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Stellar Populations in the Dwarf Elliptical Galaxy NGC 147
Krist, J.; Stapelfeldt, K.; Gallagher, J. S., III +16 more
Deep V and I CCD images in a central and an outer field of the Local Group dwarf elliptical galaxy NGC 147 have been obtained with the Wide Field and Planetary Camera-2 (WFPC2) on board of the Hubble Space Telescope. The color-magnitude diagram shows a number of interesting features, including a well defined red giant branch (RGB), a red horizonta…
Observations of the Hubble Deep Field with the Infrared Space Observatory - III. Source counts and P(D) analysis
Elbaz, D.; Danese, L.; Franceschini, A. +19 more
We present source counts at 6.7 and 15 µm from our maps of the Hubble Deep Field (HDF) region, reaching 38.6 muJy at 6.7 µm and 255 muJy at 15 mum. These are the first ever extragalactic number counts to be presented at 6.7 mum, and are three decades fainter than IRAS at 12 mum. Both source counts and a P(D) analysis suggest that we ha…
Stellar Populations in the Large Magellanic Cloud:Evidence for a Significant Number of Older Stars or a Steeper IMF?
Stapelfeldt, K. R.; Clarke, J. T.; Grillmair, Carl J. +14 more
We present deep photometry obtained with the HST in an outer LMC field. A well-defined main sequence is seen down to V>26. We derive a luminosity function from the data and use it to constrain the IMF and the star formation history. We derive limits on the IMF slope, alpha (with dN/dM~ M(alpha ) ), from stars on the main sequence which are fain…
Metals in the variable DA G29-38
Koester, D.; Shipman, H. L.; Provencal, J.
We report the detection of the heavy elements Ca, Mg, Fe in the atmosphere of the variable DA white dwarf G29-38. The abundance of Ca can be understood only if accretion from interstellar matter is going on currently at a high rate. This lends support also the interpretation of the observed infrared excess as due to heated circumstellar material, …
A Comparison of Deep HST Luminosity Functions of Four Globular Clusters
Piotto, Giampaolo; Cool, Adrienne M.; King, Ivan R.
From deep color-magnitude arrays made from V and I images taken with Hubble Space Telescope's WFPC2 camera we have determined luminosity functions (LFs) down to a level that corresponds to ~ 0.13 \msun, for the low-metal-abundance globular clusters M15, M30, M92, and NGC 6397. Because of the similarity of the metallicities of these clusters, diffe…
Nearby Young Dwarf Galaxies: Primordial Gas and Lyα Emission
Thuan, Trinh X.; Izotov, Yuri I.
We present Hubble Space Telescope UV spectrophotometry of three extremely metal-deficient blue compact dwarf (BCD) galaxies, SBS 0335-052 (Z ~ Z⊙/40), Tol 65 (Z ~ Z⊙/24), and T1214-277 (Z ~ Z⊙/23). Broad damped Lyα absorption is seen in the first two BCDs. For SBS 0335-052, the H I column density derived by fitting…
The Nuclear Stellar Core, the Hot Dust Source, and the Location of the Nucleus of NGC 1068
Genzel, R.; Maiolino, R.; Quirrenbach, A. +2 more
We present new near-infrared speckle and adaptive optics imaging and integral field spectroscopy of the nuclear region of NGC 1068. Ninety-four percent of the K-band light in the central 1" originates from a <=30 milliarcsecond diameter source whose position we determine to coincide within +/-0.15" with the apex of the cone structure seen in th…
Turbulent Velocities and Ion Temperatures in the Solar Corona Obtained from SUMER Line Widths
Wilhelm, K.; Curdt, W.; Schühle, U. +3 more
Turbulent plasma velocities and ion temperatures were determined from the line widths recorded by the Solar Ultraviolet Measurements of Emitted Radiation instrument on the Solar and Heliospheric Observatory spacecraft. From the widths of the lines of five light elements (Ne, Na, Mg, Si, and S) and a heavy element (Fe), it was possible to determine…
Local Interstellar Medium Properties and Deuterium Abundances for the Lines of Sight toward HR 1099, 31 Comae, β Ceti, and β Cassiopeiae
Wood, Brian E.; Linsky, Jeffrey L.; Dempsey, Robert C. +2 more
We analyze Goddard High-Resolution Spectrograph data to infer the properties of local interstellar gas and the deuterium/hydrogen (D/H) ratio for lines of sight toward four nearby late-type stars--HR 1099, 31 Comae, β Ceti, and β Cassiopeiae. The data consist of spectra of the hydrogen and deuterium Lyα lines, and echelle spectra of the Mg II h an…
Hubble Space Telescope Imaging of Compact Steep-Spectrum Radio Sources
Golombek, D.; Sparks, W. B.; Macchetto, F. +8 more
We present Hubble Space Telescope WFPC2 images taken through a broad red filter (F702W) of 30 Third Cambridge Catalog compact steep spectrum (CSS) radio sources. We have overlaid radio maps taken from the literature on the optical images to determine the radio-optical alignment and to study detailed correspondence. All CSS sources for which the re…