Search Publications
X-Ray Absorption by the Warm-hot Intergalactic Medium in the Hercules Supercluster
Buote, David A.; Ren, Bin; Fang, Taotao
"Missing baryons," in the form of warm-hot intergalactic medium (WHIM), are expected to reside in cosmic filamentary structures that can be traced by signposts such as large-scale galaxy superstructures. The clear detection of an X-ray absorption line in the Sculptor Wall demonstrated the success of using galaxy superstructures as a signpost to se…
The Hard X-Ray Perspective on the Soft X-Ray Excess
Fabian, Andrew C.; Reynolds, Christopher S.; Zoghbi, Abderahmen +5 more
The X-ray spectra of many active galactic nuclei exhibit a "soft excess" below 1 keV, whose physical origin remains unclear. Diverse models have been suggested to account for it, including ionized reflection of X-rays from the inner part of the accretion disk, ionized winds/absorbers, and Comptonization. The ionized reflection model suggests a nat…
X-Ray Variability and the Inner Region in Active Galactic Nuclei
Mangalam, A.; Mohan, P.
We present theoretical models of X-ray variability attributable to orbital signatures from an accretion disk including emission region size, quasi-periodic oscillations (QPOs), and its quality factor Q, and the emergence of a break frequency in the power spectral density shape. We find a fractional variability amplitude of Fvar\propto M…
Temporal Spectral Shift and Polarization of a Band-splitting Solar Type II Radio Burst
Li, Gang; Chen, Yao; Feng, Shiwei +4 more
In many type II solar radio bursts, the fundamental and/or the harmonic branches of the bursts can split into two almost parallel bands with similar spectral shapes and frequency drifts. However, the mechanisms accounting for this intriguing phenomenon remain elusive. In this study, we report a special band-splitting type II event in which spectra…
Changes to Saturn's Zonal-mean Tropospheric Thermal Structure after the 2010-2011 Northern Hemisphere Storm
Fletcher, L. N.; Flasar, F. M.; Achterberg, R. K. +4 more
We use far-infrared (20-200 µm) data from the Composite Infrared Spectrometer on the Cassini spacecraft to determine the zonal-mean temperature and hydrogen para-fraction in Saturn's upper troposphere from observations taken before and after the large northern hemisphere storm in 2010-2011. During the storm, zonal mean temperatures in the la…
Far-infrared Extinction Mapping of Infrared Dark Clouds
Tan, Jonathan C.; Lim, Wanggi
Progress in understanding star formation requires detailed observational constraints on the initial conditions, i.e., dense clumps and cores in giant molecular clouds that are on the verge of gravitational instability. Such structures have been studied by their extinction of near-infrared and, more recently, mid-infrared (MIR) background light. It…
No More Active Galactic Nuclei in Clumpy Disks Than in Smooth Galaxies at z ~ 2 in CANDELS/3D-HST
Barro, Guillermo; Bell, Eric F.; Ferguson, Henry C. +23 more
We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to investigate if active galactic nuclei (AGNs) are preferentially fueled by violent disk instabilities funneling gas into galaxy centers at 1.3 < z < 2.4. We select galaxies undergoing gravitational instabilities using the number of clumps and degree of patchiness as proxie…
Characterizing the Structure of Diffuse Emission in Hi-GAL Maps
Natoli, P.; Paladini, R.; Rygl, K. L. J. +18 more
We present a study of the structure of the Galactic interstellar medium (ISM) through the Δ-variance technique, related to the power spectrum and the fractal properties of infrared/submillimeter maps. Through this method, it is possible to provide quantitative parameters, which are useful for characterizing different morphological and physical con…
Formation and Decay of Rudimentary Penumbra around a Pore
Kitai, Reizaburo; Otsuji, Kenichi; Watanabe, Hiroko
We analyze the evolution of a pore in the active region NOAA 10940 using the data obtained by the Hinode satellite on 2007 February 3. The pore we analyzed showed the formation of a rudimentary penumbra structure, succeeded by an abrupt disappearance after about 5 hr. The pore had an approximate radius of 3.5 Mm and a total magnetic flux of 3.0 × …
Discovery of Enhanced Radiative Recombination Continua of He-like Iron and Calcium from IC 443 and its Implications
Koyama, Katsuji; Uchida, Hiroyuki; Tsuru, Takeshi Go +3 more
We present deep observations of the Galactic supernova remnant IC 443 with the Suzaku X-ray satellite. We find prominent K-shell lines from iron and nickel, together with a triangle residual at 8-10 keV, which corresponds to the energy of the radiative recombination continuum (RRC) of He-like iron. In addition, the wavy residuals have been seen at…