Search Publications
The merging cluster Abell 1758 revisited: multi-wavelength observations and numerical simulations
Durret, F.; Laganá, T. F.; Haider, M.
Context. Cluster properties can be more distinctly studied in pairs of clusters, where we expect the effects of interactions to be strong.
Aims: We here discuss the properties of the double cluster Abell 1758 at a redshift z ~ 0.279. These clusters show strong evidence for merging.
Methods: We analyse the optical properties of the North …
A Study of Gravitational Lens Chromaticity with the Hubble Space Telescope
Kochanek, C. S.; Muñoz, J. A.; Falco, E. E. +2 more
We report Hubble Space Telescope observations of six gravitational lenses with the Advanced Camera for Surveys. We measured the flux ratios between the lensed images in seven filters from 8140 Å to 2200 Å. In three of the systems, HE0512-3329, B1600+434, and H1413+117, we were able to construct UV extinction curves partially overlapping the 2175 Å…
In search of massive single-population globular clusters
D'Antona, Francesca; Caloi, Vittoria
The vast majority of globular clusters so far examined shows the chemical signatures of hosting (at least) two stellar populations. According to recent ideas, this feature requires a two-step process, in which the nuclearly processed matter from a 'first generation' (FG) of stars gives birth to a 'second generation' (SG), bearing the fingerprint o…
HST-COS Observations of Hydrogen, Helium, Carbon, and Nitrogen Emission from the SN 1987A Reverse Shock
Smith, Nathan; Pun, Chun S. J.; France, Kevin +18 more
We present the most sensitive ultraviolet observations of Supernova 1987A to date. Imaging spectroscopy from the Hubble Space Telescope-Cosmic Origins Spectrograph shows many narrow (Δv ~ 300 km s-1) emission lines from the circumstellar ring, broad (Δv ~ 10-20 × 103 km s-1) emission lines from the reverse shock, a…
A statistical analysis of the SOT-Hinode observations of solar spicules and their wave-like behavior
Koutchmy, S.; Tavabi, E.; Ajabshirizadeh, A.
Spicules are an important very dynamical and rather cool structure extending between the solar surface and the corona. They are partly filling the space inside the chromosphere and they are surrounded by a transition thin layer. New space observations taken with the SOT of the Hinode mission shed some light on their still mysterious formation and …
Simultaneous Cassini VIMS and UVIS observations of Saturn's southern aurora: Comparing emissions from H, H2 and H3+ at a high spatial resolution
Brown, R. H.; Baines, K. H.; Badman, S. V. +7 more
Here, for the first time, temporally coincident and spatially overlapping Cassini VIMS and UVIS observations of Saturn's southern aurora are presented. Ultraviolet auroral H and H2 emissions from UVIS are compared to infrared H3+ emission from VIMS. The auroral emission is structured into three arcs - H, H2
The White Dwarf Age of NGC 2477
van Dyk, David A.; von Hippel, Ted; Jeffery, Elizabeth J. +3 more
We present deep photometric observations of the open cluster NGC 2477 using HST/WFPC2. By identifying seven cluster white dwarf candidates, we present an analysis of the white dwarf age of this cluster, using both the traditional method of fitting isochrones to the white dwarf cooling sequence, and by employing a new Bayesian statistical technique…
A solar eruption triggered by the interaction between two magnetic flux systems with opposite magnetic helicity
Romano, P.; Pariat, E.; Zuccarello, F. +1 more
Context. In recent years the accumulation of magnetic helicity via emergence of new magnetic flux and/or shearing photospheric motions has been considered to play an important role in the destabilization processes that lead to eruptive phenomena occurring in the solar atmosphere.
Aims: In this paper we want to highlight a specific aspect of m…
Statistics of plasma sheet convection
Østgaard, N.; Juusola, L.; Tanskanen, E.
Determining the characteristics of plasma sheet convection and their response to changes in various solar wind parameters is important for understanding the energy and mass transport, as well as disturbance propagation, through geospace. We use 15 years of data obtained by Geotail, Cluster, and THEMIS to study statistically the characteristics of …
The evolution of stellar structures in dwarf galaxies
Walter, F.; Bastian, N.; Kennicutt, R. C. +8 more
We present a study of the variation of spatial structure of stellar populations within dwarf galaxies as a function of the population age. We use deep Hubble Space Telescope/Advanced Camera for Surveys imaging of nearby dwarf galaxies in order to resolve individual stars and create composite colour-magnitude diagrams (CMDs) for each galaxy. Using …