71 research outputs found
Quantum super-resolution imaging and hypothesis testing
No full textDetecting the faint emission of a secondary source in the proximity of the much brighter one has been the most severe obstacle for using direct imaging in searching for exoplanets. Estimating the angular separation between two incoherent thermal sources is a also challenging task for direct imaging. Here, we experimentally demonstrate two tasks for super-resolution imaging based on hypothesis testing, quantum state discrimination and quantum imaging techniques. We show that one can significantly reduce the probability of error for detecting the presence of a weak secondary source (e.g. a planet), especially when the two sources have small angular separations. We reduce the experimental complexity down to a single two-input interferometer: we show that (1) this simple set-up is suffficient for the state discrimination task, and (2) if the two sources are of equal brightness, then this measurement can super-resolve their angular separation, saturating the quantum Cramér-Rao bound. By using a collection baseline of 5.3 mm, we resolve the angular separation of two sources that are placed 15 µm apart at a distance of 1.0 m with an accuracy of 1:7% - this is between 2 to 3 orders of magnitudes more accurate than shot-noise limited direct imaging.</p
Mercer 5: A probable new globular cluster in the Galactic bulge
No full textWe present a detailed study of a dust-obscured Galactic star cluster Mercer 5 ([MCM2005b] 5) in an extremely crowded field in the Milky Way. Near-infrared (near-IR) photometry from United Kingdom Infrared Digital Sky Surveys (UKIDSS) and the Son of ISAAC on the New Technology Telescope (SofI/NTT), combined with near-IR spectroscopy also from SofI, indicates that it is almost certainly a Galactic globular cluster, located at the edge of the Galactic bulge. The cluster suffers ~9 mag of visual extinction, with strong evidence for an extinction gradient across the cluster. A simulation of the differential reddening in the cluster using empirical data from NGC 6539 (chosen because it had high signal-to-noise ratio data and low field star contamination) as a template mimics the observations extremely well. This simulation and other arguments are used to indicate that the most prominent clump of stars in the colour-magnitude diagrams is a horizontal branch clump. On this basis we conclude that the cluster is at a distance of ~5.5kpc and suffers from visual extinction ranging from ~8.5 to ~12.5 mag. Alternative explanations for its nature, such as a young cluster or an old open cluster, are much less likely, on the grounds of no visible main sequence or stars with IR excesses for the former and location versus lifetime arguments for the latter. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
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