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Comparison between observed and theoretical Red Giant Branch luminosity functions of galactic globular clusters
Zoccali, M.; Piotto, G.
V-band luminosity functions (LF) have been obtained for the upper main-sequence (MS), sub-giant branch (SGB) and red giant branch (RGB) of 18 galactic globular clusters (GGC) from HST data. A comparison with four sets of theoretical models has been performed. In contrast with what was found in several previous works, a good general agreement has b…
Recent Changes in the Near-Ultraviolet and Optical Structure of η Carinae
Smith, Nathan; Humphreys, Roberta M.; Davidson, Kris +1 more
Multiepoch HST/WFPC2 images of η Carinae are used to investigate the relationship between the photometric variability of the circumstellar nebula and the variability of the central star. In the past few years, the central star has brightened considerably, and the response of the reflection nebula to this brightening has been surprisingly complex. …
Color Gradients in Early-Type Galaxies in Clusters at Redshift 0.37-0.56
Tamura, Naoyuki; Ohta, Kouji
Color gradients in elliptical galaxies in distant clusters (z=0.37-0.56) are examined by using the archival deep imaging data of the Wide Field Planetary Camera 2 on board the Hubble Space Telescope (HST). Obtained color gradients are compared with the two model gradients to examine the origin of the color gradients. In one model, a color gradient…
Low-mass spectroscopic binaries in the Hyades: a candidate brown dwarf companion
Reid, I. Neill; Mahoney, S.
We have used the HIRES echelle spectrograph on the Keck I telescope to obtain high-resolution spectroscopy of 51 late-type M dwarfs in the Hyades cluster. Cross-correlating the calibrated data against spectra of white dwarfs allows us to determine heliocentric velocities with an accuracy of +/-0.3kms-1. 27 stars were observed at two epo…
Resolving the Controversy over the Core Radius of 47 Tucanae (NGC 104)
Gilliland, Ronald L.; Guhathakurta, Puragra; Howell, Justin H.
This paper investigates the discrepancy between recent measurements of the density profile of the globular cluster 47 Tuc that have used Hubble Space Telescope data sets. A large core radius would support the long-held view that 47 Tuc is a relaxed cluster, while a small core radius may indicate that it is in a post-core-collapse phase or possibly…
Nuclear Gas and Dust Disks in Nearby 3CR Elliptical Galaxies
Baum, Stefi A.; Sparks, William B.; Turner, Neal J. +1 more
Using WFPC2 V, R, I, and Hα+[N II] images, we examine the morphologies, environments, colors, and line emission of dust and gas disks located in the cores of seven low-redshift elliptical galaxies hosting 3C radio sources: NGC 383 (3C 31)/NGC 382, NGC 547 (3C 40), NGC 3862 (3C 264), NGC 4261 (3C 270), NGC 5532 (3C 296), NGC 7720 (3C 465)/NGC 7720A…
Hubble Space Telescope NICMOS Observations of the Host Galaxies of Powerful Radio Sources: Does Size Matter?
O'Dea, C. P.; Lehnert, M. D.; Fanti, R. +3 more
We present near-infrared J- and K-band imaging of a sample of powerful radio source host galaxies with the Hubble Space Telescope NICMOS2 camera. These sources have been selected on their double-lobed radio structure and include a wide range of projected radio source sizes. The largest projected linear sizes range from the compact gigahertz peaked…
Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases
Sciortino, S.; Maggio, A.; Pizzolato, N.
We have investigated the variation of coronal X-ray emission during early post-main-sequence phases for a sample of 120 late-type stars within 100 pc, and with estimated masses in the range 1-3 Msun, based on Hipparcos parallaxes and recent evolutionary models. These stars were observed with the ROSAT/PSPC, and the data processed with t…
Circumnuclear Star Formation in the Early-Type Resonance Ring Barred Spiral Galaxy NGC 1326
Buta, R.; Treuthardt, Patrick M.; Crocker, D. A. +1 more
We present multiband WFPC2 images of the nuclear ring of NGC 1326, an early-type southern barred spiral in the nearby Fornax galaxy cluster. The ring is a typical example of a 1 kpc-sized star-forming ring located in the region of the inner Lindblad resonances with the weak primary bar. The images reveal nearly 1000 point sources in and around the…
Infrared Space Observatory Spectroscopy of HH 7-11 Flow and Its Redshifted Counterpart
Ceccarelli, Cecilia; Giannini, Teresa; Nisini, Brunella +7 more
We have used the two spectrometers on the Infrared Space Observatory to observe the HH 7-11 flow, its redshifted counterpart, and the candidate exciting source SVS 13 in the star formation region NGC 1333. We detect atomic ([O I] 63 µm, [O I] 145 µm, [Si II] 34.8 µm, [C II] 158 µm) and molecular (H2, CO, H2<…