Science News Archive

Science News

1 Feb 2010 Parallax measurement of the first T9 brown dwarf discovered, ULAS J0034-0052, by Ricky Smart, Torino. The measured distance of 12.6+/-0.6pc allows the measurement of the source's bolometric luminosity, and confirms the very cool temperature of 550-600K previously inferred from spectroscopic modelling. The source is the coolest brown dwarf known with a directly measured parallax.The parallax program will lead to measurements for several more UKIDSS brown dwarfs over 2010 and 2011. For further info see the press release (in Italian).

18 Dec 2009 Optical spectrum of the new L subdwarf ULAS1350 (middle spectrum - click for larger version), obtained with the OSIRIS spectrograph on the 10.4-m Gran Telescopio de Canarias (GTC). This object was identified photometrically, by Lodieu and collaborators, in a search of a 234 sq. degs region common to the Sloan Digital Sky Survey and the UKIDSS Large Area Survey. This is the fifth L subdwarf known to date, the first one discovered in UKIDSS, and the furthest known. Fur further info see the press release.

1 Oct 2009 The bivariate brightness distribution for a sample of 40,111 galaxies in the UKIDSS Large Area Survey (Smith et al. 2009, MNRAS, 397, 868). The shaded regions show how the number of galaxies per unit volume depends on the galaxies' K-band luminosity (increasing towards the right) and surface brightness (increasing towards the top). It can be seen that there is a strong correlation between surface brightness and luminosity, and that this correlation flattens at high luminosity. This can be used to inform our understanding of how galaxies form.

16 Jul 20009 Evolution of the galaxy luminosity function between z=5 and z=6 (McLure et al. 2009, MNRAS 395, 2196). The plot combines data from the UKIDSS Ultra-deep survey at the bright-end, L>L*, with the results from deep Hubble Space Telescope (HST) images for the faint end, to cover a wide luminosity range (0.1L* < L < 10L*) at z=5 and z=6. In the redshift interval 5 < z < 6 the galaxy luminosity function appears to undergo simple luminosity evolution, with L* dimming by a factor of ~2 from z=6 to z=5.

27 May 2009 Gemini GMOS-N spectrum of the newly discovered quasar ULAS J1207+0630, with redshift z=6.04, from DR5. The object is detected in z in SDSS, but lies just below the S/N cut of the SDSS quasar searches. The absorption complex just blueward of the NV emission line is resolved into a set of NV doublets.

20 Apr 2009 Discovery of Wolf 940B, a very cool brown dwarf in a binary system, announced in a press release today. The brown dwarf is one of the coolest known with effective temperature 570K, adding to the handful of extreme cool brown dwarfs discovered by UKIDSS. Wolf 940B is the first such object discovered in a binary system, providing an accurate distance measurement. This allows a stringent test of theoretical brown dwarf spectra, and suggests a revision of the temeprature scale to cooler tmeperatures.

12 Feb 2009 Bimodality of restframe galaxy colours (from Williams et al 2009 ApJ 691). Restframe U-V and V-J colours and photometric redshifts were computed for 30,108 galaxies in the UKIDSS UDS. In the U-V vs V-J diagram galaxies separate into two sequences, an upper sequence of passive galaxies, and a lower sequence of star-forming galaxies, of increasing dust content from lower left to upper right. The bimodality is clearly seen up to z=2.

13 June 2008 The clustering of BzK galaxies (Hartley et al., in prep.). Galaxies in the UDS have been selected to lie in the redshift range 1.4 < z < 2.5 and can be characterised as either star-forming (sBzK) or passive (pBzK) by the Daddi et al. (2004) criterea. In this redshift range it is the passive galaxies that are found to be the more highly clustered. The clustering of a set of galaxies can be directly linked to the mass of the dark matter halos in which they reside; in the case of the pBzKs the dark matter halos have mass in excess of 1013 solar masses.

24 January 2008 A recently discovered high-redshift quasar in the LAS, ULAS J131911.29+095051.4 (Mortlock et al., in prep). The redshift has been estimated from the wavelength at which absorption to the blue of the emission line cuts on, and assuming this point to be the centre of the Lya emission line. The source has i(AB)=22.6, Y=19.2, J=18.8.

1 June 2007 Spitzer view of the cool brown dwarf ULAS J0034-00. In this rgb image, the blue channel is the z band, and the green and red channels are Spitzer channels 1 and 2 (3.55 and 4.49 um). Therefore main-sequence stars, relatively faint in the mid-ir, appear blue.