S. Parnovsky - Academia.edu (original) (raw)

Papers by S. Parnovsky

Research paper thumbnail of Catastrophic dark matter particle capture

Physical Review D

In this paper we describe a new idea which may be relevant to the formation of galaxies via the i... more In this paper we describe a new idea which may be relevant to the formation of galaxies via the infall of baryonic matter (BM) and dark matter (DM) onto a preexisting overdensity. While BM can under certain circumstances be captured by thermal processes, DM particles fly through a static overdensity without being captured. We propose a simple model for DM capture: if during the passage through it, the mass of the overdensity increases, then slow DM particles are captured by it, further increasing its mass, while faster particles slow down, transferring part of their energy to the galaxy. We estimate the minimum initial velocity of a particle required for a passage without capture through the center of the galaxy and derive a nonlinear equation describing the rate of galaxy mass increase. An analysis carried out using the ideas of catastrophes theory shows that if the increase in the mass of baryonic matter exceeds a certain threshold value, this can lead to a very intensive capture of dark matter. We speculate that this process may be associated on the one hand with the accretion of matter during the early stages of galaxy formation and, on the other hand, also later with the merger of galaxies. For the studied process to take place, the density of intergalactic DM must exceed some threshold value. Then the rate of increase in the mass of DM can be much higher than the one of baryonic matter. The capture sharply decreases after the DM density drops below the threshold value, e.g., due to the expansion of the Universe.

Research paper thumbnail of N-body simulations: advantages and problems

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy

The N-body simulations method is widely used in astrophysics and cosmology. The article briefly l... more The N-body simulations method is widely used in astrophysics and cosmology. The article briefly lists its advantages, disadvantages and possible errors. It is concluded that the results of computer simulation not only cannot replace the data of astronomical observations, but also are not a sufficient reason to reject new hypotheses that do not have other drawbacks, other than the discrepancy between their conclusions and the results of N-body simulations.

Research paper thumbnail of Compact galaxies with active star formation: statistical properties of subsamples with the Hβ line emission flow threshold

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy

We study the dependence of the luminosity of starburst galaxy on the young age (< 10 Myr) of s... more We study the dependence of the luminosity of starburst galaxy on the young age (< 10 Myr) of star formation burst and metallicity. We also study the luminosity function (LF) for different subsamples of starburst galaxies. These subsamples with different threshold values of the Hβ emission line fluxes were formed from a sample of 14,000 local compact galaxies with active star formation. We obtain relations for a temporal evolution of luminosity-to-stellar mass of young stellar population ratio on the starburst age and metallicity. Luminosity functions for subsamples of galaxies with Hβ fluxes exceeding a certain threshold value are shown to differ from Schechter’s LF at the high luminosity end. They are adequately described by a log-normal function with parameters determined by the maximum likelihood method. The results confirm and complement the conclusions made in previous studies of the starburst galaxy samples.

Research paper thumbnail of Reply to Comment on ‘The egg steamer paradox’

Research paper thumbnail of Multi-wave luminosity functions of starburst galaxies

Bulletin of Taras Shevchenko National University of Kyiv Astronomy, Dec 1, 2015

Research paper thumbnail of Emission of Compact Starburst Galaxies in Radio Continuum at 1.4 GHz

Bulletin of Taras Shevchenko National University of Kyiv Astronomy, Dec 1, 2014

Research paper thumbnail of Vacuum solutions of Einstein equations that depend on one coordinate

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, 2020

In the famous textbook written by Landau and Lifshitz all the vacuum metrics of the general theor... more In the famous textbook written by Landau and Lifshitz all the vacuum metrics of the general theory of relativity are derived, which depend on one coordinate in the absence of a cosmological constant. Unfortunately, when considering these solutions the authors missed some of the possible solutions discussed in this article. An exact solution is demonstrated, which is absent in the book by Landau and Lifshitz. It describes space-time with a gravitational wave of zero frequency. It is shown that there are no other solutions of this type than listed above and Minkowski’s metrics. The list of vacuum metrics that depend on one coordinate is not complete without solution provided in this paper.

