Search Publications
The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. II. Basic Parameters of Program Stars and the Role of Microturbulence
Gray, R. O.; Graham, P. W.; Hoyt, S. R.
Paper I of this series presented precise MK spectral types for 372 late A-, F-, and early G-type stars with the aim of understanding the nature of luminosity classification on the MK spectral classification system for this range of spectral types. In this paper, a multidimensional downhill simplex technique is introduced to determine the basic par…
The Globular Cluster System in the Outer Regions of NGC 4472
Zepf, Stephen E.; Rhode, Katherine L.
We have undertaken a study of the globular cluster (GC) systems of a large sample of elliptical and spiral galaxies in order to test specific predictions of galaxy formation models. Here we present results for the first elliptical in the study, the giant Virgo cluster galaxy NGC 4472 (M49). The galaxy was observed in three filters (BVR) using the …
Radial Velocity Studies of Close Binary Stars. IV.
Rucinski, Slavek M.; Lu, Wenxian; Ogłoza, Waldemar
Radial velocity measurements and sine-curve fits to the orbital velocity variations are presented for the fourth set of 10 close binary systems: 44 Boo, FI Boo, V2150 Cyg, V899 Her, EX Leo, VZ Lib, SW Lyn, V2377 Oph, Anon Psc (GSC 8-324), and HT Vir. All systems are double-lined spectroscopic binaries, with only two of them not being contact syste…
The Spatial Distribution of O-B5 Stars in the Solar Neighborhood as Measured by Hipparcos
Maíz-Apellániz, Jesús
We have developed a method to calculate the fundamental parameters of the vertical structure of the Galaxy in the solar neighborhood from trigonometric parallaxes alone. The method takes into account Lutz-Kelker-type biases in a self-consistent way and has been applied to a sample of O-B5 stars obtained from the Hipparcos catalog. We find that the…
High-Resolution Mid-Infrared Imaging of Infrared-Luminous Starburst Galaxies
Egami, E.; Scoville, N. Z.; Matthews, K. +7 more
Observations for seven infrared-luminous starburst galaxies are reported in the mid-infrared from 8 to 18 µm using the Keck telescopes with spatial resolution approaching the diffraction limit. All of the galaxies observed show evidence of strong interactions based on optical morphologies. For these galaxies, a substantial fraction, usually …
A Multiwavelength Study of Stephan's Quintet
Trinchieri, Ginevra; Xu, Cong; Sulentic, Jack W. +4 more
Stephan's Quintet (SQ) is a compact group that we find in an atypical moment when a high-velocity intruder is passing through it. The intrusion is particularly interesting because a previous intruder had stripped most of the gas from the group members. This debris field was shocked in the ongoing collision with the new intruder. This evolutionary …
Fractal Structure in Galactic Star Fields
Elmegreen, Bruce G.; Elmegreen, Debra Meloy
The fractal structure of star formation on large scales in disk galaxies is studied using the size distribution function of stellar aggregates in kiloparsec-scale star fields. Archival Hubble Space Telescope images of 10 galaxies are Gaussian-smoothed to define the aggregates, and a count of these aggregates versus smoothing scale gives the fracta…
A Chandra Study of the Circinus Galaxy Point-Source Population
Bauer, F. E.; Brandt, W. N.; Netzer, H. +4 more
We have used the Chandra X-Ray Observatory to resolve spatially and spectrally the X-ray emission from the Circinus galaxy. We report here on the nature of the X-ray emission from the off-nuclear point sources associated with the disk of Circinus, which make up ~34% of the total 0.5-10 keV emission. We find that many of the serendipitous X-ray sou…
New Insights from Hubble Space Telescope Studies of Globular Cluster Systems. II. Analysis of 29 S0 Systems
Kundu, Arunav; Whitmore, Bradley C.
We examine the globular cluster systems (GCSs) of a sample of 34 S0 galaxies from a WFPC2 snapshot survey in the V and I bands. Of these 34 galaxies, 29 have measurable globular cluster systems. The mean color of the GCSs of individual galaxies vary from V-I=0.85 mag to V-I=1.17 mag. The average color of GCSs in all 29 S0 galaxies, V-I=1.00+/-0.07…
Young Clusters in the Nuclear Starburst of M83
Conselice, Christopher J.; Calzetti, Daniela; Gallagher, John S., III +2 more
We present a photometric catalog of 45 massive star clusters in the nuclear starburst of M83 (NGC 5236), observed with the Hubble Space Telescope Wide Field Planetary Camera 2, in both broadband (F300W, F547M, and F814W) and narrowband (F656N and F487N) filters. By comparing the photometry with theoretical population synthesis models, we estimate …