seismic changes. The contractions in strain and the changes in the electric self-potential and water-elevation rate strongly suggest an increase in pore pressure. An increase in microseismic activity (M?M 7.2 earthquake.