Search Publications
The origin of ultrafast outflows in AGN: Monte Carlo simulations of the wind in PDS 456
Done, Chris; Gandhi, Poshak; Takahashi, Tadayuki +4 more
Ultrafast outflows (UFOs) are seen in many AGN, giving a possible mode for AGN feedback on to the host galaxy. However, the mechanism(s) for the launch and acceleration of these outflows are currently unknown, with UV line driving apparently strongly disfavoured as the material along the line of sight is so highly ionized that it has no UV transit…
SN 2009ip at late times - an interacting transient at +2 years
Gilmore, Gerard; Fraser, Morgan; Elias-Rosa, Nancy +31 more
We present photometric and spectroscopic observations of the interacting transient SN 2009ip taken during the 2013 and 2014 observing seasons. We characterize the photometric evolution as a steady and smooth decline in all bands, with a decline rate that is slower than expected for a solely 56Co-powered supernova at late phases. No furt…
Free-form lensing implications for the collision of dark matter and gas in the frontier fields cluster MACS J0416.1-2403
Broadhurst, Tom; Lam, Daniel; Lim, Jeremy +2 more
We present a free-form mass reconstruction of the massive lensing cluster MACS J0416.1-2403 using the latest Hubble Frontier Fields data. Our free-form method finds that the extended lensing pattern is generated by two elongated, closely projected clusters of similar mass. Our lens model identifies new lensed images with which we improve the accur…
Multi-wavelength observations of the binary system PSR B1259-63/LS 2883 around the 2014 periastron passage
Krivonos, R.; Tsygankov, S.; Tomsick, J. A. +16 more
We report on the results of the extensive multi-wavelength campaign from optical to GeV γ-rays of the 2014 periastron passage of PSR B1259-63, which is a unique high-mass γ-ray emitting binary system with a young pulsar companion. Observations demonstrate the stable nature of the post-periastron GeV flare and prove the coincidence of the flare wit…
Detecting dark matter substructures around the Milky Way with Gaia
Feldmann, Robert; Spolyar, Douglas
Cold dark matter (CDM) theory, a pillar of modern cosmology and astrophysics, predicts the existence of a large number of starless dark matter haloes surrounding the Milky Way (MW). However, clear observational evidence of these `dark' substructures remains elusive. Here, we present a detection method based on the small, but detectable, velocity c…
Herschel-ATLAS: the surprising diversity of dust-selected galaxies in the local submillimetre Universe
Ivison, R. J.; de Zotti, G.; Baes, M. +20 more
We present the properties of the first 250 µm blind sample of nearby galaxies (15 < D < 46 Mpc) containing 42 objects from the Herschel Astrophysical Terahertz Large Area Survey. Herschel's sensitivity probes the faint end of the dust luminosity function for the first time, spanning a range of stellar mass (7.4 < M⋆ < …
The identification of dust heating mechanisms in nearby galaxies using Herschel 160/250 and 250/350 µm surface brightness ratios
Boquien, M.; Bianchi, S.; Fritz, J. +15 more
We examined variations in the 160/250 and 250/350 µm surface brightness ratios within 24 nearby (<30 Mpc) face-on spiral galaxies observed with the Herschel Space Observatory to identify the heating mechanisms for dust emitting at these wavelengths. The analysis consisted of both qualitative and quantitative comparisons of the 160/250 and…
The Comptonization of accretion disc X-ray emission: consequences for X-ray reflection and the geometry of AGN coronae
Gallo, L. C.; Wilkins, D. R.
We consider the Comptonization of the photons that make up the relativistically blurred reflection that is commonly detected from the accretion discs of active galactic nuclei by the coronae of energetic particles believed to give rise to the powerful X-ray continua by the inverse-Compton scattering of thermal seed photons from the disc. Recent me…
An extended star formation history in an ultra-compact dwarf
van den Bosch, Remco C. E.; Forte, Juan Carlos; Faifer, Favio R. +3 more
There has been significant controversy over the mechanisms responsible for forming compact stellar systems like ultra-compact dwarfs (UCDs), with suggestions that UCDs are simply the high-mass extension of the globular cluster population, or alternatively, the liberated nuclei of galaxies tidally stripped by larger companions. Definitive examples …
Identification of a new γ-ray-emitting narrow-line Seyfert 1 galaxy, at redshift ∼1
Komossa, S.; Yuan, Weimin; Zhou, Hongyan +4 more
We report on the identification of a new γ-ray-emitting narrow-line Seyfert 1 (NLS1) galaxy, SDSS J122222.55+041315.7, which increases the number of known objects of this remarkable but rare type of active galactic nuclei to seven. Its optical spectrum, obtained in the Sloan Digital Sky Survey-Baryon Oscillation Spectroscopic Survey, reveals a bro…