Research paper thumbnail of The egg steamer paradox

Physics Education, 2021

Why do we need to pour less water in an egg steamer to prepare more eggs to the same degree of ‘d... more Why do we need to pour less water in an egg steamer to prepare more eggs to the same degree of ‘doneness’? We discuss the physical processes at work in the electric egg steamer and resolve this seeming paradox. We demonstrate that the main heat transfer mechanism from steam to egg is due to latent heat through condensation. This not only explains the paradox, but also allows us to estimate the amount of water reduction. Comparing the preparation time to the one for traditional boiling, we estimate the eggshell temperature during steaming. We also describe the device design and provide further theoretical estimates and experimental kitchen measurement data for this appealing kitchen experiment that can be easily accomplished at home.

Research paper thumbnail of Dependence of the Ratio of Luminosity to Mass of Young Stellar Population on their Metallicity and Star Burst Age for Luminous Compact Galaxies

Research paper thumbnail of Mathematical problems associated with errors in estimating distances to galaxies

I generate many mock samples for applying the Monte Carlo method in order to estimate the bias of... more I generate many mock samples for applying the Monte Carlo method in order to estimate the bias of the Hubble constant because of the use of estimates of distances to galaxies determined from statistical dependences. I add errors to the original sample generated according to the Hubble law. In doing so, I use two possible options for generating errors in distance, having a constant relative error. Both are practical, but there are some math problems with them. I discuss their effect on the properties of the mock sample. The application of the standard least squares method is discussed and shown that it leads to an underestimation of the slope in the Hubble law. A formula is derived for calculating this slope using the maximum likelihood method and it is shown that it is applicable only for one of the variants of the sample noising. All estimates were obtained theoretically, without using the results of mock samples processing, which are described in a separate paper.

Research paper thumbnail of Spectral index in the radio continuum 140 MHz – 1.4 GHz emission for compact star-forming galaxies

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy

The sample of compact star-forming galaxies (CSFGs) has been identified with sources in the catal... more The sample of compact star-forming galaxies (CSFGs) has been identified with sources in the catalogues of radio sources. It includes only galaxies with active star formation without objects with spectral signs of active galactic nuclei. For CSFGs with known flux densities in radiocontinuum at frequencies of 1.4 GHz from the FIRST or the NVSS and in the range of 120–168 MHz from the LOFAR, as well as in hydrogen emission lines from the SDSS, the spectral index and the spectral index of non-thermal emission component for these frequencies have been estimated. Note that obtaining the spectral index of nonthermal emission component is a much more difficult task than determining the spectral index of total emission. It is shown that the approximation by the model dependence using the least squares method can lead to unreliable estimates of the fraction of thermal (free-free) emission. Therefore, the flux densities of the thermal component are derived from the extinction- and aperture cor...

Research paper thumbnail of An impact of nearby attractors on the collective peculiar motion of galaxies

Отримано наближені формули для часової затримки критичних зображень точкового джерела, що знаходи... more Отримано наближені формули для часової затримки критичних зображень точкового джерела, що знаходиться поблизу каспової точки каустики. Ми обговорюємо формули нульового, першого і другого порядків за степенями параметра, який задає близькість джерела до каустики. Ці формули пов'язують час затримки з характеристиками лінзового потенціалу. Формула нульового наближення була отримана в роботі Конгдона, Кітона і Нордгрена (MNRAS, 2008). Для загального потенціалу ми знайшли до неї поправку першого порядку. У випадку потенціалу, симетричного відносно осі каспу, ця поправка тотожно дорівнює нулю. Для цього випадку ми отримали поправку другого порядку. Знайдені співвідношення проілюстровані на простому модельному прикладі.

