A unique small-scale gravitational arc in A1201

We present a snapshot Hubble Space Telescope (HST) image of the galaxy cluster A1201 (z=0.169), revealing a tangential arc 2 from the brightest cluster galaxy (BCG). Keck Echelle Spectrograph and Imager (ESI) spectroscopy confirms that the arc is gravitational in nature and that the source galaxy lies at z=0.451. We construct a model of the gravitational potential of the cluster that faithfully reproduces the observed arc morphology. Despite the relaxed appearance of the cluster in the HST frame, the best-fit ellipticity of the total matter distribution is total0.5, in contrast to the light distribution of the BCG (BCG=0.23±0.03) on 2 scales. Further deep optical observations and pointed X-ray spectro-imaging observations with Chandra are required to determine whether this elongation is due to a single elongated dark matter halo or a more complex distribution of matter in the cluster core. We compare the arc with a sample drawn from the published literature and confirm that it is unique among tangential systems in the small physical scales that it probes (6 kpc). In anticipation of a more thorough investigation of this cluster across a broad range of physical scales, we use our fiducial lens model to estimate the projected mass and mass-to-light ratio of the cluster within a radius of 6 kpc, obtaining M=(5.9+0.9-0.7)×1011 M, M/LV=9.4+2.4-2.1 (M/L). Overall our results confirm the importance of HST snapshot surveys for identifying rare lensing constraints on cluster mass distributions. In combination with follow-up optical and X-ray observations, the arc in A1201 should help to increase our understanding of the physics of cluster cores

Untersuchungen zur mikrobiellen Sicherung von Bergbaualtlasten. Teilvorhaben 1: Laugungsreduzierung in Schwermetallsulfid-belasteten Erzbergbauregionen Abschlussbericht 2000

Ziel des Projektes ist die Erarbeitung eines optimierten Massnahmenpaketes zur Sicherung und Sanierung von Bergbaualtlasten, die durch mikrobiologische Sauerwasserbildung und Schwermetallmobilisierung Boeden und Gewaesser kontaminieren. Die Problematik und der Stand der Kenntnisse sowie erste Ergebnisse der Bestandsaufnahmen wurden in den Jahresberichten 1995 und 1996 sowie im Fortsetzungsantrag ausfuehrlich dargestellt. Ueber die Versuchsergebnisse der Jahre 1997 und 1998 wurde bereits berichtet. Im Folgenden werden die in den Jahren 1999 und 2000 erzielten Ergebnisse zusammengefasst und eine Bewertung der Projektarbeit vorgenommen. Abschliessend wird ein Massnahmenkatalog vorgeschlagen, der bei der Planung und Durchfuehrung von Sanierungsaufgaben an Bergbaualtlasten den Anwendern die aus mikrobiologischer Sicht zu beruecksichtigenden Aspekte mit Loesungsmoeglichkeiten gebuendelt zur Verfuegung stellt. (orig.)The project was aimed at the development of an optimized catalogue of measures for regeneration and reclamation of polluted mining land. Reports were published in 1995, 1996, 1997 and 1998. This report summarizes the work of 1999 and 2000. A catalogue of measures is proposed on the basis of the results.SIGLEAvailable from TIB Hannover: F01B937+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany); Umweltbundesamt, Berlin (Germany)DEGerman

Low-density star cluster formation: discovery of a young faint fuzzy on the outskirts of the low-mass spiral galaxy NGC 247

The classical globular clusters found in all galaxy types have half-light radii of rh ~2-4 pc, which have been tied to formation in the dense cores of giant molecular clouds. Some old star clusters have larger sizes, and it is unclear if these represent a fundamentally different mode of low-density star cluster formation. We report the discovery of a rare, young 'faint fuzzy' star cluster, NGC 247-SC1, on the outskirts of the low-mass spiral galaxy NGC 247 in the nearby Sculptor group, and measure its radial velocity using Keck spectroscopy. We use Hubble Space Telescope imaging to measure the cluster half-light radius of rh ≃ 12 pc and a luminosity of LV ≃ 4 × 105Lθ. We produce a colour-magnitude diagram of cluster stars and compare to theoretical isochrones, finding an age of ≃300 Myr, a metallicity of [Z/H] ~-0.6 and an inferred mass of M∗ ≃ 9 × 104Mθ. The narrow width of blue-loop star magnitudes implies an age spread of ≲50 Myr, while no old red-giant branch stars are found, so SC1 is consistent with hosting a single stellar population, modulo several unexplained bright 'red straggler' stars. SC1 appears to be surrounded by tidal debris, at the end of an ∼2 kpc long stellar filament that also hosts two low-mass, low-density clusters of a similar age. We explore a link between the formation of these unusual clusters and an external perturbation of their host galaxy, illuminating a possible channel by which some clusters are born with large sizes. © 2022 The Author(s).Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]