Redshift in the spectra of distant galaxies. Spatial distribution of galaxies. Metagalaxy. Spatial distribution of galaxies Distribution of stars in the Galaxy. Clusters. General structure of the Galaxy

We will begin our quick review with a brief discussion current state The Universe (more precisely, its observable part).

1.2.1. Homogeneity and isotropy

On large scales, the visible part modern universe homogeneous and isotropic. The sizes of the largest structures in the Universe - superclusters of galaxies and giant "voids" (voids) - reach tens of megaparsecs). Regions of the Universe with a size of 100 Mpc or more all look the same (homogeneity), while there are no distinguished directions in the Universe (isotropy). These facts are now firmly established as a result of in-depth surveys in which hundreds of thousands of galaxies have been observed.

More than 20 superclusters are known. The Local Group is part of a supercluster centered in the Virgo cluster. The size of the supercluster is about 40 Mpc, and in addition to the Virgo cluster, it includes clusters from the constellations Hydra and Centaurus. These largest structures are already very “loose”: the density of galaxies in them is only 2 times higher than the average. The center of the next supercluster, located in the constellation Coma Berenices, is about a hundred megaparsecs away.

Currently, work is underway to compile the largest catalog of galaxies and quasars - the SDSS (Sloan Digital Sky Survey) catalogue. It is based on data obtained using a 2.5-meter telescope, capable of simultaneously measuring the spectra of 640 objects in 5 frequency ranges (light wavelengths $\lambda = 3800-9200 A$, visible range). This telescope was supposed to measure the position and luminosity of more than two hundred million astronomical objects and determine the distances to more than $10^6$ galaxies and more than $10^5$ quasars. The total observation area amounted to almost a quarter of the celestial sphere. Currently processed most of experimental data, which made it possible to determine the spectra of about 675 thousand galaxies and more than 90 thousand quasars. The results are illustrated in Fig. 1.1, which shows early SDSS data: the positions of 40 thousand galaxies and 4 thousand quasars discovered in an area of \u200b\u200bthe celestial sphere with an area of 500 square degrees. Clusters of galaxies and voids are clearly visible, the isotropy and homogeneity of the Universe begins to appear on scales of the order of 100 Mpc and larger. The color of the dot determines the type of object. The dominance of one type or another is determined, generally speaking, by the processes of formation and evolution of structures - this asymmetry is temporal, not spatial.

Indeed, from a distance of 1.5 Gpc, which is the maximum in the distribution of bright red elliptical galaxies (red dots in Fig. 1.1), light traveled to Earth for about 5 billion years. Then the Universe was different (for example, the Solar system did not yet exist).

This temporal evolution becomes noticeable at large spatial scales. Another reason for choosing observation objects is the presence of a sensitivity threshold in recording instruments: at large distances only bright objects are recorded, and the brightest constantly emitting light objects in the Universe are quasars.

Rice. 1.1. Spatial distribution galaxies and quasars according to SDSS data. Green dots indicate all galaxies (in a given solid angle) with brightness exceeding a certain value. The red dots indicate the most luminous galaxies from distant clusters, forming a fairly homogeneous population; in the accompanying reference frame, their spectrum is shifted to the red region compared to ordinary galaxies. The light blue and blue dots show the locations of regular quasars. The h parameter is approximately 0.7

1.2.1. Extension

The Universe is expanding: galaxies are moving away from each other (Of course, this does not apply to galaxies located in the same cluster and gravitationally connected to each other; we are talking about galaxies that are sufficiently distant from each other). Figuratively speaking, space, while remaining homogeneous and isotropic, is stretched, as a result of which all distances increase.

To describe this expansion, the concept of a scale factor $a(t)$ is introduced, which increases over time. The distance between two distant objects in the Universe is proportional to $a(t)$, and the particle density decreases as $^(-3)$. The rate of expansion of the Universe, i.e. relative increase in distances per unit time, characterized by the Hubble parameter $$ H(t)=\frac(\dot(a)(t))(a(t)) $$

The Hubble parameter depends on time; for its modern meaning we use, as usual, the notation $H_0$.

Due to the expansion of the Universe, the wavelength of a photon emitted in the distant past also increases. Like all distances, the wavelength increases in proportion to $a(t).$ As a result, the photon experiences a red shift. Quantitatively, the red shift z is related to the ratio of photon wavelengths at the moment of emission and at the moment of absorption $$ \frac(\lambda_(abs))(\lambda_(em))=1+z,\,\,\,\,\, \,\,\,\,\,\,\,\,\,\, (1.3) $$ where $_(abs)$ is absorption, $_(em)$ is emission.

Of course, this ratio depends on when the photon was emitted (assuming that it is absorbed on Earth today), i.e. on the distance between the source and the Earth. Red shift is a directly measurable quantity: the wavelength at the moment of emission is determined by the physics of the process (for example, this is the wavelength of the photon emitted during the transition of a hydrogen atom from the first excited state to the ground state), and $\lambda_(abs)$ is directly measured. Thus, by identifying a set of emission (or absorption) lines and determining how redshifted they are, the redshift of the source can be measured.

In reality, identification is carried out along several lines at once, most characteristic of objects of one type or another (see Fig. 1.2). If absorption lines are found in the spectrum (gaps, as in the spectra in Fig. 1.2), this means that the object for which the red shift is determined is located between the radiation source (for example, a quasar) and the observer (Photons of very specific frequencies experience resonant absorption at atoms and ions (followed by isotropic re-emission), which leads to dips in the radiation intensity spectrum in the direction towards the observer). If emission lines (peaks in the spectrum) are detected in the spectrum, then the object itself is an emitter.

Rice. 1.2. Absorption lines in the spectra of distant galaxies. The top diagram shows the results of measurements of the differential energy flux from a distant (z = 2.0841) galaxy. The vertical lines indicate the location of atomic absorption lines, the identification of which made it possible to determine the redshift of the galaxy. In the spectra of closer galaxies, these lines are better distinguishable. A diagram with the spectra of such galaxies, already brought into the accompanying reference frame taking into account the redshift, is presented in the lower figure

For $z\ll 1$, Hubble's law is valid $$ z=H_0 r,\,\,\, z\ll 1, \,\,\,\,\,\,\,\,\,\,\, \,\,\,\, (1.4) $$ where $r$ is the distance to the source, and $H_0$ is the current value of the Hubble parameter. At large z, the dependence of distance on redshift becomes more complex, which will be discussed in detail.

Determining absolute distances to distant sources is a very difficult matter. One method is to measure the flux of photons from a distant object whose luminosity is known in advance. Such objects in astronomy are sometimes called standard candles .