Research paper thumbnail of Large-scale galactic motions: test of the Dipole Repeller model with the RFGC galaxies data

Research paper thumbnail of Metric of the homogeneous anisotropic model of Bianchi type I with an arbitrary equation of state

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, 2016

Н а д і й ш л а д о р е д к о л е г і ї 0 1. 0 2. 1 6 Р. Гнатык, асп., В. Жданов, д-р физ.-мат. н... more Н а д і й ш л а д о р е д к о л е г і ї 0 1. 0 2. 1 6 Р. Гнатык, асп., В. Жданов, д-р физ.-мат. наук, проф. КНУ имени Тараса Шевченко, Киев ПОИСК ГАЛАКТИЧЕСКИХ ИСТОЧНИКОВ ТРИПЛЕТА КОСМИЧЕСКИХ ЛУЧЕЙ С ЭНЕРГИЯМИ СВЫШЕ 10 20 эВ Среди зарегистрированных космических лучей предельно высоких энергий (КЛПВЭ, E > 10 20 эВ) выделяется триплет событий в круге радиуса 4 0 в области Галактического центра. С применением метода обратного рассчета траекторий КЛПВЭ в магнитном поле Галактики показано, что потенциальными Галактическими источниками триплета могут быть микроквазары SS433, GRS1915+105, магнетар SGR1900+14 и шаровое звездное скопление NGC6760.

Research paper thumbnail of Luminous compact galaxies: approximations of luminosity functions by log–normal distribution and Sanders function

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, 2016

Отриманий попередній каталог положень КМАС2.0 містить 1 млн. 750 тис. зірок, розповсюджує опорну ... more Отриманий попередній каталог положень КМАС2.0 містить 1 млн. 750 тис. зірок, розповсюджує опорну систему Tycho-Hipparcos до граничної зоряної величини МАК V = 17 mag і забезпечує середню щільність біля 1400 зірок на квадратний градус, що значно більше ніж 1-5 зірок Tycho2.

Research paper thumbnail of Initial luminosity functions of starburst galaxies

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, 2016

Н а д і й ш л а д о р е д к о л е г і ї 2 7. 0 4. 1 6

Research paper thumbnail of Correction of the orbital mass of double galaxies estimation

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, 2017

We obtain a more accurate statistical estimation of the mass of double galaxies moving in circula... more We obtain a more accurate statistical estimation of the mass of double galaxies moving in circular orbits, including confidence intervals for different confidence levels.

Research paper thumbnail of Bias of the Hubble constant value caused by errors in galactic distance indicators

The bias in the determination of the Hubble parameter and the Hubble constant in the modern Unive... more The bias in the determination of the Hubble parameter and the Hubble constant in the modern Universe is discussed. It could appear due to statistical processing of data on galaxies redshifts and estimated distances based on some statistical relations with limited accuracy. This causes a number of effects leading to either underestimation or overestimation of the Hubble parameter when using any methods of statistical processing, primarily the least squares method (LSM). The value of the Hubble constant is underestimated when processing a whole sample; when the sample is constrained by distance, especially when constrained from above, it is significantly overestimated due to data selection. The bias significantly exceeds the values of the error the Hubble constant calculated by the LSM formulae. These effects are demonstrated both analytically and using Monte Carlo simulations, which introduce deviations in both velocities and estimated distances to the original dataset described by t...

Research paper thumbnail of Estimation of the combination of some cosmological parameters from large-scale motion of RFGC-galaxies

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, 2015

Построены автокорреляционные функции легких кривых микролинзирования модели удаленного источника ... more Построены автокорреляционные функции легких кривых микролинзирования модели удаленного источника с помощью стохастической системы точечных масс (звезд) и расширенных конфигураций-предполагаемые темной материи (DM) сгустки. Изолированные DM сгустки считаются суперпозициями точечных масс и глыб с тем же центром. Создан функции автокорреляции для нескольких наборов параметров, которые характеризуют относительную концентрацию точки и протяженных масс внешнего сдвига. Ключевые слова: внегалактическая гравитационное линзирование, темная материя.

Research paper thumbnail of Warm dark matter and Hubble constant tensions

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy

The tensions between the values of Hubble constant obtained from the early and the late Universe ... more The tensions between the values of Hubble constant obtained from the early and the late Universe could be eliminated if we use the ΛWDM cosmological model with dark energy, baryonic matter and warm dark matter (WDM) with characteristic velocities about 16 % of the speed of light. A pressure of WDM is equal to its energy density multiplied by factor 0.009.

