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Radio-Optical Reference Frame Link Using the U.S. Naval Observatory Astrograph and Deep CCD Imaging
Zacharias, N.; Zacharias, M. I.
Between 1997 and 2004 several observing runs were conducted, mainly with the CTIO 0.9 m, to image International Celestial Reference Frame (ICRF) counterparts (mostly QSOs) in order to determine accurate optical positions. Contemporary to these deep CCD images, the same fields were observed with the U.S. Naval Observatory astrograph in the same ban…
Close Companions to Two High-redshift Quasars
Strauss, Michael A.; Fan, Xiaohui; Jiang, Linhua +5 more
We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z = 4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyα emission extending well beyond the quasar's light profile. Further imaging and spectro…
The SLUGGS Survey: HST/ACS Mosaic Imaging of the NGC 3115 Globular Cluster System
Romanowsky, Aaron J.; Brodie, Jean P.; Strader, Jay +6 more
We present Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) g and z photometry and half-light radii R h measurements of 360 globular cluster (GC) candidates around the nearby S0 galaxy NGC 3115. We also include Subaru/Suprime-Cam g, r, and i photometry of 421 additional candidates. The well-established color bimodality of th…
Extra-nuclear Starbursts: Young Luminous Hinge Clumps in Interacting Galaxies
Soria, Roberto; Swartz, Douglas A.; Struck, Curtis +3 more
Hinge clumps are luminous knots of star formation near the base of tidal features in some interacting galaxies. We use archival Hubble Space Telescope (HST) UV/optical/IR images and Chandra X-ray maps along with Galaxy Evolution Explorer UV, Spitzer IR, and ground-based optical/near-IR images to investigate the star forming properties in a sample …
The Snapshot Hubble U-Band Cluster Survey (SHUCS). II. The Star Cluster Population of NGC 2997
Larsen, S.; Bastian, N.; Smith, L. J. +6 more
We study the star cluster population of NGC 2997, a giant spiral galaxy located at 9.5 Mpc and targeted by the Snapshot Hubble U-band Cluster Survey (SHUCS). Combining our U-band imaging from SHUCS with archival BVI imaging from the Hubble Space Telescope, we select a high confidence sample of clusters in the circumnuclear ring and disk through a …
RX J0848.6+4453: The Evolution of Galaxy Sizes and Stellar Populations in a z = 1.27 Cluster
Toft, Sune; Jørgensen, Inger; Chiboucas, Kristin +4 more
RX J0848.6+4453 (Lynx W) at redshift 1.27 is part of the Lynx Supercluster of galaxies. We present an analysis of the stellar populations and star formation history for a sample of 24 members of the cluster. Our study is based on deep optical spectroscopy obtained with Gemini North combined with imaging data from Hubble Space Telescope. Focusing o…
Dusty Disks around Central Stars of Planetary Nebulae
Rauch, Thomas; De Marco, Orsola; Chu, You-Hua +4 more
Only a few percent of cool, old white dwarfs (WDs) have infrared excesses interpreted as originating in small hot disks due to the infall and destruction of single asteroids that come within the star's Roche limit. Infrared excesses at 24 µm were also found to derive from the immediate vicinity of younger, hot WDs, most of which are still ce…
High Resolution Radio and Optical Observations of the Central Starburst in the Low-metallicity Dwarf Galaxy II Zw 40
Johnson, Kelsey E.; Reines, Amy E.; Kepley, Amanda A. +1 more
The extent to which star formation varies in galaxies with low masses, low metallicities, and high star formation rate surface densities is not well constrained. To gain insight into star formation under these physical conditions, this paper estimates the ionizing photon fluxes, masses, and ages for young massive clusters in the central region of …
Constraints on the Binary Properties of Mid- to Late T Dwarfs from Hubble Space Telescope WFC3 Observations
Mora, A.; Martín, E. L.; Solano, E. +4 more
We used Hubble Space Telescope/Wide Field Camera 3 (WFC3) observations of a sample of 26 nearby (<=20 pc) mid- to late T dwarfs to search for cooler companions and measure the multiplicity statistics of brown dwarfs (BDs). Tightly separated companions were searched for using a double point-spread-function-fitting algorithm. We also compared our…
Photometric and Structural Properties of NGC 6544: A Combined VVV-Hubble Space Telescope Study
Cohen, Roger E.; Dotter, Aaron; Geisler, Doug +3 more
We combine archival Hubble Space Telescope imaging with wide-field near-infrared photometry to study the neglected metal-poor Galactic globular cluster NGC 6544. A high spatial resolution map of differential reddening over the inner portion of the cluster is constructed, revealing variations of up to half of the total reddening, and the resulting …