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Chandra X-Ray Observatory Observations of the Globular Cluster M28 and Its Millisecond Pulsar PSR B1821-24
Pavlov, George G.; Weisskopf, Martin C.; Tennant, Allyn F. +8 more
We report here the results of the first Chandra X-Ray Observatory observations of the globular cluster M28 (NGC 6626). We detect 46 X-ray sources, of which 12 lie within 1 core radius of the center. We show that the apparently extended X-ray core emission seen with the ROSAT HRI is due to the superposition of multiple discrete sources, for which w…
The Black Hole Masses and Host Galaxies of BL Lacertae Objects
Ho, Luis C.; Barth, Aaron J.; Sargent, Wallace L. W.
We have measured the central stellar velocity dispersion in the host galaxies of 11 BL Lac objects with redshifts z<=0.125. The range of velocity dispersions, ~170-370 km s-1, is similar to that of nearby radio galaxies. Using the correlation between stellar velocity dispersion and black hole mass defined for nearby galaxies, we deri…
Star Formation at z~6: i-Dropouts in the Advanced Camera for Surveys Guaranteed Time Observation Fields
Ford, H. C.; Infante, L.; Zheng, W. +33 more
Using an i-z dropout criterion, we determine the space density of z~6 galaxies from two deep ACS GTO fields with deep optical-IR imaging. A total of 23 objects are found over 46 arcmin2, or ~0.5+/-0.1 objects arcmin-2 down to zAB~27.3 (6 σ), or a completeness-corrected ~0.5+/-0.2 objects arcmin-2 down to…
Dust Grain Size Distributions from MRN to MEM
Sofia, Ulysses J.; Gordon, K. D.; Clayton, Geoffrey C. +2 more
Employing the maximum entropy method (MEM) algorithm, we fit interstellar extinction measurements that span the wavelength range 0.125-3 µm. We present a uniform set of MEM model fits, all using the same grain materials, optical constants, and abundance constraints. In addition, we are taking advantage of improved UV and IR data and better e…
A Multitransition CO Study of the Antennae Galaxies NGC 4038/9
Kuno, Nario; Zhu, Ming; Seaquist, E. R.
For the Antennae interacting galaxy pair, we have obtained high-quality, fully sampled 12CO J=1-0 and 3-2 maps of the regions surrounding the nuclei and the area of overlap between the two galaxies. The maps possess an angular resolution of 15" or 1.5 kpc, so far the highest resolution maps available at both the J=1-0 and 3-2 transition…
Interstellar Deuterium, Nitrogen, and Oxygen Abundances toward GD 246, WD 2331-475, HZ 21, and Lanning 23: Results from the FUSE Mission
Howk, J. Christopher; Chayer, Pierre; Hébrard, Guillaume +3 more
The interstellar abundances of D I, N I, and O I in the local ISM are studied using high-resolution spectra of four hot white dwarfs. The spectra of GD 246, WD 2331-475, HZ 21, and Lan 23 were obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) in the wavelength range 905-1187 Å. The line of sight to GD 246 probes the Local Interstella…
The Formation of Nuclear Rings in Barred Spiral Galaxies
Teuben, Peter; Regan, Michael W.
Although nuclear rings of gas and star formation are common in barred spiral galaxies, current theories of why and how they form do not provide the level of detail needed to quantify the effect that these rings can have on the fueling of active galactic nuclei and on the evolution of their host galaxy. In this paper we use detailed modeling to sho…
Far-Ultraviolet Spectra of Fast Coronal Mass Ejections Associated with X-Class Flares
Raymond, J. C.; Dobrzycka, D.; Ciaravella, A. +4 more
The Ultraviolet Coronagraph Spectrometer (UVCS) on board the Solar and Heliospheric Observatory satellite has observed very fast coronal mass ejections (CMEs) associated with X-class flares. These events show spectral signatures different from those seen in most other CMEs in terms of very rapid disruption of the pre-CME streamer, very high Dopple…
Barred Galaxies at z > 0.7: NICMOS Hubble Deep Field-North Observations
Scoville, Nicholas Z.; Sheth, Kartik; Regan, Michael W. +1 more
Previous optical studies found an unexpected deficit of bars at z>0.7. To investigate the effects of band shifting, we have studied the fraction of barred spiral galaxies in the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) Hubble Deep Field-North. At z>0.7, we find at least four barred spiral galaxies, doubling the number prev…
GRB 021004: A Possible Shell Nebula around a Wolf-Rayet Star Gamma-Ray Burst Progenitor
Mirabal, N.; Filippenko, Alexei V.; Halpern, J. P. +7 more
The rapid localization of GRB 021004 by the HETE-2 satellite allowed nearly continuous monitoring of its early optical afterglow decay, as well as high-quality optical spectra that determined a redshift of z3=2.328 for its host galaxy, an active starburst galaxy with strong Lyα emission and several absorption lines. Spectral observation…