Quasars – some of the brightest known objects in the universe. Although they were originally considered nearby stars, today we know that they are galaxies with an extremely bright source at the center – a supermassive black hole that is accumulating so much matter that some of it turns into energy, and into which all of the energy is converted. The galaxy owes its exceptional brightness. Thanks to this brightness, we can notice quasars very far away from us. This allows attempts to establish universal relationships that can later be used to measure various cosmological parameters, i.e. parameters that help astronomers, among other things, determine the geometry of the universe. But before this becomes possible, such a relationship must be calibrated, that is, exactly what can affect it must be known and determined.
For this purpose, the team, which included astronomers from the Astronomical Observatory of the Jagiellonian University in Krakow, studied the so-called cover factor. Coverage factor, Coalition forces). This is the parameter that determines the amount of central source It’s full Visible and covered by a dusty rim – a donut-shaped structure surrounding the black hole inside the quasar. This is presented graphically in the illustration above. There are different ways to calculate the occultation factor, but given the data available for the sample, the team decided to use the ratio of two luminances: infrared (which consists of radiation from the dusty torus) and optical (i.e. radiation from the immediate surroundings of the supermassive black hole).
The researchers wanted to check whether the percentage of blockage depends on this Redshift. This simply means whether distant objects at high redshift have a different obscuring factor than nearby objects at low redshift. It was found that in the case of objects with similar massive masses (leading to the general physical similarity of quasars), there are no statistically significant differences between the parameter values of nearby and distant quasars.
The team also examined the relationship between infrared radiation and visual brightness. For the set of objects with the best observations, this relationship can be well determined. Based on Figure 2, we see that nearby objects (yellow dots) have a lower brightness than distant objects (red dots). We were also able to fit a single line that nicely describes both groups of quasars.
In Illustration (2): The relationship between infrared brightness (vertical axis) and optical brightness (horizontal axis). Yellow dots are objects closer to the quasars (Low-z, data from the Spitzer telescope), and red diamonds are objects farther away. A regression coefficient of approximately 0.9 indicates a very close relationship between both brightnesses. This gives hope for using relationships for objects located at further redshifts. Using the Risalitti & Lusso 2015 methodology, it will be possible to use it in cosmological applications. Source: Team publications.
However, the considerations so far raise another question, the answer to which Krakow scholars will only now seek. What types of contamination (data contamination) might affect the discovered relationship? Based on the analysis already performed, the team suspects that one important factor is the surroundings of the supermassive black hole – the so-called supermassive black hole. Polar dust found near the poles. In addition, the host galaxy may provide stellar input, or cold dust in the galaxy may affect the infrared emission.
Prepared by: Elbieta Kolegoska, Mateusz Raowski
Source: Organization of African Unity in Krakow
In illustration: The quasar in an artistic vision. The bright source at the center is a supermassive black hole, from whose poles emanate extremely parallel streams of energy. The extensive structure visible around the black hole is a dust torus, the properties of which were examined using the occultation parameter in the work discussed. Image source: ISO.
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