Search Publications
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…
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…
Non-parametric star formation histories for four dwarf spheroidal galaxies of the Local Group
Gilmore, Gerard; Valls-Gabaud, David; Hernandez, X.
We use recent Hubble Space Telescope colour-magnitude diagrams of the resolved stellar populations of a sample of local dSph galaxies (Carina, Leo I, Leo II and Ursa Minor) to infer the star formation histories of these systems, SFR(t). Applying a new variational calculus maximum likelihood method, which includes a full Bayesian analysis and allow…
Testing the connection between the X-ray and submillimetre source populations using Chandra
Kneib, J. -P.; Ivison, R. J.; Smail, Ian +8 more
The powerful combination of the Chandra X-ray telescope, the SCUBA submillimetre-wave camera and the gravitational lensing effect of the massive galaxy clusters A2390 and A1835 has been used to place stringent X-ray flux limits on six faint submillimetre SCUBA sources and deep submillimetre limits on three Chandra sources which lie in fields commo…
Galactic globular clusters as a test for very-low-mass stellar models
Zoccali, M.; Piotto, G.; Cassisi, S. +2 more
We make use of the `Next Generation' model atmospheres of Allard et al. and Hauschildt, Allard & Baron to compute theoretical models for low- and very-low-mass stars for selected metallicities in the range Z=0.0002 to 0.002. On this basis, we present theoretical predictions covering the sequence of H-burning stars as observed in Galactic globu…
The cluster environments of the z~1 3CR radio galaxies
Best, P. N.
An analysis of the environments around a sample of 28 3CR radio galaxies with redshifts 0.6<z<1.8 is presented, based primarily upon K-band images down to K~20 taken using the UK Infrared Telescope (UKIRT). A net overdensity of K-band galaxies is found in the fields of the radio galaxies, with the mean excess counts being comparable to that …
Radio, optical and X-ray nuclei in nearby 3CRR radio galaxies
Hardcastle, M. J.; Worrall, D. M.
HST observations have shown that low-redshift 3CR radio galaxies often exhibit a point-like optical component positionally coincident with the GHz-frequency radio core. In this paper we discuss the correlation between the luminosities of the radio, optical and X-ray cores in these objects, and argue that all three components have a common origin a…
Clustering of galaxies around radio quasars at 0.5<=z<=0.8
Serjeant, Stephen; Lacy, Mark; Wold, Margrethe +1 more
We have observed the galaxy environments around a sample of 21 radio-loud, steep-spectrum quasars at 0.5<=z<=0.82, spanning several orders of magnitude in radio luminosity. The observations also include background control fields used to obtain the excess number of galaxies in each quasar field. The galaxy excess was quantified using the spat…
Hubble Space Telescope observations of X-ray-selected active galactic nuclei
Schade, David J.; Boyle, B. J.; Letawsky, Michael
We report on the initial results of a comprehensive Hubble Space Telescope (HST) snapshot imaging survey of 76 low-redshift (z<0.15) X-ray-selected active galactic nuclei (AGN) in the Einstein Extended Medium Sensitivity Survey. This survey is expected to show no bias with respect to host galaxy types, and so is arguably one of the best availab…
The massive stellar content of the Hii region NGC 604 and its evolutionary state
Pérez, Enrique; González Delgado, Rosa M.
This paper analyses the integrated ultraviolet spectra taken with the International Ultraviolet Explorer (IUE) and optical ground-based spectra taken with the William Herschel Telescope (WHT) of the giant Hii region NGC 604. These data are complemented with ultraviolet (WFPC2 through F170W) and Hα (WFPC2 through F656N) images retrieved from the Hu…