Search Publications
Galaxy Disruption in a Halo of Dark Matter
Forbes, Duncan A.; Brodie, Jean P.; Beasley, Michael A. +2 more
The relics of disrupted satellite galaxies have been found around the Milky Way and Andromeda, but direct evidence of a satellite galaxy in the early stages of disruption has remained elusive. We have discovered a dwarf satellite galaxy in the process of being torn apart by gravitational tidal forces as it merges with a larger galaxy's dark matter…
Why hot horizontal branch stars can appear redder than red giants
Recio-Blanco, A.; Momany, Y.; Bedin, L. R. +4 more
In this paper we report on a curious feature in the V, (U-B) color-magnitude diagrams of globular clusters. In our database, we find that a considerable fraction of blue horizontal branch stars, hotter than the instability strip and cooler than the Grundahl et al. (1999) jump (i.e., 6000 <~ Teff(K)<~ 10 000), have (U-B) colors red…
The Recent Evolution of the Dwarf Starburst Galaxy NGC 625 from Hubble Space Telescope Imaging
Cannon, John M.; Skillman, Evan D.; Miller, Bryan W. +3 more
New Hubble Space Telescope WFPC2 imaging of the dwarf starburst galaxy NGC 625 is presented. These data, which are 80% complete to V and I magnitudes of 26.0 and 25.3, respectively, allow us to study the recent star formation history of NGC 625. Using outlying red giant stars, we derive a tip of the red giant branch (TRGB) distance modulus of 27.9…
The Long-Term Evolution of AR 7978: Testing Coronal Heating Models
Klimchuk, J. A.; Mandrini, C. H.; van Driel-Gesztelyi, L. +2 more
We derive the dependence of the mean coronal heating rate on the magnetic flux density. Our results are based on a previous study of the plasma parameters and the magnetic flux density (B) in the active region NOAA 7978 from its birth to its decay, throughout five solar rotations using the Solar and Heliospheric Observatory Michelson Doppler Image…
The redshift of the Einstein ring in MG 1549+305
Treu, T.; Koopmans, L. V. E.
A deep spectrum taken with the Echelle Spectrograph and Imager (ESI) at the Keck II Telescope as part of the Lenses Structure and Dynamics (LSD) Survey reveals the redshifts of the extremely red source of the radio Einstein ring in the gravitational lens system MG 1549+305 (zs= 1.170 +/- 0.001) and an intermediate-redshift lensed spiral…
In-flight calibration of the ISGRI camera
Goldoni, P.; Malaguti, G.; David, P. +12 more
ISGRI, the IBIS low energy camera (15 keV-1 MeV) on board INTEGRAL, is the first large CdTe gamma-ray imager in orbit. We present here an overview of the ISGRI in-flight calibrations performed during the first months after launch. We discuss the stability of the camera as well as the CdTe pixels response under cosmic radiation. The energy calibrat…
Dispersion analysis of ULF waves in the foreshock using cluster data and the wave telescope technique
Dandouras, I.; Glassmeier, K. -H.; Rème, H. +6 more
Cluster provides us with a unique possibility to study ULF waves. We analyze ULF wave activity in the near-Earth upstream solar wind. Using Cluster as a wave telescope we investigate in detail wave propagation directions and wave numbers for various frequencies, obtaining, for the first time, three dimensional dispersion relations experimentally. …
Interactions of Dust Grains with Coronal Mass Ejections and Solar Cycle Variations of the F-Coronal Brightness
Kahler, S. W.; Ragot, B. R.
The density of interplanetary dust increases sunward to reach its maximum in the F corona, where its scattered white-light emission dominates that of the electron K corona above about 3 Rsolar. The dust will interact with both the particles and fields of antisunward propagating coronal mass ejections (CMEs). To understand the effects of…
A two-arm gaseous spiral in the inner 200 pc of the early-type galaxy NGC 2974: signature of an inner bar
Emsellem, Eric; Ferruit, Pierre; Goudfrooij, Paul
TIGER integral-field spectrography and Hubble Space Telescope Wide Field and Planetary Camera 2 (WFPC2) imaging of the E3 galaxy NGC 2974 are used to derive the kinematics of the stellar and ionized gas components in its central 500 pc. We derive a numerical two-integral distribution function from a multi-Gaussian expansion (MGE) mass model using …
Searching for Embedded Super-Star Clusters in IC 4662, NGC 1705, and NGC 5398
Johnson, Kelsey E.; Indebetouw, Rémy; Pisano, D. J.
Radio observations of IC 4662, NGC 5398, and NGC 1705 are used in combination with optical images to search for extremely young star clusters that are still embedded in their birth material. Radio data were obtained at 3 and 6 cm using the Australia Telescope Compact Array, and optical data were retrieved from the Hubble Space Telescope (HST) arch…