Search Publications
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…
A month in the life of NGC 4151: velocity-delay maps of the broad-line region
Horne, Keith; Ulrich, Marie-Helene
We analyse continuum and emission-line variability in NGC 4151 based on IUE spectra taken with nearly complete 1-d sampling over a 35-d interval during 1991 November-December. The 1320-Angstroms continuum undertook a bumpy exponential decline by a factor ~3 over 25 d, and then made a dramatic recovery in ~2d near the end of the campaign. The same …
Periodic UV modulation of X1850-087: a double degenerate binary in the globular cluster NGC 6712?
van Paradijs, J.; Charles, P. A.; Naylor, T. +3 more
We report the discovery with the Hubble Space Telescope (HST) of a short-period (20.6 min) UV modulation in X1850-087, the luminous X-ray source in the globular cluster NGC 6712. The low-amplitude modulation (0.044+/-0.007 mag) is not detected in archival X-ray observations with EXOSAT. We compare the properties of X1850-087 with the 11-min binary…
Optical and ultraviolet spectrophotometry of the ONeMg Nova V838 Herculis 1991
Shore, Steven N.; Sonneborn, George; Wagner, R. Mark +2 more
We present an analysis of optical and UV spectra of the fast nova V838 Herculis 1991. IUE observations began on 1991 March 25 and continued through 1991 August 20, while optical observations began on 1991 March 29 and continued through 1991 August 20. We determine a value for the reddening of E(B-V)~0.5+/-0.1 and a distance of ~3+/-1 kpc based bot…
Star counts in the Hubble Deep Field: constraining galactic structure models.
Minniti, D.; de Marchi, G.; Méndez, R. A. +2 more
Stellar sources are identified in the Hubble Deep Field, and accurate colours and magnitudes are presented. The predictions of a Galactic star counts model are compared with the faint stellar counts in this field. The model reproduces the observations very well in the magnitude range 21.0 < V ≤ 26.4, while it overpredicts the counts by a factor…
HST star counts at high galactic latitudes
Gilmore, Gerard; Elson, Rebecca A. W.; Santiago, Basilio X.
We use star counts from 17 deep fields imaged with the Wide Field Camera 2 (WFC-2) as part of the HST Medium Deep Survey key project in order to constrain the amount of dark matter in the Galaxy that can be in the form of low-mass main-sequence stars or white dwarfs. Based on the number of red stars found in our fields, we exclude the possibility …