Gravitational redshifts and the mass distributions of galaxies and clusters

This thesis studies a new method of constraining the mass distributions of elliptical galaxies and clusters of galaxies: gravitational redshift. The aim was to determine the types of astrophysical object in which gravitational redshift can be most readily detected and to attempt to observe the effect for the first time in a single object. Longslit stellar kinematics were combined with planetary nebulae kinematics to study the mass distribution of M87. Jeans modelling showed that, although the best-fit model gave too little mass (Upsilon = 5.34+/-0.34, beta = 0.71+/-0.03, M_halo = 2.64+/-0.92 x 10^12 M_sun), by adjusting the orbital anisotropy it was possible to construct a model that was consistent with both the kinematics and existing X-ray gas measurements. Longslit kinematics from the literature were used to attempt to determine the mass-to-light ratio of a sample of elliptical galaxies using gravitational redshift. Models were developed to calculate the expected gravitational redshift from the surface brightness profile. The best-fit mass-to-light ratios were found using this model and also obtained independently using the Jeans equation. The results were not statistically inconsistent with the expected H-band mass-to-light ratios predicted by stellar population models - the Jeans modelling gave a mean mass-to-light ratio of Upsilon_sigma = 1.67+/-0.10, while the gravitational redshift predicted Upsilon_v = 4.84+/-2.67. Integral field spectroscopy of the centre of M60 was undertaken in an attempt to detect gravitational redshift in the centre of an individual galaxy for the first time. The velocity field was summed around the galaxy's isophotes to remove the effect of rotation. Models were constructed to predict the gravitational redshift, which were then compared to the data. It was found that the shallow slope of the light profile made it impossible to detect a gravitational redshift in this case, but that the scatter of the data points suggests that a signal of a few km/s could be detected. Consideration of the models led to a better understanding of the most suitable targets for this kind of study. An analysis of the 2dF groups catalogue was made in order to attempt to determine the strength of the gravitational redshift in clusters of galaxies. A new method was developed for measuring the signal in clusters. As part of the analysis, the density distribution of the clusters was obtained. It was found that they followed an exponential profile, which scaled linearly with the size of the cluster. The gravitational redshift was used to attempt to constrain the mean cluster mass, but it was found that the errors were too large to rule out all but the largest masses with any certainty. Future studies would require either a much larger sample, or one which concentrates specifically on the most uniform, high mass clusters. Gravitational redshift offers a new approach to studying the mass distributions of galaxies and clusters that requires many fewer assumptions regarding the underlying physics than many of the current methods. Unfortunately, it also suffers from a number of potential setbacks. Recent advances in instrument technology, combined with the careful selection of suitable targets should allow gravitational redshift to become a viable tool for studying the nature and distribution of dark matter

Gravitational redshifts and the mass distributions of galaxies and clusters

This thesis studies a new method of constraining the mass distributions of elliptical galaxies and clusters of galaxies: gravitational redshift. The aim was to determine the types of astrophysical object in which gravitational redshift can be most readily detected and to attempt to observe the effect for the first time in a single object. Longslit stellar kinematics were combined with planetary nebulae kinematics to study the mass distribution of M87. Jeans modelling showed that, although the best-fit model gave too little mass (Upsilon = 5.34+/-0.34, beta = 0.71+/-0.03, M_halo = 2.64+/-0.92 x 10^12 M_sun), by adjusting the orbital anisotropy it was possible to construct a model that was consistent with both the kinematics and existing X-ray gas measurements. Longslit kinematics from the literature were used to attempt to determine the mass-to-light ratio of a sample of elliptical galaxies using gravitational redshift. Models were developed to calculate the expected gravitational redshift from the surface brightness profile. The best-fit mass-to-light ratios were found using this model and also obtained independently using the Jeans equation. The results were not statistically inconsistent with the expected H-band mass-to-light ratios predicted by stellar population models - the Jeans modelling gave a mean mass-to-light ratio of Upsilon_sigma = 1.67+/-0.10, while the gravitational redshift predicted Upsilon_v = 4.84+/-2.67. Integral field spectroscopy of the centre of M60 was undertaken in an attempt to detect gravitational redshift in the centre of an individual galaxy for the first time. The velocity field was summed around the galaxy's isophotes to remove the effect of rotation. Models were constructed to predict the gravitational redshift, which were then compared to the data. It was found that the shallow slope of the light profile made it impossible to detect a gravitational redshift in this case, but that the scatter of the data points suggests that a signal of a few km/s could be detected. Consideration of the models led to a better understanding of the most suitable targets for this kind of study. An analysis of the 2dF groups catalogue was made in order to attempt to determine the strength of the gravitational redshift in clusters of galaxies. A new method was developed for measuring the signal in clusters. As part of the analysis, the density distribution of the clusters was obtained. It was found that they followed an exponential profile, which scaled linearly with the size of the cluster. The gravitational redshift was used to attempt to constrain the mean cluster mass, but it was found that the errors were too large to rule out all but the largest masses with any certainty. Future studies would require either a much larger sample, or one which concentrates specifically on the most uniform, high mass clusters. Gravitational redshift offers a new approach to studying the mass distributions of galaxies and clusters that requires many fewer assumptions regarding the underlying physics than many of the current methods. Unfortunately, it also suffers from a number of potential setbacks. Recent advances in instrument technology, combined with the careful selection of suitable targets should allow gravitational redshift to become a viable tool for studying the nature and distribution of dark matter

