Constraints on the dark energy based on observations of active galaxies

The aim of the project is to develop and to apply a totally new method to determine the expansion rate of the Universe, and thus to determine the properties of the dark energy. The method is based on active galaxies, including the most luminous ones – quasars. We will consider several variants of this general method. We expect that after refining the details and collecting the requested number of measurements some of the variants of the method to be considered in this project should give more accurate results than the estimate of the expansion rate of the Universe based on Supernovae type Ia. In this way we plan not just confirm the accelerated expansion of the Universe but to measure it accurately enough to see if this accelerated expansion will continue forever, with the Universe becoming more and more empty.

Our main method is based on the determination of the delay between the quasar emission lines and the quasar continuum, which allows to measure directly the size of the emitting region as a light travel time. This size, as we showed in our innovative model of the formation mechanism of this region, depends almost exclusively on the absolute luminosity of a quasar. Knowing the absolute luminosity and measuring – which is simple – the observed luminosity and the redshift we can locate every quasar in a Hubble diagram. Having the model of the region we will work out in detail small but necessary corrections to minimize the systematic errors. Next we will combine all available observational data in order to use the largest possible number of sources with a broad range of redshifts. This will allow us to see the history of the Universe expansion. For the observational data we will use our own data from 11-meter Southern African Large Telescope (SALT), the data from our Chinese collaborators, and delay measurements measured and published by other groups. Two other variants of the method are more difficult to use as they are based just on the line profiles. There are plentiful data available in this respect, but the modeling is more complex and it will be much more difficult to achieve the requested accuracy. The last option is the use of photometric monitoring of the sky by the Large Synoptic Survey Telescope (LSST; to be operational from 2020). This survey will be the largest sky survey ever done, in addition with particular aim to see the variability of objects so each part of the sky will be observed in six color bands, and it will be visited 1000 times during the 10 years. The survey which will bring the detection of 10 millions of quasars. The usage of these data for cosmology will again require the development of the optimum methods. Working out these methods will be also a part of this project.