Search Publications
SDSS J0926+3624: the shortest period eclipsing binary star
Drake, A. J.; Gänsicke, B. T.; Dhillon, V. S. +12 more
With orbital periods of the order of tens of minutes or less, the AM Canum Venaticorum stars are ultracompact, hydrogen-deficient binaries with the shortest periods of any binary subclass, and are expected to be among the strongest gravitational wave sources in the sky. To date, the only known eclipsing source of this type is the P= 28 min binary …
Galaxy number counts and implications for strong lensing
Koopmans, L. V. E.; Fassnacht, C. D.; Wong, K. C.
We compare galaxy number counts in Advanced Camera for Surveys (ACS) fields containing moderate-redshift (0.2 < z < 1.0) strong gravitational lenses with those in two control samples: (1) the first square degree of the COSMOS survey, comprising 259 ACS fields and (2) 20 ‘pure-parallel’ fields randomly located on the sky. Through a Bayesian a…
Ejection velocities of high Galactic latitude runaway stars
Napiwotzki, R.; Silva, M. D. V.
We estimate the distribution of ejection velocities for the known population of high Galactic latitude runaway stars. The initial sample is a collection of 174 early-type stars selected from the literature. The stars are first classified according to their evolutionary status in order to obtain a homogeneous sample of 96 genuine main-sequence star…
Intermediate-age stars as the origin of low stellar velocity dispersion nuclear rings: the case of Mrk 1157
Riffel, Rogério; Storchi-Bergmann, Thaisa; Riffel, Rogemar A. +1 more
We have used the Gemini Near-Infrared Integral-Field Spectrograph to map the age distribution of the stellar population in the inner 400 pc of the Seyfert 2 galaxy Mrk 1157 (NGC 591), at a spatial resolution of 35 pc. We have performed wavelet and principal component analysis on the data in order to remove instrumental signatures. An old stellar p…
Extreme active galactic nucleus feedback and cool-core destruction in the X-ray luminous galaxy cluster MACS J1931.8-2634
Simionescu, A.; Kelly, P.; von der Linden, A. +14 more
We report on a deep, multiwavelength study of the galaxy cluster MACS J1931.8-2634 using Chandra X-ray, Subaru optical and Very Large Array 1.4-GHz radio data. This cluster (z= 0.352) harbours one of the most X-ray luminous cool cores yet discovered, with an equivalent mass, cooling rate within the central ? is ∼700 M⊙ yr-1. …
The tumultuous formation of the Hubble sequence at z > 1 examined with HST/Wide-Field Camera-3 observations of the Hubble Ultra Deep Field
Koekemoer, A. M.; Ravindranath, S.; Conselice, C. J. +5 more
We examine in this paper a stellar-mass-selected sample of galaxies at 1 < z < 3 within the Hubble Ultra Deep Field, utilizing Wide-Field Camera-3 (WFC3) imaging, to study the rest-frame optical morphological and structural distribution of galaxies at this epoch. We measure how apparent morphologies (disc, elliptical, peculiar) correlate wit…
Evidence for environmentally dependent cluster disruption in M83
Bastian, N.; Larsen, S. S.; Smith, L. J. +8 more
Using multiwavelength imaging from the Wide Field Camera 3 on the Hubble Space Telescope we study the stellar cluster populations of two adjacent fields in the nearby face-on spiral galaxy, M83. The observations cover the galactic centre and reach out to ∼6 kpc, thereby spanning a large range of environmental conditions, ideal for testing empirica…
Positron annihilation spectrum from the Galactic Centre region observed by SPI/INTEGRAL revisited: annihilation in a cooling ISM?
Sunyaev, R.; Tsygankov, S.; Sazonov, S. +2 more
We analyse SPI/INTEGRAL data on the 511-keV line from the Galactic Centre, accumulated over ∼6 yr of observations. We decompose the X-ray and soft gamma-ray emission of the central part of the Milky Way into relatively compact 'bulge' and more extended 'disc' components and report their spectral properties. The bulge component shows a prominent 51…
Narrow-line Seyfert 1 galaxies at hard X-rays
de Rosa, A.; Miniutti, G.; Ubertini, P. +7 more
Narrow-line Seyfert 1 (NLSy1) galaxies are a peculiar class of type 1 active galactic nuclei (broad-line Seyfert 1 galaxies, hereinafter BLSy1). The X-ray properties of individual objects belonging to this class are often extreme and associated with accretion at high Eddington ratios. Here, we present a study on a sample of 14 NLSy1 galaxies selec…
A strategy to measure the dark energy equation of state using the H II galaxy Hubble function and X-ray active galactic nuclei clustering: preliminary results
Terlevich, E.; Terlevich, R.; Bresolin, F. +4 more
We explore the possibility of setting stringent constraints to the dark energy equation of state using alternative cosmic tracers like (a) the Hubble relation using H II galaxies, which can be observed at much higher redshifts (z≲ 3.5) than those currently traced by Type Ia supernovae (SNeIa) samples, and (b) the large-scale structure using the cl…