We present the first all-sky view of the Sagittarius (Sgr) dwarf galaxy mapped by M giant star tracers detected in the complete Two Micron All-Sky Survey (2MASS).Near infrared photometry of Sgr's prominent M giant population permits an unprecedentedly clear view of the center of Sgr. The main body is fit with a King profile of limiting major axis radius 30 • -substantially larger than previously found or assumed -beyond which is a prominent break in the density profile from stars in its tidal tails; thus the Sgr radial profile resembles that of Galactic dSph satellites. Adopting traditional methods for analyzing dSph light profiles, we determine the brightness of the main body of Sgr to be M V = −13.27 (the brightest of the known Galactic dSph galaxies) and the total Sgr mass-to-light ratio to be 25 in solar units. However, we regard the latter result with suspicion and argue that much of the observed structure beyond the King fit core radius (224 arcmin) may be outside the actual Sgr tidal radius as the former dwarf spiral/irregular satellite undergoes catastrophic disruption over its past last orbit. The M giant distribution of Sgr exhibits a central density cusp at the same location as, but not due to, the old stars constituting the globular cluster M54.A striking trailing tidal tail is found to extend from the Sgr center and arc across the South Galactic Hemisphere with approximately constant density and mean distance varying from ∼ 20−40 kpc. A prominent leading debris arm extends from the Sgr center northward of the Galactic plane to an apoGalacticon ∼ 45 kpc from the Sun, then turns towards the North Galactic Cap (NGC) from where it descends back towards the Galactic plane, becomes foreshortened and at brighter magnitudes covers the NGC. The leading and trailing Sgr tails lie along a well-defined orbital plane about the Galactic Center. The Sun lies within a kiloparsec of that plane and near the path of leading Sgr debris; thus, it is possible that former Sgr stars are near or in the solar neighborhood.We discuss the implications of this new view of the Sgr galaxy and its entrails for the character of the Sgr orbit, mass, mass-loss rate, and contribution of stars to the Milky Way halo. The minimal precession displayed by the Sgr tidal debris along its inclinded orbit supports the notion of a nearly spherical Galactic potential. The number of M -2giants in the Sgr tails is at least 15% that contained within the King limiting radius of the main Sgr body. The fact that M giants, presumably formed within the past few gigayears in the Sgr nucleus, are nevertheless so widespread along the Sgr tidal arms not only places limits on the dynamical age of these arms but poses a timing problem that bears on the recent binding energy of the Sgr core and that is most naturally explained by recent and catastrophic mass loss. Sgr appears to contribute more than 75% of the high latitude, halo M giants, despite substantial reservoirs of M giants in the Magellanic Clouds. No evidence of extended M giant tidal debris from the ...

The fourth generation of the Sloan

The first gamma-ray burst (GRB) confirmed to be bright enough to be seen with the naked eye, GRB 080319B at redshift z = 0.937, allowed for exquisite follow-up observations across the electromagnetic spectrum. We present our detailed optical and infrared observations of the afterglow, consisting of over 5000 images starting 51 s after the GRB trigger, in concert with our own analysis of

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