Cosmological application of the DENIS survey

Although primarily intended for stellar science through the detection of point sources with fluxes  mJy (e.g. galactic structure studies and the detection of brown dwarf candidates and obscured regions of star formation) an important extra application is the capability to obtain a complete view of the local Universe out to by virtue of a `clean' near-IR selected bandpass. Here selected galaxies are less susceptible to extinction in our own Galaxy (e.g. Rieke et al 1993) and by internal absorption of the host galaxy (e.g. Rix 1993). Samples can be obtained through the zone of avoidance whilst the stellar populations of even highly dusty galaxies can be discerned. The total luminosity of a galaxy at is thought to be an excellent tracer of the true stellar mass in a galaxy, as it sees through to the `backbone' of a galaxy unlike the B band which is biased by the effects of recent star formation. Hence a more complete sample, less biased by star-formation and internal or galactic extinction, should be produced. If one assumes that stellar mass content follows total galaxy mass (including dark matter) then a NIR survey should be a good way of measuring the matter distribution in the local Universe. All the above factors make a J/ selected sample an obvious choice for the basis of a new all southern sky galaxy redshift survey being less susceptible to problems biasing optically selected or even IRAS samples.

A detailed map of the local Universe to and determination of the J() or () band luminosity function of local galaxies will be a prime aim of the redshift survey. A catalogue of galaxy pairs, groups and clusters can also be established. The effects of galaxy environment and the distribution of galaxies on large scales can also be measured. The complete sample would also provide new estimates of the spatial correlation function to compare with results from the B and far IR selected bands which give too much power on large scales cf. CDM. The story might be different with a clean J or sample, weighted towards the old stellar population, than for a B-selected sample weighted towards the recently star-forming galaxies.

Another major difference between this and other large redshift surveys is that we propose to measure internal velocities (dispersions or rotations) for galaxies in our sample to allow determinations of distances, via the Fundamental Plane or the Tully-Fisher relation, and hence a comprehensive map of the peculiar motions and mass distribution over the southern sky.

© Copyright Astronomical Society of Australia 1997