Search Publications
The Tully-Fisher relation of distant cluster galaxies
Milvang-Jensen, B.; Aragón-Salamanca, A.; Bamford, S. P. +1 more
We have measured maximum rotation velocities (Vrot) for a sample of 111 emission-line galaxies with 0.1 <~z<~ 1, observed in the fields of six clusters. From these data we construct `matched' samples of 58 field and 22 cluster galaxies, covering similar ranges in redshift (0.25 <=z<= 1.0) and luminosity (MB<=-1…
Optical and infrared signatures of ultra-luminous X-ray sources
Copperwheat, Christopher; Cropper, Mark; Soria, Roberto +1 more
We have constructed a model to describe the optical emission from ultra-luminous X-ray sources (ULXs). We assume a binary model with a black hole accreting matter from a Roche lobe filling companion star. We consider the effects of radiative transport and radiative equilibrium in the irradiated surfaces of both the star and a thin accretion disc. …
The dark lane of the planetary nebula NGC 6302*†
Waters, L. B. F. M.; Sahai, R.; Zijlstra, A. A. +4 more
The butterfly-shaped planetary nebula, NGC 6302, shows a unique, dense equatorial dark lane, which is presumably a dusty disc, obscuring an unobserved, very hot central star. We trace the structure of this disc using Hubble Space Telescope Hα and [N II] images, Very Large Telescope L-and M-band images at 0.4-arcsec resolution, including Brα and po…
A quantum electrodynamics model for non-thermal emission from soft gamma repeaters and anomalous X-ray pulsars
Hernquist, Lars; Heyl, Jeremy S.
Previously, we showed that, owing to effects arising from quantum electrodynamics (QED), magnetohydrodynamic fast modes of sufficient strength will break down to form electron-positron pairs while traversing the magnetospheres of strongly magnetized neutron stars. The bulk of the energy of the fast mode fuels the development of an electron-positro…
AWM 4 - an isothermal cluster observed with XMM-Newton
O'Sullivan, E.; Vrtilek, J. M.; David, L. P. +2 more
We present an analysis of an XMM-Newton observation of the poor cluster AWM 4. The cluster is relaxed and its X-ray halo is regular with no apparent substructure. Azimuthally averaged radial spectral profiles suggest that the cluster is isothermal to a radius of at least 160 kpc, with no evidence of a central cooling region. Spectral mapping shows…
Rotation periods for stars of the TW Hydrae association: the evidence for two spatially and rotationally distinct pre-main-sequence populations
Lawson, Warrick A.; Crause, Lisa A.
We have conducted a photometric study of late-type members of the TW Hydrae association (TWA) and measured the rotation periods for 16 stars in 12 systems. For TWA stars listed by Webb et al. and Sterzik et al. (TWA 1-13 led by TW Hya = TWA 1) we find a median period of 4.7 d. However, for stars that we measured in the TWA 14-19 group identified b…
A Chandra X-ray survey of nearby dwarf starburst galaxies - I. Data reduction and results
Ott, Jürgen; Walter, Fabian; Brinks, Elias
We present an analysis of Chandra X-ray observations of a sample of eight dwarf starburst galaxies (IZw18, VIIZw403, NGC1569, NGC3077, NGC4214, NGC4449, NGC5253 and He2-10). Extended, diffuse X-ray emission is detected in all but two of the objects. Unresolved sources were found within all dwarf galaxies (total: 55 sources). These point sources ar…
The evolution of actively star-forming galaxies in the mid-infrared
Panuzzo, P.; Bressan, A.; Chavez, M. +3 more
In this paper we analyze the evolution of actively star-forming galaxies in the mid-infrared (MIR). This spectral region, characterized by continuum emission by hot dust and by the presence of strong emission features generally ascribed to polycyclic aromatic hydrocarbon (PAH) molecules, is the most strongly affected by the heating processes assoc…
The continuum and narrow-line region of the narrow-line Seyfert 1 galaxy Mrk 766
Contini, M.; Rodríguez-Ardila, A.; Viegas, S. M.
We present the first spectroscopic observations in the interval 0.8-4.0 µm, complemented with existing Hubble Space Telescope ultraviolet (UV) and optical spectroscopy, of the narrow-line Seyfert 1 galaxy Mrk 766. The near-infrared spectrum is characterized by numerous permitted lines of HI, HeI, HeII and FeII, and forbidden lines of [SII], …
Batch discovery of nine z~ 1 clusters using X-ray and K or R, z' images
Altieri, B.; Valtchanov, I.; Pierre, M. +5 more
We present the results of an initial search for clusters of galaxies at z~ 1 and above, using data from 2.9 square degrees of XMM-Newton images. By selecting weak potentially extended X-ray sources with faint or no identifications in deep, ground-based optical imaging, we have constructed a starting sample of 19 high-redshift cluster candidates. N…