Search Publications
Stellar Populations across the NGC 4244 Truncated Galactic Disk
de Jong, Roelof S.; Ferguson, H. C.; Dalcanton, J. J. +12 more
We use the Hubble Space Telescope ACS to study the resolved stellar populations of the nearby, nearly edge-on galaxy NGC 4244 across its outer disk surface density break. The stellar photometry allows us to study the distribution of different stellar populations and reach very low equivalent surface brightnesses. We find that the break occurs at t…
Hubble Space Telescope Advanced Camera for Surveys Coronagraphic Observations of the Dust Surrounding HD 100546
Ford, H. C.; Illingworth, G. D.; Ardila, D. R. +3 more
We present HST ACS coronagraphic observations of HD 100546, a B9.5 star, 103 pc away from the Sun, taken in the F435W, F606W, and F814W bands. Scattered light is detected up to 14" from the star. The observations are consistent with the presence of an extended flattened nebula with the same inclination as the inner disk. The well-known ``spiral ar…
A dynamic, rotating ring current around Saturn
Krupp, N.; Krimigis, S. M.; Mitchell, D. G. +2 more
The concept of an electrical current encircling the Earth at high altitudes was first proposed in 1917 to explain the depression of the horizontal component of the Earth's magnetic field during geomagnetic storms. In situ measurements of the extent and composition of this current were made some 50years later and an image was obtained in 2001 (ref.…
Constraints on physical properties of z ~ 6 galaxies using cosmological hydrodynamic simulations
Davé, Romeel; Finlator, Kristian; Oppenheimer, Benjamin D.
We conduct a detailed comparison of broad-band spectral energy distributions of six z >~ 5.5 galaxies against galaxies drawn from cosmological hydrodynamic simulations. We employ a new tool called SPOC (Simulated photometry-derived observational constraints), which constrains the physical properties of observed galaxies through a Bayesian likel…
Density of Mars’ South Polar Layered Deposits
Zuber, Maria T.; Asmar, Sami W.; Smrekar, Suzanne E. +6 more
Both poles of Mars are hidden beneath caps of layered ice. We calculated the density of the south polar layered deposits by combining the gravity field obtained from initial results of radio tracking of the Mars Reconnaissance Orbiter with existing surface topography from the Mars Orbiter Laser Altimeter on the Mars Global Surveyor spacecraft and …
A wide deep infrared look at the Pleiades with UKIDSS: new constraints on the substellar binary fraction and the low-mass initial mass function
Hambly, N. C.; Hodgkin, S. T.; Jameson, R. F. +3 more
We present the results of a deep wide-field near-infrared survey of 12 deg2 of the Pleiades conducted as part of the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) Galactic Cluster Survey (GCS). We have extracted over 340 high-probability proper motion (PM) members down to 0.03 M⊙ using a combinat…
A 0535+26 in the August/September 2005 outburst observed by RXTE and INTEGRAL
Klochkov, D.; Santangelo, A.; Wilms, J. +14 more
Aims: In this Letter we present results from INTEGRAL and RXTE observations of the spectral and timing behavior of the High Mass X-ray Binary A 0535+26 during its August/September 2005 normal (type I) outburst with an average flux F(5-100) keV ∼400 mCrab. The search for cyclotron resonance scattering features (fundamental and…
A review of selected issues concerning the chemistry in Venus’ middle atmosphere
Allen, Mark; Mills, Franklin P.
Even after decades of study using advanced observing instruments and sophisticated numerical models, a number of significant questions remain unanswered concerning the composition and chemistry of Venus' atmosphere. The primary chemical cycles and the interactions among sulfur and chlorine radicals in Venus' middle atmosphere are reviewed to asses…
Distances of the bulge globular clusters Terzan 5, Liller 1, UKS 1, and Terzan 4 based on HST NICMOS photometry
Zoccali, M.; Bica, E.; Barbuy, B. +2 more
Context: A large number of pulsars and X-rays sources are detected in globular clusters. To understand the structure and content of these clusters, accurate distances are required.
Aims: We derive the distances of Terzan 5, Liller 1 and UKS 1 using as a reference a recent distance determination of NGC 6528, based on HST/NICMOS and NTT/SOFI inf…
Physical parameters of 15 intermediate-age LMC clusters from modelling of HST colour-magnitude diagrams
Santiago, B. X.; Brocato, E.; Kerber, L. O.
Aims:We analyzed HST/WFPC2 colour-magnitude diagrams (CMDs) of 15 populous Large Magellanic Cloud (LMC) stellar clusters with ages between ~0.3 Gyr and ~3 Gyr. These (V, B-V) CMDs are photometrically homogeneous and typically reach V ∼ 22. Accurate and self-consistent physical parameters (age, metallicity, distance modulus and reddening) were extr…