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Large scale structure in the HI Parkes All-Sky Survey: Filling the Voids with HI galaxies? | | S. Basilakos
; M. Plionis
; K. Kovac
; N. Voglis
; | | Date: |
28 Mar 2007 | | Abstract: | We estimate the two-point correlation function in redshift space of the recently compiled HIPASS neutral hydrogen (HI) sources catalogue, which if modeled as a power law, $xi(r)=(r_{0}/r)^{gamma}$, the best-fitting parameters for the HI selected galaxies are found to be $r_{0}=3.3 pm 0.3 h^{-1}$ Mpc with $gamma=1.38 pm 0.24$. Fixing the slope to its universal value $gamma=1.8$, we obtain $r_{0}= 3.2pm 0.2 h^{-1}$ Mpc. Comparing the measured two point correlation function with the predictions of the concordance cosmological model, we find that at the present epoch the HI selected galaxies are anti-biased with respect to the underlying matter fluctuation field with their bias value being $b_{0}simeq 0.68$. Furthermore, dividing the HI galaxies into two richness subsamples we find that the low mass HI galaxies have a very low present bias factor ($b_{0}simeq 0.48$), while the high mass HI galaxies trace the underlying matter distribution as the optical galaxies ($b_{0}simeq 1$). Using our derived present-day HI galaxy bias we estimate their redshift space distortion parameter, and correct accordingly the correlation function for peculiar motions. The resulting real-space correlation length is $r^{
m re}_{0}=1.8 pm 0.2 h^{-1}$Mpc and $r^{
m re}_{0}=3.9 pm 0.6 h^{-1}$Mpc for the low and high mass HI galaxies, respectively. The low-mass HI galaxies appear to have the lowest correlation length among all extragalactic populations studied to-date. Also, we have correlated the IRAS-PSCz reconstructed density field, smoothed over scales of 5$h^{-1}$ Mpc, with the positions of the HI galaxies, to find that indeed the HI galaxies are typically found in negative overdensity regions ($delta
ho/
ho_{
m PSCz} mincir 0$). | | Source: | arXiv, astro-ph/0703713 | | Services: | Forum | Review | PDF | Favorites | |
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