Search Publications
The morphological identification of the rapidly evolving population of faint galaxies
Ellis, Richard; Glazebrook, Karl; Griffiths, Richard +1 more
The excess numbers of blue galaxies at faint magnitudes are a long-standing cosmological puzzle. We present new number-magnitude counts as a function of galactic morphology from the first deep fields of the Cycle 4 Hubble Space Telescope Medium Deep Survey project. From a sample of 301 galaxies we define counts for elliptical, spiral and irregular…
A new model for the infrared emission of quasars
Rowan-Robinson, Michael
The optical-UV continua of 75 PG quasars are modelled to test two extreme hypotheses: (a) the range of continuum shapes observed is the result of different amounts of reddening of a single underlying continuum, and (b) the range of continuum slopes is entirely intrinsic, due to accretion discs being viewed at different inclinations. Although (a) i…
RE J0317-853: the hottest known highly magnetic DA white dwarf
Jordan, S.; Barstow, M. A.; O'Donoghue, D. +3 more
We report the discovery of a new highly magnetic DA white dwarf, RE J0317-853, through its detection as an EUV source by the ROSAT Wide Field Camera. A combination of far-UV and optical spectra indicates that the star has an effective temperature ~=50000K, making it the hottest known white dwarf with a measurable magnetic field. Furthermore, the m…
A detailed X-ray variability study of the Seyfert galaxy NGC 4051
Papadakis, I. E.; Lawrence, A.
We present a detailed and rigorous examination of the X-ray variability characteristics of the Seyfert galaxy NGC 4051, using the 1985 EXOSAT observation and our improved power spectrum modelling techniques. The Medium Energy (ME) power spectrum is adequately fitted by a power-law model, but the Low Energy (LE) spectrum is not. We find an excellen…
The high-temperature big blue bump in the Seyfert galaxy RE J1034+396
Siemiginowska, A.; Mason, K. O.; Pounds, K. A. +1 more
X-ray, UV and optical spectra are presented for a rare, EUV-bright Seyfert galaxy, RE J1034+396 (z=0.042). When combined, these data describe a very-high temperature big blue bump (BBB; kT_eff~100 eV) whose high energy turnover is observed in soft X-rays. The soft X-ray/UV flux ratio is extremely high, L_0.2keV/L_1200A~10, compared to AGN in gener…
HST observations of three radio galaxies at redshift z~=1
Best, P. N.; Rottgering, H. J. A.; Longair, M. S.
The first results of a programme to image a sample of radio galaxies at redshift z~=1 with the Hubble Space Telescope are reported in this Letter. The images of the three galaxies presented here (3C368, 3C324 and 3C265) show a wealth of fine structure down to the resolution limit of the HST. All three systems show a clear alignment of the optical …
An independent calibration of stellar ages: Hubble Space Telescope observations of white dwarfs at V=25
Gilmore, Gerard; Jones, D. H. P.; von Hippel, Ted
The white dwarf luminosity function of a stellar cluster will have a sharp truncation at a luminosity which is determined by the time since formation of the first white dwarfs in that cluster. Calculation of the dependence of this limiting luminosity on age requires relatively well-understood physics and is independent of stellar evolutionary mode…
Long-term X-ray variability of NGC 4151
Papadakis, I. E.; McHardy, I. M.
We present a new method of estimating the power spectrum in the case of unevenly sampled data, together with its application to the long X-ray light curve of the Seyfert galaxy NGC 4151. This method is based on the Fourier transform of the observed autocovariance function. The method is simple to use and wisely applicable. The long-term power spec…
The spectrum of the planetary nebula NGC 6886
Hyung, Siek; Aller, Lawrence H.; Keyes, Charles D.
The relatively young, high-excitation planetary nebula (PN) NGC 6886 shows a remarkable variety of lines from both high- and low-excitation stages, i.e., from N^0 to N^4+, and as a result it provides unique opportunities for detailed studies of physical processes, using a theroetical model. By combining Hamilton echelle observations with UV data s…
Eclipse observations of an accretion disc wind
Knigge, C.; Horne, Keith; Mason, K. O. +5 more
The Goddard High Resolution Spectrometer on the Hubble Space Telescope has been used to monitor, through eclipse, the C iv 1550-A and He ii 1640-A lines in the spectrum of the nova-like cataclysmic variable UX UMa. Previous work has suggested that the Civ line arises in an accretion disc wind. The HST data confirm this, in that the line shows a br…