Search Publications
Active Region Loops: Temperature Measurements as a Function of Time from Joint TRACE and SOHO CDS Observations
Mason, H. E.; Del Zanna, G.; Schmelz, J. T. +3 more
In this paper, we aim to quantitatively investigate the structure and time variation of quiescent active region loop structures. We coordinated a joint program of observations (JOP 146) using TRACE, to obtain high-cadence EUV images, and SOHO CDS, to obtain spectroscopic data. Loop intensities are used to determine temperature as a function of tim…
The Sizes of Galaxy Halos in Galaxy Cluster Abell 1689
Pannella, M.; Seitz, S.; Halkola, A.
The multiple images observed in the galaxy cluster Abell 1689 provide strong constraints not only on the mass distribution of the cluster, but also on the ensemble properties of the cluster galaxies. Using parametric strong-lensing models for the cluster, and by assuming well-motivated scaling laws between the truncation radius s and the velocity …
The Ribbon-like Hard X-Ray Emission in a Sigmoidal Solar Active Region
Liu, Chang; Wang, Haimin; Gary, Dale E. +1 more
Solar flare emissions at Hα and EUV/UV wavelengths often appear in the form of two ribbons, and this has been regarded as evidence of a typical configuration of solar magnetic reconnection. However, such a ribbon structure has rarely been observed in hard X-rays (HXRs), although it is expected. We report a ribbon-like HXR source observed with the …
The Outer Solar Atmosphere during the Maunder Minimum: A Stellar Perspective
Judge, Philip G.; Saar, Steven H.
By comparing solar data with data of ``flat activity'' stars at UV and soft X-ray wavelengths, we estimate solar chromospheric, transition region, and coronal emission as it might have existed during the Maunder minimum (1645-1715), the most recent of several episodes of persistently weak sunspot activity. Several flat activity stars from the Moun…
Properties of Solar Polar Coronal Plumes Constrained by Ultraviolet Coronagraph Spectrometer Data
Solanki, S. K.; Raouafi, N. -E.; Harvey, J. W.
We investigate the plasma dynamics (outflow speed and turbulence) inside polar plumes. We compare line profiles (mainly of O VI) observed by the Ultraviolet Coronagraph Spectrometer (UVCS) instrument on SOHO at the minimum of solar cycle 22-23 with model calculations. We consider Maxwellian velocity distributions with different widths in plume and…
On the Anomalous Temperature Distribution of the Intergalactic Medium in the NGC 3411 Group of Galaxies
O'Sullivan, E.; Ponman, T. J.; Vrtilek, J. M. +1 more
We present XMM-Newton, Chandra, and VLA observations of the USGC S152 group and its central elliptical NGC 3411. Imaging of the group X-ray halo suggests that it is relaxed with little apparent structure. We investigate the temperature and metal abundance structure of the group halo and find that while the abundance distribution is fairly typical,…
General Relativistic Flux Modulations from Disk Instabilities in Sagittarius A*
Melia, Fulvio; Goldwurm, Andrea; Bélanger, Guillaume +2 more
Near-IR and X-ray flares have been detected from the supermassive black hole Sgr A* at the center of our Galaxy with a (quasi-)period of ~17-20 minutes, suggesting an emission region only a few Schwarzschild radii above the event horizon. The latest X-ray flare, detected with XMM-Newton, is notable for its detailed light curve, yielding not only t…
IR Background Anisotropies in Spitzer GOODS Images and Constraints on First Galaxies
Dickinson, Mark; Ferguson, Henry C.; Wright, Edward L. +6 more
We describe the angular power spectrum of unresolved 3.6 µm IR light in Spitzer GOODS fields. The amplitude of the anisotropy spectrum decreases with the decreasing flux threshold to which resolved sources are removed from images. When all pixels above a flux threshold of 24.6 Vega magnitudes are removed, the power spectrum of the remaining …
AEGIS: The Diversity of Bright Near-IR-selected Distant Red Galaxies
Cooper, M. C.; Georgakakis, A.; Koekemoer, A. +10 more
We use deep and wide near-infrared (NIR) imaging from the Palomar telescope combined with DEEP2 spectroscopy and HST and Chandra imaging to investigate the nature of galaxies that are red in NIR colors. We locate these ``distant red galaxies'' (DRGs) through the color cut (J-K)Vega>2.3 over 0.7 deg2, where we find 1010 DRG…
Morphologies of Galaxies in and around a Protocluster at z = 2.300
Pettini, Max; Erb, Dawn K.; Shapley, Alice E. +4 more
We present results from the first robust investigation of galaxy morphology as a function of environment at z>1.5. Our study is motivated by the fact that star-forming galaxies contained within a protocluster at z=2.3 in the HS 1700+64 field have significantly older ages and larger stellar masses on average than those at similar redshifts but m…