The Australasian Resuscitation In Sepsis Evaluation : fluids or vasopressors in emergency department sepsis (ARISE FLUIDS), a multi-centre observational study describing current practice in Australia and New Zealand

Objectives: To describe haemodynamic resuscitation practices in ED patients with suspected sepsis and hypotension. Methods: This was a prospective, multicentre, observational study conducted in 70 hospitals in Australia and New Zealand between September 2018 and January 2019. Consecutive adults presenting to the ED during a 30-day period at each site, with suspected sepsis and hypotension (systolic blood pressure <100 mmHg) despite at least 1000 mL fluid resuscitation, were eligible. Data included baseline demographics, clinical and laboratory variables and intravenous fluid volume administered, vasopressor administration at baseline and 6- and 24-h post-enrolment, time to antimicrobial administration, intensive care admission, organ support and in-hospital mortality. Results: A total of 4477 patients were screened and 591 were included with a mean (standard deviation) age of 62 (19) years, Acute Physiology and Chronic Health Evaluation II score 15.2 (6.6) and a median (interquartile range) systolic blood pressure of 94 mmHg (87–100). Median time to first intravenous antimicrobials was 77 min (42–148). A vasopressor infusion was commenced within 24 h in 177 (30.2%) patients, with noradrenaline the most frequently used (n = 138, 78%). A median of 2000 mL (1500–3000) of intravenous fluids was administered prior to commencing vasopressors. The total volume of fluid administered from pre-enrolment to 24 h was 4200 mL (3000–5661), with a range from 1000 to 12 200 mL. Two hundred and eighteen patients (37.1%) were admitted to an intensive care unit. Overall in-hospital mortality was 6.2% (95% confidence interval 4.4–8.5%). Conclusion: Current resuscitation practice in patients with sepsis and hypotension varies widely and occupies the spectrum between a restricted volume/earlier vasopressor and liberal fluid/later vasopressor strategy

