Proximity To Nearest Major Road And Time To Pregnancy In The Early Pregnancy Study

Purpose: Current literature suggests that air pollution may affect reproductive outcomes, but little research has evaluated the association between air pollution and fertility. Our aim is to further examine the relationship between distance to major roadway, a proxy for traffic-related air pollution, and fecundability. Methods: Our analysis was conducted within the North Carolina Early Pregnancy Study (n=221). Our outcome was pregnancy attempt time, an estimate of fecundability, or the per cycle probability of conception. Our primary definition of conception included early pregnancy loss, spontaneous miscarriage, ectopic and molar pregnancy, and singleton or twin pregnancies. In a secondary analysis, we defined conception as clinical pregnancy, which excluded early pregnancy loss. Residential proximity to nearest major road was calculated for each participant. We used general linear regression models to estimate fecundability ratios (FR) according to road proximity. We also used a logistic regression to estimate odds ratios (OR) for the risk of early loss within our proximity metrics. We adjusted for male and female age, education, occupation, and income. Results: In our primary analysis of all conceptions, fecundability may be slightly improved for couples living near a major road (FR range: 1.11 – 1.42). When we evaluated only clinical pregnancies, results were attenuated, suggesting that proximity to nearest major road is not associated with fecundability. In the analysis of early loss, there appeared to be a slightly increased of early loss in women who live less than 200 meters away from a major road (OR: 2.08, 95%CI: 0.85, 5.09) and in women who live between 200 -(OR: 1.82, 95%CI: 0.78, 4.24). Conclusion: We found some evidence that living near a major road may be associated with increased fecundability but there was no clear dose-response pattern. The slight increase in fecundability reflect an increased risk of early losses for participants who live closer to major roads. Further study of this association is warranted

How galaxies form in protoclusters

I will describe the cosmic star formation history of cluster galaxies using observations of clusters and protoclusters from z = 0 to 4. I will show that the star formation history of clusters differs from the global cosmic star formation history: cluster galaxies typically form their stars earlier and over a shorter period of time. I will use semi-analytic models of galaxy formation to explain why their star formation histories differ. I will show that the star formation density in protoclusters is extremely high due their high matter densities, but the simulations suggest there is no reversal in the star formation - density relation at high redshift. The differences in the star formation histories of field and cluster galaxies are caused by the gradual suppression of star formation, starting at z = 3, and getting stronger with time. The main mechanisms responsible for this suppression are tidal stripping and AGN feedback. Looking ahead, I will describe several testable predictions of the different evolutionary paths of cluster and field galaxies. Comparing these predictions with JWST observations of distant clusters and protoclusters can test our understanding of galaxy evolution

What are protoclusters? – Defining high-redshift galaxy clusters and protoclusters

We explore the structures of protoclusters and their relationship with high-redshift clusters using the Millennium Simulation combined with a semi-analytic model. We find that protoclusters are very extended, with 90 per cent of their mass spread across∼35 h−1 Mpc commoving at z =2 (∼30 arcmin). The ‘main halo’, which can manifest as a high-redshift cluster or group, is only a minor feature of the protocluster, containing less than 20 per cent of all protocluster galaxies at z = 2. Furthermore, many protoclusters do not contain a main halo that is massive enough to be identified as a high-redshift cluster. Protoclusters exist in a range of evolutionary states at high redshift, independent of the mass they will evolve to at z = 0. We show that the evolutionary state of a protocluster can be approximated by the mass ratio of the first and second most massive haloes within the protocluster, and the z = 0 mass of a protocluster can be estimated to within 0.2 dex accuracy if both the mass of the main halo and the evolutionary state are known. We also investigate the biases introduced by only observing star-forming protocluster members within small fields. The star formation rate required for line-emitting galaxies to be detected is typically high, which leads to the artificial loss of low-mass galaxies from the protocluster sample. This effect is stronger for observations of the centre of the protocluster, where the quenched galaxy fraction is higher. This loss of low-mass galaxies, relative to the field, distorts the size of the galaxy overdensity, which in turn can contribute to errors in predicting the z = 0 evolved mass