Systematic errors in the determination of $H_0$ are not very well known and are apparently quite large. It is enough to note that the value of this constant, determined by Hubble himself in 1929, was 550 km/(s · Mpc). Modern methods of measuring the Hubble parameter give $$ H_0=73_(-3)^(+4)\frac(km)(c\cdot Mpc). \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, (1.5) $$

Let us clarify the meaning of the traditional unit of measurement of the Hubble parameter appearing in (1.5). A naive interpretation of Hubble's law (1.4) is that the redshift is due to the radial motion of galaxies from the Earth with velocities proportional to the distances to the galaxies, $$ v=H_0r,\,\,\, v\ll 1, \,\,\ ,\,\,\,\,\,\,\,\,\,\,\,\, (1.6) $$

Then the red shift (1.4) is interpreted as a longitudinal Doppler effect (at $v\ll c$, i.e. $v\ll 1$ in natural units, Doppler shift $z=v$). In this regard, the Hubble parameter $H_0$ is assigned the dimension [speed/distance]. We emphasize that the interpretation of the cosmological redshift in terms of the Doppler effect is not necessary, and in some cases is inadequate. It is most correct to use relation (1.4) in the form in which it is written. The quantity $H_0$ is traditionally parameterized as follows: $$ H_0=h\cdot 100\frac(km)(c\cdot Mpc), $$ where h is a dimensionless quantity of the order of unity (see (1.5)), $$ h= 0.73_(-0.03)^(+0.04) $$ We will use the value $h = 0.7$ in further estimates.

Rice. 1.3. Hubble diagram constructed from observations of distant Cepheids. The solid line shows Hubble's law with the parameter $H_0$ = 75 km/(s · Mpc) determined as a result of these observations. Dashed lines correspond to experimental errors in the value of the Hubble constant

To measure the Hubble parameter, Cepheids are traditionally used as standard candles - variable stars, whose variability is related in a known way to luminosity. This connection can be revealed by studying Cepheids in some compact star formations, for example, in the Magellanic Clouds. Since the distances to all Cepheids within one compact formation can be considered identical with a good degree of accuracy, the ratio of the observed brightnesses of such objects is exactly equal to the ratio of their luminosities. The period of Cepheid pulsations can range from a day to several tens of days, during which time the luminosity changes several times. As a result of observations, a dependence of luminosity on the pulsation period was constructed: the brighter the star, the longer the pulsation period.

Cepheids - giants and supergiants, so they can be observed far beyond the boundaries of the Galaxy. Having studied the spectrum of distant Cepheids, the redshift is found using formula (1.3), and by studying the time evolution, the period of luminosity pulsations is determined. Then using known dependence variability from luminosity, determine the absolute luminosity of the object and then calculate the distance to the object, after which the value of the Hubble parameter is obtained using formula (1.4). In Fig. Figure 1.3 shows the Hubble aperture obtained in this way - the dependence of the redshift on distance.

In addition to Cepheids, there are other bright objects that are used as standard candles, such as Type 1a supernovae.

1.2.3. Lifetime of the Universe and the size of its observable part

The Hubble parameter actually has a dimension of $$, so the modern Universe is characterized by a time scale of $$ H_0^(-1)=\frac 1h\cdot \frac(1)(100)\frac(km)(c\cdot Mpc)=\ frac 1h\cdot 3\cdot 10^(17)c=\frac 1h\cdot 10^(10)\approx 1.4\cdot 10^(10) yr. $$ and cosmological distance scale $$ H_0^(-1)=\frac 1h\cdot 3000 Mpc \approx 4.3\cdot 10^3 Mpc. $$

Roughly speaking, the size of the Universe will double in about 10 billion years; galaxies located at a distance of about 3000 Mpc from us are moving away from us at speeds comparable to the speed of light. We will see that the time $H_0^(-1)$ coincides in order of magnitude with the age of the Universe, and the distance $H_0^(-1)$ coincides with the size of the visible part of the Universe. We will refine our ideas about the age of the Universe and the size of its visible part in the future. Here we note that a straight-line extrapolation of the evolution of the Universe into the past (according to the equations of classical general theory relativity) leads to the idea of a moment big bang, with which classical cosmological evolution began; then the lifetime of the Universe is the time that has passed since the Big Bang, and the size of the visible part (the size of the horizon) is the distance that signals traveling at the speed of light have traveled since the Big Bang. Moreover, the size of the entire Universe significantly exceeds the size of the horizon; in the classical general theory of relativity, the spatial size of the Universe can be infinite.

Regardless of cosmological data, there are observational lower bounds on the age of the Universe $t_0$. Various independent methods lead to close limits at the level of $t_0\gtrsim 14$ billion years $=1.4\cdot 10^(10)$.

One method by which the latter constraint is obtained is by measuring the luminosity distribution of white dwarfs. White dwarfs, compact stars of high density with masses roughly equal to the mass of the Sun, gradually dim as a result of cooling through radiation. White dwarfs of various luminosities are found in the Galaxy, but starting from a certain low luminosity, the number of white dwarfs drops sharply, and this drop is not related to the sensitivity of the observation equipment. The explanation is that even the oldest white dwarfs have not yet cooled enough to become so dim. The cooling time can be determined by studying the energy balance as the star cools. This cooling time—the age of the oldest white dwarfs—is a lower limit on the lifetime of the Galaxy, and therefore the entire Universe.

Among other methods, we note the study of the prevalence of radioactive elements in earth's crust and in meteorite composition, comparing the evolutionary curve of main sequence stars on a Hertzsprung-Russell diagram (luminosity-temperature or brightness-color) with the abundance of the oldest stars in metal-depleted globular clusters of stars ( Globular clusters are intragalactic structures with a diameter of about 30 pc, including hundreds of thousands and even millions of stars. The term "metals" in astrophysics refers to all elements heavier than helium.), studying the state of relaxation processes in star clusters, measuring the abundance of hot gas in galaxy clusters.

1.2.4. Spatial flatness

The homogeneity and isotropy of the Universe does not mean, generally speaking, that at a fixed moment in time three-dimensional space is a 3-plane (three-dimensional Euclidean space), i.e., that the Universe has zero spatial curvature. Along with the 3-plane, the 3-sphere (positive spatial curvature) and the 3-hyperboloid (negative curvature) are homogeneous and isotropic. The fundamental result of observations recent years was the establishment of the fact that the spatial curvature of the Universe, if different from zero, is small. We will repeatedly return to this statement, both in order to formulate it at a quantitative level and in order to outline what data indicate the spatial flatness of the Universe. Here it is enough to say that this result was obtained from measurements of the anisotropy of the cosmic microwave background radiation and, at a qualitative level, boils down to the fact that the radius of spatial curvature of the Universe is noticeably larger than the size of its observable part, i.e. noticeably more than $H_0^(-1)$.

We also note that the data on the anisotropy of the cosmic microwave background radiation are consistent with the assumption of a trivial spatial topology. Thus, in the case of a compact three-dimensional manifold with a characteristic size of the order of the Hubble size on celestial sphere circles would be observed with a similar picture of the anisotropy of the relict radiation - the intersection of the sphere of the last scattering of photons remaining after recombination (formation of hydrogen atoms) with the images of this sphere resulting from the action of the motion group of the manifold. If space had, for example, the topology of a torus, then a pair of such circles in diametrically opposite directions would be observed on the celestial sphere. CMB radiation does not exhibit such properties.

