The HI mass function in the Parkes HI Zone of Avoidance survey
Date
2019
Authors
Said, Khaled
Kraan-Korteweg, Renee Christine
Staveley-Smith, Lister
Journal Title
Journal ISSN
Volume Title
Publisher
Royal Astronomical Society
Abstract
An H I mass function (HIMF) was derived for 751 galaxies selected from the deep Parkes
H I survey across the Zone of Avoidance (HIZOA). HIZOA contains both the Great Attractor
Wall and the Local Void, two of the most extreme environments in the local Universe, making
the sample eminently suitable to explore the overall HIMF as well as its dependence on local
environment. To avoid any selection bias because of the different distances of these large-scale
structures, we first used the 2D stepwise maximum-likelihood method for the definition of an
average HIMF. The resulting parameters of a Schechter-type HIMF for the whole sample are
α = −1.33 ± 0.05, log(M∗
H I
/M) = 9.93 ± 0.04, and φ∗ = (3.9 ± 0.6) × 10−3 Mpc−3. We
then used the k-th nearest-neighbour method to subdivide the sample into four environments
of decreasing local density and derived the Schechter parameters for each subsample. A strong
trend is observed, for the slope α of the low-mass end of the HIMF. The slope changes from
being nearly flat, i.e. α = −0.99 ± 0.19 for galaxies residing in the densest bin, to the steep
value of α = −1.31 ± 0.10 in the lowest density bin. The characteristic mass, however, does
not show a clear trend between the highest and lowest density bins. We find similar trends in
the low-mass slope when we compare the results for a region dominated by the Great Attractor,
and the Local Void, which are found to be over-, respectively underdense by 1.35 and 0.59
compared to the whole sample.
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Keywords
galaxies: distances and redshifts, large-scale structure of Universe, cosmology: observations
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Monthly Notices of the Royal Astronomical Society
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Journal article
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Open Access
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