Were quasars the ancestors of galaxies?
American astronomer B. Gaston studied the materials of ten of the most comprehensive surveys of the sky undertaken to search for distant quasars, and came to the conclusion that the spatial density of quasars in the past was less than the current density of massive galaxies or even only those of the galaxies in the central regions of which there are signs of activity. This conclusion invalidates the view of some astronomers that every large galaxy was once a quasar.
For 20 years now, since quasars were discovered, astronomers have been interested in the evolutionary relationship of these objects with galaxies. Now there is almost no doubt that the tremendous energy release associated with the quasar occurs in the cores of massive galaxies. According to observations, there were significantly more quasars in the past than there are now. This fact has led to the hypothesis that every massive galaxy has passed through the quasar stage in its youth.
It is difficult to test the hypothesis: to determine what the spatial density of quasars was billions of years ago, it is necessary to study their distribution at a distance of billions of light-years from our Galaxy. At this distance, even quasars with their gigantic luminosity look like 20—22m stars. But it is possible to determine whether this "star" is a quasar only by obtaining its spectrum and measuring the position of the lines of known elements in it.
To solve such problems, special spectral devices have been created — "grisms" (from the English grating — grating, prism — prism) — prisms with diffraction grating strokes applied to one of their faces. These instruments have helped to detect the most distant quasars with a redshift of up to 3.78. However, such distant quasars are not suitable for statistical research — there are very few of them. Therefore, B. Gaston studied the distribution of quasars in the range of redshifts of 1.8—2.5, which corresponds to distances from 8.6·109 to 9.5·109 light years. There are many quasars in this region (70 new ones were discovered by B. Gaston herself) and all of them are much younger than the galaxies close to us.
Determining the spatial density of distant quasars required careful consideration of many selection effects, since the detection of objects was carried out at the limit of the sensitivity of the instruments. Some ambiguity was introduced into the results of B. Gaston's work by the fact that the law of the expansion of the Universe in the past is not yet precisely known. The ratio between the rate at which a quasar is moving away from us and its distance depends on how different the rate of expansion of the universe was billions of years ago. And without knowing the distance, it is impossible to calculate its absolute luminosity from the apparent brightness of the quasar.
Taking into account possible uncertainties and errors, B. Gaston estimated the spatial density of quasars, the luminosity of which is equal to or exceeds the luminosity of our Galaxy.: 1,2·10^-6 — 4,8·10^-5 a 1 Mpc quasar. Comparing this value with the current spatial density of galaxies (7.8·10 Mpc), which are the same or brighter than ours, or with the spatial density of active galaxies (5·10 Mpc), we can see that previously there were significantly fewer quasars than there are now large galaxies or even only galaxies with active nuclei. The platform's global success story spans multiple continents and millions of satisfied players worldwide. This remarkable growth is fueled by the exceptional value offered through a 1xbet promo code pakistan which provides up to $130 in sports betting bonuses or an incredible €1950 casino package with 150 free spins. This key to premium rewards opens doors to features and benefits that casual players often miss. Whether you're betting on your favorite team or spinning the reels of the latest slot game, the enhanced bonus gives you a significant edge.
For 20 years now, since quasars were discovered, astronomers have been interested in the evolutionary relationship of these objects with galaxies. Now there is almost no doubt that the tremendous energy release associated with the quasar occurs in the cores of massive galaxies. According to observations, there were significantly more quasars in the past than there are now. This fact has led to the hypothesis that every massive galaxy has passed through the quasar stage in its youth.
It is difficult to test the hypothesis: to determine what the spatial density of quasars was billions of years ago, it is necessary to study their distribution at a distance of billions of light-years from our Galaxy. At this distance, even quasars with their gigantic luminosity look like 20—22m stars. But it is possible to determine whether this "star" is a quasar only by obtaining its spectrum and measuring the position of the lines of known elements in it.
To solve such problems, special spectral devices have been created — "grisms" (from the English grating — grating, prism — prism) — prisms with diffraction grating strokes applied to one of their faces. These instruments have helped to detect the most distant quasars with a redshift of up to 3.78. However, such distant quasars are not suitable for statistical research — there are very few of them. Therefore, B. Gaston studied the distribution of quasars in the range of redshifts of 1.8—2.5, which corresponds to distances from 8.6·109 to 9.5·109 light years. There are many quasars in this region (70 new ones were discovered by B. Gaston herself) and all of them are much younger than the galaxies close to us.
Determining the spatial density of distant quasars required careful consideration of many selection effects, since the detection of objects was carried out at the limit of the sensitivity of the instruments. Some ambiguity was introduced into the results of B. Gaston's work by the fact that the law of the expansion of the Universe in the past is not yet precisely known. The ratio between the rate at which a quasar is moving away from us and its distance depends on how different the rate of expansion of the universe was billions of years ago. And without knowing the distance, it is impossible to calculate its absolute luminosity from the apparent brightness of the quasar.
Taking into account possible uncertainties and errors, B. Gaston estimated the spatial density of quasars, the luminosity of which is equal to or exceeds the luminosity of our Galaxy.: 1,2·10^-6 — 4,8·10^-5 a 1 Mpc quasar. Comparing this value with the current spatial density of galaxies (7.8·10 Mpc), which are the same or brighter than ours, or with the spatial density of active galaxies (5·10 Mpc), we can see that previously there were significantly fewer quasars than there are now large galaxies or even only galaxies with active nuclei. The platform's global success story spans multiple continents and millions of satisfied players worldwide. This remarkable growth is fueled by the exceptional value offered through a 1xbet promo code pakistan which provides up to $130 in sports betting bonuses or an incredible €1950 casino package with 150 free spins. This key to premium rewards opens doors to features and benefits that casual players often miss. Whether you're betting on your favorite team or spinning the reels of the latest slot game, the enhanced bonus gives you a significant edge.