![]() ![]() As part of the analysis, the density distribution of the clusters was obtained. A new method was developed for measuring the signal in clusters. Consideration of the models led to a better understanding of the most suitable targets for this kind of study.Īn analysis of the 2dF groups catalogue was made in order to attempt to determine the strength of the gravitational redshift in clusters of galaxies. 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. Models were constructed to predict the gravitational redshift, which were then compared to the data. The velocity field was summed around the galaxy's isophotes to remove the effect of rotation. 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 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. The best-fit mass-to-light ratios were found using this model and also obtained independently using the Jeans equation. Models were developed to calculate the expected gravitational redshift from the surface brightness profile. 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. 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 stellar kinematics were combined with planetary nebulae kinematics to study the mass distribution of M87. 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. This thesis studies a new method of constraining the mass distributions of elliptical galaxies and clusters of galaxies: gravitational redshift. Improving the redshift measurement is particularly important because this test has been the least accurate among the experiments that are required to support curved spacetime theories (1).- Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader Our result supports the view that gravity is a manifestation of space-time curvature, an underlying principle of general relativity that has come under scrutiny in connection with the search for a theory of quantum gravity (11). Here we show that laboratory experiments based on quantum interference of atoms (9,10) enable a much more precise measurement, yielding an accuracy of 7 X. ![]() The gravitational redshift has been measured using clocks on a tower (6), an aircraft (7) and a rocket (8), currently reaching an accuracy of 7 X. This effect, known as gravitational redshift, is important to the operation of the global positioning system (2), timekeeping (3,4) and future experiments with ultra-precise, space-based clocks (5) (such as searches for variations in fundamental constants). Abstract : One of the central predictions of metric theories of gravity, such as general relativity, is that a clock in a gravitational potential U will run more slowly by a factor of 1 + U/, where c is the velocity of light, as compared to a similar clock outside the potential (1). ![]()
0 Comments
Leave a Reply. |