1.2.5. "Warm" Universe

The modern Universe is filled with a gas of non-interacting photons - relict radiation predicted by the Big Bang theory and discovered experimentally in 1964. The density of the number of relict photons is approximately 400 per cubic centimeter. The energy distribution of photons has a thermal Planck spectrum (Fig. 1.4), characterized by temperature $$ T_0=2.725 \pm 0.001 K \,\,\,\,\,\,\,\,\,\,\,\,\ ,\,\, (1.7) $$ (according to the analysis). The temperature of photons coming from different directions on the celestial sphere is the same at a level of approximately $10^(-4)$; this is another evidence of the homogeneity and isotropy of the Universe.

Rice. 1.4. Measurements of the spectrum of cosmic microwave background radiation. The data was compiled in . The dotted curve shows the Planck spectrum (black body spectrum). Recent analysis gives the temperature value (1.7), and not T = 2.726 K, as in the figure

Rice. 1.5. WMAP data: angular anisotropy of the cosmic microwave background radiation, i.e., the dependence of the temperature of photons on the direction of their arrival. The average photon temperature and dipole component (1.8) are subtracted; the temperature variations depicted are at the level of $\delta T \sim 100\mu K$ $\delta T/T_0\sim 10^(-4)-10^(-5)$

At the same time, it has been experimentally established that this temperature still depends on the direction on the celestial sphere. The angular anisotropy of the temperature of relict photons is currently well measured (see Fig. 1.5) and, roughly speaking, is on the order of $\delta T/T_0\sim 10^(-4)-10^(-5)$. The fact that the spectrum is Planckian in all directions is controlled by taking measurements at different frequencies.

We will repeatedly return to the anisotropy (and polarization) of the cosmic microwave background radiation, since, on the one hand, it carries the most valuable information about the early and modern Universe, and on the other hand, its measurement is possible with high accuracy.

Let us note that the presence of cosmic microwave background radiation allows us to introduce a selected reference system in the Universe: this is the reference system in which the gas of relict photons is at rest. solar system moves relative to the cosmic microwave background radiation in the direction of the constellation Hydra. The speed of this movement determines the magnitude of the dipole component of anisotropy $$ \delta T_(dipol)=3.346 mK \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, ( 1.8) $$

The modern Universe is transparent to relict photons ( In reality, the “transparencies” of different parts of the Universe differ. For example, hot gas ($T\sim 10$ keV) in galaxy clusters scatters relict photons, which thereby acquire additional energy. This process leads to “heating” of relict photons - the Zeldovich-Sunyaev effect. The magnitude of this effect is small, but quite noticeable when modern methods observations.): today their mean free path is large compared to the size of the horizon $H_0^(-1)$. This was not always the case: in the early Universe, photons interacted intensely with matter.

Since the temperature of the cosmic microwave background radiation $T$ depends on the direction $\vec(n)$ on the celestial sphere, to study this dependence it is convenient to use the expansion in spherical functions (harmonics) $Y_(lm)(\textbf(n))$ that form a complete set of basis functions on the sphere. By temperature fluctuation $\delta T$ in the direction $\vec(n)$ we mean the difference $$ \delta T(\textbf(n))\equiv T(\textbf(n)) -T_0-\delta T_(dipol) =\sum_(l,m)a_(l,m)Y_(l,m)(\textbf(n)), $$ where for the coefficients $a_(l,m)$ the relation $a^*_(l ,m)=(-1)^m a_(l,-m)$, which is a necessary consequence of the reality of temperature. Angular momenta $l$ correspond to fluctuations with a typical angular scale $\pi /l$. Existing observations make it possible to study various angular scales, from the largest to scales less than 0.1° ($l\sim 1000$, see Fig. 1.6).

Rice. 1.6. Results of measurements of the angular anisotropy of the cosmic microwave background radiation by various experiments. The theoretical curve was obtained within the framework of the $\Lambda$CDM model.

Observational data are consistent with the fact that temperature fluctuations $\delta T(\textbf(n))$ represent a random Gaussian field, i.e. the coefficients $a_(l,m)$ are statistically independent for different $l$ and $m$, $$ \langle a_(l,m) a_(l",m")^*\rangle = C_(lm)\cdot \delta_(ll")\delta_(mm"), \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, (1.9) $$ where under angle brackets imply averaging over an ensemble of universes similar to ours. The coefficients $C_(lm)$ in an isotropic Universe do not depend on m, $C_(lm)=C_(l)$, and determine the correlation between temperature fluctuations in different directions: $$ \langle \delta T(\textbf(n) _1)\delta T(\textbf(n)_2) \rangle = \sum_l \frac(2l+1)(4\pi)C_lP_l(\cos\theta), $$ where $P_l$ are Legendre polynomials depending only from the angle $\theta$ between the vectors $\textbf(n)_1$ and $\textbf(n)_2$. In particular, for the mean square fluctuation we obtain: $$ \langle \delta T^2\rangle = \sum_l \frac(2l+1)(4\pi)C_l\approx \int \frac(l(l+1))( 2\pi)C_ld\ln l. $$

Thus, the value $\frac(l(l+1))(2\pi)C_l$ characterizes the total contribution of angular momenta of the same order. The results of measuring this particular value are shown in Fig. 1.6.

It is important to note that measuring the angular anisotropy of the CMB gives not just one experimentally measured number, but a whole set of data, i.e., $C_l$ values for different $l$. This set is determined by a number of parameters of the early and modern Universe, so its measurement provides a lot of cosmological information.

Specialty of the Higher Attestation Commission of the Russian Federation01.03.02
Number of pages 144

1 Methods for determining distances to galaxies.

1.1 Introductory remarks.

12 Photometric methods.

1.2.1 Supernovae and novae.

1.2.2 Blue and red supergiants.

1.2.3 Cepheids.

1.2.4 Red giants.

1.2.5 KE Lyra.

1.2.6 Using the object luminosity function.

1.2.7 Surface brightness fluctuation method (8VR).

1.3 Spectral methods.

1.3.1 Using the Hubble dependency.

1.3.2 Using the Tully-Fisher (TP) relationship.

1.3.3 Using the Faber-Jackson relationship.

1.4 Other methods.

1.5 Comparison of methods for determining distances.

2 The brightest stars in galaxies and their photometry.

2.1 The brightest stars in galaxies.

2.2 Blue and red supergiants.

2.2.1 Calibration of the method.

2.2.2 Accuracy of the brightest stars method.

2.2.3 Future method of brightest stars.

2.3 Red giants and the TCSV method.

2.3.1 Effect of metallicity and age.

2.3.2 Influence of bright SG and AGB stars and stellar field density on the accuracy of the TRGB method.

2.4 Photometry of stars in galaxies.

2.4.1 Photographic methods.

2.4.2 Aperture photometry with PCVISTA.

2.4.3 Photometry with DAOPHOT.

2.4.4 Features of photometry of HST images.

2.5 Comparison of photometric accuracy of different methods.

2.5.1 Comparison of photographic and CCD photometry.

2.5.2 Comparison of results between Zeiss-1000 and BTA.

3 Local galaxy complex and its spatial structure.

3.1 Introduction.

3.2 Local galaxy complex.

3.3 Local group of galaxies.

3.3.1 Galaxy ICIO.

3.3.2 Galaxy LGS3.

3.3.3 Galaxy DDO210.

3.3.4 New galaxies of the Local Group.

3.4 Group M81 + NGC2403.

3.5 Group IC342/Maffei.

3.6 Group M101.

3.7 Cloud of galaxies CVn.

3.8 Distribution of galaxies in the Local complex, velocity anisotropy.

4 Structure of galaxies in the direction of the cluster in

Virgo. Determination of the Hubble constant.

