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Is the Gini Coefficient a Stable Measure of Galaxy Structure?
Lisker, Thorsten
The Gini coefficient, a nonparametric measure of galaxy morphology, has recently taken up an important role in the automated identification of galaxy mergers. I present a critical assessment of its stability, based on a comparison of HST ACS imaging data from the GOODS and UDF surveys. Below a certain signal-to-noise level, the Gini coefficient de…
Impact effects from small size meteoroids and space debris
Drolshagen, Gerhard
When the impact risk from meteoroids and orbital debris is assessed the main concern is usually structural damage. With their high impact velocities of typically 10 20 km/s millimeter or centimeter sized objects can puncture pressure vessels and other walls or lead to destruction of complete subsystems or even whole spacecraft. Fortunately chances…
Conservation of open solar magnetic flux and the floor in the heliospheric magnetic field
St. Cyr, O. C.; Owens, M. J.; Crooker, N. U. +5 more
The near-Earth heliospheric magnetic field intensity, |B|, exhibits a strong solar cycle variation, but returns to the same ``floor'' value each solar minimum. The current minimum, however, has seen |B| drop below previous minima, bringing in to question the existence of a floor, or at the very least requiring a re-assessment of its value. In this…
Kinematic properties of solar coronal mass ejections: Correction for projection effects in spacecraft coronagraph measurements
Howard, T. A.; Nandy, D.; Koepke, A. C.
One of the main sources of uncertainty in quantifying the kinematic properties of coronal mass ejections (CMEs) using coronagraphs is the fact that coronagraph images are projected into the sky plane, resulting in measurements which can differ significantly from their actual values. By identifying solar surface source regions of CMEs using X-ray a…
Two-dimensional kinematics of SLACS lenses - I. Phase-space analysis of the early-type galaxy SDSSJ2321-097 at z ~ 0.1
Treu, Tommaso; Czoske, Oliver; Koopmans, Léon V. E. +2 more
We present the first results of a combined VLT VIMOS integral-field unit and Hubble Space Telescope (HST)/ACS study of the early-type lens galaxy SDSSJ2321-097 at z = 0.0819, extending kinematic studies to a look-back time of 1Gyr. This system, discovered in the Sloan Lens ACS Survey, has been observed as part of a VLT Large Programme with the goa…
XMM-Newton observations of the Small Magellanic Cloud: Be/X-ray binary pulsars active between October 2006 and June 2007
Pietsch, W.; Haberl, F.; Eger, P.
Aims: We analysed eight XMM-Newton observations toward the Small Magellanic Cloud (SMC), performed between October 2006 and June 2007, to investigate high mass X-ray binary systems.
Methods: We produced images from the European Photon Imaging Cameras (EPIC) and extracted X-ray spectra and light curves in different energy bands from sources tha…
X-Ray and Near-IR Variability of the Anomalous X-Ray Pulsar 1E 1048.1-5937: From Quiescence Back to Activity
Kaspi, Victoria M.; Bassa, Cees; Woods, Peter M. +3 more
We report on new and archival X-ray and near-IR observations of the anomalous X-ray pulsar 1E 1048.1-5937 performed between 2001 and 2007 with the Rossi X-Ray Telescope Explorer (RXTE), the Chandra X-Ray Observatory, the Swift Gamma-Ray Burst Explorer, the Hubble Space Telescope (HST), and the Very Large Telescope. Monitoring with RXTE revealed th…
Starbursts in the Local Universe: New Hubble Space Telescope Advanced Camera for Surveys Observations of the Irregular Galaxy NGC 4449
Leitherer, C.; Tosi, M.; van der Marel, R. P. +5 more
We present photometry with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope of stars in the Magellanic starburst galaxy NGC 4449. The galaxy has been imaged in the F435W (B), F555W (V), and F814W (I) broadband filters, and in the F658N (Hα) narrowband filter. Our photometry includes ≈300,000 objects in the (B, V) color-magnitude…
NGC 3147: a `true' type 2 Seyfert galaxy without the broad-line region
Bianchi, S.; Jiménez-Bailón, E.; Barcons, X. +5 more
We report on simultaneous optical and X-ray observations of the Seyfert galaxy, NGC 3147. The XMM-Newton spectrum shows that the source is unabsorbed in the X-rays (NH < 5 × 1020 cm-2). On the other hand, no broad lines are present in the optical spectrum. The origin of this optical/X-rays misclassification (wit…
Constraining Cosmic Evolution of Type Ia Supernovae
Becker, A. C.; Sollerman, J.; Spyromilio, J. +27 more
We present a large-scale effort of creating composite spectra of high-redshift SNe Ia and comparing them to low-redshift counterparts in an attempt to understand possible cosmic evolution of SNe Ia, which has major implications for studies of dark energy. Through the ESSENCE project, we have obtained 107 spectra of 88 high-redshift SNe Ia with exc…