Fluctuations of K-band galaxy counts

Free access article

Issue		A&A Volume 416, Number 1, March II 2004


Page(s)		1 - 7
Section		Cosmology (including clusters of galaxies)
DOI		http://dx.doi.org/10.1051/0004-6361:20031718

A&A 416, 1-7 (2004)
DOI: 10.1051/0004-6361:20031718

Fluctuations of K-band galaxy counts

M. López-Corredoira¹ and J. E. Betancort-Rijo^{2, 3}

¹ Astronomisches Institut der Universität Basel, Venusstrasse 7, 4102 Binningen, Switzerland
² Instituto de Astrofísica de Canarias, C/. Vía Láctea, s/n, 38200 La Laguna (Tenerife), Spain
³ Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain

(Received 15 May 2003 / Accepted 31 October 2003)

Abstract
We measure the variance in the distribution of off-plane ( $\vert b\vert>20^\circ$ ) galaxies with m_K<13.5 from the 2MASS K-band survey in circles of diameter between 0.344 $^\circ$ and 57.2 $^\circ$ . The use of a near-infrared survey makes the contribution of Galactic extinction to these fluctuations negligible. We calculate these variances within the standard $\Lambda$ CDM 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 $\xi (z=0, r<10~h^{-1}~{\rm Mpc})=(29.8\pm 0.5) (r/h^{-1}~{\rm Mpc})^{-1.79\pm 0.03}$ , which is the first measure of the amplitude of $\xi$ 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.

Key words: cosmology: large-scale structure of Universe -- infrared: galaxies -- galaxies: statistics -- cosmology: theory

Offprint request: M. López-Corredoira, martinlc@astro.unibas.ch

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