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The Chemical Properties of Milky Way and M31 Globular Clusters. I. A Comparative Study
Forbes, Duncan A.; Brodie, Jean P.; Beasley, Michael A. +4 more
A comparative analysis is performed between high-quality integrated spectral indices of 30 M31 globular clusters, 20 Milky Way globular clusters, and a sample of field and cluster elliptical galaxies. We find that the Lick CN indices in the M31 and Galactic clusters are enhanced relative to the bulges of the Milky Way, M31, and elliptical spheroid…
RR Lyrae Stars in the Andromeda Halo from Deep Imaging with the Advanced Camera for Surveys
Ferguson, Henry C.; Brown, Thomas M.; Rich, R. Michael +4 more
We present a complete census of RR Lyrae stars in a halo field of the Andromeda galaxy. These deep observations, taken as part of a program to measure the star formation history in the halo, spanned a period of 41 days with sampling on a variety of timescales, enabling the identification of short- and long-period variables. Although the long-perio…
The Solar Neighborhood. IX. Hubble Space Telescope Detections of Companions to Five M and L Dwarfs within 10 Parsecs of the Sun
Illingworth, Garth D.; Nelan, Edmund P.; Ardila, David R. +10 more
We report the detections of low-mass companions to five M and L dwarfs within 10 pc of the Sun using the Hubble Space Telescope (HST) Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). Follow-up observations using the HST Advanced Camera for Surveys (ACS) and Fine Guidance Sensor 1r (FGS1r) confirm our NICMOS discoveries of companions to…
The Secrets of the Nearest Starburst Cluster. I. Very Large Telescope/ISAAC Photometry of NGC 3603
Grebel, Eva K.; Brandner, Wolfgang; Stolte, Andrea +2 more
VLT/ISAAC JHKL photometry with subarcsecond resolution of the dense, massive starburst cluster NGC 3603 YC forming the core of the NGC 3603 giant molecular cloud is analyzed to reveal characteristics of the stellar population in unprecedented detail. The color-magnitude plane features a strong pre-main-sequence/main-sequence (PMS/MS) transition re…
The Ionized Gas in Local Starburst Galaxies: Global and Small-Scale Feedback from Star Formation
Conselice, Christopher J.; Calzetti, Daniela; Gallagher, John S., III +4 more
The small- and intermediate-scale structure and the fraction of the interstellar medium (ISM) ionized by nonradiative processes are investigated in a small sample of four local starburst galaxies, imaged with the Hubble Space Telescope (HST) Wide Field Planetary Camera 2. The sample comprises three dwarf galaxies, NGC 3077, 4214, and 5253, and one…
Evolution in the Color-Magnitude Relation of Early-Type Galaxies in Clusters of Galaxies at z~=1
Dickinson, M.; Stanford, S. A.; Holden, B. P. +1 more
We present a study of the color evolution of elliptical and S0 galaxies in six clusters of galaxies inside the redshift range 0.78<z<1.27. For each cluster, we used imaging from the Hubble Space Telescope (HST) to determine morphological types of the galaxies. These types were determined both by an automated technique and from visual inspect…
WFI J2026-4536 and WFI J2033-4723: Two New Quadruple Gravitational Lenses
Rix, Hans-Walter; Dressler, Alan; Egami, Eiichi +3 more
We report the discovery of two new gravitationally lensed quasars, WFI J2026-4536 and WFI J2033-4723, at respective source redshifts of z=2.23 and z=1.66. Both systems are quadruply imaged and have similar PG 1115-like image configurations. WFI J2026-4536 has a maximum image separation of 1.4", a total brightness of g=16.5, and a relatively simple…
Resolving OB Systems in the Carina Nebula with the Hubble Space Telescope Fine Guidance Sensor
Gies, Douglas R.; Walborn, Nolan R.; Moffat, Anthony F. J. +4 more
We observed 23 OB stars in the Carina Nebula (NGC 3372) with the Hubble Space Telescope's Fine Guidance Sensor 1r (FGS1r) in its high angular resolution mode. Five of these OB stars are newly resolved binaries with projected separations ranging from 0.015" to 0.352" (37 to 880 AU at a distance of 2.5 kpc), and V-band magnitude differences ranging …
Mass Segregation in the Globular Cluster Palomar 5 and its Tidal Tails
Grebel, Eva K.; Caldwell, John A. R.; Koch, Andreas +2 more
We present the stellar main-sequence luminosity function (LF) of the disrupted, low-mass, low-concentration globular cluster Palomar 5 and its well-defined tidal tails, which emanate from the cluster as a result of its tidal interaction with the Milky Way. The results of our deep (B~24.5) wide-field photometry unequivocally indicate that preferent…
Empirically Constrained Color-Temperature Relations. II. uvby
Grundahl, Frank; VandenBerg, Don A.; Bell, Roger A. +1 more
A new grid of theoretical color indices for the Strömgren uvby photometric system has been derived from MARCS model atmospheres and SSG synthetic spectra for cool dwarf and giant stars having -3.0<=[Fe/H]<=+0.5 and 3000<=Teff<=8000 K. At warmer temperatures (i.e., 8000<Teff<=40,000 K), this grid has been sup…