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Frew D.J.,Macquarie University | Madsen G.J.,University of Sydney | O'Toole S.J.,AngloAustralian Observatory | Parker Q.A.,Macquarie University
Publications of the Astronomical Society of Australia | Year: 2010

The emission nebula around the subdwarf B (sdB) star PHL 932 is currently classified as a planetary nebula (PN) in the literature. Based on a large body of multi-wavelength data, both new and previously published, we show here that this low-excitation nebula is in fact a small Störmgren sphere (Hii region) in the interstellar medium around this star. We summarise the properties of the nebula and its ionizing star, and discuss its evolutionary status. We find no compelling evidence for close binarity, arguing that PHL 932 is an ordinary sdB star. We also find that the emission nebulae around the hot DO stars PG 0108 + 101 and PG 0109 + 111 are also Störmgren spheres in the ISM, and along with PHL 932, are probably associated with the same extensive region of high-latitude molecular gas in PiscesPegasus. © Astronomical Society of Australia 2010.

Robotham A.,University of St. Andrews | Driver S.P.,University of St. Andrews | Norberg P.,University of Edinburgh | Baldry I.K.,Liverpool John Moores University | And 22 more authors.
Publications of the Astronomical Society of Australia | Year: 2010

A heuristic greedy algorithm is developed for efficiently tiling spatially dense redshift surveys. In its first application to the Galaxy and Mass Assembly (GAMA) redshift survey we find it rapidly improves the spatial uniformity of our data, and naturally corrects for any spatial bias introduced by the 2dF multi-object spectrograph. We make conservative predictions for the final state of the GAMA redshift survey after our final allocation of time, and can be confident that even if worse than typical weather affects our observations, all of our main survey requirements will be met. © 2010 Astronomical Society of Australia.

Ryder S.D.,AngloAustralian Observatory | Illingworth S.M.,University of Leicester | Sharp R.G.,AngloAustralian Observatory | Farage C.L.,Australian National University
Publications of the Astronomical Society of Australia | Year: 2010

We present infrared imaging from IRIS2 on the Anglo-Australian Telescope that shows the barred spiral galaxy IC 4933 has not just an inner ring encircling the bar, but also a star-forming nuclear ring 1.5 kpc in diameter. Imaging in the u′ band with GMOS on Gemini South confirms that this ring is not purely an artifact due to dust. Optical and near-infrared colours alone however cannot break the degeneracy between age, extinction, and burst duration that would allow the star formation history of the ring to be unraveled. Integral field spectroscopy with the GNIRS spectrograph on Gemini South shows the equivalent width of the Paβ line to peak in the north and south quadrants of the ring, indicative of a bipolar azimuthal age gradient around the ring. The youngest star-forming regions do not appear to correspond to where we expect to find the contact points between the offset dust lanes and the nuclear ring unless the nuclear ring is oval in shape, causing the contact points to lead the bar by more than 90°. © 2010 Astronomical Society of Australia.

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