Research paper thumbnail of Catastrophic dark matter particle capture

Physical Review D

In this paper we describe a new idea which may be relevant to the formation of galaxies via the i... more In this paper we describe a new idea which may be relevant to the formation of galaxies via the infall of baryonic matter (BM) and dark matter (DM) onto a preexisting overdensity. While BM can under certain circumstances be captured by thermal processes, DM particles fly through a static overdensity without being captured. We propose a simple model for DM capture: if during the passage through it, the mass of the overdensity increases, then slow DM particles are captured by it, further increasing its mass, while faster particles slow down, transferring part of their energy to the galaxy. We estimate the minimum initial velocity of a particle required for a passage without capture through the center of the galaxy and derive a nonlinear equation describing the rate of galaxy mass increase. An analysis carried out using the ideas of catastrophes theory shows that if the increase in the mass of baryonic matter exceeds a certain threshold value, this can lead to a very intensive capture of dark matter. We speculate that this process may be associated on the one hand with the accretion of matter during the early stages of galaxy formation and, on the other hand, also later with the merger of galaxies. For the studied process to take place, the density of intergalactic DM must exceed some threshold value. Then the rate of increase in the mass of DM can be much higher than the one of baryonic matter. The capture sharply decreases after the DM density drops below the threshold value, e.g., due to the expansion of the Universe.

Research paper thumbnail of N-body simulations: advantages and problems

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy

The N-body simulations method is widely used in astrophysics and cosmology. The article briefly l... more The N-body simulations method is widely used in astrophysics and cosmology. The article briefly lists its advantages, disadvantages and possible errors. It is concluded that the results of computer simulation not only cannot replace the data of astronomical observations, but also are not a sufficient reason to reject new hypotheses that do not have other drawbacks, other than the discrepancy between their conclusions and the results of N-body simulations.

Research paper thumbnail of Compact galaxies with active star formation: statistical properties of subsamples with the Hβ line emission flow threshold

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy

We study the dependence of the luminosity of starburst galaxy on the young age (< 10 Myr) of s... more We study the dependence of the luminosity of starburst galaxy on the young age (< 10 Myr) of star formation burst and metallicity. We also study the luminosity function (LF) for different subsamples of starburst galaxies. These subsamples with different threshold values of the Hβ emission line fluxes were formed from a sample of 14,000 local compact galaxies with active star formation. We obtain relations for a temporal evolution of luminosity-to-stellar mass of young stellar population ratio on the starburst age and metallicity. Luminosity functions for subsamples of galaxies with Hβ fluxes exceeding a certain threshold value are shown to differ from Schechter’s LF at the high luminosity end. They are adequately described by a log-normal function with parameters determined by the maximum likelihood method. The results confirm and complement the conclusions made in previous studies of the starburst galaxy samples.

Research paper thumbnail of Reply to Comment on ‘The egg steamer paradox’

Research paper thumbnail of Multi-wave luminosity functions of starburst galaxies

Bulletin of Taras Shevchenko National University of Kyiv Astronomy, Dec 1, 2015

Research paper thumbnail of Emission of Compact Starburst Galaxies in Radio Continuum at 1.4 GHz

Bulletin of Taras Shevchenko National University of Kyiv Astronomy, Dec 1, 2014

Research paper thumbnail of Vacuum solutions of Einstein equations that depend on one coordinate

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, 2020

In the famous textbook written by Landau and Lifshitz all the vacuum metrics of the general theor... more In the famous textbook written by Landau and Lifshitz all the vacuum metrics of the general theory of relativity are derived, which depend on one coordinate in the absence of a cosmological constant. Unfortunately, when considering these solutions the authors missed some of the possible solutions discussed in this article. An exact solution is demonstrated, which is absent in the book by Landau and Lifshitz. It describes space-time with a gravitational wave of zero frequency. It is shown that there are no other solutions of this type than listed above and Minkowski’s metrics. The list of vacuum metrics that depend on one coordinate is not complete without solution provided in this paper.

