Search Publications
Cluster observations of electron holes in association with magnetotail reconnection and comparison to simulations
Balogh, A.; Lucek, E.; André, M. +8 more
Large-amplitude (up to ∼50 mV/m) solitary waves, identified as electron holes, have been observed during waveform captures on two of the four Cluster satellites during several plasma sheet encounters that have been identified as the passage of a magnetotail reconnection x line. The electron holes were seen near the outer edge of the plasma sheet, …
The Age Distribution of Massive Star Clusters in the Antennae Galaxies
Whitmore, Bradley C.; Fall, S. Michael; Chandar, Rupali
We determine the age distribution of star clusters in the Antennae galaxies (NGC 4038/9) for two mass-limited samples (M>3×104 Msolar and M>2×105 Msolar). This is based on integrated broadband UBVI and narrowband Hα photometry from deep images taken with the Hubble Space Telescope. We find that the…
Did most present-day spirals form during the last 8 Gyr?. A formation history with violent episodes revealed by panchromatic observations
Elbaz, D.; Cesarsky, C.; Flores, H. +3 more
Studies of distant galaxies have shown that ellipticals and large spirals (Schade et al. \cite{Schade99}, ApJ, 525, 31; Lilly et al. \cite{Lilly98}, ApJ, 500, 75) were already in place 8 Gyr ago, leading to a very modest recent star formation (Brinchmann & Ellis \cite{Brinchmann00}, ApJ, 536, L77) in intermediate mass galaxies (3-30 × 101…
Cluster observations of an intense normal component of the electric field at a thin reconnecting current sheet in the tail and its role in the shock-like acceleration of the ion fluid into the separatrix region
Balogh, A.; Lucek, E. A.; Reme, H. +12 more
Measurements from the Cluster spacecraft of electric fields, magnetic fields, and ions are used to study the structure and dynamics of the reconnection region in the tail at distances of ∼18 RE near 22.4 MLT on 1 October 2001. This paper focuses on measurements of the large amplitude normal component of the electric field observed in th…
X-ray obscuration and obscured AGN in the local universe
Perola, G. C.; Guainazzi, M.; Matt, G.
We discuss the X-ray properties of 49 local (z<0.035) Seyfert 2 galaxies with HST/WFC2 high-resolution optical coverage. It includes the results of 26 still unpublished Chandra and XMM-Newton observations, which yield 25 (22) new X-ray detections in the 0.5-2 keV (2-10 keV) energy band. Our sample covers a range in the 2-10 keV observed flux, F…
Masses of Star Clusters in the Nuclei of Bulgeless Spiral Galaxies
Ho, L. C.; Rix, H. -W.; Shields, J. C. +6 more
In the last decade star clusters have been found in the centers of spiral galaxies across all Hubble types. We here present a spectroscopic study of the exceptionally bright (106-108 Lsolar) but compact (re~5 pc) nuclear star clusters in very late type spirals with the Ultraviolet and Visual Echelle Spec…
GEMS: The Surface Brightness and Surface Mass Density Evolution of Disk Galaxies
Bell, Eric F.; Somerville, Rachel S.; Wisotzki, Lutz +14 more
We combine HST imaging from the GEMS (Galaxy Evolution from Morphologies and SEDs) survey with photometric redshifts from COMBO-17 to explore the evolution of disk-dominated galaxies since z<~1.1. The sample is composed of all GEMS galaxies with Sérsic indices n<2.5, derived from fits to the galaxy images. We account fully for selection effe…
Fluvial sedimentary deposits on Mars: Ancient deltas in a crater lake in the Nili Fossae region
Head, James W.; Fassett, Caleb I.
New spacecraft observations in the Nili Fossae region of Mars reveal two valley networks (~80 and ~200 km long) that each formed distributary fans as they entered an ancient 40-km diameter impact crater. An outlet channel on the eastern crater rim, lying at an elevation above the fans, suggests these fans formed as subaqueous deltas in a crater la…
The Surprisingly Steep Mass Profile of A1689, from a Lensing Analysis of Subaru Images
Kong, X.; Broadhurst, T.; Umetsu, K. +4 more
Subaru observations of A1689 (z=0.183) are used to derive an accurate, model-independent mass profile for the entire cluster, r<~2 Mpc h-1, by combining magnification bias and distortion measurements. The projected mass profile steepens quickly with increasing radius, falling away to zero at r~1.0 Mpc h-1, well short of th…
The Central Region of Barred Galaxies: Molecular Environment, Starbursts, and Secular Evolution
Scoville, Nick; Jogee, Shardha; Kenney, Jeffrey D. P.
Stellar bars drive gas into the circumnuclear (CN) region of galaxies. To investigate the fate of the CN gas and star formation (SF), we study a sample of barred nonstarbursts and starbursts with high-resolution CO, optical, Hα, radio continuum, Brγ, and HST data, and find the following. (1) The inner kiloparsec of bars differs markedly from the o…