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Principles of Seismic Holography for Diagnostics of the Shallow Subphotosphere
Braun, D. C.; Lindsey, Charles
We develop the wave-mechanical formalism for phase-correlation computational seismic holography of the shallow subphotosphere under the plane-parallel approximation and apply it to helioseismic Doppler observations from the Michelson Doppler Imager on the SOHO spacecraft of both the quiet Sun and active regions. We compare holographic signatures c…
Accurate X-Ray Position of the Anomalous X-Ray Pulsar XTE J1810-197 and Identification of Its Likely Infrared Counterpart
Covino, S.; Campana, S.; Mereghetti, S. +13 more
We report the accurate subarcsecond X-ray position of the new anomalous X-ray pulsar (AXP) XTE J1810-197, derived with a Chandra High Resolution Camera Target of Opportunity observation carried out in 2003 November. We also report the discovery of a likely IR counterpart based on a Very Large Telescope (IR band) Target of Opportunity observation c…
Observations and three-dimensional photoionization modelling of the Wolf-Rayet planetary nebula NGC 1501
Rauch, T.; Barlow, M. J.; Zhang, Y. +4 more
Deep optical spectra of the high-excitation planetary nebula NGC 1501 and its W04 central star are presented. A recombination line abundance analysis of the emission-line spectrum of the central star yields He:C:O mass fractions of 0.36:0.48:0.16, similar to those of PG 1159 stars. A detailed empirical analysis of the nebular collisionally excited…
Chandra and XMM-Newton observations of NGC 5253: analysis of the X-ray emission from a dwarf starburst galaxy
Heckman, Timothy M.; Stevens, Ian R.; Strickland, David K. +1 more
We present Chandra and XMM-Newton X-ray data of NGC 5253, a local starbursting dwarf elliptical galaxy, in the early stages of a starburst episode. Contributions to the X-ray emission come from discrete point sources and extended diffuse emission, in the form of what appear to be multiple superbubbles, and smaller bubbles probably associated with …
Australia Telescope Compact Array Survey of Candidate Ultracompact and Buried H II Regions in the Magellanic Clouds
Johnson, Kelsey E.; Indebetouw, Rémy; Conti, Peter
We present a systematic survey for ultracompact (UC) H II regions in the Magellanic Clouds. Understanding the physics of massive star formation (MSF) is a critical astrophysical problem. The study of MSF began in our Galaxy with surveys of UC H II regions, but before now this has not been done for other galaxies. We selected candidates on the basi…
Optical nuclei of radio-loud AGN and the Fanaroff-Riley divide
Kharb, P.; Shastri, P.
We investigate the nature of the point-like optical nuclei that have been found in the centres of the host galaxies of a majority of radio galaxies by the Hubble Space Telescope. We examine the evidence that these optical nuclei are relativistically beamed, and look for differences in the behaviour of the nuclei found in radio galaxies of the two …
Emission Line Properties of Active Galactic Nuclei from a Post-COSTAR Hubble Space Telescope Faint Object Spectrograph Spectral Atlas
Green, Paul J.; Vestergaard, Marianne; Aldcroft, Tom L. +4 more
We present consistent emission-line measurements for active galactic nuclei (AGNs), useful for reliable statistical studies of emission line properties. This paper joins a series including similar measurements of 993 spectra from the Large Bright Quasar Survey and 174 spectra of AGNs obtained from the Faint Object Spectrograph (FOS) on the Hubble …
The Extinction Law in High-Redshift Galaxies
Kochanek, C. S.; Muñoz, J. A.; Falco, E. E. +2 more
We estimate the dust extinction laws in two intermediate-redshift galaxies. The dust in the lens galaxy of LBQS 1009-0252, which has an estimated lens redshift of zl~=0.88, appears to be similar to that of the SMC, with no significant feature at 2175 Å. Only if the lens galaxy is at a redshift of zl~=0.3, which is completely …
The Properties and Evolution of the Highly Ionized Gas in MR 2251-178
Kaspi, Shai; Nandra, Kirpal; Turner, T. J. +3 more
We present the first XMM-Newton observations of the radio-quiet quasar MR 2251-178 obtained in 2000 and 2002. The EPIC pn spectra show a power-law continuum with a slope of Γ=1.6 at high energies absorbed by at least two warm absorbers (WAs) intrinsic to the source. The underlying continuum in the earlier observation shows a ``soft excess'' at low…
The Radio Continuum of the Metal-deficient Blue Compact Dwarf Galaxy SBS 0335-052
Hunt, Leslie K.; Thuan, Trinh X.; Ulvestad, James S. +1 more
We present new Very Large Array observations at five frequencies, from 1.4 to 22 GHz, of the extremely low metallicity blue compact dwarf SBS 0335-052. The radio spectrum shows considerable absorption at 1.49 GHz and a composite thermal plus nonthermal slope. After fitting the data with a variety of models, we find the best-fitting geometry to be …