Research paper thumbnail of The egg steamer paradox

Physics Education, 2021

Why do we need to pour less water in an egg steamer to prepare more eggs to the same degree of ‘d... more Why do we need to pour less water in an egg steamer to prepare more eggs to the same degree of ‘doneness’? We discuss the physical processes at work in the electric egg steamer and resolve this seeming paradox. We demonstrate that the main heat transfer mechanism from steam to egg is due to latent heat through condensation. This not only explains the paradox, but also allows us to estimate the amount of water reduction. Comparing the preparation time to the one for traditional boiling, we estimate the eggshell temperature during steaming. We also describe the device design and provide further theoretical estimates and experimental kitchen measurement data for this appealing kitchen experiment that can be easily accomplished at home.

Research paper thumbnail of Dependence of the Ratio of Luminosity to Mass of Young Stellar Population on their Metallicity and Star Burst Age for Luminous Compact Galaxies

Research paper thumbnail of Mathematical problems associated with errors in estimating distances to galaxies

I generate many mock samples for applying the Monte Carlo method in order to estimate the bias of... more I generate many mock samples for applying the Monte Carlo method in order to estimate the bias of the Hubble constant because of the use of estimates of distances to galaxies determined from statistical dependences. I add errors to the original sample generated according to the Hubble law. In doing so, I use two possible options for generating errors in distance, having a constant relative error. Both are practical, but there are some math problems with them. I discuss their effect on the properties of the mock sample. The application of the standard least squares method is discussed and shown that it leads to an underestimation of the slope in the Hubble law. A formula is derived for calculating this slope using the maximum likelihood method and it is shown that it is applicable only for one of the variants of the sample noising. All estimates were obtained theoretically, without using the results of mock samples processing, which are described in a separate paper.

Research paper thumbnail of Spectral index in the radio continuum 140 MHz – 1.4 GHz emission for compact star-forming galaxies

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy

The sample of compact star-forming galaxies (CSFGs) has been identified with sources in the catal... more The sample of compact star-forming galaxies (CSFGs) has been identified with sources in the catalogues of radio sources. It includes only galaxies with active star formation without objects with spectral signs of active galactic nuclei. For CSFGs with known flux densities in radiocontinuum at frequencies of 1.4 GHz from the FIRST or the NVSS and in the range of 120–168 MHz from the LOFAR, as well as in hydrogen emission lines from the SDSS, the spectral index and the spectral index of non-thermal emission component for these frequencies have been estimated. Note that obtaining the spectral index of nonthermal emission component is a much more difficult task than determining the spectral index of total emission. It is shown that the approximation by the model dependence using the least squares method can lead to unreliable estimates of the fraction of thermal (free-free) emission. Therefore, the flux densities of the thermal component are derived from the extinction- and aperture cor...

Research paper thumbnail of An impact of nearby attractors on the collective peculiar motion of galaxies

Отримано наближені формули для часової затримки критичних зображень точкового джерела, що знаходи... more Отримано наближені формули для часової затримки критичних зображень точкового джерела, що знаходиться поблизу каспової точки каустики. Ми обговорюємо формули нульового, першого і другого порядків за степенями параметра, який задає близькість джерела до каустики. Ці формули пов'язують час затримки з характеристиками лінзового потенціалу. Формула нульового наближення була отримана в роботі Конгдона, Кітона і Нордгрена (MNRAS, 2008). Для загального потенціалу ми знайшли до неї поправку першого порядку. У випадку потенціалу, симетричного відносно осі каспу, ця поправка тотожно дорівнює нулю. Для цього випадку ми отримали поправку другого порядку. Знайдені співвідношення проілюстровані на простому модельному прикладі.

