Search Publications
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…
When Is a Bulge Not a Bulge? Inner Disks Masquerading as Bulges in NGC 2787 and NGC 3945
Beckman, John E.; Graham, Alister W.; Erwin, Peter +1 more
We present a detailed morphological, photometric, and kinematic analysis of two barred S0 galaxies with large, luminous inner disks inside their bars. We show that these structures, in addition to being geometrically disklike, have exponential profiles (scale lengths ~300-500 pc) distinct from the central, nonexponential bulges. We also find them …
Multiwavelength Spectrum of the Black Hole XTE J1118+480 in Quiescence
Remillard, Ronald A.; McClintock, Jeffrey E.; Orosz, Jerome A. +3 more
We present an X-ray/UV/optical spectrum of the black hole primary in the X-ray nova XTE J1118+480 in quiescence at LX~4×10-9LEdd. The Chandra, Hubble Space Telescope, and Multiple Mirror Telescope spectroscopic observations were performed simultaneously on 2002 January 12 UT. Because this 4.1 hr binary is located a…
Luminous Supersoft X-Ray Sources in External Galaxies
Kong, A. K. H.; Di Stefano, R.
We use a set of conservative criteria to identify luminous supersoft X-ray sources (SSSs) in external galaxies. We test this approach on blackbody models and then apply it to Chandra data from four galaxies: an elliptical galaxy (NGC 4967), two face-on spiral galaxies (M101 and M83), and an interacting galaxy (M51). We find SSSs in every galaxy an…