Search Publications
The Young Cluster Population of M82 Region B
O'Connell, R. W.; Bastian, N.; Larsen, S. S. +6 more
We present observations obtained with the Advanced Camera for Surveys on board the Hubble Space Telescope of the ``fossil'' starburst region B in the nearby starburst galaxy M82. By comparing UBVI photometry with models, we derive ages and extinctions for 35 U-band-selected star clusters. We find that the peak epoch of cluster formation occurred ~…
A Radio through X-Ray Study of the Hot Spots, Active Nucleus, and Environment of the Nearby FR II Radio Galaxy 3C 33
Hardcastle, M. J.; Croston, J. H.; Birkinshaw, M. +4 more
We present results from Chandra ACIS-S, Spitzer, XMM-Newton, HST, and VLA observations of the radio hot spots, extended environment, and nucleus of the nearby (z=0.0597) FR II radio galaxy 3C 33. This is a relatively low power FR II radio galaxy, so we expect, a priori, to detect a significant X-ray synchrotron component to the emission from the h…
Three-dimensional Tomographic Analysis of a High-Cadence LASCO-C2 Polarized Brightness Sequence
Frazin, Richard A.; Kamalabadi, Farzad; Vásquez, Alberto M. +1 more
We present the first 3D tomographic reconstructions of the coronal electron density from an extended, high-cadence sequence of images of the corona's polarized brightness (pB). While the standard LASCO synoptic sequence is only 1 pB image per day, during the 14 day period covering 2006 June 9-22, the C2 coronagraph took about 6.5 pB images per day…
Imaging of the Stellar Population of IC 10 with Laser Guide Star Adaptive Optics and the Hubble Space Telescope
Graham, James R.; Vacca, William D.; Sheehy, Christopher D.
We present adaptive optics (AO) images of the central starburst region of the dwarf irregular galaxy IC 10. The Keck II telescope laser guide star was used to achieve near diffraction-limited performance at H and K' (Strehl ratios of 18% and 32%, respectively). The images are centered on the putative Wolf-Rayet (W-R) object [MAC92]24. W…
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,…