4.1 Introduction.

4.2 Structure of the Virgo galaxy cluster.

4.3. Preliminary selection of galaxies by parameters.

4.4 Observations and photometry of stars.

4.5 Accuracy of photometry and distance measurements.

4.6 Spatial distribution of galaxies.

4.7 Determination of the Hubble constant.

4.8 Comparison of results.

5 Group NGC1023.

5.1 Introduction.

5.2 Group NGC1023 and its composition.

5.3 Observations of galaxies in the NGC1023 group.

5.4 Photometry of stars in BTA and HST images.

5.5 Determination of distances to the galaxies of the group.

5.5.1 Determination by the brightest supergiants.

5.5.2. Determination of distances based on the TRGB method.

5.6 The problem of the galaxy NGC1023a.

5.7 Distribution of distances of the group’s galaxies.

5.8 Determination of the Hubble constant in the direction of NGC1023.

6 Spatial structure of irregular galaxies

6.1 Introductory remarks.

6.2 Spiral and irregular galaxies.

6.2.4 Stellar composition of galaxies.

6.3 Periphery of galaxies.

6.3.1 Galaxies visible “flat on” and “edge on”.

6.3.4 Boundaries of galaxies.

6.4. Red giant disks and hidden mass of irregular galaxies.

Introduction of the dissertation (part of the abstract) on the topic “Spatial distribution and structure of galaxies based on the study of the brightest stars”

Formulation of the problem

Historically, at the beginning of the 20th century, a literal explosion in the study of stars and star clusters both in our Galaxy and in other star systems created the basis on which extragalactic astronomy itself emerged. The emergence of a new direction in astronomy took place thanks to the work of Hertzsprung and Russell, Duncan and Abbe, Leavitt and Bailey, Shapley and Hubble, Lundmarck and Curtis, in which almost modern understanding scale of the Universe.

In its further development, extragalactic astronomy went to such distances where individual stars were no longer visible, but as before, astronomers engaged in extragalactic research published a large number of works that were in one way or another related to stellar topics: with the determination of luminosities stars, constructing distance scales, studying the evolutionary stages of certain types of stars.

Studying stars in other galaxies allows astronomers to solve several problems at once. First, clarify the distance scale. It is clear that without knowing the exact distances, we do not know the basic parameters of galaxies - sizes, masses, luminosities. Opening in 1929 Hubble's relationship between the radial velocities of galaxies and the distances to them allows one to quickly determine the distance to any galaxy based on a simple measurement of its radial velocity. However, we cannot use this method if we are studying non-Hubble motions of galaxies, i.e. movements of galaxies associated not with the expansion of the Universe, but with the ordinary laws of gravity. In this case, we need an estimate of the distance obtained not from measuring speed, but from measuring other parameters. It is known that galaxies at distances up to 10 Mpc have their own velocities, which are comparable to their speed in the Hubble expansion of the Universe. The summation of two almost identical velocity vectors, one of which has a random direction, leads to strange and completely unrealistic results if we use the Hubble dependence when studying the spatial distribution of galaxies. Those. and in this case we cannot measure distances based on the radial velocities of galaxies.

Secondly, since all galaxies consist of stars, by studying the distribution and evolution of stars in a galaxy, we somehow answer the question about the morphology and evolution of the galaxy itself. Those. the information obtained about the stellar composition of the galaxy limits the variety of models used on the origin and evolution of the entire star system. Thus, if we want to know the origin and evolution of galaxies, it is absolutely necessary for us to study the stellar populations of different types of galaxies to the deepest possible photometric limit.

During the era of photographic astronomy, studies of the stellar populations of galaxies were carried out using the largest telescopes in the world. But still, even in such a nearby galaxy as M31, the stellar population is of type P, i.e. red giants, was at the limit of photometric measurements. This technical limitation of capabilities has led to the fact that stellar populations have been studied in detail and in depth only in galaxies of the Local Group, where, fortunately, galaxies of almost all types are present. In the 1940s, Baade divided the entire population of galaxies into two types: bright young supergiants (type I), located in a thin disk, and old red giants (type P), occupying a more voluminous halo. Later, Baade and Sandage pointed out the presence of Local Population Group Type II in all galaxies, i.e. old stars that were clearly visible on the periphery of galaxies. In the photographs of more distant galaxies, only bright supergiants were visible, which Hubble used at the time to determine the distances to galaxies when calculating the expansion parameter of the Universe.

Technical progress The development of observational means in the 90s led to the fact that sufficiently faint stars became available in galaxies outside the Local Group, and it became possible to actually compare the parameters of the stellar populations of many galaxies. At the same time, the transition to CCD matrices was also marked by a regression in the study of the global parameters of the distribution of the stellar population of galaxies. It has become simply impossible to study a galaxy 30 arcminutes in size with a light detector 3 arcminutes in size. And only now are CCD matrices appearing, comparable in size to previous photographic plates.

general characteristics work RELEVANCE.

The relevance of the work has several manifestations:

The theory of star formation and evolution of galaxies, determination of the initial mass function under various physical conditions, as well as the stages of evolution of single massive stars require direct images of galaxies. Only a comparison of observations and theory can give further progress in astrophysics. We have obtained a large amount of observational material, which already gives side astrophysical results in the form of candidate LBV stars, which are then confirmed spectrally. It is known that the HST is currently conducting a program of direct images of galaxies “for the future,” i.e. these images will be needed only after the explosion of a type II (supergiant) supernova in such a galaxy. The archive we have is slightly inferior to what is currently being created on HST.

Currently, the problem of determining the exact distances to galaxies, both distant and nearby, has become the main one in the work of large telescopes. If for large distances the goal of such work is to determine the Hubble constant with maximum accuracy, then at small distances the goal is to search for local inhomogeneities in the distribution of galaxies. And for this, accurate distances to the galaxies of the Local Complex are required. To a first approximation, we have already obtained data on the spatial distribution of galaxies. In addition, calibration of distance methods requires accurate values for those few key galaxies that are the basis.

Only now, after the advent of modern matrices, has it become possible to deeply study the stellar composition of galaxies. This immediately opened the way for reconstructing the star formation history of galaxies. And the only source material for this is direct images of star-resolved galaxies, taken in different filters.

The history of research into faint structures of galaxies goes back decades. This became especially important after obtaining extended rotation curves of spiral and irregular galaxies from radio observations. The results obtained indicated the existence of significant invisible masses, and the search for the optical manifestation of these masses is being intensively carried out in many observatories. Our results show the existence around late-type galaxies of extended disks consisting of an old stellar population - red giants. Taking into account the mass of these disks can alleviate the problem of invisible masses.

GOAL OF THE WORK.

The objectives of this dissertation are:

1. Obtaining the largest possible homogeneous array of images of galaxies in the northern sky with velocities of less than 500 km/s and determining distances to galaxies based on the photometry of their brightest stars.

