Astronomy and Astrophysics | VOL. 416

Fluctuations of K-band galaxy counts

Publication Date Mar 1, 2004


We measure the variance in the distribution of off-plane (|b| > 20 ◦ ) galaxies with mK < 13.5 from the 2MASS K-band survey in circles of diameter between 0.344 ◦ and 57.2 ◦ . The use of a near-infrared survey makes the contribution of Galactic extinction to these fluctuations negligible. We calculate these variances within the standard ΛCDM model assuming that the sources are distributed like halos of the corresponding mass, and it reproduces qualitatively the galaxy count variance. Therefore, we conclude that the counts can be explained in terms only of the large scale structure. A second result of this paper is a new method to determine the two point correlation function obtained by forcing agreement between model and data. This method does not need the knowledge of the two-point angular correlation function, allows an estimation of the errors (which are low with this method), and can be used even with incomplete surveys. Using this method we get ξ(z = 0,r < 10 h −1 Mpc) = (29.8 ± 0.5)(r/h −1 Mpc) −1.79±0.03 , which is the first measure of the amplitude of ξ in the local Universe for the K-band. It is more or less in agreement with those obtained through red optical filter selected samples, but it is larger than the amplitude obtained for blue optical filter selected samples. The distribution of the number of galaxies or clusters of galax- ies in a certain volume V can be used to test the large-scale structure of the universe. The calculation of probabilities of finding different structures in a clustering model are some-...

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Two-point Correlation Function
Number Of Galaxies
Galaxy Counts
Two-point Angular Correlation Function
Cluster Density Profiles
Standard ΛCDM Model
Correlation Function
Sky Survey

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