J. A. Cooke

Southern infrared proper motion survey I. Discovery of new high proper motion stars from first full hemisphere scan

We present the first results from the Southern Infrared Proper Motion Survey. Using 2 Micron All Sky Survey data along with that of the SuperCOSMOS sky survey we have been able to produce the first widefield infrared proper motion survey. Having targeted the survey to identify nearby M, L and T dwarfs we have discovered 70 such new objects with proper motions greater than 0.5 �� /yr with 10 of these having proper motions in excess of 1 �� /yr. The most interesting of these objects is SIPS1259-4336 a late M dwarf. We have calculated a trigonometric parallax for this object of π = 276±41 milliarcsec yielding a distance of 3.62 ± 0.54 pc. We have also discovered a common proper motion triple system and an object with a common proper motion with LHS 128. The survey completeness is limited by the small epoch differences between many 2MASS and UKI observations. Hence we only recover 22% of Luyten objects with favourable photometry. However the Luyten study is itself unquantifiably incomplete. We discuss the prospect of enhancing the survey volume by reducing the lower proper motion limit.

The subdwarf luminosity function

Using data from the Sloan Digital Sky Survey Early Data Release and SuperCOSMOS Sky Survey scans of POSS-I plates we identify a sample of �2600 subdwarfs using reduced proper motion methods and strict selection criteria. This forms one of the largest and most reliable samples of candidate subdwarfs known, and enables us to determine accurate luminosity functions along many different lines of sight. We derive the subdwarf luminosity function with unprecedented accuracy to MV . 13, finding good agreement with recent local estimates but discrepancy with results for the more distant spheroid. This provides further evidence that the inner and outer parts of the stellar halo cannot be described by a single density distribution. We also find that the form of the inner spheroid density profile within distances of 2.5 kpc is closely matched by a power law with an index of α = 3.15± 0.3.

Three-Dimensional Structure in the Indus Supercluster

Redshifts of large numbers of galaxies can be obtained to an accuracy of ±0.01 in Z by measurement of their spectra on UK Schmidt Telescope objective-prism plates using the COSMOS plate-scanning machine. 2294 redshifts have been measured in a 4.7 × 5.2 deg area of the sky which includes part of the Indus supercluster. The redshifts enable the three-dimensional distribution of the galaxies within the supercluster to be investigated, and a subset of this data is presented here. A 6.8 h−1 bridge of galaxies connecting the rich clusters 2151–5805 and 2143–5732 is revealed (h = Ho/100 km sec−1 Mpc−1). A concentration of galaxies, apparently coincident with 2151–5805 on the sky, is found to lie in the background at a higher redshift, illustrating how the knowledge of redshifts can resolve structure in three dimensions. Much faster and more objective automatic methods of determining the redshifts are currently being developed.