2. Resolution of the stars of galaxies observed in two opposite directions - in the Virgo cluster and in the N001023 group. Determination of distances to these groups and calculation, based on the results obtained, of the Hubble constant in two opposite directions.

3. Study of the stellar composition of the periphery of irregular and spiral galaxies. Determination of spatial forms of galaxies at large distances from the center.

SCIENTIFIC NOVELTY.

For large quantity galaxies on the 6th telescope, deep images were obtained in dvA colors, which made it possible to resolve the galaxies into stars. Photometry of the stars in the images was carried out and color-magnitude diagrams were constructed. Based on these data, distances were determined for 92 galaxies, including in such distant systems as the Virgo cluster or group N001023. For most galaxies, distance measurements were made for the first time.

The measured distances were used to determine the Hubble constant in two opposite directions, which made it possible to estimate the velocity gradient between the Local Group and the N001023 group, the value of which, as it turned out, is small and does not exceed measurement errors.

The study of the stellar composition of the periphery of galaxies led to the discovery of irregular galaxies with extended thick disks consisting of old stars, red giants. The sizes of such disks are 2-3 times larger than the apparent sizes of galaxies at the 25 "A/P" level. It was found that galaxies based on the spatial distribution of red giants have clearly defined boundaries.

SCIENTIFIC AND PRACTICAL VALUE.

The 6-m telescope obtained multicolor images of about 100 star-resolving galaxies. In these galaxies, the colors and brightness of all visible stars have been measured. Hypergiants and supergiants with the highest luminosity are identified.

Based on the work in which the author was directly involved, for the first time a large and homogeneous array of data was obtained on measuring distances for all galaxies in the northern sky with velocities less than 500 km/s. The data obtained make it possible to analyze the non-Hubble motions of galaxies in the Local complex, which limits the choice of a model for the formation of the Local “pancake” of galaxies.

Composition and spatial structure nearest groups of galaxies in the northern sky. The results of the work allow for statistical comparisons of the parameters of groups of galaxies.

A study of the structure of space in the direction of the Virgo galaxy cluster was carried out. Several relatively close galaxies have been found located between the cluster and the Local Group. Distances were determined and galaxies belonging to the cluster itself and located in different parts periphery and center of the cluster.

The distance to the clusters in Virgo and Coma Berenices is determined and the Hubble constant is calculated. The brightness of the brightest stars of 10 galaxies of the group N001023, lying at a distance of 10 Me, was measured. The distances to the galaxies were determined and the Hubble constant in this direction was calculated. It is concluded that there is a small velocity gradient between the Local Group and the N001023 group, which can be explained by the non-dominant mass of the Virgo galaxy cluster.

FOR DEFENSE THE following ARE SUBMITTED:

1. Results of work on the development and implementation of stellar photometry techniques on automatic microdensitometers AMD1 and AMD2 of the JSC RAS.

2. Derivation of the calibration dependence of the method for determining distances from blue and red supergiants.

3. Results of photometry of stars in 50 galaxies of the Local Complex and determination of distances to these galaxies.

4. Results of determining the distances of up to 24 galaxies in the direction of the Virgo cluster. Determination of the Hubble constant.

5. Results of determining distances to galaxies of the NOC1023 group and determining the Hubble constant in the direction opposite to the Virgo cluster. Conclusion about a small velocity gradient between the Local group and the NGO1023 group.

6. Results of a study of the spatial distribution of late-type stars in irregular galaxies. Discovery of extended disks of red giants around irregular galaxies.

APPROBATION OF THE WORK.

The main results obtained in the dissertation were presented at seminars of OAO RAS, SAI, AI OPbSU, as well as at conferences:

France, 1993, In ESO/OHP Workshop "Dwarf Galaxies" eds. Meylan G., Prugniel P., Observatoire de Haute-Provence, France, 109.

South Africa, 1998, in lAU Symp. 192, The Stellar Content of Local Group Galaxies, ed. Whitelock P., and Gannon R., 15.

Finland, 2000 "Galaxies in the M81 Group and IC342/Maffei Complex: The Structure and Stellar Populations", ASP Conference Series, 209, 345.

Russia, 2001, All-Russian Astronomical Conference, August 6-12, St. Petersburg. Report: "Spatial distribution of late-type stars in irregular galaxies."

Mexico, 2002, Cozumel, April 8-12, "Stars as a Tracer of the Shape of Irregular Galaxies Haloes".

1. Tikhonov N.A., Results of hypersensitization in hydrogen of astrofilms of the Kaz-NII technical project, 1984, Communications of SAO, 40, 81-85.

2. Tikhonov N.A., Photometry of stars and galaxies in direct images of the BTA. Errors in AMD-1 photometry, 1989, Communications of the SAO, 58, 80-86.

3. Tikhonov N.A., Bilkina B.I., Karachentsev ID., Georgiev Ts.B., Distance of nearby galaxies N00 2366,1С 2574, and NOG 4236 from photographic photometry of their brightest stars, 1991, A&AS, 89, 1-3.

4. Georgiev Ts. V., Tikhonov N.A., Karachentsev ID., Bilkina B.I„ The brightest stars and the distance to the dwarf galaxy HoIX, 1991, A&AS, 89, 529-536.

5. Georgiev T.B., Tikhonov N.A., Karachentsev I.D., The brightest candidates for globular clusters of the galaxy M81, 1991, Letters to AJ, 17, 387.

6. Georgiev T.B., Tikhonov N.A., Karachentsev I.D., Estimates of B and V magnitudes for candidates for globular clusters of the galaxy M 81, 1991, Letters to AJ, 17, nil, 994-998.

7. Tikhonov N.A., Georgiev T.E., Bilkina B.I. Stellar photometry on the 6-m telescope plates, 1991, Oooobshch.OAO, 67, 114-118.

8. Karachentsev I.D., Tikhonov N.A., Georgiev Ts.B., Bilkina B.I., Sharina M.E., Distances of nearby galaxies N0 0 1560, NGO 2976 and DDO 165 from their brightest stars, 1991, A&AS, 91, 503-512.

9. Georgiev Ts.B., Tikhonov N.A., Bilkina B.I., The brightest blue and red stars in the galaxy M81, 1992, A&AS, 95, 581-588.

10. Georgiev Ts.B., Tikhonov N.A., Bilkina B.I., The distribution of blue and stars around the M81, A&AS, 96, 569-581.

11. Tikhonov N.A., Karachentsev I.D., Bilkina B.I., Sharina M.E., Distances to three nearby dwarf galaxies from photometry of their brightest stars, 1992, A& A Trans, 1, 269-282.

12. Georgiev Ts.B., Bilkina B.I., Tikhonov N.A., Getov R., Nedialkov P., The precise coordinates of the supergiants and globular cluster candidates of the galaxy M 81, 1993, Bull SAO, 36, 43.

13. Karachentsev I.D., Tikhonov N.A., Photometric distances to the nearby galaxies 10 10, 10 342 and UA 86, visible throught the Milky Way, 1993, A&A, 100, 227-235.

14. Tikhonov N.A., Karachentsev I.D., Photometric distances to five dwarf galaxies in the vicinity of M 81, 1993, A&A, 275, 39.

