Search Publications
Wide-field HST/ACS images of M81: the population of compact star clusters
Mayya, Y. D.; Rosa-González, D.; Santiago-Cortés, M.
We study the population of compact star clusters (CSCs) in M81, using the Hubble Space Telescope/Advanced Camera for Surveys (ACS) images in the filters F435W, F606W and F814W covering, for the first time, the entire optical extent of the galaxy. Our sample contains 435 clusters of full width at half-maximum less than 10 ACS pixels (9pc). The samp…
Determining the extragalactic extinction law with SALT - II. Additional sample
O'Donoghue, Darragh; Buckley, David A. H.; Sefako, Ramotholo +8 more
We present new results from an ongoing programme to study the dust extragalactic extinction law in E/S0 galaxies with dust lanes with the Southern African Large Telescope (SALT) during its performance verification phase. The wavelength dependence of the dust extinction for seven galaxies is derived in six spectral bands ranging from the near-ultra…
Central galaxy growth and feedback in the most massive nearby cool core cluster
Böhringer, H.; Simionescu, A.; Fabian, A. C. +4 more
We present multiwavelength observations of the centre of RXCJ1504.1 - 0248 - the galaxy cluster with the most luminous and relatively nearby cool core at z ~ 0.2. Although there are several galaxies within 100kpc of the cluster core, only the brightest cluster galaxy (BCG), which lies at the peak of the X-ray emission, has blue colours and strong …
First high-resolution detection of a warm absorber in the Broad Line Radio Galaxy 3C 382
Guainazzi, M.; Grandi, P.; Tombesi, F. +4 more
Recent high-resolution measurements suggest that the soft X-ray spectrum of obscured radio galaxies exhibits signatures of photoionized gas (e.g. 3C 445 and 3C 33) similar to those observed in radio-quiet obscured active galactic nuclei. While signatures of warm absorbing gas covering a wide range of temperature and ionization states have been det…
A census of nuclear stellar discs in early-type galaxies
Morelli, L.; Sarzi, M.; Dotti, M. +2 more
Nuclear stellar discs (NSDs), of a few tens to hundreds of parsec across, are a common and yet poorly studied feature of early-type galaxies. Still, such small discs represent a powerful tool to constrain the assembling history of galaxies, since they can be used to trace to the epoch when galaxies experienced their last major merger event. By stu…
The BLAST 250 µm-selected galaxy population in GOODS-South
Smail, I.; Ivison, R. J.; Ade, P. A. R. +33 more
We identify and investigate the nature of the 20 brightest 250µm sources detected by the Balloon-borne Large Aperture Submillimetre Telescope (BLAST) within the central 150arcmin2 of the Great Observatories Origins Deep Survey (GOODS)-South field. Aided by the available deep VLA 1.4GHz radio imaging, reaching S1.4 ~= 40…
X-ray emission from the extended emission-line region of the powerful radio galaxy 3C171
Hardcastle, M. J.; Massaro, F.; Harris, D. E.
We present Chandra X-ray observations of the powerful radio galaxy 3C171, which reveal an extended region of X-ray emission spatially associated with the well-known 10-kpc scale optical emission-line region around the radio jets. We argue that the X-ray emission comes from collisionally ionized material, originally cold gas that has been shock hea…
Type I X-ray bursts, burst oscillations and kHz quasi-periodic oscillations in the neutron star system IGRJ17191-2821
Altamirano, D.; Degenaar, N.; Wijnands, R. +6 more
We present a detailed study of the X-ray energy and power spectral properties of the neutron star transient IGRJ17191-2821. We discovered four instances of pairs of simultaneous kilohertz quasi-periodic oscillations (kHz QPOs). The frequency difference between these kHz QPOs is between 315 and 362Hz. We also report on the detection of five thermon…
New measurement of orbital and spin period evolution of the accretion disc corona source 4U 1822-37
Paul, Biswajit; Jain, Chetana; Dutta, Anjan
4U 1822-37 is a low mass X-ray binary (LMXB) system with an accretion disc corona. It is one of the very few LMXBs that shows narrow X-ray eclipses and small amplitude pulsations of the neutron star. The X-ray eclipse is an excellent reference for measurement of orbital evolution of the binary, and we have obtained 16 new mid-eclipse time measurem…
The evolutionary status of the blue hook stars in ω Centauri
D'Antona, Francesca; Ventura, Paolo; Caloi, Vittoria
Core helium burning is the dominant source of energy of extreme horizontal branch stars, as the hydrogen envelope is too small to contribute to the nuclear energy output. The evolution of each mass in the HR diagram occurs along vertical tracks that, when the core helium is consumed, evolve to higher Teff and then to the white dwarf sta…