Semi-analytic model predictions of the galaxy population in protoclusters

We investigate the galaxy population in simulated protocluster regions using a semi-analytic model of galaxy formation, coupled to merger-trees extracted from N-body simulations. We select the most massive clusters at redshift z = 0 from our set of simulations, and follow their main progenitors back in time. The analysis shows that protocluster regions are dominated by central galaxies and their number decreases with time as many become satellites, clustering around the central object. In agreement with observations, we find an increasing velocity dispersion with cosmic time, the increase being faster for satellites. The analysis shows that protoclusters are very extended regions, 7320 Mpc at z 73 1. The fraction of galaxies in protocluster regions that are not progenitor of cluster galaxies varies with redshift, stellar mass and area considered. It is about 20-30 per cent for galaxies with stellar mass \u2dc109 M 99, while negligible for the most massive galaxies considered. Nevertheless, these objects have properties similar to those of progenitors. We investigate the building-up of the passive sequence in clusters, and find that their progenitors are on average always active at any redshift of interest of protoclusters. The main mechanism which quenches their star formation is the removal of the hot gas reservoir at the time of accretion. The later galaxies are accreted (become satellite), and the more the cold gas available, the longer the time spent as active. Central galaxies are active over all redshift range considered, although a non-negligible fraction of them become passive at redshift z < 1, due to strong feedback from active galactic nuclei

Environmental Policy Update 2012: Development Strategies and Environmental Policy in East Africa

The seven chapters that comprise this report explore ways to integrate sustainability goals and objectives into Ethiopia's current development strategies

Searching for the shadows of giants II: the effect of local ionisation on the Lyman-alpha absorption signatures of protoclusters at redshift z=2.4

Local variations in the intergalactic medium (IGM) neutral hydrogen fraction will affect the Ly-α absorption signature of protoclusters identified in tomographic surveys. Using the IllustrisTNG simulations, we investigate how the AGN proximity effect and hot, collisionally ionised gas arising from gravitational infall and black hole feedback changes the Ly-α absorption associated with Mz = 0 ≃ 1014 M⊙ protoclusters at z ≃ 2.4. We find that protocluster galaxy overdensities exhibit a weak anti-correlation with Ly-α transmission in IGM transmission maps, but local HI ionisation enhancements due to hot T>106K gas or nearby AGN can disrupt this relationship within individual protoclusters. On average, however, we find that strong reductions in the IGM neutral fraction are limited to within ≲ 5h−1 cMpc of the dark matter haloes. Local ionisation enhancements will therefore have a minimal impact on the completeness of protocluster identification in tomographic surveys if smoothing Ly-α transmission maps over scales of ∼4h−1 cMpc, as is typically done in observations. However, if calibrating the relationship between the matter density and Ly-α transmission in tomographic maps using simple analytical models for the Ly-α forest opacity, the presence of hot gas around haloes can still result in systematically lower estimates of Mz = 0 for the most massive protoclusters

Searching for the shadows of giants: characterizing protoclusters with line of sight Lyman-α absorption

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. We use state-of-the-art hydrodyamical simulations from the Sherwood, EAGLE, and Illustris projects to examine the signature of Mz = 0 ≃ 1014 M protoclusters observed in Ly α absorption at z ≃ 2.4. We find that there is a weak correlation between the mass overdensity, δm, and the Ly α effective optical depth relative to the mean, δτeff, averaged over 15 h−1 cMpc scales, although scatter in the δm–δτeff plane means it is not possible to uniquely identify large-scale overdensities with strong Ly α absorption. Although all protoclusters are associated with large-scale mass overdensities, most sightlines through protoclusters in a ∼106 cMpc3 volume probe the low column density Ly α forest. A small subset of sightlines that pass through protoclusters exhibit coherent, strong Ly α absorption on 15h−1 cMpc scales, although these correspond to a wide range in mass overdensity. Assuming perfect removal of contamination by Ly α absorbers with damping wings, more than half of the remaining sightlines with δτeff > 3.5 trace protoclusters. It is furthermore possible to identify a model-dependent δτeff threshold that selects only protoclusters. However, such regions are rare: excluding absorption caused by damped systems, less than 0.1 per cent of sightlines that pass through a protocluster have δτeff > 3.5, meaning that any protocluster sample selected in this manner will also be highly incomplete. On the other hand, coherent regions of Ly α absorption also provide a promising route for identifying and studying filamentary environments at high redshift

