Search Publications
The stellar halo of isolated central galaxies in the Hyper Suprime-Cam imaging survey
Sonnenfeld, Alessandro; Wang, Wenting; Han, Jiaxin +14 more
We study the faint stellar halo of isolated central galaxies, by stacking galaxy images in the HSC survey and accounting for the residual sky background sampled with random points. The surface brightness profiles in HSC r band are measured for a wide range of galaxy stellar masses (9.2 < log10M∗/M⊙ < 11.4) an…
The sdA problem - III. New extremely low-mass white dwarfs and their precursors from Gaia astrometry
Kepler, S. O.; Bell, Keaton J.; Pelisoli, Ingrid +1 more
The physical nature of the sdA stars - cool hydrogen-rich objects with spectroscopic surface gravities intermediate between main-sequence and canonical-mass white dwarfs - has been elusive since they were found in Sloan Digital Sky Survey Data Release 12 spectra. The population is likely dominated by metal-poor A/F stars in the halo with overestim…
Mass function and dynamical study of the open clusters Berkeley 24 and Czernik 27 using ground based imaging and Gaia astrometry
Bisht, D.; Yadav, R. K. S.; Fynbo, J. P. U. +3 more
We present a UBVI photometric study of the open clusters Berkeley 24 (Be 24) and Czernik 27 (Cz 27). The radii of the clusters are determined as 2{^'.}7 and 2{^'.}3 for Be 24 and Cz 27, respectively. We use the Gaia Data Release 2 (GDR2) catalogue to estimate the mean proper motions for the clusters. We found the mean proper …
Spectroscopic detection of multiple populations in the ∼2 Gyr old cluster Hodge 6 in the LMC
Martocchia, S.; Dalessandro, E.; Salaris, M. +8 more
We report the spectroscopic discovery of abundance spreads (i.e. multiple populations) in the ∼2 Gyr old cluster in the LMC, Hodge 6. We use low-resolution VLT FORS2 spectra of 15 member stars in the cluster to measure their CN and CH band strengths at ≃3883 and 4300 Å, respectively, as well as [C/Fe] and [N/Fe] abundances. We find a subpopulation…
Star-disc (mis-)alignment in Rho Oph and Upper Sco: insights from spatially resolved disc systems with K2 rotation periods
Davies, Claire L.
The discovery of close in, giant planets (hot Jupiters) with orbital angular momentum vectors misaligned with respect to the rotation axis of their host stars presents problems for planet formation theories in which planets form in discs with angular momentum vectors aligned with that of the star. Violent, high-eccentricity migration mechanisms pu…
High-energy monitoring of NGC 4593 II. Broad-band spectral analysis: testing the two-corona model
Bianchi, S.; Cappi, M.; Ponti, G. +9 more
It is widely believed that the primary X-ray emission of AGN is due to the Comptonization of optical-UV photons from a hot electron corona, while the origin of the `soft-excess' is still uncertain and matter of debate. A second Comptonization component, called warm corona, was therefore proposed to account for the soft-excess, and found in agreeme…
Detections and constraints on white dwarf variability from time-series GALEX observations
Hermes, J. J.; Shappee, B. J.; Tucker, M. A. +1 more
We search for photometric variability in more than 23 000 known and candidate white dwarfs (WDs), the largest ultraviolet survey compiled for a single study of WDs. We use GPHOTON, a publicly available calibration/reduction pipeline, to generate time-series photometry of WDs observed by GALEX. By implementing a system of weighted metrics, we selec…
Linking the rotation of a cluster to the spins of its stars: the kinematics of NGC 6791 and NGC 6819 in 3D
Balbinot, E.; Hénault-Brunet, V.; Gieles, M. +2 more
The physics governing the formation of star clusters is still not entirely understood. One open question concerns the amount of angular momentum that newly formed clusters possess after emerging from their parent gas clouds. Recent results suggest an alignment of stellar spins and binary orbital spins in star clusters, which support a scenario in …
Secularly powered outflows from AGNs: the dominance of non-merger driven supermassive black hole growth
Simmons, B. D.; Smethurst, R. J.; Lintott, C. J. +1 more
Recent observations and simulations have revealed the dominance of secular processes over mergers in driving the growth of both supermassive black holes (SMBHs) and galaxy evolution. Here, we obtain narrow-band imaging of AGN powered outflows in a sample of 12 galaxies with disc-dominated morphologies, whose history is assumed to be merger-free. W…
A low-flux state in IRAS 00521-7054 seen with NuSTAR and XMM-Newton: relativistic reflection and an ultrafast outflow
Harrison, F. A.; Stern, D.; Fabian, A. C. +8 more
We present results from a deep, coordinated XMM-Newton + NuSTAR observation of the Seyfert 2 galaxy IRAS 00521-7054. The NuSTAR data provide the first detection of this source in high-energy X-rays (E > 10 keV), and the broad-band data show this to be a highly complex source which exhibits relativistic reflection from the inner accretion disc, …