Search Publications
Evolution of dwarf galaxies in the Centaurus A group
Crnojević, D.; Grebel, E. K.; Koch, A.
The study of (dwarf) galaxies in nearby groups is one among the most powerful tools that can be used to investigate galaxy evolution, chemical enrichment and environmental effects on these objects. The Centaurus A group (at a distance of ∼ 4 Mpc) is dynamically evolved and contains about 30 dwarf companions of different morphologies and stellar co…
Dwarf spheroidal galaxies in the M81 group of galaxies
Grebel, E. K.; Koch, A.; Lianou, S.
We study the properties of the dwarf galaxy population in the nearby interacting M81 group of galaxies. In particular, we are deriving the metallicity distribution functions, the ages and the star formation histories of these dwarf galaxies based on data from the Hubble Space Telescope's Advanced Camera for Surveys and the Sloan Digital Sky Survey…
Galaxy-galaxy interactions as triggers of star formation
Popescu, N. A.
Galaxy-galaxy interactions represent the main physical processes that trigger substantial star formation in galaxies. In order to study the galaxy interactions effects on color and morphology of the galaxies in the fields of two radio galaxies at z∼ 1, we combined optical-NIR photometry and HST/WFPC2 morphology data from the Stanford et al. (2002)…
On the distance to the Ophiuchus star-forming region
Mamajek, E. E.
The Ophiuchus molecular cloud complex has produced in Lynds 1688 the richest known embedded cluster within ∼300 pc of the Sun. Unfortunately, distance estimates to the Oph complex vary by nearly ∼40% (∼120-165 pc). Here I calculate a new independent distance estimate of 135 ± 8 pc to this benchmark star-forming region based on Hipparcos trigonomet…
Speckle observations with PISCO in Merate: IV. Astrometric measurements of visual binaries in 2005
Scardia, M.; Prieur, J. -L.; Pansecchi, L. +6 more
We present relative astrometric measurements of visual binaries made during the second semester of 2005, with the speckle camera PISCO at the 102 cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. The purpose of this long term program is to impro…
New absolute magnitude calibrations for detached binaries
Demircan, O.; Eker, Z.; Soydugan, F. +6 more
Lutz-Kelker bias corrected absolute magnitude calibrations for the detached binary systems with main-sequence components are presented. The absolute magnitudes of the calibrator stars were derived at intrinsic colours of Johnson-Cousins and 2MASS (Two Micron All Sky Survey) photometric systems. As for the calibrator stars, 44 detached binaries wer…
A revisit to agglomerates of early-type Hipparcos stars
Caballero, J. A.; Dinis, L.
% We study the spatial structure and sub-structure of regions rich in {Hipparcos} stars with blue B_T-V_T colours. These regions, which comprise large stellar complexes, OB associations, and young open clusters, are tracers of on-going star formation in the Galaxy. The DBSCAN (Density-Based Spatial Clustering of Applications with Noise) data clust…
Preliminary orbital elements of six visual binary stars
Scardia, M.; Prieur, J. -L.; Pansecchi, L. +1 more
Preliminary new orbital elements were computed for the visual binary stars A 1 - ADS 1345, A 2629 - ADS 3610, BU 560 - ADS 4371, STF 3115 - ADS 4376, STF 1426 AB - ADS 7730 and STF 2437 - ADS 11956. Using Straizys and Kuriliene's data, we derived new formulae for computing dynamical parallaxes for luminosity classes IV and V. The values found for …
Extragalactic X-ray surveys: AGN physics and evolution
Comastri, A.; Brusa, M.
We review the most important findings on AGN physics and cosmological evolution as obtained by extragalactic X-ray surveys and associated multiwavelength observations. We briefly discuss the perspectives for future enterprises and in particular the scientific case for an extremely deep (2-3 Ms) XMM survey
The Planck cluster survey
Arnaud, M.; Bartlett, J. G.; Chamballu, A. +2 more
The Planck Satellite will survey the entire sky in 9 millimeter/submillimeter bands and detect thousands of galaxy clusters via their thermal Sunyaev-Zel'dovich (SZ) effect. The unprecedented volume of the survey will permit the construction of a unique catalog of massive clusters out to redshifts of order unity. We describe the expected contents …