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Large scale structure in the HI parkes all-sky survey: filling the voids with HI galaxies?
Manolis Plionis
Acceso Abierto
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, ξ(r) = (r0/r)γ, the best-fitting parameters for the HI selected galaxies are found to be r0 = 3.3 ± 0.3 h−1 Mpc with γ= 1.38 ± 0.24. Fixing the slope to its universal value γ = 1.8, we obtain r0 = 3.2 ± 0.2 h−1 Mpc. Comparing the measured two point correlation function with the predictions of the concordance cosmological model (ΩΛ = 0.74), 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 b0 ≃ 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 (b0 ≃ 0.48), while the high mass HI galaxies trace the underlying matter distribution as the optical galaxies (b0 ≃ 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 rre 0 = 1.8 ± 0.2 h−1Mpc and rre0 = 3.9 ± 0.6 h−1Mpc 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 todate. In order to corroborate these results 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 (δρ / ρPSCz∼ < 0), even more so the low HI-mass galaxies. Finally, we also study the redshift evolution of the HI galaxy linear bias factor and find that the HI-galaxy population is anti-biased up to z ∼ 1.3. While at large redshifts z ∼ 3, we predict that the HI galaxies are strongly biased. Our bias evolution predictions are consistent with the observational bias results of Lyman-α galaxies.
Monthly Notices of the Royal Astronomical Society
Público en general
Basilakos, S., et al., (2007). Large scale structure in the HI parkes all-sky survey: filling the voids with HI galaxies?, Monthly Notices of the Royal Astronomical Society, Vol.378(1):1-9
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Appears in Collections:Artículos de Astrofísica

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