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The Metallicity and Dust Content of HVC 287.5+22.5+240: Evidence for a Magellanic Clouds Origin
Sembach, Kenneth R.; Savage, Blair D.; Wakker, Bart P. +3 more
We estimate the abundances of S and Fe in the high-velocity cloud HVC 287.5+22.5+240, which has a velocity of 240 km s^-1 with respect to the local standard of rest and Galactic direction l ~ 287 deg and b ~ 23 deg. The measurements are based on UV absorption lines of these elements in the Hubble Space Telescope spectrum of NGC 3783, a background …
Discovery of a late-type stellar population associated with the Gould Belt
Schmitt, J. H. M. M.; Motch, C.; Guillout, P. +2 more
We report the detection of a late-type stellar population in the direction of the Gould Belt among stars found by cross-correlating the ROSAT All-Sky Survey with the Tycho catalog. Regions of the Gould Belt located between l = 195°\ and l = 15°\ exhibit a strong density enhancement of X-ray active stars with associated X-ray luminosities LX
Asymmetry in Velocity and Intensity Helioseismic Spectra: A Solution to a Long-standing Puzzle
Kosovichev, A. G.; Scherrer, P. H.; Schou, J. +1 more
We give an explanation for the opposite sense of asymmetry of the solar acoustic mode lines in velocity and intensity oscillation power spectra, thereby solving the half-decade-old puzzle of Duvall and coworkers. The solution came after comparing the velocity and intensity oscillation data of medium angular degree l obtained from the Michelson Dop…
Fine structure of the red giant clump from HIPPARCOS data, and distance determinations based on its mean magnitude
Salaris, Maurizio; Girardi, Leo; Groenewegen, Martin A. T. +1 more
The I-band brightness M_I of clump stars is a possible distance indicator for stellar populations. Investigations have shown that M_I is almost insensitive to the V-I colour within the clump. Based on this, it was assumed that M_I was insensitive to age and composition of the stellar population and therefore an ideal standard candle, which could b…
Photospheric Magnetic Field Changes Associated with Transition Region Explosive Events
Wang, Haimin; Chae, Jongchul; Schühle, Udo +2 more
From a comparison of the Solar and Heliospheric Observatory SUMER spectral data and a time series of Big Bear Solar Observatory magnetograms, we present observational clues to the physical origin of transition region explosive events. First, explosive events rarely occur in the interior of strong magnetic flux concentrations but rather are prefere…
A Spectroscopic Survey of the Galaxy Cluster CL 1358+62 at Z = 0.328
Franx, Marijn; van Dokkum, Pieter; Fisher, David +1 more
We present a spectroscopic survey of the rich X-ray-selected galaxy cluster CL 1358+6245 at z = 0.328. When our 173 new multislit spectra of cluster galaxies are combined with data from the literature, we produce a catalog of 232 cluster members in a region 10' × 11' (3.5 Mpc × 3.8 Mpc) surrounding the brightest cluster galaxy. These data are used…
A Blind Test of Photometric Redshift Prediction
Dickinson, Mark; Sawicki, Marcin; Hogg, David W. +16 more
Results of a blind test of photometric redshift predictions against spectroscopic galaxy redshifts obtained in the Hubble Deep Field with the Keck Telescope are presented. The best photometric redshift schemes predict spectroscopic redshifts with a redshift accuracy of Deltaz < 0.1 for more than 68% of sources and with Deltaz < 0.3 for 100%,…
Hubble Space Telescope V-Band Imaging of the Bipolar Proto-Planetary Nebula IRAS 17150-3224
Kwok, Sun; Hrivnak, Bruce J.; Su, Kate Y. L.
We report Hubble Space Telescope Wide Field Planetary Camera 2 imaging of the bipolar proto-planetary nebula IRAS 17150-3224. We find a series of concentric arcs superposed on the two reflection nebular lobes, similar to those observed in AFGL 2688. This suggests that periodic mass-loss enhancement is a common phenomenon in the asymptotic giant br…
On the age of the nearby blue compact dwarf galaxy SBS 0335-052
Thuan, T. X.; Izotov, Y. I.; Papaderos, P. +2 more
UBVRI surface photometry and long-slit spectrophotometric observations are used to investigate the evolutionary status and put constraints on the age of the underlying stellar population of the eastern component of a nearby pair of dwarf galaxies, the blue compact dwarf galaxy SBS\ 0335-052E. We show that ionized gas emission extending out to dist…
A new analysis of the red giant branch `tip' distance scale and the value of the Hubble constant
Salaris, Maurizio; Cassisi, Santi
The theoretical evaluations of the red giant branch tip (TRGB) luminosity presented previously by Salaris & Cassisi are extended to higher metallicities, and compared with analogous independent results recently published. The present sets of stellar models agree quite well in the determination of the TRGB brightness. Relations between TRGB bol…