Search Publications
Travel Time Sensitivity Kernels
Kosovichev, A. G.; Birch, A. C.
We derive, following the standard first Born approximation approach used in the geophysics literature, an expression for the travel time perturbation caused by a perturbation to sound speed. In our simple model we employ a point source at one point and calculate the time taken for a wave packet created at the source to move to a second point. In t…
Heliospheric, Astrospheric, and Interstellar Lyα Absorption toward 36 Ophiuchi
Zank, Gary P.; Wood, Brian E.; Linsky, Jeffrey L.
We use high-resolution UV spectra taken by the Space Telescope Imaging Spectrograph instrument on board the Hubble Space Telescope to study the 5.5 pc line of sight to the K0 V star 36 Oph A. The one interstellar component detected for this line of sight has a velocity inconsistent with the local interstellar cloud (LIC) flow vector but consistent…
Space Telescope Imaging Spectrograph Long-Slit Spectroscopy of the Narrow-Line Region of NGC 4151. II. Physical Conditions along Position Angle 221 deg
Gull, T. R.; Kraemer, S. B.; Crenshaw, D. M. +4 more
We have examined the physical conditions in the narrow-line region of the well-studied Seyfert galaxy NGC 4151, using long-slit spectra obtained with the Hubble Space Telescope Space Telescope Imaging Spectrograph. The data were taken along a position angle of 221 deg, centered on the optical nucleus. We have generated photoionization models for a…
Radio, optical and X-ray nuclei in nearby 3CRR radio galaxies
Hardcastle, M. J.; Worrall, D. M.
HST observations have shown that low-redshift 3CR radio galaxies often exhibit a point-like optical component positionally coincident with the GHz-frequency radio core. In this paper we discuss the correlation between the luminosities of the radio, optical and X-ray cores in these objects, and argue that all three components have a common origin a…
3C 48: Stellar Populations and the Kinematics of Stars and Gas in the Host Galaxy
Stockton, Alan; Canalizo, Gabriela
We present deep Keck LRIS spectroscopy of the host galaxy of 3C 48. Our observations at various slit positions sample the different luminous components near the quasar, including the apparent tidal tail to the northwest and several strong emission line regions. By fitting Bruzual & Charlot population synthesis models to our spectra, we obtain …
Characteristics of solar coronal streamers. Element abundance, temperature and density from coordinated CDS and UVCS SOHO observations
Bromage, G. E.; Parenti, S.; Raymond, J. C. +3 more
This paper presents the results from coordinated observations of streamers acquired by the SOHO Coronal Diagnostic Spectrometer (CDS) and UltraViolet Coronograph Spectrometer (UVCS) experiments. Data from different altitudes within the solar corona were taken, with the purpose of determining their physical parameters - densities, electron temperat…
Clustering of galaxies around radio quasars at 0.5<=z<=0.8
Serjeant, Stephen; Lacy, Mark; Wold, Margrethe +1 more
We have observed the galaxy environments around a sample of 21 radio-loud, steep-spectrum quasars at 0.5<=z<=0.82, spanning several orders of magnitude in radio luminosity. The observations also include background control fields used to obtain the excess number of galaxies in each quasar field. The galaxy excess was quantified using the spat…
The Active Jet in NGC 4258 and Its Associated Shocks
Pérez-Fournon, I.; Wilson, A. S.; Nagar, N. +6 more
We present images and spectra of the active jet and anomalous arms on subparsec through kiloparsec scales in the LINER/Seyfert galaxy NGC 4258 (M106). New VLBA and multiconfiguration VLA images show that, on 0.3-300 pc scales, the jet in projection aligns with (1) the spin axis of the underlying accretion disk and (2) two radio hot spots 24" S (84…
The Evolution of Early-Type Galaxies in Distant Clusters. I. Surface Photometry and Structural Parameters for 53 Galaxies in the z=0.33 Cluster CL 1358+62
van Dokkum, Pieter G.; Franx, Marijn; Kelson, Daniel D. +1 more
Using wide-field, two-color Hubble Space Telescope (HST) imaging of the cluster Cl 1358+62 (z=0.33), we derive structural parameters for a large, magnitude-limited sample of cluster members. These structural parameters are combined with accurate velocity dispersions in another paper to investigate the fundamental plane in the cluster. We fit integ…
The Starfish Twins: Two Young Planetary Nebulae with Extreme Multipolar Morphology
Sahai, Raghvendra
We present Hα images of two objects, He 2-47 and M1-37, obtained during a Hubble Space Telescope imaging survey of young planetary nebulae (PNs) selected on the basis of their low-excitation characteristics. The two objects show a highly aspherical morphology, characterized by multiple lobes distributed around the central star. Such a morphology h…