Research paper thumbnail of Large-scale galactic motions: test of the Dipole Repeller model with the RFGC galaxies data

Research paper thumbnail of Metric of the homogeneous anisotropic model of Bianchi type I with an arbitrary equation of state

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, 2016

Н а д і й ш л а д о р е д к о л е г і ї 0 1. 0 2. 1 6 Р. Гнатык, асп., В. Жданов, д-р физ.-мат. н... more Н а д і й ш л а д о р е д к о л е г і ї 0 1. 0 2. 1 6 Р. Гнатык, асп., В. Жданов, д-р физ.-мат. наук, проф. КНУ имени Тараса Шевченко, Киев ПОИСК ГАЛАКТИЧЕСКИХ ИСТОЧНИКОВ ТРИПЛЕТА КОСМИЧЕСКИХ ЛУЧЕЙ С ЭНЕРГИЯМИ СВЫШЕ 10 20 эВ Среди зарегистрированных космических лучей предельно высоких энергий (КЛПВЭ, E > 10 20 эВ) выделяется триплет событий в круге радиуса 4 0 в области Галактического центра. С применением метода обратного рассчета траекторий КЛПВЭ в магнитном поле Галактики показано, что потенциальными Галактическими источниками триплета могут быть микроквазары SS433, GRS1915+105, магнетар SGR1900+14 и шаровое звездное скопление NGC6760.

Research paper thumbnail of Luminous compact galaxies: approximations of luminosity functions by log–normal distribution and Sanders function

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, 2016

Отриманий попередній каталог положень КМАС2.0 містить 1 млн. 750 тис. зірок, розповсюджує опорну ... more Отриманий попередній каталог положень КМАС2.0 містить 1 млн. 750 тис. зірок, розповсюджує опорну систему Tycho-Hipparcos до граничної зоряної величини МАК V = 17 mag і забезпечує середню щільність біля 1400 зірок на квадратний градус, що значно більше ніж 1-5 зірок Tycho2.

Research paper thumbnail of Initial luminosity functions of starburst galaxies

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, 2016

Н а д і й ш л а д о р е д к о л е г і ї 2 7. 0 4. 1 6

Research paper thumbnail of Correction of the orbital mass of double galaxies estimation

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, 2017

We obtain a more accurate statistical estimation of the mass of double galaxies moving in circula... more We obtain a more accurate statistical estimation of the mass of double galaxies moving in circular orbits, including confidence intervals for different confidence levels.

Research paper thumbnail of Bias of the Hubble constant value caused by errors in galactic distance indicators

The bias in the determination of the Hubble parameter and the Hubble constant in the modern Unive... more The bias in the determination of the Hubble parameter and the Hubble constant in the modern Universe is discussed. It could appear due to statistical processing of data on galaxies redshifts and estimated distances based on some statistical relations with limited accuracy. This causes a number of effects leading to either underestimation or overestimation of the Hubble parameter when using any methods of statistical processing, primarily the least squares method (LSM). The value of the Hubble constant is underestimated when processing a whole sample; when the sample is constrained by distance, especially when constrained from above, it is significantly overestimated due to data selection. The bias significantly exceeds the values of the error the Hubble constant calculated by the LSM formulae. These effects are demonstrated both analytically and using Monte Carlo simulations, which introduce deviations in both velocities and estimated distances to the original dataset described by t...

Research paper thumbnail of Estimation of the combination of some cosmological parameters from large-scale motion of RFGC-galaxies

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, 2015

Построены автокорреляционные функции легких кривых микролинзирования модели удаленного источника ... more Построены автокорреляционные функции легких кривых микролинзирования модели удаленного источника с помощью стохастической системы точечных масс (звезд) и расширенных конфигураций-предполагаемые темной материи (DM) сгустки. Изолированные DM сгустки считаются суперпозициями точечных масс и глыб с тем же центром. Создан функции автокорреляции для нескольких наборов параметров, которые характеризуют относительную концентрацию точки и протяженных масс внешнего сдвига. Ключевые слова: внегалактическая гравитационное линзирование, темная материя.

Research paper thumbnail of Warm dark matter and Hubble constant tensions

Bulletin of Taras Shevchenko National University of Kyiv. Astronomy

The tensions between the values of Hubble constant obtained from the early and the late Universe ... more The tensions between the values of Hubble constant obtained from the early and the late Universe could be eliminated if we use the ΛWDM cosmological model with dark energy, baryonic matter and warm dark matter (WDM) with characteristic velocities about 16 % of the speed of light. A pressure of WDM is equal to its energy density multiplied by factor 0.009.