Search Publications
NGC 6543. II. Understanding the Dilation of the Cat's Eye
Balick, Bruce; Hajian, Arsen R.
Hubble Space Telescope images of NGC 6543 taken in 1994.7 and 2000.7 reveal a pattern of overall expansion of its core over 6 years. Spatial scale changes of the sharp edges of filamentary structures are consistent with purely radial motions. One prolate ellipsoid, E25, lies along the overall symmetry axis of the core. We find that it expands unif…
Keck Spectroscopy of Two Young Globular Clusters in the Merger Remnant NGC 3921
Brodie, Jean P.; Seitzer, Patrick; Schweizer, François
Low-resolution, ultraviolet-to-visual spectra of two candidate globular clusters in the merger remnant NGC 3921 (czLG=6021 km s-1) are presented. These two clusters of apparent magnitude V~22.2 (MV~-12.5) lie at projected distances of about 5 kpc (0.9 Reff) from the center and move with halo-type radial …
Nuclear Stellar Populations in the Infrared Space Observatory Atlas of Bright Spiral Galaxies
Bendo, George J.; Joseph, Robert D.
To understand the nuclear stellar populations and star formation histories of the nuclei of spiral galaxies, we have obtained K-band nuclear spectra for 41 galaxies and H-band spectra for 20 galaxies in the Infrared Space Observatory's Atlas of Bright Spiral Galaxies. In the vast majority of the subsample (80%), the near-infrared spectra suggest t…
Hubble Space Telescope Spectroscopy of Four Luminous Compact Blue Galaxies at Intermediate Redshift
Hoyos, C.; Koo, D. C.; Guzmán, R. +2 more
We present a spectroscopic study of four blue (B-V<=0.6) compact (µB<=21.0 mag arcsec-2) field galaxies with redshifts 0.095<=z<=0.438 and absolute magnitudes MB between -17.5 and -21.1. The spectra, taken with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, show prom…
Concerning the White Dwarf Cooling Age of M4: A Reply to De Marchi et al. on ``A Different Interpretation of Recent Deep HST Observations''
Stetson, P. B.; Rich, R. M.; Shara, M. +7 more
We respond to the recent paper by De Marchi et al. on the white dwarf cooling age of M4. The authors question the data analysis and interpretation that led to our conclusions in Hansen et al. in 2002. In their paper, De Marchi et al. are unable to obtain photometry as deep as ours from the same data set and therefore assert that only a lower limit…
RR Lyrae Stars in M32: Signatures of an Ancient Population
Mateo, Mario; Alonso-García, Javier; Worthey, Guy
We report the discovery of variable stars in the dwarf elliptical galaxy M32 using a series of images obtained with the Wide Field Planetary Camera 2 on the Hubble Space Telescope. The colors, luminosities, and approximate periods of the majority of these stars indicate that they are RR Lyrae stars. Comparisons with the number of such stars identi…
Physical Structure of Planetary Nebulae. II. NGC 7662
Guerrero, Martín A.; Chu, You-Hua; Jaxon, Elizabeth G.
We present a study of the structure and kinematics of the triple-shell planetary nebula NGC 7662 based on long-slit echelle spectroscopic observations and Hubble Space Telescope archival narrowband images. The structure of the main nebula consists of a central cavity surrounded by two concentric shells. The bright inner shell has a nonnegligible t…
Pulsational Evidence for Mass Loss in NGC 1866 Cepheids
Marconi, M.; Musella, I.; Caputo, F. +2 more
Available observational data for the 20 known Cepheids in the LMC cluster NGC 1866 have been compared with Hubble Space Telescope observations, discovering in the cluster central region five additional variables, one of which appears to be a Cepheid candidate. We also reach the conclusion that only the photometric data for the seven variables in t…
Composite Accretion Disk and White Dwarf Photosphere Analyses of the FUSE and Hubble Space Telescope Observations of EY Cygni
Sion, Edward M.; Orio, M.; Gänsicke, Boris T. +4 more
We explore the origin of FUSE and Hubble Space Telescope STIS far-UV spectra of the dwarf nova EY Cygni during its quiescence using combined high-gravity photosphere and accretion disk models, as well as model accretion belts. The best-fitting single-temperature white dwarf model to the FUSE plus STIS spectrum of EY Cyg has Teff=24,000 …
Subaru Deep Spectroscopy of a Star-forming Companion Galaxy of BR 1202-0725 at z=4.7
Ohyama, Youichi; Taniguchi, Yoshiaki; Shioya, Yasuhiro
We present deep spatially resolved optical spectroscopy of the northwest companion galaxy of the quasar BR 1202-0725 at z=4.7. Its rest-frame UV spectrum shows star-forming activity in the nuclear region. The Lyα emission profile is symmetric with wavelength, while its line width is unusually wide (FWHM~=1100 km s-1) for such a high-z s…