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Research Interests

Observational cosmology

New project: Constraints on the properties of the dark energy from active galactic nuclei

The aim of the project is to implement a new method to determine the expansion rate of the Universe, and in this way to constrain the properties of the dark energy. The method is based on active galaxies, mostly on the brighest of them - quasars. We will consider a few variants of the general method. We expect that with the method refinement and after colleting enough of observational data some of these methods should give more precise and less biased estimates of the Universe expansion than Supernovae Ia. We plan not just to confirm the accelerated expansion of the Universe but to measure it precisely enough to know whether this accelerated expansion willl continue forever, with the Universe becoming more and more empty.

Our basic method is based on determination of the time delay between the emission lines and the continuum, which allows directly to measure the size of the emitting region. This size, as we have shown in our simple absolutely new model of the formation of the broad line region, depends almost exclusively on the absolute luminosity of a given quasar. Knowing this absolute luminosity and measuring the observed luminossity and the quasar redshift we can locate each quasar on the Hubble diagram. We will construct now more precise model of the region formation and its connection with the absolute luminosity. Next we will combine all available time delay measurements done at various redshifts to see the history of the expansion of the Universe. As the data, we will use our own observations from 11-m telescope SALT (Southern African Large Telescope), the measurements done by our Chinese collaborators and measurements published by other groups. Two other variants of the mthod are more difficult, based just on the shapes of the emission lines. The data required by these methods (single spectra) are easily availbale but modelling must be far more precise and could be too difficult. Finally, there is also a fantastic oppportunity to use photometric monitoring from the largest planned all sky survey which will start soon and will be operational for 10 yeras. This survey done by LSST (Large Synoptic Survey Telescope) will bring detection of 10 milions of quasars. However, practical use of these data will require a lot of difficult optimalizations, and working out these methods will be a part of the project.

Dark energy is a real challenge for astronomy and physics. Detections of any departures from the cosmological constant model of this accelerated expansion wil be crucial for interpretation of this phenomenon. Our method is basically similar to method based on Supernovae Ia, but it covers broader range of redshift. The method was not yet used for cosmology, and it is based on our model of the formation of the broad line region which offers also an opportunity to test the model itself.

More about the project: Constraints on the dark energy properties from observations of active galaxies

Project: Quasar main sequence

Astronomy enters the period of Big Data and Data-Driven Discovery. Data bases increase every days with terabytes of new observations, and the catalogs start to contain milions of objects. Thus the most important thing is to see certain order in these enormous data stream, and next we should gain - from this order - a real, deeper understanding of what we see. We face the same problem in quasar research. Catalogs contain 200 000 well studies quasars, over 1 000 000 of quasars are identified, and the numbers are growing. Different quasars have of course different luminosities, which is easy to understand since they differ with respect to the mass of the central black hole and the distance from us. However, stars differ between themselves not only with respect to the brightness and the distance, but they have different colors.  And then the discovery came that stars form a stream on the color-color diagram which was later named stellar main sequence. Finally, it was explained that the location of a star on the stellar main sequence is determined by the temperature of the stellar atmosphere. Quasars also have their colors, and the corresponding classification also showed a pattern, named now Quasar Main Sequence although this sequence is not as narrow as the stellar main sequence. Quasars are much more complex than stars due to the lack of spherical symmetry - material flowing onto the black hole forms an accretion disk around the central black hole, and this disk is hotter closer to the black hole and cooler further out. Therefore, it is difficult to establish what is responsible for the observed trend. The first ideas for a key parameter were the inclination of the symmetry axis with respect to the observer, and the ratio of the mass flowing toward the black hole to the black hole mass. We have our own idea and we think  that the answer is actually quite similar as in the case of stars. The aim of the project is to prove this hypothesis. We will do it through two different actions. We will calculate theoretically the quasar models for a broad range of parameters. We will also collect available observations for numerous quasars with the aim to check whether the parameter which, we think, is the key parameter, actually well describes the observed Quasar Main Sequence. 

More about the project: Quasar Main Sequence

Last 3 Publications - ORCID

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2021

1. (10/2021) Bo-Wei Jiang; Paola Marziani; Đorđe Savić; Elena Shablovinskaya; Luka Č Popović; Victor L Afanasiev; Bożena Czerny; et. al; Jian-Min Wang; Ascensión del Olmo; Mauro D’Onofrio; Marzena Śniegowska; Paola Mazzei; Swayamtrupta Panda;
Linear spectropolarimetric analysis of fairall 9 with VLT/FORS2
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 10.1093/mnras/stab2273, , , 2021-11-01  🥇

2. (9/2021) Mohammad-Hassan Naddaf; Bożena Czerny; Ryszard Szczerba;
The Picture of BLR in 2.5D FRADO: Dynamics and Geometry
THE ASTROPHYSICAL JOURNAL, 10.3847/1538-4357/ac139d, , , 2021-10-01  🥈

3. (8/2021) Mary Loli Martínez-Aldama; Swayamtrupta Panda; Bożena Czerny; Murilo Marinello; Paola Marziani; Deborah Dultzin;
The CaFe Project: Optical Fe II and Near-infrared Ca II Triplet Emission in Active Galaxies. II. The Driver(s) of the Ca II and Fe II and Its Potential Use as a Chemical Clock
THE ASTROPHYSICAL JOURNAL, 10.3847/1538-4357/ac03b6, , , 2021-09-01  🥉

Full Publications List

Last 3 Publications - PBN

Get all publications:

2021

Full Publications List

Seminars

Date Seminar
15
April
2020
Towards 3-D picture of active galactic nuclei
Prof. Bożena Czerny
(CFT PAN)
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30
October
2019
The Nobel Prize in Physics 2019
Prof. Bożena Czerny
(CFT PAN)
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25
April
2018
Accelerated expansion of the Universe
Prof. Bożena Czerny
(CFT PAN)
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25
November
2015
Czas?
Prof. Bożena Czerny
(CFT PAN)
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15
October
2014
Quasars as dark energy probes
Prof. Bożena Czerny
(CFT PAN)
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Date Seminar
Date Seminar
No future seminars!
Date Seminar