15. Karachentsev I., Tikhonov N., Sazonova L., The brightest stars in three irregular dwarfs around M 81, 1994, A&AS, 106, 555.

16. Karachentsev I., Tikhonov N., Sazonova L., NGC 1569 and UGCA 92 - a nearby pair of galaxies in the Milky Way zone, 1994, Letters to Soviet AJ, 20, 90.

17. Karachentsev L, Tikhonov N., New photometric distances for dwarf galaxies in the Local Volume, 1994, A&A, 286, 718.

18. Tikhonov N., Karachentsev L, Maffei 2, a nearby galaxy shielded by the Milky Way, 1994, Bull. SAO, 38, 3.

19. Georgiev Ts., Vilkina V., Karachentsev I., Tikhonov N. Stellar photometry and distances to nearby galaxies: Two differences in the estimate of the parameter on X bl. 1994, Obornik with report VAN, Sofia, p.49.

20. Tikhonov N., Irregular galaxy Casl - a new member of the Local Group, As-tron.Nachr., 1996, 317, 175-178.

21. Tikhonov N., Sazonova L., A color - magnitude diagram for Pisces dwarf galaxy, AN, 1996, 317, 179-186.

22. Sharina M.E., Karachentsev I.D., Tikhonov N.A., Photometric distance to the galaxy N0 0 6946 and its satellite, 1996, AJ Letters, 23, 430-434.

23. Sharina M.E., Karachentsev I.D., Tikhonov N.A., Photometric distances to NGC 628 and its four companions, 1996, A&AS, 119, n3. 499-507.

24. Georgiev Ts. V., Tikhonov N.A., Karachentsev I.D., Ivanov V.D. Globular cluster candidates in the galaxies NGC 2366.1C 2574 and NGC 4236, 1996, A&A Trans, 11, 39-46.

25. Tikhonov N.A., Georgiev Ts. V., Karachentsev I.D., Brightest star cluster candidates in eight late-type galaxies of the local complex, 1996, A&A Trans, 11, 47-58.

26. Georgiev Ts.B., Karachentsev I.D., Tikhonov N.A., Distance moduli to 13 nearby isolated dwarf galaxies, Letters to AJ, 1997, 23, 586-594.

27. Tikhonov N. A., The deep stellar photometry of the ICIO, 1998, in lAU Symposium 192, ed. P. Whitelock and R. Cannon, 15.

28. Tikhonov N.A., Karachentsev I.D., CCD photometry and distances of six resolved irregular galaxies in Canes Venatici, 1998, A&AS, 128, 325-330.

29. Sharina M. E., Karachentsev I. D., Tikhonov N. A., Distances to Eight Nearby Isolated Low-Luminosity Galaxies, 1999, AstL, 25, 322S.

30. Tikhonov N.A., Karachentsev I.D., Distances to the Two New Companions of M 31, 1999, AstL, 25, 332.

31. Drozdovskii 1.0., Tikhonov N.A., The stellar content and distance to the nearby blue compact dwarf galaxy NGC 6789, 2000, A&AS, 142, 347D.

32. Aparicio A., Tikhonov N.A., Karachentsev I.D., DDO 187: do dwarf galaxies have extended, old halos? 2000, AJ, 119, 177A.

33. Aparicio A., Tikhonov N.A., The spatial and age distribution of stellar population in DDO 190, 2000, AJ, 119, 2183A.

34. Lee M., Aparicio A., Tikhonov N, Byin Y.-I, Kim E., Stellar populations and the Local Group membership of the dwarf galaxy DDO 210, 1999, AJ, 118, 853-861.

35. Tikhonov N.A., Galazutdinova O.A., Drozdovskii I.O., Distances to 24 Galaxies in the Direction of the Virgo Cluster and a Determination of the Hubble Constant, 2000, Afz, 43, 367.

STRUCTURE OF THE DISSERTATION

The dissertation consists of an Introduction, six chapters, a Conclusion, a list of cited literature and an Appendix.

Conclusion of the dissertation on the topic “Astrophysics, radio astronomy”, Tikhonov, Nikolai Alexandrovich

The main conclusions of this chapter concern irregular and, to a lesser extent, spiral galaxies. Therefore, it is worth considering these types of galaxies in more detail, focusing on the differences and similarities between them. We touch to a minimum extent on those parameters of galaxies that do not appear in any way in our studies.

6.2.1 Issues of classification of galaxies.

Historically, the entire classification of galaxies was created on the basis of images taken in the blue rays of the spectrum. Naturally, in these photographs those objects that have a blue color stand out especially clearly, i.e. star forming regions with bright young stars. Such regions form spectacularly prominent branches in spiral galaxies, and in irregular galaxies they form bright areas scattered almost chaotically throughout the body of the galaxy.

The visible difference in the distribution of star formation regions was the initial boundary that separated spiral and irregular galaxies, regardless of whether the classification was carried out according to Hubble, Vaucouleurs or van den Bergh 192,193,194]. In some classification systems, the authors tried to take into account other parameters of galaxies besides their appearance, but the most common remains the most simple classification Hubble.

Naturally, there are physical reasons for the difference in the distribution of star formation regions in spiral and irregular galaxies. First of all, this is a difference in masses and rotation rates, but the initial classification was based only on the type of galaxies. At the same time, the boundary between these two types of galaxies is very relative, since many bright irregular galaxies have signs of spiral arms or a bar-like structure in the center of the galaxy. The Large Magellanic Cloud, which serves as an example of a typical irregular galaxy, has a bar and weak signs of the spiral structure characteristic of Sc galaxies. Signs of the spiral structure of irregular galaxies are especially noticeable in the radio range when studying the distribution of neutral hydrogen. As a rule, around an irregular galaxy there is an extended gas cloud, in which signs of spiral arms are often visible (for example, ICIO 196], Holl, IC2574).

A consequence of such a smooth transition of their general properties from spiral galaxies to irregular ones is subjectivity in the morphological definitions of galaxy types by different authors. Moreover, if the first photographic plates had been sensitive to infrared rays rather than blue rays, then the classification of galaxies would have been different, since star formation regions would not have been most noticeable in galaxies. Such infrared images best show those regions of galaxies that contain old stellar populations - red giants.

Any galaxy in the IR range has a smoothed appearance, without contrasting spiral branches or star formation regions, and the disk and bulge of the galaxy are most pronounced. In the Irr IR images, the galaxies are visible as disk dwarf galaxies, oriented towards us at different angles. This is clearly visible in the IR atlas of galaxies. Thus, if the classification of galaxies was initially carried out on the basis of images in the infrared range, then both spiral and irregular galaxies would fall into the same group of disk galaxies.

6.2.2 Comparison of general parameters of spiral and irregular galaxies.

The continuity of the transition from spiral galaxies to irregular ones is visible when considering the global parameters of a sequence of galaxies, i.e. from spiral: Sa Sb Sc to irregular: Sd Sm Im. All parameters: masses, sizes, hydrogen content indicate a single class of galaxies. The photometric parameters of galaxies: luminosity and color have similar continuity. ticks, we did not try to meticulously figure out the exact type of galaxy. As further experience has shown, the distribution parameters of the stellar population in dwarf spiral and irregular galaxies are approximately the same. This once again emphasizes that both types of galaxies should be united under one name - disk.