Probing quasar lifetimes with proximate 2121-centimetre absorption in the diffuse intergalactic medium at redshifts z≥6z\geq 6

Enhanced ionizing radiation in close proximity to redshift $z\gtrsim 6$ quasars creates short windows of intergalactic Ly$\alpha$ transmission blueward of the quasar Ly$\alpha$ emission lines. The majority of these Ly$\alpha$ near-zones are consistent with quasars that have optically/UV bright lifetimes of $t_{\rm Q}\sim 10^{5}-10^{7}\rm\,yr$. However, lifetimes as short as $t_{\rm Q}\lesssim 10^{4}\rm\,yr$ appear to be required by the smallest Ly$\alpha$ near-zones. These short lifetimes present an apparent challenge for the growth of $\sim 10^{9}\rm\,M_{\odot}$ black holes at $z\gtrsim 6$. Accretion over longer timescales is only possible if black holes grow primarily in an obscured phase, or if the quasars are variable on timescales comparable to the equilibriation time for ionized hydrogen. Distinguishing between very young quasars and older quasars that have experienced episodic accretion with Ly$\alpha$ absorption alone is challenging, however. We therefore predict the signature of proximate 21-cm absorption around $z\gtrsim 6$ radio-loud quasars. For modest pre-heating of intergalactic hydrogen by the X-ray background, where the spin temperature $T_{\rm S} \lesssim 10^{2}\rm\,K$ prior to any quasar heating, we find proximate 21-cm absorption should be observable in the spectra of radio-loud quasars. The extent of the proximate 21-cm absorption is sensitive to the integrated lifetime of the quasar. Evidence for proximate 21-cm absorption from the diffuse intergalactic medium within $2-3\rm\,pMpc$ of a (radio-loud) quasar would be consistent with a short quasar lifetime, $t_{\rm Q}\lesssim 10^{5}\rm\,yr$, and would provide a complementary constraint on models for high redshift black hole growth.Comment: 19 pages, 12 figures, 2 tables. Accepted for publication in MNRA

The structure and evolution of a forming galaxy cluster at z = 1.62

We present a comprehensive picture of the Cl 0218.3−0510 protocluster at z = 1.623 across 10 comoving Mpc. Using filters that tightly bracket the Balmer and 4000 Å breaks of the protocluster galaxies we obtain precise photometric redshifts resulting in a protocluster galaxy sample that is 89 ± 5 per cent complete and has a contamination of only 12 ± 5 per cent. Both star-forming and quiescent protocluster galaxies are located, which allows us to map the structure of the forming cluster for the first time. The protocluster contains six galaxy groups, the largest of which is the nascent cluster. Only a small minority of the protocluster galaxies are in the nascent cluster (11 per cent) or in the other galaxy groups (22 per cent), as most protocluster galaxies reside between the groups. Unobscured star-forming galaxies predominantly reside between the protocluster’s groups, whereas red galaxies make up a large fraction of the groups’ galactic content, so observing the protocluster through only one of these types of galaxies results in a biased view of the protocluster’s structure. The structure of the protocluster reveals how much mass is available for the future growth of the cluster and we use the Millennium Simulation, scaled to a Planck cosmology, to predict that Cl 0218.3−0510 will evolve into a 2.7+3.9 −1.7 × 1014M cluster by the present day