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HST color-magnitude diagrams of 74 galactic globular clusters in the HST F439W and F555W bands
Djorgovski, S. G.; Recio-Blanco, A.; Zoccali, M. +9 more
We present the complete photometric database and the color-magnitude diagrams for 74 Galactic globular clusters observed with the HST/WFPC2 camera in the F439W and F555W bands. A detailed discussion of the various reduction steps is also presented, and of the procedures to transform instrumental magnitudes into both the HST F439W and F555W flight …
The M 81 group of galaxies: New distances, kinematics and structure
Sarajedini, A.; Dolphin, A. E.; Grebel, E. K. +7 more
We present Hubble Space Telescope/WFPC2 images of the galaxies NGC 2366, NGC 2976, NGC 4236, IC 2574, DDO 53, DDO 82, DDO 165, Holmberg I, Holmberg II, Holmberg IX, K52, K73, BK3N, Garland, and A0952+69 in the M 81 complex. Their true distance moduli, derived from the brightness of the tip of the red giant branch, lie in the range of 27fm 52 (NGC …
Stellar and wind properties of LMC WC4 stars. A metallicity dependence for Wolf-Rayet mass-loss rates
Hillier, D. J.; Crowther, P. A.; Fullerton, A. W. +2 more
We use ultraviolet space-based (FUSE, HST) and optical/IR ground-based (2.3 m MSSSO, NTT) spectroscopy to determine the physical parameters of six WC4-type Wolf-Rayet stars in the Large Magellanic Cloud. Stellar parameters are revised significantly relative to Gräfener et al. (\cite{Grafener1998}) based on improved observations and more sophistica…
New distances to galaxies in the Centaurus A group
Sarajedini, A.; Dolphin, A. E.; Grebel, E. K. +7 more
We present Hubble Space Telescope/WFPC2 images of seventeen dwarf galaxies in the Centaurus A group. Their distances derived from the magnitudes of the tip of the red giant branch are 5.2 Mpc (KK112), 3.2 Mpc (ESO 321-014), 3.5 Mpc (KK179), 3.4 Mpc (NGC 5102), 4.6 Mpc (KK200), 3.7 Mpc (ESO 324-024), 4.7 Mpc (KK208), 4.6 Mpc (ESO 444-084), 4.4 Mpc …
The very local Hubble flow
Sarajedini, A.; Dolphin, A. E.; Grebel, E. K. +8 more
We present Hubble Space Telescope/WFPC2 images of eighteen galaxies situated in the vicinity of the Local Group (LG) as part of an ongoing snapshot survey of nearby galaxies. Their distances derived from the magnitude of the tip of the red giant branch are 1.92±0.10 Mpc (ESO 294-010), 3.06±0.37 (NGC 404), 3.15±0.32 (UGCA 105), 1.36±0.07 (Sex B), 1…
The mass function of the Arches cluster from Gemini adaptive optics data
Brandner, W.; Grebel, E. K.; Stolte, A. +1 more
We have analysed high resolution adaptive optics (AO) science demonstration data of the young, massive stellar cluster Arches near the Galactic Center, obtained with the Gemini North telescope in combination with the University of Hawai'i AO system Hokupa'a. The AO H and K' photometry is calibrated using HST/NICMOS observations in the equivalent f…
Extragalactic globular clusters in the near-infrared. II. The globular clusters systems of NGC 3115 and NGC 4365
Minniti, D.; Hilker, M.; Kissler-Patig, M. +3 more
We combine near-infrared photometry obtained with the VLT/ISAAC instrument and archival HST/WFPC2 optical images to determine VIK magnitudes and colours of globular clusters in two early-type galaxies, NGC 3115 and NGC 4365. The combination of near-IR and optical photometry provides a way to lift the age-metallicity degeneracy. For NGC 3115, the g…
Dynamical masses of young star clusters in NGC 4038/4039
Genzel, R.; Lehnert, M. D.; Mengel, S. +1 more
In order to estimate the masses of the compact, young star clusters in the merging galaxy pair, NGC 4038/4039 (``the Antennae''), we have obtained medium and high resolution spectroscopy using ISAAC on VLT-UT1 and UVES on VLT-UT2 of five such clusters. The velocity dispersions were estimated using the stellar absorption features of CO at 2.29 mu m…
The blue compact dwarf galaxy I Zw 18: A comparative study of its low-surface-brightness component
Thuan, T. X.; Izotov, Y. I.; Green, R. F. +4 more
Using HST and ground-based optical and NIR imaging data we investigate whether the blue compact dwarf (BCD) galaxy I Zw 18 possesses an extended low-surface-brightness (LSB) old stellar population underlying its star-forming regions, as is the case in the majority of BCDs. This question is central to the long-standing debate on the evolutionary st…
Spectroscopic diagnostics of stellar transition regions and coronae in the XUV: AU Mic in quiescence
Mason, H. E.; Landini, M.; Del Zanna, G.
In this paper we review the spectroscopic diagnostic techniques that can be applied to XUV observations of active stars. In particular, we discuss methods for the determination of electron densities, emission measures and the chemical composition of the stellar transition regions and coronae. We pay particular attention to the atomic data used and…