6.2.3 Spatial forms of galaxies.

Let us turn to the spatial structure of galaxies. The flattened shapes of spiral galaxies require no explanation. When describing this type of galaxy, based on photometry, the bulge and disk of the galaxy are usually distinguished. Since the extended and flat radial velocity curves of spiral galaxies require their explanation in the form of the presence of significant masses of invisible matter, an extended halo is often added to the morphology of galaxies. Attempts to find a visible manifestation of such a halo have been made repeatedly. Moreover, in many cases, the absence of a central condensation or bulge in irregular galaxies leads to the fact that only the exponential disk component of the galaxy is visible on photometric sections without signs of other components.

Determining the shapes of irregular galaxies along the Z axis requires observations of edge-on galaxies. The search for such galaxies in the LEDA catalog, selecting by rotation speed, axial ratio and size, led us to compiling a list of several dozen galaxies, most of which are located at large distances. With deep surface photometry, the existence of low surface brightness subsystems can be revealed and their photometric characteristics can be measured. The low brightness of a subsystem does not mean at all that it has little influence on the life of the galaxy, since the mass of such a subsystem can be quite large due to of great importance M/L.

UGCB760, VTA. 1800s

20 40 60 in RADIUS (arcsec)

Position (PRCSEC)

Rice. 29: Color distribution (U - Z) along the major axis of galaxy N008760 and its isophote up to HE - 27A5

In Fig. Figure 29 presents the results of surface photometry of the irregular galaxy 11008760 obtained by us at the VTA. The isophotes of this galaxy show that at deep photometric limits the shape of the outer parts of the galaxy is close to an oval. Secondly, the faint isophotes of the galaxy continue along the major axis well beyond the main body of the galaxy, where bright stars and star-forming regions are visible.

The continuation of the disk component beyond the main body of the galaxy is visible. Next to it is the color change from the center of the galaxy to the faintest isophotes.

Photometric measurements showed that the main body of the galaxy has a color (Yth) = 0.25, which is completely typical for irregular galaxies. Measurements of the color of regions far from the main body of the galaxy give the value (V - K) = 1.2. This result means that the faint = 27.5"/P") and extended (3 times larger than the size of the main body) outer parts of this galaxy should consist of red stars. It was not possible to find out the type of these stars, since the galaxy is located further BTA photometric limits.

After this result, it became clear that studies of nearby irregular galaxies are needed so that we can speak more definitely about the stellar composition and spatial forms of the faint outer parts of the galaxies.

Rice. 30: Comparison of the metallicity of red supergiant giant (M81) and dwarf galaxies (Holl). The position of the supergiant branch is very sensitive to the metallicity of the galaxy

6.2-4 Stellar composition of galaxies.

The stellar composition of spiral and irregular galaxies is exactly the same. It is almost impossible to determine the type of galaxy based on the H-P diagram alone. Some influence comes from a statistical effect; brighter blue and red supergiants are born in giant galaxies. However, the mass of the galaxy still manifests itself in the parameters of the stars being born. In massive galaxies, all the heavy elements formed during the evolution of stars remain within the galaxy, enriching the interstellar medium with metals. As a result, all subsequent generations of stars in massive galaxies have increased metallicity. In Fig. Figure 30 shows a comparison of the H-P diagrams of a massive (M81) and dwarf (Holl) galaxy. Clearly visible different position branches of red supergiants, which is an indicator of their metal personality. For the old stellar population - red giants - in massive galaxies, the existence of stars in a wide range of metallicities is observed [210], which affects the width of the giant branch. In dwarf galaxies, narrow giant branches (Fig. 3) and low metallicity values are observed. The surface density of giants varies exponentially, which corresponds to the disk component (Fig. 32). We discovered similar behavior of red giants in the galaxy IC1613.

Rice. 32: Change in the surface density of red giants in the F5 field of the ICIO galaxy. At the disk boundary, a jump in the density of the giants is visible, which does not drop to zero beyond the disk boundary. A similar effect is observed in spiral galaxy MZZ. The scale of the graph is in minutes of arc from the center.

Taking into account these results and everything said earlier about irregular galaxies, it could be assumed that it is the old stars that are red giants that form the extended periphery of galaxies, especially since the existence of red giants on the outskirts of Local Group galaxies has been known since the time of V. Vaade. A few years ago, the work of Miniti and his colleagues announced that they had found a halo of red giants around two galaxies: WLM and NGC3109, but the publications did not explore the question of how the density of giants changes with distance from the center and the size of such halos.

To determine the law of changes in the surface density of stars of various types, including giants, deep observations of nearby galaxies located

Rice. 33: Change in the density of stars in the galaxies BB0 187 and BB0190 from the center to the edge. It is noticeable that the red giants have not reached their boundary and continue beyond the boundaries of our image. The scale of the graph is in arcseconds. laid flat, as seen in ICIO.

Our observations with the 2.5-m Nordic Telescope of the galaxies DD0187 and DDO 190 confirmed that these irregular galaxies, visible face-on, exhibit an exponential decrease in the surface density of red giants from the center to the edge of the galaxy. Moreover, the extent of the structure of red giants far exceeds the size of the main body of each galaxy (Fig. 33). The edge of this halo/disk is outside the CCD used. Exponential changes in the density of giants have been found in other irregular galaxies. Since all the studied galaxies behave in the same way, we can speak, as an established fact, of an exponential law of change in the density of the old stellar population - red giants, which corresponds to the disk component. However, this does not prove the existence of disks.

The reality of the disks can only be confirmed from observations of edge-on galaxies. Observations of such galaxies to search for the visible manifestation of a massive halo were carried out repeatedly using a variety of equipment and in different regions of the spectrum. The discovery of such a halo has been announced repeatedly. A good example The complexity of this task can be seen in publications. Several independent researchers have announced the discovery of such a halo around N005007. Subsequent observations with a high-aperture telescope with a total exposure of 24 hours (!) closed the question of the existence of a visible halo of this galaxy.

Among nearby irregular galaxies visible edge-on, the dwarf in Pegasus, which has been repeatedly studied, attracts attention. Observations of several fields at the BTA allowed us to completely trace the change in the density of stars of different types in it, both along the major and minor axis. The results are presented in Fig. 34, 35. They prove that, firstly, the structure of red giants is three times larger than the main body of the galaxy. Secondly, the shape of the distribution along the b axis is close to an oval or ellipse. Third, there is no visible halo of red giants.

Rice. 34: Boundaries of the Pegasus Dwarf galaxy based on studies of red giants. The locations of the BTA images are marked.

AGB blue stars Q O O

PegDw w « «(Zhoko* 0 0 ooooooooo

200 400 600 majoraxis

Rice. 35: Surface density distribution of different types of stars along the major axis of the Pegasus Dwarf galaxy. The disk boundary is visible, where a sharp drop in the density of red giants occurs. o 1

Our further results are based on photometry of NCT images that we obtained from a freely accessible archive. The search for galaxies photographed on NZT, resolved into red giants and visible face-on and edge-on, gave us about two dozen candidates for study. Unfortunately, the field of view of the NCT, which was insufficient for us, sometimes interfered with the goals of our work - to trace the parameters of the distribution of stars.

