Search Publications
The recent star formation history of the Hipparcos solar neighbourhood
Gilmore, Gerard; Valls-Gabaud, David; Hernandez, X.
We use data from the Hipparcos catalogue to construct colour-magnitude diagrams for the solar neighbourhood, which are then treated using advanced Bayesian analysis techniques to derive the star formation rate history, SFR(t), of this region over the last 3Gyr. The method we use allows the recovery of the underlying SFR(t) without the need of assu…
The European Large Area ISO Survey - II. Mid-infrared extragalactic source counts
McMahon, Richard G.; Serjeant, Stephen; Clements, David L. +20 more
We present preliminary source counts at 6.7 and 15µm from the preliminary analysis of the European Large Area ISO Survey, with limiting flux densities of ~2mJy at 15µm and ~1mJy at 6.7µm. We separate the stellar contribution from the extragalactic using identifications with automated plate measurement sources made with the likeli…
Hipparcos parallaxes for Mira-like long-period variables
Feast, Michael; Whitelock, Patricia
This paper concerns the calibration of the K period-luminosity relation for Mira variables using Hipparcos parallaxes. K magnitudes are available for 255 Mira-like variables which were observed by Hipparcos. Period-luminosity zero-points are evaluated for various subgroups of data. The best solution for oxygen-rich Miras, which uses 180 stars, omi…
Mira kinematics from Hipparcos data: a Galactic bar to beyond the Solar circle
Whitelock, Patricia A.; Feast, Michael W.
The space motions of Mira variables are derived from radial velocities, Hipparcos proper motions and a period-luminosity relation. The previously known dependence of Mira kinematics on the period of pulsation is confirmed and refined. In addition, it is found that Miras with periods in the range 145-200d in the general Solar neighbourhood have a n…
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…
The distribution of bright OB stars in the Canis Major-Puppis-Vela region of the Milky Way
Kaltcheva, N. T.; Hilditch, R. W.
The picture of the young stellar groups in the Canis Major-Puppis-Vela (215 deg<l<275 deg) section of the Milky Way is studied and updated utilizing uvbyβ photometry of intrinsically luminous OB stars. We use all data from the literature to create a sample with 98per cent completeness to 9.5mag. The very dense low reddened OB association CMa…
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…