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Exploring the Virgo Stellar Stream with SEKBO Survey RR Lyrae Stars
Sayuri L Prior, G S Da Costa, Stefan C Keller +1
A subset of the RR Lyrae (RRL) candidates identified from the Southern Edgeworth-Kuiper Belt Object (SEKBO) survey data has been followed up photometrically (n=106) and spectroscop…
The Extragalactic Distance Scale without Cepheids
Jeremy Mould, Shoko Sakai
Distances of galaxies in the Hubble Space Telescope Key Project are based on the Cepheid period-luminosity relation. An alternative basis is the tip of the red giant branch. Using…
A new red giant-based distance modulus of 13.3 Mpc to the Antennae galaxies and its consequences
Ivo Saviane, Yazan Momany, Gary S. Da Costa +2
The Antennae galaxies are the closest example of an ongoing major galaxy merger, and thereby represent a unique laboratory for furthering the understanding of the formation of exot…
Abundances on the Main Sequence of Omega Centauri
Laura M. Stanford, G. S. Da Costa, John E. Norris
Abundance ratios of carbon, nitrogen and strontium relative to iron, calculated using spectrum synthesis techniques, are given for a sample of main sequence and turnoff stars that…
A Sr-Rich Star on the Main Sequence of Omega Centauri
Laura M. Stanford, G. S. Da Costa, John E. Norris +1
Abundance ratios relative to iron for carbon, nitrogen, strontium and barium are presented for a metal-rich main sequence star ([Fe/H]=--0.74) in the globular cluster omega Centaur…
Interstellar medium disruption in the Centaurus A group
A. Bouchard, H. Jerjen, G. S. Da Costa +1
We present the results of a 21 cm neutral hydrogen (HI) line detection experiment in the direction of 18 low luminosity dwarf galaxies of the Centaurus A group, using the Australia…
The Age and Metallicity Relation of Omega Centauri
L. M. Stanford, G. S. Da Costa, J. E. Norris +1
We present a metallicity distribution based on photometry and spectra for 442 omega Cen cluster members that lie at the main sequence turnoff region of the color-magnitude diagram.…
The Nature of the Density Clump in the Fornax Dwarf Spheroidal Galaxy
Edward W. Olszewski, Mario Mateo, Jason Harris +3
We have imaged the recently discovered stellar overdensity located approximately one core radius from the center of the Fornax dwarf spheroidal galaxy using the Magellan Clay 6.5m…
Detection of neutral hydrogen in early-type dwarf galaxies of the Sculptor Group
Antoine Bouchard, Helmut Jerjen, Gary S. Da Costa +1
We present our results of deep 21 cm line (HI) observations of five early and mixed-type dwarf galaxies in the nearby Sculptor group using the ATNF 64m Parkes Radio Telescope. Four…
The Absence of Extra-Tidal Structure in the Sculptor Dwarf Spheroidal Galaxy
Matthew G. Coleman, G. S. Da Costa, Joss Bland-Hawthorn
The results of a wide-field survey of the Sculptor dwarf spheroidal galaxy are presented. Our aims were to obtain an accurate map of the outer structure of Sculptor, and to determi…
An HST Study of the Supernovae Accompanying GRB 040924 and GRB 041006
A. M. Soderberg, S. R. Kulkarni, P. A. Price +23
We present the results from a {\it Hubble Space Telescope/ACS} study of the supernovae associated with gamma-ray bursts 040924 () and 041006 (). We find evidence th…
The Dwarf Spheroidal Companions to M31: Variable Stars in Andromeda I and Andromeda III
Barton J. Pritzl, Taft E. Armandroff, George H. Jacoby +1
(Abridged) We present the results of variable star searches of the M31 dwarf spheroidal companions Andromeda I and Andromeda III using the Hubble Space Telescope. A total of 100 va…
