Search Publications
An HST/WFC3 view of stellar populations on the horizontal branch of NGC 2419
Di Criscienzo, M.; Milone, A. P.; D'Antona, F. +4 more
We use images acquired with the Hubble Space Telescope Wide Field Camera 3 and new models to probe the horizontal branch (HB) population of the Galactic globular cluster (GC) NGC 2419. A detailed analysis of the composite HB highlights three populations: (1) the blue luminous HB, hosting standard helium stars (Y = 0.25) with a very small spread of…
Genus topology and cross-correlation of BICEP2 and Planck 353 GHz B-modes: further evidence favouring gravity wave detection
Colley, Wesley N.; Gott, J. Richard
We have analysed the genus topology of the BICEP2 B-modes and found them to be Gaussian random phase as expected if they have a cosmological origin. These BICEP2 B-modes can be produced by gravity waves in the early Universe, but question has arisen as to whether these B-modes (for 50 < l < 120) may instead be produced by foreground-polarize…
Towards a fully consistent Milky Way disc model - III. Constraining the initial mass function
Rybizki, J.; Just, A.
We use our vertical Milky Way disc model together with Galaxia to create mock observations of stellar samples in the solar neighbourhood. We compare these to the corresponding volume complete observational samples of dereddened and binary accounted data from Hipparcos and the Catalogue of Nearby Stars. Sampling the likelihood in the parameter spac…
Interstellar Flow Longitude from the Symmetry of the Pickup Ion Cut-off at 1 AU
Möbius, E.; Lee, M. A.; Drews, C.
We provide a proof of concept that the pickup ion (PUI) cutoff speed variation with ecliptic longitude can provide the interstellar neutral (ISN) flow longitude {λ }{ISN∞ } outside the heliosphere with a precision of the order of 0.°1. We compare 2007-2014 STEREO A PLASTIC observations in the solar wind frame with a simple analytical cu…
The Cepheid distance to the maser-host galaxy NGC 4258: studying systematics with the Large Binocular Telescope
Kochanek, C. S.; Stanek, K. Z.; Fausnaugh, M. M. +3 more
We identify and phase a sample of 81 Cepheids in the maser-host galaxy NGC 4258 using the Large Binocular Telescope, and obtain calibrated mean magnitudes in up to four filters for a subset of 43 Cepheids using archival Hubble Space Telescope data. We employ three models to study the systematic effects of extinction, the assumed extinction law, an…
From forced collapse to H ii region expansion in Mon R2: Envelope density structure and age determination with Herschel⋆
Bernard, J. -P.; Hill, T.; White, G. J. +32 more
Context. The surroundings of H ii regions can have a profound influence on their development, morphology, and evolution. This paper explores the effect of the environment on H ii regions in the MonR2 molecular cloud.
Aims: We aim to investigate the density structure of envelopes surrounding H ii regions and to determine their collapse and ion…
Autoclassification of the Variable 3XMM Sources Using the Random Forest Machine Learning Algorithm
Farrell, Sean A.; Murphy, Tara; Lo, Kitty K.
In the current era of large surveys and massive data sets, autoclassification of astrophysical sources using intelligent algorithms is becoming increasingly important. In this paper we present the catalog of variable sources in the Third XMM-Newton Serendipitous Source catalog (3XMM) autoclassified using the Random Forest machine learning algorith…
Dawn-dusk scale of dipolarization front in the Earth's magnetotail: multi-cases study
André, M.; Vaivads, A.; Deng, X. H. +10 more
We analyze three dipolarization front (DF) events to investigate their dawn-dusk scales in the Earth's magnetotail using the Cluster measurements in year 2007, when the spacecraft separation is about 1.8 Re (Re is the Earth's radius) and is appropriate for investigating the DF scale. Based on the Minimum Variance Analysis (MVA) and the general sha…
Fermi-LAT observations of the Sagittarius B complex
Aharonian, Felix; Yang, Rui-zhi; Jones, David I.
Aims: We use 5 years of Fermi-LAT data towards the Galactic-centre giant molecular cloud complex, Sagittarius B, to test questions of how well-mixed the Galactic component of cosmic rays are and what the level of the cosmic-ray sea in different parts of the Galaxy is.
Methods: We use dust-opacity maps from the Planck satellite to obtain …
Weather on Other Worlds. III. A Survey for T Dwarfs with High-amplitude Optical Variability
Metchev, Stanimir; Heinze, Aren N.; Kellogg, Kendra
We have monitored 12 T dwarfs with the Kitt Peak 2.1 m telescope using an F814W filter (0.7-0.95 µm) to place in context the remarkable 10%-20% variability exhibited by the nearby T dwarf Luhman 16B in this wavelength regime. The motivation was the poorly known red optical behavior of T dwarfs, which have been monitored almost exclusively at…