Imprint of DESI fiber assignment on the anisotropic power spectrum of emission line galaxies

The Dark Energy Spectroscopic Instrument (DESI), a multiplexed fiber-fed spectrograph, is a Stage-IV ground-based dark energy experiment aiming to measure redshifts for 29 million Emission-Line Galaxies (ELG), 4 million Luminous Red Galaxies (LRG), and 2 million Quasi-Stellar Objects (QSO). The survey design includes a pattern of tiling on the sky and the locations of the fiber positioners in the focal plane of the telescope, with the observation strategy determined by a fiber assignment algorithm that optimizes the allocation of fibers to targets. This strategy allows a given region to be covered on average five times for a five-year survey, but with coverage varying between zero and twelve, which imprints a spatially-dependent pattern on the galaxy clustering. We investigate the systematic effects of the fiber assignment coverage on the anisotropic galaxy clustering of ELGs and show that, in the absence of any corrections, it leads to discrepancies of order ten percent on large scales for the power spectrum multipoles. We introduce a method where objects in a random catalog are assigned a coverage, and the mean density is separately computed for each coverage factor. We show that this method reduces, but does not eliminate the effect. We next investigate the angular dependence of the contaminated signal, arguing that it is mostly localized to purely transverse modes. We demonstrate that the cleanest way to remove the contaminating signal is to perform an analysis of the anisotropic power spectrum $P(k,\mu)$ and remove the lowest $\mu$ bin, leaving $\mu>0$ modes accurate at the few-percent level. Here, $\mu$ is the cosine of the angle between the line-of-sight and the direction of $\vec{k}$. We also investigate two alternative definitions of the random catalog and show they are comparable but less effective than the coverage randoms method.Comment: Submitted to JCA

Demons of Discord: Violence and the Socio-political Growth of Colonial South Carolina and Georgia, 1690-1776

Life in the colonial American south was filled with brutality and inequality. Whether it was the violence of slavery and colonial expansion or the inherent inequalities of gender relations, violence and oppression permeated nearly every facet of life. This dissertation will look critically at the development of what I am calling a culture of violence in the colonies of Georgia and South Carolina. By studying the ways in which violence effected family, social, and political interactions, my work argues that the crucible of social, racial, and political issues of these two colonies created a culture in which violence or the threat of violence permeated most human interactions. Not only was violence commonplace, violence perpetrated by the individual as well as the state came to be seen as the only legitimate way to punish someone or defend oneself. Social and political historians have dealt with one or two of spheres in which violence occurred. For instance, many studies focus on the violence of slavery and gender relations. However, no one has yet attempted to view all the forms of violence in the South and use that as a lens for understanding southern culture both in the Colonial era and beyond. I argue that by investigating all forms of brutality and the rhetoric associated with such acts, a more complete picture of southern culture emerges – a culture which did not just accept brutality in one area of society but rather in every aspect of life. This acceptance of the necessity of violence went on to inform southerners’ responses to the Imperial Crisis, American Revolution, and even the racial upheaval of the post-Civil War Years

Localised Laser Joining of Glass to Silicon with BCB Intermediate Layer

The use of a laser to provide localised heating is an ideal solution to the problem of packaging microelectro- mechanical-systems (MEMS) whilst maintaining a low device temperature to avoid changes in temperaturesensitive materials in the device. In this paper we present localised laser bonding of glass to silicon (normally used as the MEMS substrate) by using a fibre-delivered high power laser diode array to cure an intermediate layer of the thermosetting polymer Benzocyclobutene (BCB). In our experiments, we use two techniques to realise localised heating: one is to use an axicon together with a conventional positive lens to generate a ring focus; the other is to use a scanning focused laser beam. In both cases localised cooling is required to confine the elevated temperatures to the bonding area