Search Publications
Maximum-entropy weak lens reconstruction: improved methods and application to data
Marshall, P. J.; Bridle, S. L.; Hobson, M. P. +1 more
We develop the maximum-entropy weak shear mass reconstruction method presented in earlier papers by taking each background galaxy image shape as an independent estimator of the reduced shear field and incorporating an intrinsic smoothness into the reconstruction. The characteristic length-scale of this smoothing is determined by Bayesian methods. …
A Chandra High Resolution Camera Observation of X-Ray Point Sources in M31
Kaaret, Philip
We present results from a 47 ks observation of the Andromeda galaxy, M31, using the High Resolution Camera of the Chandra X-Ray Observatory. We detect 142 point sources spanning 3 orders of magnitude in luminosity, from LX=2×1035 to 2×1038 ergs s-1 in the 0.1-10 keV band. The X-ray source location accura…
Density modulated whistler mode emissions observed near the plasmapause
Santolik, O.; Parrot, M.; Andre, M. +4 more
Electron density fluctuations are regularly observed near the plasmapause together with electromagnetic waves below the electron cyclotron frequency (usually called hiss or chorus). Instruments on board CLUSTER spacecraft often observe two such emission bands with fluctuating wave intensities that suggest wave ducting in density enhancements as we…
Hubble Space Telescope Space Telescope Imaging System Observations of the He II Gunn-Peterson Effect toward HE 2347-4342
Tripp, Todd M.; Jenkins, Edward B.; Heap, Sara R. +3 more
We present an HST Space Telescope Imaging System (STIS) spectrum of the He II Gunn-Peterson effect toward HE 2347-4342. Compared to the previous HST Goddard High Resolution Spectrograph data obtained by Reimers et al. the STIS spectrum has a much improved resolution. The two-dimensional detector also allows us to better characterize the sky and da…
[CII] at 158 mu m as a star formation tracer in late-type galaxies
Boselli, A.; Gavazzi, G.; Lequeux, J. +1 more
We present a calibration of the massive star formation rate vs. [CII] luminosity relation based on a sample of nearby, late-type galaxies observed with ISO-LWS and imaged in the Hα +[NII] line. The relation holds for far-IR luminosities 108 <= LFIR <=1010.5 Lsun. The derived star formation rates ha…
Deep Hubble Space Telescope Imaging of Sextans A. I. The Spatially Resolved Recent Star Formation History
Skillman, Evan D.; Dolphin, Andrew; Cole, Andrew A. +5 more
We have measured stellar photometry from deep Cycle 7 Hubble Space Telescope/WFPC2 imaging of the dwarf irregular galaxy Sextans A. The imaging was taken in three filters: F555W (V; eight orbits), F814W (I; 16 orbits), and F656N (Hα one orbit). Combining these data with Cycle 5 WFPC2 observations provides nearly complete coverage of the optically …
The peculiar variable V838 Mon
Kimeswenger, S.; Lederle, C.; Schmeja, S. +1 more
V838 Mon underwent, after a first nova-like outburst in January and a usual decline, a second outburst after one month, and a third weak one again a month later. Moreover, a very small increase of the temperature at the beginning of April gives us a hint about a physical process with a period of one month. We obtained a BVRIC time-seque…
An Enshrouded Active Galactic Nucleus in the Merging Starburst System Arp 299 Revealed by BeppoSAX
Maraschi, L.; Cappi, M.; Franceschini, A. +9 more
Using a long (~=150 ks) broadband (0.1-40 keV) BeppoSAX observation of the merging starburst system Arp 299 (=IC 694+NGC 3690), we found the first unambiguous evidence of the presence of a deeply buried (NH~=2.5×1024 cm-2) active galactic nucleus (AGN) having  an intrinsic luminosity of L0.5-100keV~=1.9…
Energetics and Propagation of Coronal Mass Ejections in Different Plasma Environments
Lin, Jun
Based on previous work, we investigate the propagation of CMEs in a more realistic plasma environment than the isothermal atmosphere, and find that it is a slightly faster reconnection for flux ropes to break free. The average Alfvén Mach number MA for the inflow into the reconnection site has to be at least 0.013 in order to give a pla…
Coronal White-Light Jets near Sunspot Maximum
Sheeley, N. R., Jr.; Wang, Y. -M.
During the 1996-1997 activity minimum, the Large Angle and Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) recorded numerous jetlike ejections above the Sun's polar regions. In a previous study, we showed that these white-light ejections were the outward extensions of extreme-ultraviolet (EUV) jets, which in turn…