Search Publications
The Opacity of Spiral Galaxy Disks. III. Automating the Synthetic Field Method
Allen, Ronald J.; Holwerda, B. W.; van der Kruit, P. C. +1 more
Dust extinction in spiral disks can be estimated from the counts of background field galaxies, provided the deleterious effects of confusion introduced by structure in the image of the foreground spiral disk can be calibrated. González et al. developed a method for this calibration, the Synthetic Field Method (SFM), and applied this concept to a H…
Stellar Populations in the Wing of the Small Magellanic Cloud from Hubble Space Telescope Photometry
Garnett, Donald R.; Dufour, Reginald J.; McCumber, Michael P.
We have used the Wide Field Planetary Camera 2 on the Hubble Space Telescope to image a star field in the wing of the Small Magellanic Cloud (SMC), near the H II region N81. The images were taken in the F336W, F547M, F675W, and F814W filters. From photometry of stars in this field, we construct color-magnitude diagrams (CMDs) for about 4200 stars …
The Nuclear Disk in the Dwarf Elliptical Galaxy NGC 4486A
Gebhardt, Karl; Kormendy, John; Sparks, W. B. +3 more
Many ellipticals contain nuclear disks of dust and gas. Some ellipticals contain nuclear disks of stars that are distinct from the rest of the galaxy. We show that the dwarf E2 galaxy NGC 4486A contains both-it is a ``Rosetta stone'' object that tells us how nuclear disks evolve. Its properties suggest that, as accreted gas dissipates and settles …
Discovery of a Solitary Dwarf Galaxy in the APPLES Survey
Pirzkal, Norbert; Walsh, Jeremy R.; Malhotra, Sangeeta +5 more
During the APPLES parallel campaign, the Hubble Space Telescope (HST) Advanced Camera for Surveys has resolved a distant stellar system, which appears to be an isolated dwarf galaxy. It is characterized by a circularly symmetric distribution of stars with an integrated magnitude mF775W=20.13+/-0.02, a central surface brightness µ<…
Keck HIRES Spectroscopy of Four Candidate Solar Twins
King, Jeremy R.; Boesgaard, Ann M.; Schuler, Simon C.
We use high signal-to-noise ratio, high-resolution Keck HIRES spectroscopy of four solar twin candidates (HIP 71813, 76114, 77718, and 78399) pulled from our Hipparcos-based Ca II H and K survey to carry out parameter and abundance analyses of these objects. Our spectroscopic Teff estimates are ~100 K hotter than the photometric scale of the recen…
Cool Customers in the Stellar Graveyard. II. Limits to Substellar Objects around Nearby DAZ White Dwarfs
Debes, John H.; Woodgate, Bruce E.; Sigurdsson, Steinn
Results from a concerted Hubble Space Telescope (HST) survey of nearby white dwarfs for substellar objects are presented. A total of seven DAZ white dwarfs with distances of <50 pc had high-contrast and high spatial resolution NICMOS coronagraphic images taken to search for candidate substellar objects at separations <~10" away. Limits to un…
VLA Observations of ζ Aurigae: Confirmation of the Slow Acceleration Wind Density Structure
Harper, Graham M.; Bennett, Philip D.; Brown, Alexander +3 more
Studies of the winds from single K and early M evolved stars indicate that these flows typically reach a significant fraction of their terminal velocity within the first couple of stellar radii. The most detailed spatially resolved information of the extended atmospheres of these spectral types comes from the ζ Aur eclipsing binaries. However, the…
Outflows in the Orion Nebula: HH 540 from the Beehive Proplyd
Smith, Nathan; Bally, John; Walawender, Josh +1 more
We present Hubble Space Telescope Advanced Camera for Surveys images of the giant proplyd 181-826 in the southern Orion Nebula. This object exhibits a variety of known proplyd properties-an optically visible central star, a silhouette disk, a bright proplyd ionization front, and a bipolar microjet emerging along the disk axis that powers a larger …
Measurement of Noisy Absorption Lines Using the Apparent Optical Depth Technique
Savage, Blair D.; Fox, Andrew J.; Wakker, Bart P.
To measure the column densities of interstellar and intergalactic gas clouds using absorption-line spectroscopy, the apparent optical depth (AOD) technique of Savage & Sembach can be used instead of a curve-of-growth analysis or profile fit. We show that the AOD technique, while an excellent tool when applied to data with good signal-to-noise …
Deep ALTAIR+NIRI Imaging of the Disk and Bulge of M31
Davidge, T. J.; Olsen, K. A. G.; Rigaut, F. +2 more
Deep J, H, and K' images, recorded with the ALTAIR adaptive optics system and NIRI imager on Gemini North, are used to probe the stellar content of the disk and bulge of the Local Group galaxy M31. With an FWHM near 0.08" in K, these are the highest angular resolution near-infrared images yet obtained of this galaxy. One field samples the outer di…