Project: ERC Synergy Grant UniverScale "Sub-percent calibration of the extragalactic distance scale in the era of big surveys"
After the detection of the accelerated expansion of the Universe, the main goal of astronomers and physicists has become to explain the nature of dark energy responsible for this phenomenon. The current empirical measurements of the H0 parameter differ significantly from the values resulting from the measurements of the microwave background radiation and the LambdaCDM model. The aim of our project is to calibrate two measurement methods that will allow for precise determination of distances with an accuracy of better than 1% to distances a thousand times further than the range of parallax measurements by the Gaia satellite. This will allow H0 values to be determined based on the Cepheids and SN Ia with an accuracy of just 1%. Independently, an innovative method based on the study of quasar variability will allow testing these results and determining the expansion rate of the Universe at even greater distances and imposing restrictions on other cosmological parameters.
Project: Constraints on dark energy properties based on observations of active galaxies
The aim of the project is to implement a completely new method for determining the rate of expansion of the Universe, and therefore the properties of dark energy. The method is based on the use of active galaxies, including to a large extent the brightest active galaxies - quasars. We will consider several variants of this general method. We expect that after fine-tuning the details and collecting enough measurements, some of them should give more precise results than the assessment of the expansion of the Universe based on the study of Type Ia Supernovae. In this way, we plan not only to confirm the accelerated expansion of the Universe, but to measure the effect precisely enough to see if this accelerated expansion will continue indefinitely in the future, and the Universe will become increasingly empty. Our basic method is based on measuring the delay quasar emission lines relative to the continuum, which allows a direct measurement of the size of the emitting region, and this size, as we have shown in our simple and novel model of its formation, depends almost entirely on the quasar's absolute brightness. Knowing the absolute magnitude and - which is easy to measure - the observed brightness and redshift, we can place each of the objects on the Hubble diagram. Having a model of the line formation area, we will work out in detail the relationship between the area size and brightness. We will then combine all available observational data to use as many objects with different redshift values as possible to see the expansion history of the universe. As observation data, we will use our own data from the 11-meter SALT (Southern African Large Telescope) and data from our collaborators in China, and delays measured and published by other groups of observers. Two other variants of the methods are more difficult, based on the shape of the emission lines alone , and here observational data exist, but modeling is much more complex and it may not be possible to achieve adequate accuracy. The last option is to use photometric sky monitoring as part of the planned world's largest sky survey, with an emphasis on object variability - each patch of sky will be observed multiple times, in six different colors, for a total of 1,000 times over 10 years. This survey (Large Synoptic Survey Telescope - LSST) will begin operations in 2020 and will result in the detection of 10 million quasars. The use of these observations will require the selection of optimal methods. Their work will be part of this project. Dark energy is a great challenge for modern astronomy and physics. The discovery of deviations of its properties from the predictions related to the cosmological constant is of key importance for a deeper interpretation of this phenomenon. Our quasar-based method is similar in character to the constraints of Supernova Ia stars, but covers a wide range of redshift values much better. The method has not yet been used in cosmology, and is also based on an innovative model of the formation of emission lines in quasars, which gives us the opportunity to use its full potential.
More about the project: Constraints on the properties of dark energy based on observations of active galaxies
Project: Main Sequence of Quasars
In astronomy, the time of Big Data and the discoveries made thanks to it has come. New observations are constantly yielding terabytes of data, and the catalogs in preparation already contain millions of objects. In this situation, the most important task becomes to organize the huge stream of incoming information, which should enable a real, deep understanding of what the telescopes are recording. This problem also applies to the study of quasars. Currently, there are more than 1 million identified quasars in catalogs, of which about 200,000 have been studied. These numbers are constantly increasing. Quasars, like stars, vary in brightness. The reason is the different masses of their central black holes, as well as different distances from us. However, stars differ not only in brightness and distance from Earth, but also in color. It was found that in a graph with color indicators on the axes (the so-called color-color diagram), most stars lie on a relatively narrow line. It was called the main sequence. It turned out later that the temperature of the star's atmosphere determines its position on the main sequence. Quasars also have different colors. Statistical analysis of these objects shows that also in their case there is a clear trend, which is now called the main sequence of quasars. The quasar main sequence, however, is not as narrow as the stellar main sequence. Quasars are much more complex objects than stars. This is due to the lack of spherical symmetry: material falling into the black hole forms an accretion disk around it, the temperature of which increases towards the center. For this reason, it is difficult to determine the cause of the observed trend. It seems that the key parameters may be the angle of inclination of the axis of symmetry of the accretion disk to the direction of view and the ratio of the rate of accretion of matter into the black hole to the mass of the black hole. We have our own ideas on this. We believe that the solution to the problem will turn out to be similar to the explanation of the essence of the stellar main sequence. The main goal of the project is to verify our hypothesis. We're going to do this in two different ways. Using computers, we will prepare theoretical models of quasars with a very wide range of parameters. We will also collect available observational data for as many quasars as possible. By comparing theoretical models with observations, we will be able to determine whether the parameter we suspect is indeed the key factor that determines the observed properties of the main sequence of quasars.
More about the project: Main Sequence of Quasars
Multiwavelength analysis and modeling of OJ 287 during 2017–2020
PERSISTENT EMISSION AND BURSTS FROM AQUILA X-1 OBSERVED BY EINSTEIN
