Search Publications
Local stellar kinematics from HIPPARCOS data
Dehnen, Walter; Binney, James J.
From the parallaxes and proper motions of a kinematically unbiased subsample of the Hipparcos Catalogue, we have re-determined as a function of colour the kinematics of main-sequence stars. Whereas the radial and vertical components of the mean heliocentric velocity of stars show no trend with colour, the component in the direction of Galactic rot…
A hyperluminous galaxy at z=2.8 found in a deep submillimetre survey
Kneib, J. -P.; Ivison, R. J.; Smail, Ian +5 more
We present a detailed study of SMM02399-0136, a hyperluminous, active galaxy selected from a submm survey of the distant Universe. This galaxy is the brightest source in the fields of six rich, lensing clusters, with a total area of 0.01deg^2, that we have mapped with a sensitivity of ~2mJybeam^-1 at 850mum. We identify a compact optical counterpa…
A spectral decomposition of the variable optical, ultraviolet and X-ray continuum of NGC 5548
Zdziarski, Andrzej A.; Smith, David A.; Johnson, W. Neil +2 more
We present an analysis and decomposition of the broad-band optical/UV/X-ray/gamma-ray spectrum of the Seyfert 1 galaxy NGC 5548. The spectrum consists of an average of simultaneous optical/IUE/Ginga observations accompanied by ROSATCGRO/OSSE data from non-simultaneous observations. We show that the overall optical/UV/X-ray/gamma-ray spectrum can b…
HIPPARCOS observations of pre-main-sequence stars
Bastian, U.; Krautter, J.; Rucinski, S. M. +2 more
We present first results of Hipparcos observations of nearby low-mass pre-main-sequence (PMS) stars (TTauri and Herbig Ae/Be stars). The data obtained by Hipparcos allow us to derive weighted mean parallaxes for three major nearby star-forming regions (SFRs), Lupus, Chamaeleon I and Taurus-Auriga. Furthermore, results on the isolated objects AB Do…
HST, radio and infrared observations of 28 3CR radio galaxies at redshift z~1 - II. Old stellar populations in central cluster galaxies
Best, P. N.; Longair, M. S.; Roettgering, H. J. A.
Hubble Space Telescope images of 3CR radio galaxies at redshifts 0.6<z<1.8 have shown a remarkable variety of structures, generally aligned along the radio axis, indicating that the radio source strongly influences the optical appearance of these galaxies. In this paper we investigate the host galaxies underlying this aligned emission, combi…
Quantitative spectroscopy of Wolf-Rayet stars in HD97950 and R136a - the cores of giant HII regions
Crowther, P. A.; Dessart, Luc
We present quantitative analyses of Wolf-Rayet stars in the cores of two giant Hii regions - HD97950 in NGC3603 and R136a in 30 Doradus - based on archive Hubble Space Telescope (HST) spectroscopy. We confirm previous WN6h+abs classifications for components A1, B and C in HD97950, while classifications for R136a1-3 are revised from O3If^*/WN6 to W…
High-redshift galaxies in the Hubble Deep Field - II. Colours and number counts
Ferguson, Henry C.; Madau, Piero; Zamorani, Gianni +2 more
We discuss the deep galaxy counts from the Hubble Deep Field (HDF) imaging survey. At faint magnitudes, the slope of the differential number-magnitude relation is flatter than 0.2 in all four HDF bandpasses. In the ultraviolet, a fluctuation analysis shows that the flattening observed below U_300~26 mag is not caused by incompleteness and is more …
Refining the Oort and Galactic constants
Merrifield, Michael R.; Olling, Rob P.
The local stellar kinematics of the Milky Way offer a useful tool for studying the rotation curve of the Galaxy. These kinematics - usually parametrized by the Oort constants AB - depend on the local gradient of the rotation curve as well as its absolute value (Theta_0), and the Sun's distance to the Galactic Centre (R_0). The density of interstel…
HSTcolour-magnitude diagrams of six old globular clusters in the LMC
Suntzeff, N. B.; Walker, A. R.; Mateo, M. +4 more
We report on HST observations of six candidate old globular clusters in the Large Magellanic Cloud (LMC): NGC 1754, 1835, 1898, 1916, 2005 and 2019. Deep exposures with the F555W and F814W filters provide us with colour-magnitude diagrams that reach to an apparent magnitude in V of ~25, well below the main-sequence turn-off. These particular clust…
The EC 14026 stars - VIII. PG 1336-018: a pulsating sdB star in an HWVir-type eclipsing binary
O'Donoghue, D.; Kilkenny, D.; Lynas-Gray, A. E. +2 more
The sdB star PG 1336-018 is found to be a very short-period eclipsing binary system, remarkably similar to the previously unique system HW Vir. In addition, and unlike HW Vir, the sdB star in the PG 1336 system shows rapid oscillations of the type found in the recently discovered sdB pulsators, or EC 14026 stars. The orbital period, 0.101 0174 d, …