Search Publications
Testing Lorentz Invariance with GRB 021206
Hurley, K.; Wunderer, C. B.; Boggs, Steven E. +1 more
Since the discovery of the cosmological origin of gamma-ray bursts (GRBs), there has been growing interest in using these transient events to probe the quantum gravity energy scale in the range 1016-1019 GeV, up to the Planck mass scale. This energy scale can manifest itself through a measurable modification in the electromag…
The Stellar Populations of Low-Luminosity Active Galactic Nuclei. II. Space Telescope Imaging Spectrograph Observations
Heckman, Timothy; Leitherer, Claus; Storchi-Bergmann, Thaisa +5 more
We present a study of the stellar populations of low-luminosity active galactic nuclei (LLAGNs). Our goal is to search for spectroscopic signatures of young and intermediate-age stars and to investigate their relationship with the ionization mechanism in LLAGNs. The method used is based on the stellar population synthesis of the optical continuum …
Highly Ionized High-Velocity Clouds toward PKS 2155-304 and Markarian 509
Shull, J. Michael; Giroux, Mark L.; Collins, Joseph A.
To gain insight into four highly ionized high-velocity clouds (HVCs) discovered by Sembach et al., we have analyzed data from the Hubble Space Telescope (HST) and Far Ultraviolet Spectroscopic Explorer (FUSE) for the PKS 2155-304 and Mrk 509 sight lines. We measure strong absorption in O VI and column densities of multiple ionization stages of sil…
Evolution of Solar Supergranulation
Toomre, Juri; De Rosa, Marc L.
The structure and evolution of solar supergranulation is studied using horizontal velocity fields, deduced from applying local correlation tracking (LCT) techniques to full-disk, line-of-sight Doppler velocity data observed by the Michelson Doppler Imager on board the Solar and Heliospheric Observatory spacecraft. Two 45° square regions of photosp…
A Synoptic X-Ray Study of M31 with the Chandra High Resolution Camera
Williams, Benjamin F.; Kong, Albert K. H.; King, A. R. +4 more
We have obtained 17 epochs of Chandra High Resolution Camera (HRC) snapshot images, each covering most of the M31 disk. The data cover a total baseline of ~2.5 yr and contain a mean effective exposure of 17 ks. We have measured the mean fluxes and long-term light curves for 166 objects detected in these data. At least 25% of the sources show signi…
External and Internal Reconnection in Two Filament-Carrying Magnetic Cavity Solar Eruptions
Moore, Ronald L.; Sterling, Alphonse C.
We observe two near-limb solar filament eruptions, one of 2000 February 26 and the other of 2002 January 4. For both we use 195 Å Fe XII images from the Extreme-Ultraviolet Imaging Telescope (EIT) and magnetograms from the Michelson Doppler Imager (MDI), both of which are on the Solar and Heliospheric Observatory (SOHO). For the earlier event we a…
Near-Infrared Observations at 1.56 Microns of the 2003 October 29 X10 White-Light Flare
Xu, Yan; Cao, Wenda; Liu, Chang +5 more
We present high-resolution observations of an X10 white-light flare in solar NOAA Active Region 10486 obtained with the Dunn Solar Telescope (DST) at the National Solar Observatory/Sacramento Peak on 2003 October 29. Our investigation focuses on flare dynamics observed in the near-infrared (NIR) continuum at 1.56 µm. This is the first report…
An 850 Micron SCUBA Survey of the Hubble Deep Field-North GOODS Region
Wang, W. -H.; Barger, A. J.; Cowie, L. L.
The Hubble Deep Field-North (HDF-N) is one of the best-studied extragalactic fields, and ultradeep optical, radio, X-ray, and mid-infrared wide-field images are available for this area. Here we present an 850 µm survey around the HDF-N, covering most of the area imaged by the Advanced Camera for Surveys as a part of the Great Observatories O…
Metals and Dust in Intermediate-Redshift Damped Lyα Galaxies
York, Donald G.; Kulkarni, Varsha P.; Lauroesch, James T. +3 more
We report on spectroscopic observations with the Multiple Mirror Telescope for 11 damped Lyα absorbers (DLAs) or strong DLA candidates at 0.1<z<1.5, including several absorbers discovered in the Sloan Digital Sky Survey. In particular, we have measured absorption lines of Zn II, Cr II, Ni II, Fe II, Mn II, Ti II, Ca II, and Si II. These meas…
The Detailed Fundamental Plane of Two High-Redshift Clusters: MS 2053-04 at z=0.58 and MS 1054-03 at z=0.83
van Dokkum, Pieter G.; Franx, Marijn; Kelson, Daniel D. +2 more
We study the fundamental plane relation in high-redshift clusters using a sample of 26 galaxies in MS 2053-04 (z=0.583) and 22 galaxies in MS 1054-03 (z=0.83). The zero point and scatter are compared to results for lower redshift clusters in order to trace evolutionary effects. Furthermore, our large sample enables us to investigate correlations b…