Chandra observation of a cold front in Abell 2554

We present the evidence for the existence of substructure in the cold front cluster A2554 based on a 20.14 ks Chandra observation. Using centroid shift and X-ray brightness concentration parameters, we confirm that A2554 is a dynamically disturbed system. We detect two dominant structures; a main cluster at z = 0.1108 and a foreground northern substructure at z = 0.1082. The analysis reveals an X-ray surface brightness edge at r \simeq 60 kpc from the cluster core. The thermodynamical profiles across the edge are ruling out the shock scenario. The temperature jump (from \sim 6 keV to \sim 10 keV), and pressure equilibrium (P0/P1 = 1.01 \pm 0.23) across the edge, are consistent with the definition of a cold front with a Mach number M=0.94^{+0.13}_{-0.17} also observed a weak bow-shock at \sim 100 kpc in front of the cold cloud, corresponding an upper limit to the Mach number M \sim 1.1. If the northern substructure was not related to the cold front, we conclude that the transonic motion of the cloud is caused by a merger, which was weak or occurred long ago.Comment: 9 pages, 7 figure

Chandra observation of a cold front in Abell 2554

Abstract We present the evidence for the existence of sub-structure in the cold front cluster A2554 based on a 20.14 ks Chandra observation. Using centroid shift and X-ray brightness concentration parameters, we confirm that A2554 is a dynamically disturbed system. We detect two dominant structures: a main cluster at z = 0.1108 and a foreground northern sub-structure at z = 0.1082. The analysis reveals an X-ray surface brightness edge at r ≃ 60 h−1 kpc from the cluster core. The thermodynamical profiles across the edge are ruling out the shock scenario. The temperature jump (from ∼6 keV to ∼10 keV), and pressure equilibrium (P0/P1 = 1.01 ± 0.23) across the edge, are consistent with the definition of a cold front with a Mach number $\mathcal {M}_1=0.94^{+0.13}_{-0.17}$. We also observed a weak bow-shock at ∼100 kpc in front of the cold cloud, corresponding an upper limit to the Mach number $\mathcal {M}_1$ ∼1.1. If the northern sub-structure was not related to the cold front, we conclude that the transonic motion of the cloud is caused by a merger, which was weak or occurred long ago.</jats:p

Evaluation of sludge management alternatives in Istanbul metropolitan area

The main concern of this paper was to predict the sludge quantities generated from 18 wastewater treatment plants, which were stated to be established in the “Istanbul Water Supply, Sewerage and Drainage, Sewage Treatment and Disposal Master Plan”, 10 of which are in operation at present. Besides this, obtaining the required data to compare various treatment schemes was another goal of the study. Especially, the estimation of the sludge quantity in the case of enhanced primary sedimentation was of importance. Wastewater sludge management strategies were discussed in order to develop suggestions for Istanbul Metropolitan city. Within this context, the wastewater treatment facilities, mentioned in the Master Plan that had been completed by 2000, were evaluated in terms of sludge production rates, locations and technical and management aspects. Disposal alternatives of the wastewater treatment sludge were also evaluated in this study. Using of the dewatered sludge as a landfill cover material seems the best alternative usage. Up to the year of 2040, the requirement of cover material for landfills in İstanbul will be met by the dewatered sludge originated from wastewater treatment plants in the region.</jats:p