Constraining Galaxy Haloes from the Dispersion and Scattering of Fast Radio Bursts and Pulsars

Fast radio bursts (FRBs) can be scattered by ionized gas in their local environments, host galaxies, intervening galaxies along their lines-of-sight, the intergalactic medium, and the Milky Way. The relative contributions of these different media depend on their geometric configuration and the internal properties of the gas. When these relative contributions are well understood, FRB scattering is a powerful probe of density fluctuations along the line-of-sight. The precise scattering measurements for FRB 121102 and FRB 180916 allow us to place an upper limit on the amount of scattering contributed by the Milky Way halo to these FRBs. The scattering time $\tau\propto(\tilde{F} \times {\rm DM}^2) A_\tau$, where ${\rm DM}$ is the dispersion measure, $\tilde{F}$ quantifies electron density variations with $\tilde{F}=0$ for a smooth medium, and the dimensionless constant $A_\tau$ quantifies the difference between the mean scattering delay and the $1/e$ scattering time typically measured. A likelihood analysis of the observed scattering and halo DM constraints finds that $\tilde{F}$ is at least an order of magnitude smaller in the halo than in the Galactic disk. The maximum pulse broadening from the halo is $\tau\lesssim12$ $\mu$s at 1 GHz. We compare our analysis of the Milky Way halo with other galaxy haloes by placing limits on the scattering contributions from haloes intersecting the lines-of-sight to FRB 181112 and FRB 191108. Our results are consistent with haloes making negligible or very small contributions to the scattering times of these FRBs.Comment: 14 pages, 6 figures, accepted to Ap

Mothers of Men: the A&M Mothers' Clubs and coeducation

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 36-38).In 1933 the Texas A&M Mothers' Clubs sent petitions and letters to the Board of Advisors requesting that Texas A&M University retain its all-male status. While most studies of women opposed to equal rights center on the women maintaining power through their feminine sphere of influence, the mothers of the A&M Mothers' Clubs at this time were more concerned with being defined as good mothers by maintaining their sons' power. My research of the action of the A&M Mothers' Clubs focuses on two main aspects: a historical perspective and the social construction of motherhood. In 1933, the United States faced the worst of the Great Depression, with no end in sight. Every spot a woman had in either education or the workforce was considered one less spot for a man. Gender, or the social construct defining roles for men and women, at the time dictated that men become wage earners and support a family. It was very important in a time of high unemployment that men find a way to fulfill their roles. Men spent most of their time outside of the home, and mothers stayed home with their children. Society feared that males raised by mothers would become too feminine, so mothers were advised to teach their sons masculinity, or their proper gender role. The social construction of motherhood also greatly changed during the 1910s when these women were raising their sons. Society began to treat motherhood as a profession, and like all professions of the times, there was a right way and a wrong way to perform your job. Known as scientific motherhood, mothers during this time were advised exactly how to raise a child. Direct participation in a child's education was also common, with Parent Teachers' Associations springing up across the country. Psychologically, mothers began to bear the brunt of disorders. More and more problems were attributed to the effects of bad mothering upon a child, and mothers strove to earn the label of good mother. The Victorian era glorification of the mother was slowly disappearing when these women entered motherhood. When these forces combined to work on mothers from the 1910s to 1930s, women cared about the status of their sons. In an effort to maintain their sons' gender role of provider, secure him a spot in education, and be an involved mother, the mothers of the Texas A&M Mothers' Clubs worked to maintain the all-male status of Texas A&M University. Like other women opposed to equal rights, these women organized themselves into an effective group, but unlike those women, the mothers of the A&M Mothers' Clubs strove to maintain their sons' power, and not their own

Spin-orbit torques for current parallel and perpendicular to a domain wall

We report field- and current-induced domain wall (DW) depinning experiments in Ta/Co20Fe60B20/MgO nanowires through a Hall cross geometry. While purely field-induced depinning shows no angular dependence on in-plane fields, the effect of the current depends crucially on the internal DW structure, which we manipulate by an external magnetic in-plane field. We show for the first time depinning measurements for a current sent parallel to the DW and compare its depinning efficiency with the conventional case of current flowing perpendicularly to the DW. We find that the maximum efficiency is similar for both current directions within the error bars, which is in line with a dominating damping-like spin-orbit torque (SOT) and indicates that no large additional torques arise for currents parallel to the DW. Finally, we find a varying dependence of the maximum depinning efficiency angle for different DWs and pinning levels. This emphasizes the importance of our full angular scans compared to previously used measurements for just two field directions (parallel and perpendicular to the DW) and shows the sensitivity of the spin-orbit torque to the precise DW structure and pinning sites.Comment: 11 pages, 3 figure