Search Publications
Nuclear absorption and emission in the AGN merger NGC 6240 : the hard X-ray view
Nardini, Emanuele
We present the analysis of four NuSTAR observations of the luminous infrared galaxy merger NGC 6240 , hosting a close pair of highly obscured active galactic nuclei (AGNs). Over a period of about 2 yr, the source exhibits hard X-ray variability of the order of 20 per cent, peaking around 20 keV. When the two AGNs are resolved with Chandra , column…
The effect of stellar and AGN feedback on the low-redshift Lyman α forest in the Sherwood simulation suite
Viel, Matteo; Sijacki, Debora; Kim, Tae-Sun +4 more
We study the effect of different feedback prescriptions on the properties of the low-redshift (z ≤ 1.6) Lyα forest using a selection of hydrodynamical simulations drawn from the Sherwood simulation suite. The simulations incorporate stellar feedback, active galactic nuclei (AGN) feedback and a simplified scheme for efficiently modelling the low co…
A comparison between the soft X-ray and [O III] morphologies of active galactic nuclei
Gallego, Jesús; Gómez-Guijarro, Carlos; Rodríguez-Espinosa, José Miguel +2 more
Several studies of nearby active galactic nuclei (AGNs) have shown that the soft X-ray emission presents a size and morphology resembling that of the narrow-line region (NLR) traced by [O III]. Since the NLR is mainly constituted by gas photoionized by the AGN, it seems logical to assume that this is also the primary source of the soft X-ray emiss…
Population mixtures and searches of lensed and extended quasars across photometric surveys
Treu, Tommaso; Agnello, Adriano; Williams, Peter
Wide-field photometric surveys enable searches of rare yet interesting objects, such as strongly lensed quasars or quasars with a bright host galaxy. Past searches for lensed quasars based on their optical and near-infrared properties have relied on photometric cuts and spectroscopic preselection (as in the Sloan Quasar Lens Search), or neural net…
Sulphur isotope mass-independent fractionation observed in comet 67P/Churyumov-Gerasimenko by Rosetta/ROSINA
Altwegg, K.; Balsiger, H.; Fuselier, S. A. +12 more
The knowledge about sulphur isotopic fractionation in volatile cometary species is limited as only measurements in five comets have been done and only for 34S/32S. The lack of information about the fractionation of 33S/32S makes it impossible to compare them with what is known from refractories. We prese…
CONSERT constrains the internal structure of 67P at a few metres size scale
Plettemeier, Dirk; Kofman, Wlodek; Herique, Alain +6 more
The internal properties of cometary nuclei are the best clues to the size distribution and properties of the early planetesimals that formed the planets during the early Solar system nebula processes. The CONSERT radar was designed to probe the interior of comet 67P/Churyumov-Gerasimenko with a wavelength of about 3 m. It was successfully operated…
Star formation history of And XVIII: a dwarf spheroidal galaxy in isolation
Rizzi, L.; Karachentsev, I. D.; Makarova, L. N. +2 more
We present a photometric study of the Andromeda XVIII dwarf spheroidal galaxy associated with M31, and situated well outside of the virial radius of the M31 halo. The galaxy was resolved into stars with Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) revealing the old red giant branch and red clump. With the new observational data, we…
Models for 60 double-lined binaries containing giants
Eggleton, Peter P.; Yakut, Kadri
The observed masses, radii and temperatures of 60 medium- to long-period binaries, most of which contain a cool, evolved star and a hotter less evolved one, are compared with theoretical models which include (a) core convective overshooting, (b) mass-loss, possibly driven by dynamo action as in RS CVn binaries, and (c) tidal friction, including it…
Young LMC clusters: the role of red supergiants and multiple stellar populations in their integrated light and CMDs
Beasley, Michael A.; Vazdekis, Alexandre; Cerviño, Miguel +3 more
The optical integrated spectra of three Large Magellanic Cloud young stellar clusters (NGC 1984, NGC 1994 and NGC 2011) exhibit concave continua and prominent molecular bands which deviate significantly from the predictions of single stellar population (SSP) models. In order to understand the appearance of these spectra, we create a set of young s…
On the discrepancy between asteroseismic and Gaia DR1 TGAS parallaxes
Gontcharov, George A.; Mosenkov, Aleksandr V.
Recently, a deviation of the Gaia Tycho-Gaia Astrometric Solution (TGAS) parallaxes from the asteroseismic ones for giants was found. We show that for parallaxes ϖ < 1.5 mas it can be explained by a selection effect in favour of bright and luminous giants in the Tycho-2 and TGAS catalogues. Another explanation of this deviation seems to be vali…