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| Paper: |
Time Dilation in Quasar Light Curves |
| Volume: |
413, 2nd Crisis in Cosmology Conference, CCC-2 |
| Page: |
24 |
| Authors: |
Hawkins, M. R. S. |
| Abstract: |
In this paper we make a new attempt to measure time dilation in quasar light curves, using the better data which are now available, extending to longer and shorter timescales. In order to detect the effects of time dilation in quasar light curves, data from two monitoring programmes are used to construct Fourier power spectra covering timescales from 50 days to 25 years. Characteristic timescales are measured from these power spectra for high and low redshift samples to look for changes in timescale with redshift. If time dilation affects quasar light curves, which will be the case if the variations are intrinsic to the quasars, then in the observer's frame one would expect to measure a longer timescale in the high redshift sample than in the low redshift one. In fact, the two timescales are not significantly different. In the quasar rest frame, where the light curves have been corrected for time dilation, the effect is to reduce the timescale of variation at higher redshift. Attempts are made to explain this in terms of a growth in black hole mass with time, but no consistent picture is found to fit the observations. An alternative hypothesis is that the observed variations are dominated by the effects of gravitational microlensing. In this case, any effect of time dilation is expected to be small, and the timescales of high and low redshift samples should not differ significantly. This is consistent with the observations, and implies a population of compact lensing bodies sufficient to make up the dark matter. The lenses are most plausibly primordial black holes, with a characteristic mass of around 0.4Mʘ. The main result of this paper is that timescale measures of a large sample of quasar light curves do not show the effects of time dilation. However, the measures can be explained if the observed quasar variations are dominated by the effects of microlensing. This implies a population of compact lensing bodies sufficient to account for the dark matter. |
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