Search

Dwarf spheroidal (dSph) galaxies are the smallest galactic systems known. Also, under standard gravity, they are the most dark matter dominated systems known in astrophysics. The local sample of dSph satellites of the Milky Way comprise some two dozen systems, ranging from a few million, down to just a few thousand solar masses in stellar content, for the recently discovered ones. High quality observations of their stellar kinematics now allow detailed inferences of their structural and dynamical properties. We perform a modeling of the gravitational equilibrium configurations for a sample of he best studied dSphs under MOND, and find that a satisfactory description is obtained, without the need to invoke the presence of dark matter or any tidal effects, for a particular interpolation function, valid at this regime. We find also that the now well established scalings of the structural properties of these systems are naturally accounted for, while they require fine tuning under the dark matter hypothesis. In particular we find a previously unrecognized scaling between the inferred mass to light ratio of a particular dSph, with the age of most recent star formation episode for the system. Again, a trait which emerges naturally under any modified gravity scheme, and which appears as an unexplained coincidence under the dark matter hypothesis. [ABSTRACT FROM AUTHOR]

At present, dwarf spheroidal galaxies satellites of the Milky Way may represent the best astrophysical objects for dark matter (DM) searches with gamma-ray telescopes. They present the highest mass-to-light ratios known in the Universe. Furthermore, many of them are near enough from the Earth to be able to yield high predicted DM annihilation fluxes that might be observed by current gamma-ray instruments like MAGIC. The picture has become even better with the recent discovery of new dwarfs. These new objects are expected to yield even higher DM annihilation fluxes, since most of them are nearer than the previously known dwarfs and are even more DM dominated systems. Here a tentative list of the best candidates is given. The observational results obtained with MAGIC from the Draco dwarf as well as the observation of other dwarfs carried out by other Cherenkov telescopes are presented as well. Finally, we discuss the detection prospects of such kind of objects in the context of DM searches. [ABSTRACT FROM AUTHOR]

We summarize the talks and the public discussion from Session V of the conference, a session devoted to exploring the breadth of scientific results from FUSE observations. [ABSTRACT FROM AUTHOR]

We derive the chemical composition of the neutral gas in the blue compact dwarf (BCD) Pox 36 observed with FUSE. Metals (N, O, Ar, and Fe) are underabundant as compared to the ionized gas associated with H II regions by a factor ∼7. The neutral gas, although it is not pristine, is thus probably less chemically evolved than the ionized gas. This could be due to different dispersal and mixing timescales. Results are compared to those of other BCDs observed with FUSE. The metallicity of the neutral gas in BCDs seems to reach a lower threshold of ∼1/50Z⊙ for extremely-metal poor galaxies. [ABSTRACT FROM AUTHOR]

During the 2007/2008 season, VERITAS was used for observations at E>200 GeV of several extragalactic non-blazar objects such as galaxy clusters, starburst and interacting galaxies, dwarf galaxies, and nearby galaxies. In these proceedings, we present preliminary results from our observations of dwarf galaxies and M87. Results from observation of other non-blazar sources are presented in separate papers in the proceedings. [ABSTRACT FROM AUTHOR]

Radiation from the first stars expel most of the gas from the shallow DM potential wells in which they formed. We use cosmological radiation hydrodynamical AMR simulations that include self-consistent Population III star formation and feedback. Radiative transport is accurately modelled with adaptive ray tracing. We include supernova (SN) explosions and follow the metal enrichment of the intergalactic medium and surrounding star forming halos. We focus on the formation of several dwarf galaxies and their progenitors. Baryon fractions in Tvir = 104 K halos decrease to 10% with stellar feedback and 5% with SN explosions. We find that gaseous spin parameters increase up to a factor of 5 when SN feedback is included. [ABSTRACT FROM AUTHOR]

A new revision of the gamma flux that we expect to detect in Imaging Atmospheric Cherenkov Telescopes (IACTs) from SUSY dark matter annihilation in the Draco dSph is presented using the dark matter density profiles compatible with the latest observations. This revision takes also into account the important effect of the Point Spread Function (PSF) of the Cherenkov telescope. We show that this effect is crucial in the way we will observe and interpret a possible signal profile in the telescope. Given these new considerations, some light can be shed on the recent signal excess reported by the CACTUS experiment. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Dwarf galaxies are important to study because they potentially provide a direct connection to the earliest epochs of galaxy formation. They also allow us to study the star formation process at relatively low abundances. Our understanding of the origins and evolution of dwarf galaxies has been changing very rapidly. New observations are giving better insight into the relationship between the two main families of dwarf galaxies, the dwarf ellipticals and the dwarf irregulars. Here I review a broad range of topics related to the formation and evolution of dwarf galaxies. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A new estimation of the γ-ray flux that we expect to detect from SUSY dark matter annihilation from the Draco dSph is presented using the DM density profiles compatible with the latest observations. This calculation takes also into account the important effect of the Point Spread Function (PSF) of the telescope. We show that this effect is crucial in the way we will observe and interpret a possible signal detection. Finally, we discuss the prospects to detect a possible gamma signal from Draco for MAGIC and GLAST. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]