Optical altimeter receiver systems study and design for a spaceborne laser altimeter

Design and specifications for optical altimeter receiver system

Gaia 1 and 2. A pair of new Galactic star clusters

We present the results of the very first search for faint Milky Way satellites in the Gaia data. Using stellar positions only, we are able to re-discover objects detected in much deeper data as recently as the last couple of years. While we do not identify new prominent ultra-faint dwarf galaxies, we report the discovery of two new star clusters, Gaia 1 and Gaia 2. Gaia 1 is particularly curious, as it is a massive (2.2$\times$10$^4$ M$_\odot$), large ($\sim$9 pc) and nearby (4.6 kpc) cluster, situated 10' away from the brightest star on the sky, Sirius! Even though this satellite is detected at significance in excess of 10, it was missed by previous sky surveys. We conclude that Gaia possesses powerful and unique capabilities for satellite detection thanks to its unrivalled angular resolution and highly efficient object classification.Comment: 9 pages, accepted to MNRA

Nine tiny star clusters in Gaia DR1, PS1 and DES

We present the results of a systematic Milky Way satellite search performed across an array of publicly available wide-area photometric surveys. Our aim is to complement previous searches by widening the parameter space covered. Specifically, we focus on objects smaller than $1'$ and include old, young, metal poor and metal rich stellar population masks. As a result we find 9 new likely genuine stellar systems in data from GAIA, DES, and Pan-STARRS, which were picked from the candidate list because of conspicuous counterparts in the cut-out images. The presented systems are all very compact ($r_h<1'$) and faint ($M_V\gtrsim-3$), and are associated either with the Galactic disk, or the Magellanic Clouds. While most of the stellar systems look like Open Clusters, their exact classification is, as of today, unclear. With these discoveries, we extend the parameter space occupied by star clusters to sizes and luminosities previously unexplored and demonstrate that rather than two distinct classes of Globular and Open clusters, there appears to be a continuity of objects, unmarked by a clear decision boundary.Comment: 17 pages, 13 figures, accepted in MNRAS. v1 submitted version; v2 accepted Versio

The feeble giant: Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater

© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.We announce the discovery of the Crater 2 dwarf galaxy, identified in imaging data of the VLT Survey Telescope ATLAS survey. Given its half-light radius of ~1100 pc, Crater 2 is the fourth largest satellite of the Milky Way, surpassed only by the Large Magellanic Cloud, Small Magellanic Cloud and the Sgr dwarf. With a total luminosity of MV ≈ -8, this galaxy is also one of the lowest surface brightness dwarfs. Falling under the nominal detection boundary of 30 mag arcsec-2, it compares in nebulosity to the recently discovered Tuc 2 and Tuc IV and UMa II. Crater 2 is located ~120 kpc from the Sun and appears to be aligned in 3D with the enigmatic globular cluster Crater, the pair of ultrafaint dwarfs Leo IV and Leo V and the classical dwarf Leo II. We argue that such arrangement is probably not accidental and, in fact, can be viewed as the evidence for the accretion of the Crater-Leo group

Maureen G. Shanahan y Ana María Reyes, eds. Simón Bolívar: Travels and Transformations of a Cultural Icon.

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Luis Duno-Gottberg, ed. La política encarnada. Biopolítica y cultura en la Venezuela bolivariana. Caracas: Equinoccio, Universidad Simón Bolívar, 2015.

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