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X-Ray Observations of the Young Cluster NGC 2264
Simon, Theodore; Patten, B. M.; Dahm, S. E. +1 more
We present results from an X-ray imaging survey of the young cluster NGC 2264, carried out with the European Photon Imaging Cameras (EPIC) on board the XMM-Newton spacecraft. The X-ray data are merged with extant optical and near-infrared photometry, spectral classifications, Hα emission strengths, and rotation periods to examine the interrelation…
Distances to Populous Clusters in the Large Magellanic Cloud via the K-band Luminosity of the Red Clump
Sarajedini, Ata; Grocholski, Aaron J.; Tiede, Glenn P. +2 more
We present results from a study of the distances and distribution of a sample of intermediate-age clusters in the Large Magellanic Cloud (LMC). Using deep near-infrared photometry obtained with ISPI on the CTIO 4 m, we have measured the apparent K-band magnitude of the core helium-burning red clump stars in 17 LMC clusters. We combine cluster ages…
The Mid-Infrared Emission of Seyfert Galaxies: A New Analysis of ISOCAM Data
Pérez García, A. M.; Acosta-Pulido, J. A.; Ramos Almeida, C. +1 more
We present mid-infrared data of a sample of 57 AGNs obtained with the instrument ISOCAM on board the Infrared Space Observatory (ISO) satellite. The images were obtained through the LW2 (6.75 µm) and LW7 (9.62 µm) filters. This is a new analysis of the Clavel et al. galaxy sample, which is divided into 26 type 1 (<=1.5) and 28 type …
Hubble Space Telescope NICMOS Imaging Polarimetry of Proto-Planetary Nebulae. II. Macromorphology of the Dust Shell Structure via Polarized Light
Ueta, Toshiya; Meixner, Margaret; Murakawa, Koji
The structure of the dusty circumstellar envelopes (CSEs) of proto-planetary nebulae (PPNs) reveals the mass-loss history of these sources and how such histories may differ for elliptical (SOLE) and bipolar (DUPLEX) PPNs. To study the PPN structures via dust-scattered linearly polarized starlight, we have compiled the imaging-polarimetric data for…
Velocity Structure in the Orion Nebula. I. Spectral Mapping in Low-Ionization Lines
Henney, W. J.; García-Díaz, Ma. T.
High-dispersion echelle spectroscopy in optical forbidden lines of O0, S+, and S2+ is used to construct velocity-resolved images and electron-density maps of the inner region of the Orion Nebula with a resolution of 10 km s-1×3''×2''. Among the objects and regions revealed in this s…
The Three-Dimensional Ionization Structure and Evolution of NGC 6720, The Ring Nebula
O'Dell, C. R.; Henney, W. J.; Sabbadin, F.
We have determined the gas kinematics, diagnostic and ionic radial profiles, spatial structure, and evolutionary phase of NGC 6720 (the Ring Nebula) by means of tomography and a three-dimensional recovery technique applied to long-slit high-resolution spectra. The main shell of the Ring Nebula is a triaxial ellipsoid (radii of 0.10, 0.13, and 0.20…
The Stellar Populations in the Outer Regions of M33. II. Deep ACS Imaging
Sarajedini, Ata; Schommer, Robert; Geisler, Doug +2 more
Studying the stellar populations in the outskirts of spiral galaxies can provide important constraints on their structure, formation, and evolution. To that end, we present VI photometry obtained with the Advanced Camera for Surveys for three fields located ~20'-30' in projected distance southeast of M33's nucleus (corresponding to approximately f…
Large-Scale Flows from Orion South
O'Dell, C. R.; Henney, W. J.; Zapata, Luis A. +3 more
Multiple optical outflows are known to exist in the vicinity of the active star formation region called Orion South (Orion-S). We have mapped the velocity of low-ionization features in the brightest part of the Orion Nebula, including Orion-S, and imaged the entire nebula with the Hubble Space Telescope. These new data, combined with recent high-r…
The Three-Dimensional Morphology of VY Canis Majoris. II. Polarimetry and the Line-of-Sight Distribution of the Ejecta
Humphreys, Roberta M.; Helton, L. Andrew; Jones, Terry Jay +2 more
We use imaging polarimetry taken with the HST Advanced Camera for Surveys High Resolution Camera to explore the three-dimensional structure of the circumstellar dust distribution around the red supergiant VY Canis Majoris. The polarization vectors of the nebulosity surrounding VY CMa show a strong centrosymmetric pattern in all directions except d…
Redshifts of Emission-Line Objects in the Hubble Ultra Deep Field
Ferguson, Henry C.; Hathi, Nimish P.; Koekemoer, Anton M. +16 more
We present redshifts for 115 emission-line objects in the Hubble Ultra Deep Field identified through the Grism ACS Program for Extragalactic Science (GRAPES) project using the slitless grism spectroscopy mode of the Advanced Camera for Surveys on the Hubble Space Telescope (HST). The sample was selected by an emission-line search on all extracted …