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…
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…
Unveiling the nature of the γ-ray emitting active galactic nucleus PKS 0521-36
Ghisellini, G.; Pian, E.; Tosti, G. +11 more
PKS 0521-36 is an active galactic nucleus (AGN) with uncertain classification. We investigate the properties of this source from radio to γ-rays. The broad emission lines in the optical and ultraviolet bands and steep radio spectrum indicate a possible classification as an intermediate object between broad-line radio galaxies (BLRG) and steep spec…
HST/COS detection of a Ne VIII absorber towards PG 1407+265: an unambiguous tracer of collisionally ionized hot gas?
Narayanan, A.; Wakker, B. P.; Muzahid, S. +4 more
We report the detection of Ne VIII in a zabs = 0.599 61 absorber towards the QSO PG1407+265 (zem= 0.94). Besides Ne VIII, absorption from H I Lyman series lines (H I λ1025-λ915), several other low (C II, N II, O II and S II), intermediate (C III, N III, N IV, O III, S IV and S V) and high (S VI, O VI and Ne VIII) ionization m…
Shapley Supercluster Survey: Galaxy evolution from filaments to cluster cores
Okabe, N.; Bourdin, H.; Mazzotta, P. +11 more
We present an overview of a multiwavelength survey of the Shapley Supercluster (SSC; z ∼ 0.05) covering a contiguous area of 260 h^{-2}_{70} Mpc2 including the supercluster core. The project main aim is to quantify the influence of cluster-scale mass assembly on galaxy evolution in one of the most massive structures in the local Univers…
Tracing cool molecular gas and star formation on ∼100 pc scales within a z ∼ 2.3 galaxy
Thomson, A. P.; Ivison, R. J.; Smail, Ian +3 more
We present new, high-angular resolution interferometric observations with the Karl G. Jansky Very Large Array of 12CO J = 1-0 line emission and 4-8 GHz continuum emission in the strongly lensed, z = 2.3 submillimetre galaxy, SMM J21352-0102. Using these data, we identify and probe the conditions in ∼100 pc clumps within this galaxy, whi…
SCORPIO: a deep survey of radio emission from the stellar life-cycle
Umana, G.; Agliozzo, C.; Trigilio, C. +7 more
Radio emission has been detected in a broad variety of stellar objects from all stages of stellar evolution. However, most of our knowledge originates from targeted observations of small samples, which are strongly biased to sources which are peculiar at other wavelengths. In order to tackle this problem we have conducted a deep 1.4 GHz survey by …
Spectral and timing analysis of the mHz QPOs in the neutron-star low-mass X-ray binary 4U 1636-53
Méndez, Mariano; Keek, L.; Zhang, Guobao +1 more
We investigate the spectral and timing properties of the millihertz quasi-periodic oscillations (mHz QPOs) in neutron-star low-mass X-ray binary 4U 1636-53 using XMM-Newton and Rossi X-ray Timing Explorer (RXTE) observations. The mHz QPOs in the XMM-Newton/RXTE observations show significant frequency variation and disappear right before type I X-r…