Characterizing the Epoch of Reionization with the small-scale CMB: constraints on the optical depth and physical parameters

Patchy reionization leaves a number of imprints on the small-scale cosmic microwave background (CMB) temperature fluctuations, the largest of which is the kinematic Sunyaev-Zel'dovich (kSZ), the Doppler shift of CMB photons scattering off moving electrons in ionized bubbles. It has long been known that in the CMB power spectrum, this imprint of reionization is largely degenerate with the kSZ signal produced by late-time galaxies and clusters, thus limiting our ability to constrain reionization. Following Smith & Ferraro (2017), it is possible to isolate the reionization contribution in a model independent way, by looking at the large scale modulation of the small scale CMB power spectrum. In this paper we extend the formalism to use the full shape information of the small scale power spectrum (rather than just its broadband average), and argue that this is necessary to break the degeneracy between the optical depth $\tau$ and parameters setting the duration of reionization. In particular, we show that the next generation of CMB experiments could achieve up to a factor of 3 improvement on the optical depth $\tau$ and at the same time, constrain the duration of reionization to $\sim$ 25 %. This can help tighten the constrains on neutrino masses, which will be limited by our knowledge of $\tau$, and shed light on the physical processes responsible for reionization.Comment: 8 pages, 3 figures. Comments welcom

Detecting patchy reionization in the CMB

Upcoming cosmic microwave background (CMB) experiments will measure temperature fluctuations on small angular scales with unprecedented precision. Small-scale CMB fluctuations are a mixture of late-time effects: gravitational lensing, Doppler shifting of CMB photons by moving electrons (the kSZ effect), and residual foregrounds. We propose a new statistic which separates the kSZ signal from the others, and also allows the kSZ signal to be decomposed in redshift bins. The decomposition extends to high redshift, and does not require external datasets such as galaxy surveys. In particular, the high-redshift signal from patchy reionization can be cleanly isolated, enabling future CMB experiments to make high-significance and qualitatively new measurements of the reionization era

Evaluation of fostering network Scottish care mentoring projects

Looked after children and young people are some of the most vulnerable in our society. For Scotland’s Children highlighted the ‘continuing failure of many local authorities as ‘corporate parents’ to provide these young people with the care and education they are entitled to by law’ (Scottish Executive, 2001, p. 10). One of the major issues facing looked after young people is the process of transition from care to independence. It is a time when they have ‘a right to expect the sort of help that loving parents would provide for their children, help to reach their full potential, and the same chance to make mistakes secure in the knowledge that there is a safety net of support’ (Jamieson, 2002, p. 2). However, over a number of years, research has highlighted the poor outcomes for children leaving care. Longitudinal studies which have followed up children and young people in care as part of national cohort studies present the stark contrast in life outcomes between those who have experienced care and those who have not. Cheung and Heath (1994) compare these two groups at age 33. Only one fifth of those who had been in care had achieved O levels compared to one-third of those who had not; only half as many had achieved A levels. Only one in a hundred of those who had been in care achieved a university degree compared to one on ten of those who had not. Two fifths of those who had been in care had no formal qualifications compared to one in seven (Cheung and Heath, 1994). This lack of qualifications converted into lack of success in the job market with three times as many being unemployed (10.8 % compared to 3.6 %) and larger proportions having manual jobs as opposed to professional or non-manual jobs

B-mode CMB Polarization from Patchy Screening during Reionization

B-modes in CMB polarization from patchy reionization arise from two effects: generation of polarization from scattering of quadrupole moments by reionization bubbles, and fluctuations in the screening of E-modes from recombination. The scattering contribution has been studied previously, but the screening contribution has not yet been calculated. We show that on scales smaller than the acoustic scale (l>300), the B-mode power from screening is larger than the B-mode power from scattering. The ratio approaches a constant ~2.5 below the damping scale (l>2000). On degree scales relevant for gravitational waves (l<100), screening B-modes have a white noise tail and are subdominant to the scattering effect. These results are robust to uncertainties in the modeling of patchy reionization.Comment: 4 pages, 1 figure; minor changes matching PRD published versio