A Wide-Field Survey of the Fornax Dwarf Spheroidal Galaxy
M. G. Coleman, G. S. Da Costa, J. Bland-Hawthorn +1
The results of a photometric survey of the Fornax dwarf spheroidal galaxy are presented herein. Accurate photometry in two colours (V and I) was collected over a 10 square degree a…
Clarification of the Nature of the Galaxy CFC97 Cen 05
Antoine Bouchard, Gary S. Da Costa, Helmut Jerjen
The galaxy CFC97 Cen 05 has in the past been considered an HI-rich dwarf galaxy in the nearby Centaurus A group. We have used Australia Telescope Compact Array observations to show…
Shell Structure in the Fornax Dwarf Spheroidal Galaxy
Matthew Coleman, G. S. Da Costa, Joss Bland-Hawthorn +3
We present initial results from a wide field photometric survey of the Fornax dwarf spheroidal (dSph) galaxy. The focus here is on a small overdensity of stars located approximatel…
The Dwarf Spheroidal Companions to M31: Variable Stars in Andromeda VI
Barton J. Pritzl, Taft E. Armandroff, George H. Jacoby +1
We have surveyed Andromeda VI, a dwarf spheroidal galaxy companion to M31, for variable stars using F450W and F555W observations obtained with the Hubble Space Telescope. A total o…
The Dwarf Spheroidal Companions to M31: WFPC2 Observations of Andromeda III
G. S. Da Costa, T. E. Armandroff, Nelson Caldwell
The Hubble Space Telescope WFPC2 camera has been used to image Andromeda III, a dwarf spheroidal companion (dSph) to M31. The resulting color-magnitude (c-m) diagrams reveal the mo…
The Evolution of Copper in the Globular Cluster Omega Centauri
K. Cunha, V. V. Smith, N. B. Suntzeff +3
Copper abundances are presented for 40 red-giant stars in Omega Cen as well as 15 red-giant members of the globular clusters NGC288, NGC362, NGC3201, NGC6752, and M4. A comparison…
Young Clusters in the Magellanic Clouds II
Stefan C. Keller, G. S. Da Costa, M. S. Bessell
We present the results of a quantitative study of the degree of extension to the boundary of the classical convective core within intermediate mass stars. The basis of our empirica…
The Dwarf Spheroidal Companions to M31: WFPC2 Observations of Andromeda II
G. S. Da Costa, T. E. Armandroff, Nelson Caldwell +1
The HST WFPC2 camera has been used to image Andromeda II, a dwarf spheroidal (dSph) companion to M31. The resulting color-magnitude diagrams reveal the morphology of the horizontal…
The Spectroscopic Age of 47 Tuc
Brad K. Gibson, Darren S. Madgwick, Lewis A. Jones +2
High signal-to-noise integrated spectra of the metal-rich globular cluster 47 Tuc, spanning the H-gamma(HR) and Fe4668 line indices, have been obtained. The combination of these in…
Ca II Triplet Spectroscopy of Giants in SMC Star Clusters: Abundances, Velocities and the Age-Metallicity Relation
G. S. Da Costa, D. Hatzidimitriou
We have obtained spectra at the Ca II triplet of individual red giants in seven SMC star clusters whose ages range from ~4 to 12 Gyr. The spectra have been used to determine mean a…
Dwarf Elliptical Galaxies in the M81 Group: The Structure and Stellar Populations of BK5N and F8D1
Nelson Caldwell, Taft E. Armandroff, G. S. Da Costa +1
We have obtained HST WFPC2 images through the F555W and F814W filters of two M81 group dE's: BK5N and a new system, designated F8D1. The resulting color-magnitude diagrams show the…
The Dwarf Spheroidal Companions to M31: WFPC2 Observations of Andromeda I
G. S. Da Costa, T. E. Armandroff, Nelson Caldwell +1
Images have been obtained with the Hubble Space Telescope WFPC2 camera of Andromeda I, a dwarf spheroidal (dSph) galaxy that lies in the outer halo of M31. The resulting color-magn…