With ACS-HST images we produced continuum subtracted photometric maps in Hα for the galaxies M51 and NGC 4449. From the Hα luminosity (L), equivalent radius (R) and coordinates of the HII regions with respect to the galaxy centers (over 2000 regions for M51, over 200 regions for NGC 4449), we derived the mean luminosity weighted electron density,

The goal of this work is to study the evolution of high-redshift (z≥ 1.4) quiescent galaxies over an effective area of ˜1.7 deg2 in the COSMOS field. Galaxies have been divided according to their star formation activity and the evolution of the different populations, in particular of the quiescent galaxies, has been investigated in detail. We have

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We report on the cometary activity of the minor body P/2010 C1 (Scotti), an active Centaur observed at 5.51 AU. The long-term dynamical behavior of this target is characterized by a close encounter with Saturn, which in 1877 drastically decreased its perihelion distance and semi-major axis to present values. It is probably a "transition" active

Aims: We introduce the Chromospheric Telescope (ChroTel) at the Observatorio del Teide in Izaña on Tenerife as a new multi-wavelength imaging telescope for full-disk synoptic observations of the solar chromosphere. We describe the design of the instrument and summarize its performance during the first one and a half years of operation. We present a

Between February 2010 and May 2011, our group has observed five stellar occultations by Trans-Neptunian Objects (TNOs), giving the size and shape for some of the biggest TNO's: Varuna, Eris, 2003 AZ84, Makemake and Quaoar. Here we present two of them: the January 08 stellar occultation by 2003 AZ84, and the May 04 by Quaoar. For the event of 2003