Search Publications
Two formation channels of ultra-compact dwarf galaxies in Hickson compact groups
Mendes de Oliveira, C.; Hilker, M.; Ziegler, B. L. +3 more
Context. The formation of ultra-compact dwarf galaxies (UCDs) is believed to be driven by interaction, and UCDs are abundant in the cores of galaxy clusters, environments that mark the end-point of galaxy evolution. Nothing is known about the properties of UCDs in compact groups of galaxies, environments where most of galaxy evolution and interact…
The Non-segregated Population of Blue Straggler Stars in the Remote Globular Cluster Palomar 14
Ferraro, Francesco R.; Lanzoni, Barbara; Beccari, Giacomo +5 more
We used deep wide-field observations obtained with the Canada-France-Hawaii Telescope to study the blue straggler star (BSS) population in the innermost 5 arcmin of the remote Galactic globular cluster Palomar 14. The BSS radial distribution is found to be consistent with that of the normal cluster stars, showing no evidence of central segregation…
Searching for Compton-thick active galactic nuclei at z∼ 0.1
Alexander, D. M.; Watson, M. G.; Ward, M. +4 more
Using a suite of X-ray, mid-infrared (mid-IR) and optical active galactic nuclei (AGN) luminosity indicators, we search for Compton-thick AGNs with intrinsic LX > 1042 erg s-1 at z∼ 0.03-0.2, a region of parameter space which is currently poorly constrained by deep narrow-field and high-energy (E > 10 keV) al…
Hemispheric Helicity Trend for Solar Cycle 24
Zhang, Mei; Hao, Juan
Using vector magnetograms obtained with the Spectro-polarimeter (SP) on board Hinode satellite, we studied two helicity parameters (local twist and current helicity) of 64 active regions that occurred in the descending phase of solar cycle 23 and the ascending phase of solar cycle 24. Our analysis gives the following results. (1) The 34 active reg…
Radial profiles of Fe abundance in the intracluster medium of nearby clusters observed with XMM-Newton
Matsushita, K.
Aims: The abundances of Fe in the intracluster medium of nearby (z < 0.08) clusters were measured up to 0.3 ~ 0.5r180.
Methods: We analyzed 28 clusters of galaxies observed with XMM-Newton. We derived Fe abundances from the flux ratios of Fe lines to the continuum within an energy range of 3.5-6 keV to minimize and evaluate…
Upstream of Saturn and Titan
André, N.; Coates, A. J.; Jackman, C. M. +8 more
The formation of Titan's induced magnetosphere is a unique and important example in the solar system of a plasma-moon interaction where the moon has a substantial atmosphere. The field and particle conditions upstream of Titan are important in controlling the interaction and also play a strong role in modulating the chemistry of the ionosphere. In…
Image reconstruction in optical interferometry: benchmarking the regularization
Thiébaut, E.; Malbet, F.; Renard, S.
Context. With the advent of visible and infrared long-baseline interferometers with more than two telescopes, both the size and the completeness of interferometric data sets have significantly increased, allowing images based on models with no a priori assumptions to be reconstructed with an aperture synthesis technique.
Aims: Our main object…
Discovery and Analysis of 21 µm Feature Sources in the Magellanic Clouds
Gordon, Karl D.; Matsuura, Mikako; Volk, Kevin +15 more
Spitzer Space Telescope mid-infrared spectroscopy has been obtained for 15 carbon-rich protoplanetary nebulae (PPNe) in the Large Magellanic Cloud (LMC) and for two other such stars in the Small Magellanic Cloud (SMC). Of these 17 PPNe, the unidentified 21 µm feature is strong in 7 spectra, weak in 2 spectra, and very weak or questionable in…
The Cluster Population of the Irregular Galaxy NGC 4449 as Seen by the Hubble Advanced Camera for Surveys
Tosi, M.; van der Marel, R. P.; Aloisi, A. +1 more
We present a study of the star cluster population in the starburst irregular galaxy NGC 4449 based on B, V, I, and Hα images taken with the Advanced Camera for Surveys on the Hubble Space Telescope. We derive cluster properties such as size, ellipticity, and total magnitude. Cluster ages and masses are derived fitting the observed spectral energy …
Dust Production and Mass Loss in the Galactic Globular Cluster 47 Tucanae
van Loon, J. Th.; Zijlstra, A. A.; Boyer, M. L. +1 more
Dust production among post-main-sequence stars is investigated in the Galactic globular cluster 47 Tucanae (NGC 104) based on infrared photometry and spectroscopy. We identify metallic iron grains as the probable dominant opacity source in these winds. Typical evolutionary timescales of asymptotic giant branch stars suggest the mass-loss rates we …