Gravitational redshifts and the mass distributions of galaxies and clusters

This thesis studies a new method of constraining the mass distributions of elliptical galaxies and clusters of galaxies: gravitational redshift. The aim was to determine the types of astrophysical object in which gravitational redshift can be most readily detected and to attempt to observe the effect for the first time in a single object. Longslit stellar kinematics were combined with planetary nebulae kinematics to study the mass distribution of M87. Jeans modelling showed that, although the best-fit model gave too little mass (Upsilon = 5.34+/-0.34, beta = 0.71+/-0.03, M_halo = 2.64+/-0.92 x 10^12 M_sun), by adjusting the orbital anisotropy it was possible to construct a model that was consistent with both the kinematics and existing X-ray gas measurements. Longslit kinematics from the literature were used to attempt to determine the mass-to-light ratio of a sample of elliptical galaxies using gravitational redshift. Models were developed to calculate the expected gravitational redshift from the surface brightness profile. The best-fit mass-to-light ratios were found using this model and also obtained independently using the Jeans equation. The results were not statistically inconsistent with the expected H-band mass-to-light ratios predicted by stellar population models - the Jeans modelling gave a mean mass-to-light ratio of Upsilon_sigma = 1.67+/-0.10, while the gravitational redshift predicted Upsilon_v = 4.84+/-2.67. Integral field spectroscopy of the centre of M60 was undertaken in an attempt to detect gravitational redshift in the centre of an individual galaxy for the first time. The velocity field was summed around the galaxy's isophotes to remove the effect of rotation. Models were constructed to predict the gravitational redshift, which were then compared to the data. It was found that the shallow slope of the light profile made it impossible to detect a gravitational redshift in this case, but that the scatter of the data points suggests that a signal of a few km/s could be detected. Consideration of the models led to a better understanding of the most suitable targets for this kind of study. An analysis of the 2dF groups catalogue was made in order to attempt to determine the strength of the gravitational redshift in clusters of galaxies. A new method was developed for measuring the signal in clusters. As part of the analysis, the density distribution of the clusters was obtained. It was found that they followed an exponential profile, which scaled linearly with the size of the cluster. The gravitational redshift was used to attempt to constrain the mean cluster mass, but it was found that the errors were too large to rule out all but the largest masses with any certainty. Future studies would require either a much larger sample, or one which concentrates specifically on the most uniform, high mass clusters. Gravitational redshift offers a new approach to studying the mass distributions of galaxies and clusters that requires many fewer assumptions regarding the underlying physics than many of the current methods. Unfortunately, it also suffers from a number of potential setbacks. Recent advances in instrument technology, combined with the careful selection of suitable targets should allow gravitational redshift to become a viable tool for studying the nature and distribution of dark matter.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Concentrations of perfluoroalkyl substances in human milk from Ireland: Implications for adult and nursing infant exposure

Concentrations of 10 perfluoroalkyl substances (PFASs) were measured in 16 pools of human milk from Ireland. Only four PFASs were detected (PFOA, PFNA, PFHxS and PFOS), with concentrations dominated by PFOA which was detected in all samples at a median of 0.10 ng/mL. Concentrations and the relative abundance of PFASs in human milk from Ireland are within the range reported for other countries. Estimated exposures for nursing infants to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) do not suggest a health concern. A one compartment pharmacokinetic model was used to predict the intakes of PFOS and PFOA required to support the observed concentrations in human milk. This suggests current adult exposure in Ireland to PFOS is below the provisional tolerable weekly intake (TWI) proposed by EFSA. In contrast, the model predicts that the maximum concentration detected in human milk in this study, implies a level of adult exposure that would exceed EFSA s provisional TWI for PFOA. As exposure of the Irish population to PFASs via drinking water, indoor air and dust is well-characterised, current understanding suggests that the major contributor to overall exposure of the Irish population is via the diet and/or less well-studied pathways like dermal uptake from PFAS-containing fabrics and cosmetics.This project (ELEVATE, reference 2015-HW-MS-4) is funded under the EPA Research Programme 2014–2020. The EPA Research Programme is a Government of Ireland initiative funded by the Department of Communications, Climate Action and Environment. We gratefully acknowledge all the mothers who donated milk samples for this study.2021-12-2

Concentrations of perfluoroalkyl substances in human milk from Ireland: Implications for adult and nursing infant exposure

Concentrations of 10 perfluoroalkyl substances (PFASs) were measured in 16 pools of human milk from Ireland. Only four PFASs were detected (PFOA, PFNA, PFHxS and PFOS), with concentrations dominated by PFOA which was detected in all samples at a median of 0.10 ng/mL. Concentrations and the relative abundance of PFASs in human milk from Ireland are within the range reported for other countries. Estimated exposures for nursing infants to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) do not suggest a health concern. A one compartment pharmacokinetic model was used to predict the intakes of PFOS and PFOA required to support the observed concentrations in human milk. This suggests current adult exposure in Ireland to PFOS is below the provisional tolerable weekly intake (TWI) proposed by EFSA. In contrast, the model predicts that the maximum concentration detected in human milk in this study, implies a level of adult exposure that would exceed EFSA s provisional TWI for PFOA. As exposure of the Irish population to PFASs via drinking water, indoor air and dust is well-characterised, current understanding suggests that the major contributor to overall exposure of the Irish population is via the diet and/or less well-studied pathways like dermal uptake from PFAS-containing fabrics and cosmetics.This project (ELEVATE, reference 2015-HW-MS-4) is funded under the EPA Research Programme 2014–2020. The EPA Research Programme is a Government of Ireland initiative funded by the Department of Communications, Climate Action and Environment. We gratefully acknowledge all the mothers who donated milk samples for this study.peer-reviewed2021-12-2