Search Publications
Obscured Active Galactic Nuclei and the X-Ray, Optical, and Far-Infrared Number Counts of Active Galactic Nuclei in the GOODS Fields
Brandt, William N.; Van Duyne, Jeffrey; Chary, Ranga-Ram +12 more
The deep X-ray, optical, and far-infrared fields that constitute the Great Observatories Origins Deep Survey (GOODS) are sensitive to obscured active galactic nuclei (AGNs; NH>~1022 cm-2) at the quasar epoch (z~2-3), as well as to unobscured AGNs as distant as z~7. Luminous X-ray emission is a sign of accretion …
The Origins of X-Ray Emission from the Hot Spots of FR II Radio Sources
Hardcastle, M. J.; Birkinshaw, M.; Worrall, D. M. +1 more
We use new and archival Chandra data to investigate the X-ray emission from a large sample of compact hot spots of FR II radio galaxies and quasars from the 3C catalog. We find that only the most luminous hot spots tend to be in good agreement with the predictions of a synchrotron self-Compton model with equipartition magnetic fields. At low hot s…
Magnetic Doppler imaging of 53 Camelopardalis in all four Stokes parameters
Petit, P.; Piskunov, N.; Wade, G. A. +5 more
We present the first investigation of the structure of the stellar surface magnetic field using line profiles in all four Stokes parameters. We extract the information about the magnetic field geometry and abundance distributions of the chemically peculiar star 53 Cam by modelling time-series of high-resolution spectropolarimetric observations wit…
High-resolution imaging of the HeII λ4686 emission line nebula associated with the ultraluminous X-ray source in Holmberg II
Zezas, A.; Kaaret, P.; Ward, M. J.
We present Hubble Space Telescope images of the HeIII region surrounding the bright X-ray source in the dwarf irregular galaxy Holmberg II. Using Chandra, we find a position for the X-ray source of (J2000) with an uncertainty of 0.6 arcsec. We identify a bright, point-like optical counterpart centred in the nebula with the X-ray source. The optica…
The Formation of Dust Lanes: Implications for Galaxy Evolution
Yoachim, Peter; Dalcanton, Julianne J.; Bernstein, Rebecca A.
From a survey of edge-on disks, we find that disk galaxies show a sharp, mass-dependent transition in the structure of their dusty ISM. In more massive, rapidly rotating disks with Vc>120kms-1, we see the well-defined dust lanes traditionally associated with edge-on galaxies. However, in more slowly rotating, lower mass ga…
The Role of Magnetic Reconnection in the Observable Features of Solar Eruptions
Raymond, J. C.; van Ballegooijen, A. A.; Lin, J.
There are two competing classes of models for coronal mass ejections (CMEs): those that assume a preexisting magnetic flux rope and those that can make a flux rope during the eruption by magnetic reconnection. The present work is based on the model with a preexisting flux rope. We investigate the evolution of morphological features of the magnetic…
Downflow Motions Associated with Impulsive Nonthermal Emissions Observed in the 2002 July 23 Solar Flare
Shibata, Kazunari; Shimojo, Masumi; Yokoyama, Takaaki +1 more
We present a detailed examination of downflow motions above flare loops observed in the 2002 July 23 flare. The extreme-ultraviolet images obtained with the Transition Region and Coronal Explorer show dark downflow motions (sunward motions) above the postflare loops, not only in the decay phase but also in the impulsive and main phases. We also fo…
X-ray reflection in the narrow-line Seyfert 1 galaxy 1H 0707-495
Vaughan, S.; Fabian, A. C.; Boller, Th. +4 more
We apply a reflection-dominated model to the second XMM-Newton observation of the narrow-line Seyfert 1 galaxy 1H 0707-495. As in the first XMM-Newton observation, a sharp spectral drop is detected with energy that has shifted from 7 to 7.5 keV in two years. The drop is interpreted in terms of relativistically blurred ionized reflection from the a…
The Local Lyα Forest. IV. Space Telescope Imaging Spectrograph G140M Spectra and Results on the Distribution and Baryon Content of H I Absorbers
Shull, J. Michael; Stocke, John T.; Penton, Steven V.
We present Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) G140M spectra of 15 extragalactic targets, which we combine with GHRS/G160M data to examine the statistical properties of the low-z Lyα forest. With STIS, we detect 109 Lyα absorbers at significance level (SL) of >=4 σ over 0.002<z<0.069, with a total reds…
Deflection of coronal mass ejection in the interplanetary medium
Wang, Yuming; Shen, Chenglong; Wang, S. +1 more
A solar coronal mass ejection (CME) is a large-scale eruption of plasma and magnetic fields from the Sun. It is believed to be the main source of strong interplanetary disturbances that may cause intense geomagnetic storms. However, not all front-side halo CMEs can encounter the Earth and produce geomagnetic storms. The longitude distribution of t…