Search Publications
Asteroseismic signatures of stellar magnetic activity cycles
Judge, P. G.; Dziembowski, W. A.; Metcalfe, T. S. +1 more
Observations of stellar activity cycles provide an opportunity to study magnetic dynamos under many different physical conditions. Space-based asteroseismology missions will soon yield useful constraints on the interior conditions that nurture such magnetic cycles, and will be sensitive enough to detect shifts in the oscillation frequencies due to…
Continuous statistics of the Lyα forest at 0 < z < 1.6: the mean flux, flux distribution and autocorrelation from HST FOS spectra
Charlton, Jane; Tytler, David; Lubin, Dan +1 more
We measure the amount of absorption in the Lyα forest at 0 < z < 1.6 in Hubble Space Telescope Faint Object Spectrograph spectra of 74 quasi-stellar objects (QSOs). Starting with a 334 QSO sample compiled by Bechtold et al., we selected 74 QSOs that have the highest signal-to-noise ratio and complete coverage of rest-frame wavelengths 1070-1…
Constraining the geometry of the neutron star RX J1856.5-3754
Ho, Wynn C. G.
RX J1856.5-3754 is one of the brightest, nearby isolated neutron stars (NSs), and considerable observational resources have been devoted to its study. In previous work, we found that our latest models of a magnetic, hydrogen atmosphere match well the entire spectrum, from X-rays to optical (with best-fitting NS radius R ~ 14 km, gravitational reds…
The initial conditions of isolated star formation - VII. Spitzer mapping of pre-stellar cores
Ward-Thompson, D.; André, P.; Kirk, J. M.
We have retrieved Spitzer archive data of pre-stellar cores taken with the Multiband Imaging Photometer for Spitzer (MIPS) at a wavelength of 160 µm. Seventeen images, containing 18 cores, were constructed. Flux densities were measured for each core, and background estimates were made. Mean off-source backgrounds were found to be 48 +/- 10 M…
Deconstructing dwarf galaxies: a Suprime-Cam survey of Andromeda II
McConnachie, Alan W.; Arimoto, Nobuo; Irwin, Mike
We present deep, subhorizontal-branch, multicolour photometry of the Andromeda II dwarf spheroidal (And II dSph) taken with the Subaru Suprime-Cam wide-field camera. We identify a red clump population in this galaxy, the first time this feature has been detected in an M31 dSph, which are normally characterized as having no significant intermediate…
Evidence for relativistic features in the X-ray spectrum of Mrk 335
Nandra, K.; Cappi, M.; Longinotti, A. L. +1 more
We present an analysis of hard X-ray features in the spectrum of the bright Sy 1 galaxy Mrk 335 observed by the XMM-Newton satellite. Our analysis confirms the presence of a broad, ionized Fe Kα emission line in the spectrum, first found by Gondoin et al. The broad line can be modelled successfully by relativistic accretion disc reflection models.…
A deficit of faint red galaxies in the possible large-scale structures around the RDCS J1252.9-2927 cluster at z = 1.24
Kodama, Tadayuki; Rosati, Piero; Kajisawa, Masaru +5 more
We report a discovery of possible large-scale structures around the RDCS J1252.9-2927 cluster at z = 1.24 based on photometric redshifts. We carried out multiband wide-field imaging with Suprime-Cam on the Subaru Telescope and WFCAM on the United Kingdom Infrared Telescope (UKIRT). Our data cover an approximately 35 × 30-arcmin2 field i…
What is the origin of the soft excess in active galactic nuclei?
Done, Chris; Sobolewska, Małgorzata A.
We investigate the nature of the soft excess below 1 keV observed in active galactic nuclei. We use the XMM-Newton data of the low-redshift, optically bright quasar, PG 1211+143, and we compare it with the narrow-line Seyfert 1 galaxy, 1H 0707-495, which has one of the strongest soft excesses seen. We test various ideas for the origin of the soft …
Gemini GMOS/integral field unit spectroscopy of NGC 1569 - II. Mapping the roots of the galactic outflow
Gallagher, J. S.; Smith, L. J.; Westmoquette, M. S. +1 more
We present a set of four Gemini-North Multi-Object Spectrograph/integral field unit (IFU) observations of the central disturbed regions of the dwarf irregular starburst galaxy NGC 1569, surrounding the well-known superstar clusters A and B. This continues on directly from a companion paper, in which we describe the data reduction and analysis tech…
The iron K feature in narrow line Seyfert 1 galaxies: evidence for a P Cygni profile?
Done, Chris; Gierliński, Marek; Sobolewska, Małgorzata A. +1 more
Narrow line Seyfert 1 galaxies are generally accreting at high fractions of the Eddington limit. They can show complex X-ray spectra, with a strong `soft excess' below 2 keV and a sharp drop at ~7 keV. There is strong evidence linking the soft excess to either reflection or absorption from relativistic, partially ionized material close to the blac…