Search Publications
High-redshift galaxies in the Hubble Deep Field: colour selection and star formation history to z~4
Ferguson, Henry C.; Giavalisco, Mauro; Dickinson, Mark E. +3 more
The Lyman decrement associated with the cumulative effect of HI in QSO absorption systems along the line of sight provides a distinctive feature for identifying galaxies at z>~2.5. Colour criteria, which are sensitive to the presence of a Lyman continuum break superposed on an otherwise flat UV spectrum, have been shown, through Keck spectrosco…
Galaxy morphology to I=25 mag in the Hubble Deep Field
Santiago, B. X.; Glazebrook, K.; Abraham, R. G. +3 more
The morphological properties of galaxies in the range 21<<e1>I<</e1>25 mag in the Hubble Deep Field are investigated using a quantitative classification system based on measurements of the central concentration and asymmetry of galaxian light. The class distribution of objects in the Hubble Deep Field is strongly skewed towards h…
The life-cycle of star formation in distant clusters
Smail, I.; Barger, A. J.; Ellis, R. S. +3 more
We analyse the detailed distribution of star-forming and post-starburst members in three distant (z=0.31) galaxy clusters in terms of evolutionary sequences that incorporate secondary bursts of star formation on pre-existing stellar populations. Using the number density of spectroscopically confirmed members of the EW(Hdelta) versus B-R plane from…
Evolution of the aligned structures in z~1 radio galaxies
Best, P. N.; Rottgering, H. J. A.; Longair, M. S.
Hubble Space Telescope observations are presented of eight 3CR radio galaxies in the redshift interval 1<~<e1>z<~</e1>1.3. The optical morphologies of these galaxies change dramatically as the radio size increases. It is shown that this evolution is entirely consistent with large-scale star formation induced by the radio jet, and…
The average X-ray/gamma-ray spectrum of radio-quiet Seyfert 1s
Zdziarski, Andrzej A.; George, Ian M.; Gondek, Dorota +5 more
We have obtained the average 1-500 keV spectrum of radio-quiet Seyfert 1s using data from EXOSAT, Ginga, HEAO-1 and GRO OSSE. The spectral fit to the combined average EXOSAT and OSSE data is fully consistent with that for Ginga and OSSE, confirming results from an earlier Ginga/OSSE sample. The average spectrum is well fitted by a power-law X-ray …
The nature of the faint galaxies in the Hubble Deep Field
Georgakakis, A.; Rowan-Robinson, M.; Mobasher, B. +1 more
We present a study of the galaxies found in the Hubble Deep Field (HDF). A high proportion of HDF galaxies are undergoing a strong episode of star formation, as evidenced by their very blue colours. A wide range of morphological types is found, with a high proportion of peculiar and merger morphologies. Fitting the multiband spectra with redshifte…
Faint galaxy counts as a function of morphological type in a hierarchical merger model
Cole, S.; Baugh, C. M.; Frenk, C. S.
The unprecedented resolution of the refurbished Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST) has led to major advances in our understanding of galaxy formation. The high image quality in the Medium Deep Survey and Hubble Deep Field has made it possible, for the first time, to classify faint distant galaxies accordi…
The compact radio nucleus of the Seyfert galaxy NGC 1068
Muxlow, T. W. B.; Antonucci, R. R. J.; Holloway, A. J. +2 more
We present a 5-GHz MERLIN map of the central arcsecond of the Seyfert 2 galaxy NGC 1068. We detect the four-component structure reported in earlier observations. The higher angular resolution and sensitivity of the MERLIN measurements show extended emission consistent with a flaring jet which appears to originate from the vicinity of a 100-mas com…
Weak gravitational lensing around field galaxies in Hubble Space Telescope survey images
Im, M.; Griffiths, R. E.; Casertano, S. +1 more
Using data from the Hubble Space Telescope (HST) Medium Deep Survey, a long-term key project, together with generically similar archived data, we have discovered evidence for weak gravitational `shear' of background field galaxies (I=22-26) in the vicinity of isolated, foreground galaxies (I=15-22), especially those of early type. The statistical …
Identification of a gravitationally lensed z=2.515 star-forming galaxy
Smail, I.; Kneib, J. -P.; Sanahuja, B. +4 more
We discuss the optical spectrum of a multiply imaged arc resolved by the Hubble Space Telescope in the z=0.175 cluster A2218. The spectrum, obtained with LDSS-2 on the 4.2-m William Herschel Telescope, reveals the source to be a galaxy at a redshift z=2.515, in excellent agreement with the value predicted by Kneib et al. on the basis of their inve…