Search Publications
A Treasury Study of Star-forming Regions in the Local Group. I. HST Photometry of Young Populations in Six Dwarf Galaxies
Massey, Philip; Bianchi, Luciana; Olsen, K. A. G. +2 more
We present a comprehensive study of young stellar populations in six dwarf galaxies in or near the Local Group: Phoenix, Pegasus, Sextans A, Sextans B, WLM, and NGC 6822. Their star-forming regions, selected from GALEX wide-field far-UV imaging, were imaged (at sub-pc resolution) with the WFPC2 camera on board the Hubble Space Telescope (HST) in s…
HST/COS Observations of Thirteen New He II Quasars
Anderson, Scott F.; Schneider, Donald P.; York, Donald G. +3 more
The full reionization of intergalactic helium was a major event in the history of the intergalactic medium (IGM), and UV observations of the He II Gunn-Peterson trough allow us to characterize the end of this process at z ~ 3. Due to intervening hydrogen absorption, quasars allowing such study are rare, with only 33 known in the literature, and mo…
Revealing Companions to Nearby Stars with Astrometric Acceleration
Tokovinin, Andrei; Makarov, Valeri V.; Hayward, Thomas L. +1 more
A subset of 51 Hipparcos astrometric binaries among FG dwarfs within 67 pc has been surveyed with the Near-Infrared Coronagraphic Imager adaptive optics system at Gemini-S, directly resolving for the first time 17 subarcsecond companions and 7 wider ones. Using these data together with published speckle interferometry of 57 stars, we compare the s…
GK Per (Nova Persei 1901): Hubble Space Telescope Imagery and Spectroscopy of the Ejecta, and First Spectrum of the Jet-like Feature
Livio, Mario; De Marco, Orsola; Shara, Michael M. +3 more
We have imaged the ejecta of GK Persei (Nova Persei 1901 A.D.) with the Hubble Space Telescope (HST), whose 0.1 arcsec resolution reveals hundreds of cometary-like structures with long axes aligned toward GK Per. One or both ends of the structures often show a brightness enhancement relative to the structures' middle sections, but there is no simp…
New X-Ray Detections of WNL Stars
Skinner, Stephen L.; Zhekov, Svetozar A.; Güdel, Manuel +2 more
Previous studies have demonstrated that putatively single nitrogen-type Wolf-Rayet stars (WN stars) without known companions are X-ray sources. However, almost all WN star X-ray detections so far have been of earlier WN2-WN6 spectral subtypes. Later WN7-WN9 subtypes (also known as WNL stars) have proved more difficult to detect, an important excep…
Metallicities of Emission-line Galaxies from HST ACS PEARS and HST WFC3 ERS Grism Spectroscopy at 0.6 < z < 2.4
Pirzkal, Nor; Cohen, Seth; Windhorst, Rogier A. +9 more
Galaxies selected on the basis of their emission-line strength show low metallicities, regardless of their redshifts. We conclude this from a sample of faint galaxies at redshifts between 0.6 < z < 2.4, selected by their prominent emission lines in low-resolution grism spectra in the optical with the Advanced Camera for Surveys on the Hubble…
The Photometric Study of a Neglected Near Contact Binary: BS Vulpeculae
Zejda, M.; Liška, J.; Qian, S. -B. +3 more
We present a detailed study of the close eclipsing binary BS Vulpeculae. Although it is relatively bright (V: 10.9-11.6 mag) and belongs to short-periodic variable stars (P = 0.48 days), it is rather neglected. To perform a thorough period analysis, we collected all available photometric observations that span the time interval of 1898-2010. Obser…
The Connection between 3.3 µm Polycyclic Aromatic Hydrocarbon Emission and Active Galactic Nucleus Activity
Imanishi, Masatoshi; Kim, Ji Hoon; Woo, Jong-Hak +1 more
We investigate the connection between starburst and active galactic nucleus (AGN) activity by comparing 3.3 µm polycyclic aromatic hydrocarbon (PAH) emission with AGN properties. Utilizing the slitless spectroscopic capability of the AKARI space telescope, we observe a moderate-luminosity Type I AGN at z ~ 0.4 to measure global starburst act…
The Orbit of Charon is Circular
Buie, Marc W.; Grundy, William M.; Tholen, David J.
We present a detailed analysis of the orbit of Charon where we show its orbit to be circular. This analysis explores the effects of surface albedo variations on the astrometry and the resulting errors in the orbital elements. We present two new epochs of data from the Hubble Space Telescope taken in 2008 and 2010 and combine that with a re-analysi…
The Road to the Red Sequence: A Detailed View of the Formation of a Massive Galaxy at z ~ 2
Hathi, Nimish P.; Pirzkal, Nor; Cohen, Seth +11 more
Over half of the census of massive galaxies at z ~ 2 are dominated by quiescent stellar populations. The formation mechanism for these galaxies is still under debate, with models relying either on massive and early mergers or cold accretion. It is therefore imperative to understand in detail the properties of these galaxies. We present here a deta…