Two New Milky Way Companions
نویسنده
چکیده
We discuss the detection limits and current status of a uniform survey of SDSS I for ultra-faint Milky Way dwarf galaxies. We present the properties of two new, low surface brightness Milky Way companions discovered as a result of this survey. One of these companions is the Ursa Major dwarf, the newest dwarf spheroidal companion to the Milky Way and the lowest luminosity galaxy yet known. Ursa Major is about 100 kpc away and is similar to Sextans, but with roughly an order of magnitude fewer stars. The other companion, SDSSJ1049+5103, lies ∼ 50 kpc away. Its stellar distribution suggests that it may be undergoing tidal stripping. This companion is extremely faint (MV ∼ -3) but has a large half-light size for its luminosity. It is therefore unclear whether it is a globular cluster or a dwarf galaxy.
منابع مشابه
Towards a kinematic model of the Local Group
Measuring the proper motions and geometric distances of galaxies within the Local Group is very important for our understanding of its history, present state and future. Currently, proper motion measurements using optical methods are limited only to the closest companions of the Milky Way. However, given that VLBI provides the best angular resolution in astronomy and phasereferencing techniques...
متن کاملGlobular Cluster and Galaxy Formation: M31, the Milky Way and Implications for Globular Cluster Systems of Spiral Galaxies
We find that the globular cluster systems of the Milky Way and of our neighboring spiral galaxy, M31, comprise two distinct entities, differing in three respects. First, M31 has a set of young globular clusters (GCs), ranging in age from a few 100 Myr to 5 Gyr old, as well as old globular clusters. No such very young GCs are known in the Milky Way. Second, we confirm that the oldest M31 GCs hav...
متن کامل3 High Mass X - ray Binary Pulsars in the Small Magellanic Cloud
We report two additions to the class of accreting X-ray pulsars from the direction of the Small Magellanic Cloud with periods of 263 and 202 s. (Recently Haberl & Pietsch (2004) reported the 263 s pulsar.) The source positions of these two pulsars are consistent with early B stars in the SMC and therefore we identify them as high mass X-ray binaries (HMXBs). Properties of an ensemble of 24 opti...
متن کاملThe Fate of Former Companions to Hypervelocity Stars Originating at the Galactic Center
The hypervelocity star SDSS J090745.0+024507 in the halo of the Milky Way galaxy (Brown et al. 2005) most likely originated from the breakup of a binary star system by the central black hole, SgrA* (Hills 1988). We examine the fate of former binary companions to similar hypervelocity stars (HVSs) by simulating 600 different binary orbits around SgrA* with a direct N-body integration code. For s...
متن کاملTime-scale for Accretion of Matter
Mass accretion is the key factor for evolution of galaxies. It can occur through secular evolution, when gas in the outer parts is driven inwards by dynamical instabilities, such as spirals or bars. This secular evolution proceeds very slowly when spontaneous, and can be accelerated when triggered by companions. Accretion can also occur directly through merging of small companions, or more viol...
متن کامل