Search Publications
A panoramic Hα imaging survey of the z= 0.4 cluster Cl0024.0+1652 with Subaru
Smail, Ian; Kodama, Tadayuki; Nakata, Fumiaki +2 more
We employ panoramic, multicolour (BRz') and narrow-band Hα imaging of the cluster Cl0024.0+1652 (z= 0.39) from Subaru covering a ~30-arcmin field, to determine cluster membership and star formation rates for a large sample of galaxies across a wide field in the cluster, ~10 Mpc. We use photometric redshifts to identify cluster members, and statist…
Exploring the complex X-ray spectrum of NGC 4051
King, A. R.; Reeves, J. N.; Page, K. L. +1 more
Archival XMM-Newton data on the nearby Seyfert galaxy NGC 4051, taken in relatively high- and low-flux states, offer a unique opportunity to explore the complexity of its X-ray spectrum. We find the hard X-ray band to be significantly affected by reflection from cold matter, which can also explain a non-varying, narrow Fe K fluorescent line. We in…
A transition in the accretion properties of radio-loud active nuclei
Marchesini, Danilo; Ferrarese, Laura; Celotti, Annalisa
We present evidence for the presence of a transition in the accretion properties of radio-loud sources. For a sample of radio galaxies and radio-loud quasars, selected based on their extended radio properties, the accretion rate is estimated from the black hole mass and nuclear luminosity. The inferred distribution is bimodal, with a paucity of so…
Discovery of the galaxy counterpart of HDF 850.1, the brightest submillimetre source in the Hubble Deep Field
Muxlow, T. W. B.; Smail, I.; Smith, G. P. +14 more
Despite extensive observational efforts, a convincing optical/infrared identification of the brightest submm source in the Hubble Deep Field, HDF 850.1, has remained elusive after almost four years. This failure is all the more notable given the availability of supporting multifrequency data of unparalleled depth, and subarcsec positional accuracy…
The 2003 shell event in η Carinae
Breedt, Elmé; Whitelock, Patricia A.; Feast, Michael W. +1 more
Near-infrared, JHKL, photometry of η Car is reported covering the period 2000-2004. This includes the 2003 shell event which was the subject of an international multiwavelength campaign. The fading that accompanied this event was similar to, although slightly deeper than, that which accompanied the previous one. The period between these events is …
On the origin of the C IV Baldwin effect in active galactic nuclei
Laor, Ari; Baskin, Alexei
The origin of the luminosity dependence of the equivalent width (EW) of broad emission lines in active galactic nuclei (AGN) - the Baldwin effect - is not firmly established yet. We explore this question for the broad C IVλ1549 line using the Boroson & Green sample of the 87 z<= 0.5 Bright Quasar Survey (BQS) quasars. Useful UV spectra of t…
Star cluster formation and evolution in the dwarf starburst galaxy NGC 1569
de Grijs, R.; Anders, P.; Fritze-v. Alvensleben, U. +1 more
We analyse multiwavelength Hubble Space Telescope (HST) observations of a large number of star clusters in the nearby (post-)starburst dwarf galaxy NGC 1569. Their spectral energy distributions (SEDs) cover at least the wavelength range from U to I in equivalent HST filters, in most cases supplemented by near-infrared data. Using our most up-to-da…
Probable intermediate-mass black holes in NGC 4559: XMM-Newton spectral and timing constraints
Cropper, Mark; Soria, Roberto; Wu, Kinwah +3 more
We have examined X-ray and optical observations of two ultraluminous X-ray sources, X7 and X10 in NGC 4559, using XMM-Newton, Chandra and the Hubble Space Telescope (HST). The ultraviolet/X-ray luminosity of X7 exceeds 2.1 × 1040 erg s-1 in the XMM-Newton observation, and that of X10 is > 1.3 × 1040 erg s-1…
X-ray emission from the nuclei, lobes and hot-gas environments of two FR II radio galaxies
Hardcastle, M. J.; Croston, J. H.; Birkinshaw, M. +1 more
We report on the detection of multiple components of X-ray emission from the two FR II radio galaxies, 3C 223 and 3C 284, based on new XMM-Newton observations. We attribute the detected X-ray emission from the lobes of both sources to inverse-Compton scattering of cosmic microwave background photons. With this model, we find that the magnetic fiel…
Displacement of X-ray sources from star clusters in starburst galaxies
Zezas, A.; Gallagher, J. S.; Kaaret, P. +3 more
We examine the spatial offsets between X-ray point sources and star clusters in three starburst galaxies. We find that the X-ray sources are preferentially located near the star clusters. Because the star clusters are very good tracers of the star formation activity in the galaxies, this indicates that the X-ray sources are young objects associate…