Day 1119

Monday.

1607.02215
Dawes Review 5: Australian Aboriginal Astronomy and Navigation
Norris

The traditional cultures of Aboriginal Australians include a significant astronomical component, perpetuated through oral tradition, ceremony, and art.  This astronomical knowledge includes a deep understanding of the motion of objects in the sky, which was used for practical purposes such as constructing calendars and for navigation.  There is also evidence that traditional Aboriginal Australians made careful records and measurements of cyclical phenomena, recorded unexpected phenomena such as eclipses and meteorite impacts, and could determine the cardinal points to an accuracy of a few degrees.  Putative explanations of celestial phenomena appear throughout the oral record, suggesting traditional Aboriginal Australians sought to understand the natural world around them, in the same way as modern scientists, but within their own cultural context.  There is also a growing body of evidence for sophisticated navigational skills, including the use of astronomically based longlines.  Longlines are effectively oral maps of the landscape, and are an efficient way of transmitting oral navigational skills in cultures that do not have a written language.  The study of Aboriginal astronomy has had an impact extending beyond mere academic curiosity, facilitating cross-cultural understanding, demonstrating the intimate links between science and culture, and helping students to engage with science.


1607.02417
Unbiased contaminant removal for 3D galaxy power spectrum measurements
Klaus, Percival, Bacon, Samushia

Assess and develop techniques to remove contaminants when calculating the 3d galaxy power spectrum.  Separate the process into 3 separate stages: (i) removing the contaminant signal, (ii) estimating the uncontaminated cosmo power spectrum, (iii) debasing the resulting estimates.  For (i), show that removing the best-fit contaminant (template subtraction), and setting the contaminated components of the covariance to be infinite (mode deprojection) are mathematically equivalent.  For (ii), performing a Quadratic Maximum Likelihood (QML) estimate after mode deprojection gives an optimal unbiased solution, although it requires the manipulation of large (N^2-mode) matrices, which is unfeasible for recent 3d galaxy surveys.  Measuring a binned average of the modes for (ii) as proposed by Feldman, Kaiser & Peacock (1994, FKP) is faster and simpler, but is sub-optimal and gives rise to a biased solution.  Present a method to debits the resulting FKP measurements that does not require any large matrix calculations.  Argue that the sub-optimality of the FKP estimator compared with the QML estimator, caused by contaminants is less severe than that commonly ignored due to the survey window.