Distances to Local Group Galaxies

Distances to galaxies in the Local Group are reviewed. In particular, the distance to the Large Magellanic Cloud is found to be $(m-M)_0 = 18.52 \pm 0.10$, corresponding to $50,600 \pm 2,400$ pc. The importance of M31 as an analog of the galaxies observed at greater distances is stressed, while the variety of star formation and chemical enrichment histories displayed by Local Group galaxies allows critical evaluation of the calibrations of the various distance indicators in a variety of environments.Comment: 15 pages, no figures, to appear in "Stellar Candles for the Extragalactic Distance Scale", Lecture Notes in Physics (Springer), ed. D. Alloin and W. Giere

The CTIO Prime Focus CCD: System Characteristics from 1982-1988

The CTIO Prime Focus CCD instrument with an RCA CCD was in operation at the CTIO 4-m telescope for six years between 1982-1988. A large body of literature has been published based on CCD images taken with this instrument. We review the general properties of the now-retired PFCCD system to aid astronomers in the interpretation of the photometric data in the literature.Comment: Accepted for publication in the PASP. 15 pages, AASTeX V4.0 latex format (including figures), 4 ps figures, 4 separate AASTeX V4.0 latex table

A Survey for EHB Stars in the Galactic Bulge

We present a progress report on an extensive survey to find and characterize all types of blue horizontal-branch stars in the nuclear bulge of the Galaxy. We have obtained wide, shallow imaging in UBV of ~12 square degrees in the bulge, with follow-up spectroscopy for radial velocities and metal abundance determinations. We have discovered a number of metal-rich blue HB stars, whose presence in the bulge is expected by the interpretation of the extragalactic ultraviolet excess. Very deep images have been obtained in UBV and SDSS u along the bulge minor axis, which reveal a significant number of EHB candidates fainter than B = 19, i.e., with the same absolute magnitudes as EHB stars in several globular clusters.Comment: To appear in "Extreme Horizontal Branch Stars and Related Objects", Astrophysics and Space Science, Kluwer Academic Publishers, proceedings of the meeting held in Keele, UK, June 16-20, 200

The Color-Magnitude Diagram of the Globular Cluster NGC 6362 and the Canonical Tilt of Horizontal Branches

In this paper we present new and accurate photometry for stars in the Galactic globular cluster NGC 6362. The color-magnitude diagram discloses two peculiarities in the distribution of stars: (1) a slightly tilted horizontal branch (HB) (Δ = 0.1 mag) and (2) a clump of stars near the red edge of the HB. We perform a detailed comparison with theoretical stellar models in both the HB and red giant branch (RGB) phases. It appears that in the moderately metal rich NGC 6362 the tilted HB can be explained as a natural product of canonical evolutionary theories, being a consequence of the minimum in the bolometric correction near 7500 K. We also investigate the effect of decreasing the efficiency of convective transport in stars climbing the RGB. Adopting Z = 0.002 and Y = 0.23, and performing a global fitting with the theoretical isochrones and zero-age HB, an age of 12 ± 1 Gyr is found, together with (m - M)V = 14.68 and E(B-V) = 0.08

Hot Horizontal Branch Stars in the Galactic Bulge. I

We present the first results of a survey of blue horizontal branch (BHB) stars in the Galactic bulge. 164 candidates with 15 < V < 17.5 in a field 7.5deg from the Galactic Center were observed in the blue at 2.4A FWHM resolution with the AAT 2dF spectrograph. Radial velocities were measured for all stars. For stars with strong Balmer lines, their profiles were matched to theoretical spectrum calculations to determine stellar temperature Teff and gravity log g; matches to metal lines yielded abundances. CTIO UBV photometry then gave the reddening and distance to each hot star. Reddening was found to be highly variable, with E(B-V) from 0.0 to 0.55 around a mean of 0.28. Forty-seven BHB candidates were identified with Teff >= 7250K, of which seven have the gravities of young stars, three are ambiguous, and 37 are HB stars. They span a wide metallicity range, from solar to 1/300 solar. The warmer BHB's are more metal-poor and loosely concentrated towards the Galactic center, while the cooler ones are of somewhat higher metallicity and closer to the center. Their red B-V colors overlap main-sequence stars, but the U-B vs. B-V diagram separates them until E(B-V) > 0.5. We detect two cool solar-metallicity HB stars in the bulge of our own Galaxy, the first such stars known. Still elusive are their hot counterparts, the metal-rich sdB/O stars causing excess UV light in metal-rich galaxies; they have V ~ 20.5 in the Bulge.Comment: 29 pages, 4 figures (the third with 4 panels, the fourth with 2 panels). To appear in the Astrophysical Journal v571n1, Jan. 20, 2000. Abstract is shortened here, and figures compresse