Search Publications
Radial Color Gradients in K+A Galaxies in Distant Clusters of Galaxies
Caldwell, Nelson; Rose, James A.; Bartholomew, Lindsay J. +1 more
Galaxies in rich clusters with z>~0.3 are observed to have a higher fraction of photometrically blue galaxies than their nearby counterparts. This raises the important question of what environmental effects can cause the termination of star formation between z~0.3 and the present. The star formation may be truncated because of ram pressure stri…
The Metal-rich Globular Cluster NGC 6553: Observations with WFPC2, STIS, and NICMOS
Tanvir, Nial; Gilmore, Gerard; Santiago, Basilio +4 more
We present a Hubble Space Telescope study of the metal-rich globular cluster NGC 6553 using WFPC2, NICMOS, and STIS. Our primary motivation is to calibrate the STIS broadband LP magnitude against V555 and I814 magnitudes for stars of known metallicity and absolute (visual) magnitude, for application to our study of LMC globul…
A Mid-Infrared Spectral Survey of Galactic Wolf-Rayet Stars
Houck, J. R.; Smith, J. D. T.
We present 8-13 µm spectra at resolution R~600 of 29 northern Galactic Wolf-Rayet stars, including the first ever reported mid-infrared (MIR) spectrum for many. Among the subtypes of the stars studied were 14 WC, 13 WN, 1 WN/WC, and an additional reclassified WN. Lines of He I and He II, along with fine-structure lines of Ne II and S IV, are…
Near-Infrared Photometry of Globular Clusters NGC 6287 and NGC 6341 (M92): The Formation of the Galactic Halo
Stetson, Peter B.; Lee, Jae-Woo; Carney, Bruce W. +1 more
We present Hubble Space Telescope (HST) Near Infrared Camera and Multi-Object Spectrometer (NICMOS) camera 3 photometry of the inner halo globular cluster NGC 6287 and the intermediate halo globular cluster NGC 6341 (M92). Our photometric measurements range from the lower red giant branch to ~3 mag below the main-sequence turnoff, allowing us to d…
The Rapid Burster in Liller 1: The Chandra X-Ray Position and a Search for an Infrared Counterpart
Anderson, Scott F.; Margon, Bruce; Deutsch, Eric W. +1 more
Despite the unique X-ray behavior of the compact bursting X-ray source MXB 1730-335, the ``Rapid Burster'' (RB) in the highly reddened globular cluster Liller 1, to date there has been no known optical/IR counterpart for the object, no precise astrometric solution that correlates X-ray, radio, and optical positions and thus restricts the number of…
A Comparison between PAα and Hα Emission: The Relation between Mean H II Region Reddening, Local Gas Density, and Metallicity
Quillen, Alice C.; Yukita, Mihoko
We measure reddenings to H II regions in NGC 1512, 2903, 4449, and 6946, and M51 from Hubble Space Telescope (HST) Paα and Hα images. Extinctions range from AV~5 to 0 depending upon the galaxy. For the galaxies with HST images in both lines, NGC 1512, NGC 2903, and M51, the Paα and Hα emission are almost identical in morphology, which i…
WIYN Open Cluster Study. VII. NGC 2451A and the Hipparcos Distance Scale
Deliyannis, Constantine P.; Kozhurina-Platais, Vera; Girard, Terrence M. +5 more
We provide new evidence that NGC 2451A is undoubtedly a young open cluster, although sparsely populated. New cluster membership has been derived from relative proper motions of 5868 stars. In total, 136 stars down to V~15 have membership probability Pµ>=2%. New CCD BV photometry indicates that about 70 stars are indeed main-seq…
Compact Star Clusters in M81. II. Two Populations
Chandar, Rupali; Ford, Holland C.; Tsvetanov, Zlatan
We present the color and magnitude distributions of compact star clusters discovered in the early-type spiral galaxy M81, from Hubble Space Telescope Wide Field Planetary Camera 2 B, V, and I-band imaging. These clearly show the presence of two cluster populations-a typical red globular cluster system, as well as a young population, which was not …
Molecular Gas and Star Formation in NGC 3077
Meier, David S.; Turner, Jean L.; Beck, Sara C.
We present high-resolution (~2.5") CO(1-0) and CO(2-1) images of the central 1 kpc of NGC 3077 made with the Owens Valley Millimeter Array. CO emission is distributed in three major complexes, which resolve into at least seven giant molecular clouds (GMCs). Two complexes are associated with the central starburst. A third, more distant complex is n…
Diameters of δ Cephei and η Aquilae Measured with the Navy Prototype Optical Interferometer
Hajian, Arsen R.; Hummel, C. A.; Germain, M. E. +5 more
We have measured the diameters of the Cepheid variables δ Cephei (18 nights) and η Aquilae (11 nights) with the Navy Prototype Optical Interferometer. The primary results of these observations are the mean angular diameters <θLD> of these Cepheids: 1.520+/-0.014 milliseconds of arc (mas) for δ Cep and 1.69+/-0.04 mas for η Aql. We…