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Detection of a Red Supergiant Progenitor Star of a Type II-Plateau Supernova
Smartt, Stephen J.; Mattila, Seppo; Gilmore, Gerard F. +4 more
We present the discovery of a red supergiant star that exploded as supernova 2003gd in the nearby spiral galaxy M74. The Hubble Space Telescope (HST) and the Gemini Telescope imaged this galaxy 6 to 9 months before the supernova explosion, and subsequent HST images confirm the positional coincidence of the supernova with a single resolved star tha…
The Parsec-Scale Radio Structure of NGC 1068 and the Nature of the Nuclear Radio Source
Baum, Stefi A.; O'Dea, Christopher P.; Gallimore, Jack F.
We present sensitive, multifrequency Very Long Baseline Array (VLBA) images of the nuclear radio sources of NGC 1068. At 5 and 8.4 GHz, the radio continuum source S1, argued to mark the location of the hidden active nucleus, resolves into an elongated, ~0.8 pc source oriented nearly at right angles to the radio jet axis but more closely aligned to…
Structure of the Magnetic Reconnection Diffusion Region from Four-Spacecraft Observations
André, M.; Khotyaintsev, Y.; Vaivads, A. +6 more
Magnetic reconnection leads to energy conversion in large volumes in space but is initiated in small diffusion regions. Because of the small sizes of the diffusion regions, their crossings by spacecraft are rare. We report four-spacecraft observations of a diffusion region encounter at the Earth's magnetopause that allow us to reliably distinguish…
A Large Sample of Spectroscopic Redshifts in the ACS-GOODS Region of the Hubble Deep Field North
Capak, P.; Barger, A. J.; Cowie, L. L. +2 more
We report the results of an extensive spectroscopic survey of galaxies in the roughly 160 arcmin2 ACS-GOODS region surrounding the Hubble Deep Field North (HDF-N). We have identified 892 galaxies or stars with z'<24, R<24.5, or B<25 in the region. The spectra were obtained with either the DEIMOS or LRIS spectrographs…
Difficulties with Recovering the Masses of Supermassive Black Holes from Stellar Kinematical Data
Emsellem, Eric; Merritt, David; Valluri, Monica
We investigate the ability of three-integral, axisymmetric, orbit-based modeling algorithms to recover the parameters defining the gravitational potential (mass-to-light ratio Υ and black hole mass M•) in spheroidal stellar systems using stellar kinematical data. We show that the potential estimation problem is generically underdetermin…
Galaxies at z~7-8: z850-Dropouts in the Hubble Ultra Deep Field
Bouwens, R. J.; Illingworth, G. D.; Thompson, R. I. +6 more
We have detected likely z~7-8 galaxies in the 144''×144'' Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) observations of the Hubble Ultra Deep Field. Objects are required to be >=3 σ detections in both NICMOS bands, J110 and H160. The selection criteria for this sample are (z850
The Evolution of Disk Galaxies in the GOODS-South Field: Number Densities and Size Distribution
Jogee, S.; Dickinson, M.; Ferguson, H. C. +14 more
We examine the evolution of the sizes and number densities of disk galaxies using the high-resolution images obtained by the Great Observatories Origins Deep Survey (GOODS) with the Advanced Camera for Surveys on the Hubble Space Telescope. The multiwavelength images are used to classify galaxies based on their rest-frame B-band morphologies out t…
X-ray emission from a metal depleted accretion shock onto the classical T Tauri star TW Hya
Schmitt, J. H. M. M.; Stelzer, B.
We present the X-ray spectrum of TW Hya observed at high and intermediate spectral resolution with the Reflection Grating Spectrometer (RGS) and the European Photon Imaging Camera (EPIC) onboard the XMM-Newton satellite. TW Hya is the first classical T Tauri star for which simultaneous X-ray data with both high spectral resolution and high sensiti…
A long hard look at MCG-6-30-15 with XMM-Newton- II. Detailed EPIC analysis and modelling
Vaughan, S.; Fabian, A. C.
The bright Seyfert 1 galaxy MCG-6-30-15 has provided some of the best evidence to date for the existence of supermassive black holes in active galactic nuclei. Observations with ASCA revealed an X-ray iron line profile shaped by strong Doppler and gravitational effects. In this paper the shape of the iron line, its variability characteristics and …
Ultraviolet Extinction Properties in the Milky Way
Gordon, Karl D.; Clayton, Geoffrey C.; Valencic, Lynne A.
We have assembled a homogeneous database of 417 ultraviolet (UV) extinction curves for reddened sight lines having International Ultraviolet Explorer spectra. We have combined these with optical and Two Micron All Sky Survey photometry, allowing estimates of the ratio of total-to-selective extinction, RV, for the entire sample. Fitzpatr…