Search Publications

Numerical modelling of gamma radiation from galaxy clusters

Miniati, Francesco

We investigate the spatial and spectral properties of non-thermal emission from clusters of galaxies at γ-ray energies. We estimate the radiation flux between 10 keV and 10 TeV due to inverse-Compton (IC) emission, π⁰-decay and non-thermal bremsstrahlung (NTB) from cosmic ray (CR) ions and electrons accelerated at cosmic shocks as well …

Physical conditions in the planetary nebula Abell 30

Barlow, M. J.; Liu, X. -W.; Wesson, R.

We have analysed optical spectra of two of the hydrogen-deficient knots (J1 and J3) in the born-again planetary nebula Abell 30, together with ultraviolet (UV) spectra of knots J3 and J4. We determine electron temperatures in the knots based on several diagnostics. The [OIII] nebular-to-auroral transition ratio yields temperatures of the order of …

Periodicities in solar coronal mass ejections

Wang, Shui; Fan, Zuhui; Lou, Yu-Qing +2 more

Mid-term quasi-periodicities in solar coronal mass ejections (CMEs) during the most recent solar maximum cycle 23 are reported here for the first time using the four-year data (1999 February 5 to 2003 February 10) of the Large Angle Spectrometric Coronagraph on board the Solar and Heliospheric Observatory. In parallel, mid-term quasi-periodicities…

Star cluster formation and evolution in nearby starburst galaxies - I. Systematic uncertainties

Bastian, N.; Gallagher, J. S.; de Grijs, R. +4 more

The large majority of extragalactic star cluster studies performed to date have essentially used two- or three-passband aperture photometry, combined with theoretical stellar population synthesis models, to obtain age, mass and extinction estimates, and sometimes also metallicities. The accuracy to which this can be performed depends on the choice…

Heavy-element abundance patterns in hot DA white dwarfs

Barstow, M. A.; Bruhweiler, F. C.; Holberg, J. B. +5 more

We present a series of systematic abundance measurements for 25 hot DA white dwarfs in the temperature range ~20 000-110 000 K, based on far-ultraviolet spectroscopy with the Space Telescope Imaging Spectrograph (STIS)/Goddard High Resolution Spectrograph (GHRS) on-board Hubble Space Telescope, IUE and FUSE. Using our latest heavy-element blankete…

The nature, evolution, clustering and X-ray properties of extremely red galaxies in the Chandra Deep Field South/Great Observatories Origins Deep Survey field

Almaini, Omar; Dunlop, James; Roche, Nathan D.

We identify a very deep sample of 198 extremely red objects (EROs) in the Chandra Deep Field South, selected on the basis of I₇₇₅-K_s > 3.92, to a limit K_s~= 22 using the public European Southern Observatory (ESO)/Great Observatories Origins Deep Survey (GOODS) survey.

The ERO number counts flatten from a sl…

Iron and nickel line properties in the X-ray-reflecting region of the Circinus galaxy

Bianchi, Stefano; Matt, Giorgio; Molendi, Silvano

We discuss the iron and nickel properties in the nuclear X-ray-reflecting region of the Circinus galaxy, studied with XMM-Newton. The main results are as follows. (i) From the depth of the Fe Kα edge, a value of A_Fe= 1.7 in number with respect to the cosmic value (as for Anders & Grevesse) is measured, if the (not directly visible) …

F stars, metallicity and the ages of red galaxies at z > 1

Dunlop, J. S.; Nolan, L. A.; Jimenez, R. +1 more

We explore whether the rest-frame near-ultraviolet spectral region, observable in high-redshift galaxies via optical spectroscopy, contains sufficient information to allow the degeneracy between age and metallicity to be lifted. We do this by first testing the ability of evolutionary synthesis models to reclaim the correct metallicity when fitted …

XMM-Newton observations of the hot-gas atmospheres of 3C 66B and 3C 449

Hardcastle, M. J.; Croston, J. H.; Birkinshaw, M. +1 more

We present new XMM-Newton observations of the hot-gas environments of two low-power twin-jet radio galaxies, 3C 66B and 3C 449, showing direct evidence for the interactions between X-ray-emitting gas and radio plasma that are thought to determine the large-scale radio structure of these sources. The temperatures that we measure for the two environ…

Mission: impossible (escape from the Lyman limit)

Fernández-Soto, A.; Chen, H. -W.; Lanzetta, K. M.

We investigate the intrinsic opacity of high-redshift galaxies to outgoing ionizing photons using high-quality photometry of a sample of 27 spectroscopically identified galaxies of redshift 1.9 < z < 3.5 in the Hubble Deep Field. Our measurement is based on maximum-likelihood fitting of model galaxy spectral energy distributions - including …