Search Publications
Two-colour photometric selection of high-redshift galaxies
Lacy, Mark; Stevens, Robin
In this paper we describe a set of models to predict the colours of galaxies over a wide range of redshifts. We present examples of output from the simulations, and discuss their application to the selection of galaxies at high redshifts, particularly through identification of the Lyman break. Additionally we consider the optimal choices of filter…
Modelling the H Lyman lines in evolved late-type stars
Sim, S. A.
The importance of partial redistribution (PRD) in the modelling of the Lyman α and Lyman β emission lines of hydrogen in stellar atmospheres is examined using simple atmospheric models of a range of late-type stars. These models represent the subgiant Procyon (F5 IV-V), and the two giants β Gem (K0 III) and α Tau (K5 III). These stars are selected…
Variation mechanisms in symbiotic nova V1329 Cygni
Chochol, D.; Wilson, R. E.
U,B,V light curves of symbiotic nova V1329 Cygni (=HBV 475) are modelled in terms of combined wind and chromospheric fluorescence, with eclipses and shadowing of fluorescent regions, eccentric orbit effects, and conversion of far-ultraviolet energy into the optical bands. Observational evidence regarding fluorescent brightness variation mechanisms…
The low-mass white dwarf companion to β Crateris
Barstow, M. A.; Wynn, G. A.; Burleigh, M. R. +4 more
We present FUSE H Lyman series spectroscopy of the hot white dwarf companion to the 4th magnitude A1III star βCrt, which shows that it has an unusually low mass, MWD=0.43Msolar, and has almost certainly evolved through binary interaction. This system could be a long-sought remnant of Algol-type evolution, although radial velo…
Harmonizing the RR Lyrae and clump distance scales - stretching the short distance scale to intermediate ranges?
Popowski, Piotr
I explore the consequences of making the RR Lyrae and clump giant distance scales consistent in the solar neighbourhood, Galactic bulge and Large Magellanic Cloud (LMC). I employ two major assumptions: (i) that the absolute magnitude-metallicity, MV(RR)-[Fe/H], relation for RR Lyrae stars is universal, and (ii) that absolute I magnitude…
An astrophysical oscillator strength for the S ii 94.7-nm resonance line and S abundances in DLAs
Bonifacio, Piercarlo; Molaro, Paolo; Caffau, Elisabetta +2 more
By using UV spectra for the O star HD 93521 taken with the ORFEUS II echelle spectrograph, we determine an `astrophysical' f value for the Siiλ94.7-nm line: f=0.00498-0.00138+0.00172, error at 1σ level. This is almost a factor of 30 smaller than the guessed value found in the Kurucz data base (f=0.1472), which was until now the only one available …
Deep galaxy counts, extragalactic background light and the stellar baryon budget
Madau, Piero; Pozzetti, Lucia
We assess the constraints imposed by the observed extragalactic background light (EBL) on the cosmic history of star formation and the stellar-mass density today. The logarithmic slope of the galaxy number-magnitude relation from the Southern Hubble Deep Field imaging survey is flatter than 0.4 in all seven UBVIJHK optical bandpasses, i.e. the lig…
NGC 6153: a super-metal-rich planetary nebula?
Barlow, M. J.; Cohen, M.; Liu, X. -W. +3 more
We have obtained deep optical spectra of the planetary nebula NGC 6153, both along its minor axis and by uniformly scanning a long slit across the whole nebula. The scanned spectra, when combined with the nebular total Hβ flux, yield integrated fluxes for all the lines (~400) in our spectra, which are rich in strong recombination lines from C, N, …
Hubble Space Telescope imaging of the CFRS and LDSS redshift surveys - IV. Influence of mergers in the evolution of faint field galaxies from z~1
Glazebrook, K.; Le Fèvre, O.; Brinchmann, J. +9 more
Hubble Space Telescope images of a sample of 285 galaxies with measured redshifts from the Canada-France Redshift Survey (CFRS) and Autofib-Low Dispersion Spectrograph Survey (LDSS) redshift surveys are analysed to derive the evolution of the merger fraction out to redshifts z~1. We have performed visual and machine-based merger identifications, a…
The local density of matter mapped by Hipparcos
Flynn, Chris; Holmberg, Johan
We determine the velocity distribution and space density of a volume-complete sample of A and F stars, using parallaxes and proper motions from the Hipparcos satellite. We use these data to solve for the gravitational potential vertically in the local Galactic disc, by comparing the Hipparcos measured space density with predictions from various di…