Search Publications
Simultaneous Observations of Solar Energetic Particle Events by imp 8 and the Ulysses Cospin High Energy Telescope at High Solar Latitudes
McKibben, R. B.; Zhang, M.; Lopate, C.
With Ulysses approaching the south solar polar latitudes during a period of high solar activity, it is for the first time possible to study the distribution of solar energetic particles (SEPs) in solar latitude as well as in radius and longitude. From July 1997 to August 2000, Ulysses moved from near the solar equator at ∼5 AU to ∼67° S latitude a…
Discovery of an Extremely Red Galaxy at z=0.65 with Dusty Star Formation and Nuclear Activity
Mobasher, B.; Afonso, J.; Chan, B. +1 more
In the course of the follow-up multiwavelength study of a deep radio survey, we have discovered that the millijansky radio source PDF J011423 is a low-redshift (z=0.65) extremely red galaxy (ERG) with K=15.3, R-K=5.8, and J-K=3.1. Optical, infrared, and radio photometry, together with optical and near-infrared spectroscopy, reveal a heavily obscur…
QSO 2359-1241: A Bright, Highly Polarized, Radio-moderate, Reddened, Low-Ionization Broad Absorption Line Quasar
Gregg, Michael D.; Becker, R. H.; Arav, Nahum +5 more
We report the discovery of a bright quasar (E=15.8, z=0.868) associated with the flat-spectrum radio source NVSS J235953-124148. This quasar, which we designate QSO 2359-1241, possesses a rare combination of extreme properties that make it of special interest. These properties include intrinsic high-velocity outflow seen in absorption for both hig…
Topology of the Galaxy Distribution in the Hubble Deep Fields
Park, Changbom; Gott, J. Richard, III; Choi, Y. J.
We have studied topology of the distribution of the high-redshift galaxies identified in the Hubble Deep Field (HDF) North and South. The two-dimensional genus is measured from the projected distributions of the HDF galaxies at angular scales from 3.8" to 6.1". We have also divided the samples into three redshift slices with roughly equal numbers …
Rapid Submillimeter Brightenings Associated with a Large Solar Flare
Rovira, M.; Costa, J. E. R.; Levato, H. +8 more
We present high time resolution observations of Active Region 8910 obtained simultaneously at 212 and 405 GHz during a large Hα flare, which produced a soft X-ray class X1.1 event. Data were obtained with the new solar submillimeter telescope recently installed at the El Leoncito Observatory to explore this poorly known part of the solar emission …
Scattered Light Models of Protostellar Envelopes: Multiple Outflow Cavities and Misaligned Circumstellar Disks
Wood, Kenneth; Wolff, Michael J.; Bjorkman, Karen S. +4 more
Ground-based imaging, imaging polarimetry, and recent Hubble Space Telescope WFPC2 and NICMOS images of protostars have revealed very complex scattered light patterns that cannot be entirely explained by two-dimensional radiation transfer models. We present here for the first time radiation transfer models of T Tau and IRAS 04016+2610 that are ful…
The Planetary Nebula A39: An Observational Benchmark for Numerical Modeling of Photoionized Plasmas
Korista, Kirk T.; Jacoby, George. H.; Ferland, Gary. J.
Galactic nebulae are the main probes for the chemical evolution of the interstellar medium. Yet, recent observations have shown that chemical abundances determined from recombination and collisionally excited emission lines can differ by as much as an order of magnitude in some planetary nebulae (PNs). Many PNs have complex geometries and morpholo…
A Spectroscopic Study of Component C and the Extended Emission around I Zw 18
Green, Richard F.; Chaffee, Frederic H.; Thuan, Trinh X. +5 more
Long-slit Keck II,1 4 m Kitt Peak,2 and 4.5 m MMT3 spectrophotometric data are used to investigate the stellar population and the evolutionary status of I Zw 18C, the faint C component of the nearby blue compact dwarf galaxy I Zw 18. Hydrogen Hα and Hβ emission lines are detected in the spectra of I Zw 18C, which implies that ionizing massive star…
Reconciling Extreme-Ultraviolet and Radio Observations of the Sun's Corona
Zhang, J.; Kundu, M. R.; White, S. M. +2 more
The Sun's corona, which is composed of plasma at a temperature of a few millions of degrees, can be best viewed in two electromagnetic domains, one from wavelengths of a few angstroms to hundreds of angstroms (in the soft X-ray and EUV domain), the other from wavelengths of a few centimeters to several tens of centimeters (in the radio domain). In…
Identification and Analysis of Young Star Cluster Candidates in M31
Williams, Benjamin F.; Hodge, Paul W.
We present a method for finding clusters of young stars in M31 using broadband WFPC2 data from the HST data archive. Applying our identification method to 13 WFPC2 fields, covering an area of ~60 arcmin2, has revealed 79 new candidate young star clusters in these portions of the M31 disk. Most of these clusters are small (<~5 pc), yo…