After standard photometric processing, H-P diagrams were constructed for these galaxies and stars of different types were identified. Their research showed:

1) For galaxies visible flat, the decrease in the surface density of red giants follows an exponential law (Fig. 36).

-|-1-1-1-E-1-1-1-1-1-1-1-1--<тГ

PGC39032/w "".

15 red giants Z w

Rice. 36: Exponential change in the density of red giants in the dwarf galaxy RSS39032 from center to edge based on NCT observations

2) Not a single edge-on galaxy has an extended halo of red giants along axis 2 (Fig. 37).

3) The shape of the distribution of red giants along the b axis looks like an oval or ellipse (Fig. 38).

Taking into account the randomness of the sample and the uniformity of the results obtained regarding the shape of the distribution of giants for all the studied galaxies, it can be argued that most galaxies have such a law of distribution of red giants. Deviations from the general rule are possible, for example, in interacting galaxies.

It should be noted that among the studied galaxies there were both irregular and spiral galaxies that were not giant. We have not found any significant differences between them in the laws of distribution of red giants along axis 2, with the exception of the gradient of the decrease in the density of the giants.

6.3.2 Spatial distribution of stars.

By highlighting stars of different types on the G-R diagram, we can see their distribution in an image of the galaxy or calculate the parameters of their spatial distribution over the body of the galaxy.

It is well known that the young stellar population of irregular galaxies is concentrated in star-forming regions, which are randomly scattered throughout the body of the galaxy. However, the apparent chaos immediately disappears if we trace the change in the surface density of young stars along the radius of the galaxy. On the graphs in Fig. 33 it is clear that local fluctuations associated with individual star formation regions are superimposed on the general, close to exponential, distribution.

For the older population - extended asymptotic giant branch stars - the distribution has a smaller gradient of density decline. And the smallest gradient has the ancient population - red giants. It would be interesting to check this dependence for the obviously most ancient population - the stars of the horizontal branch, however, in those galaxies where these stars are reachable, we see an insufficient number of them for statistical studies. The clearly visible dependence of the age of stars and spatial density parameters can have a completely logical explanation: although star formation occurs most intensely near the center of the galaxy, the orbits of stars become larger and larger over time, and over a period of several billion years, stars can move to the periphery of galaxies . It's hard to

Rice. 37: Drop in density of red giants along axis 2 in several edge-on galaxies

Rice. 38: An image of an edge-on dwarf galaxy shows the positions of the red giants found. The general form of the distribution is an oval or an ellipse, how such an effect can be verified in observations. Probably, only modeling the evolution of the galactic disk can help in resolving such hypotheses.

6.3.3 Structure of irregular galaxies.

Summarizing what has been said in other sections, we can imagine the structure of an irregular galaxy as follows: the most extensive star system in all coordinates is formed by red giants. The shape of their distribution is a thick disk, with an exponential drop in the surface density of the giants from the center to the edge. The thickness of the disk is almost the same throughout its entire length. Younger star systems have their own subsystems embedded in this disk. The younger the stellar population, the thinner the disk it forms. And although the youngest stellar population, blue supergiants, is distributed among individual chaotic regions of star formation, in general it also follows a general pattern. All nested subsystems do not avoid each other, i.e. Star forming regions may contain old red giants. For the most dwarf galaxies, where one star-forming region occupies the entire galaxy, this scheme is very arbitrary, but the relative sizes of the disks of the young and old populations hold true for such galaxies as well.

If radio data is also used to complete the review of the structure of irregular galaxies, it turns out that the entire stellar system is immersed in a disk or cloud of neutral hydrogen. The dimensions of the HI disk, as follows from the statistics of 171 galaxies, are approximately 5-6 times larger than the visible body of the galaxy at the level of Iv = 25"*. For a direct comparison of the sizes of hydrogen disks and disks from red giants, we have too little data.

In the ICIO galaxy, the sizes of both disks are approximately equal. For the Pegasus galaxy, the hydrogen disk is almost half the size of the red giant disk. And the galaxy NGC4449, which has one of the most extensive hydrogen disks, is unlikely to have an equally extensive disk of red giants. Kakh is confirmed not only by our observations. We have already mentioned the reports of Miniti and his colleagues about the discovery of a halo. Having imaged only part of the galaxy, they took the size of the thick disk along the b axis as a manifestation of the halo, which they reported, without attempting to study the distribution of stars in these galaxies along the major axis.

In our research we did not touch upon giant galaxies, but if we consider the structure of our Galaxy, then for it there already exists the concept of a “thick disk” for a metal-poor old population. As for the term “halo,” it seems to us to be applicable to spherical systems, but not to flattened systems, although this is only a matter of terminology.

6.3.4 Boundaries of galaxies.

The question of the boundaries of galaxies has probably not yet been fully explored. Nevertheless, our results can make a certain contribution to its solution. It is usually believed that the stellar density at the edges of galaxies gradually decreases to zero and the boundaries of galaxies, as such, simply do not exist. We measured the behavior of the most extended subsystem, consisting of red giants, along the Z axis. In those edge-on galaxies for which we obtained data from photometric images, the behavior of the density of red giants was uniform: the density dropped exponentially to zero (Fig. 37) . Those. the galaxy has a sharply defined edge along the Z axis, and its stellar population has a well-defined boundary, and does not gradually disappear.

It is more difficult to study the behavior of stellar density along the radius of the galaxy at the point where the stars disappear. For edge-on galaxies, it is more convenient to determine the size of the disk. The Pegasus galaxy shows a sharp drop in the number of red giants to zero along the major axis (Fig. 36). Those. the galaxy has a very sharp disk boundary, beyond which there are practically no red giants. Galaxy J10, to a first approximation, behaves in a similar way. The density of stars decreases, and at some distance from the center of the galaxy a sharp decrease in their number is observed (Fig. 33). However, in this case the reduction does not occur to zero. It is noticeable that red giants exist beyond the radius of their density jump, but beyond this limit they have a different spatial distribution than the one they had closer to the center. It is interesting to note that in the ISM spiral galaxy, red giants are distributed similarly. Those. exponential drop in density, jump and continuation beyond the radius of this jump. There was an assumption that this behavior is related to the mass of the galaxy (ICIO is the most massive irregular galaxy, after the Magellanic clouds, in the Local Group), but a small galaxy was found with the same behavior of red giants (Fig. 37). The parameters of red giants outside the shock radius are unknown; do they differ in age and metallicity? What is the type of spatial distribution for these distant stars? Unfortunately, today we cannot answer these questions. Research is needed on large telescopes with a wide field.

How large are the statistics of our studies to speak about the existence of thick disks in late-type galaxies as a widespread or general phenomenon? For all galaxies that had sufficiently deep images, we identified extended structures of giant giants.

Having examined the NZT archive, we found images of 16 galaxies, visible edge-on or face-on, and resolved into red giants. These galaxies are located at distances of 2-5 Me. Their list: N002976, VB053, 000165, K52, K73, 000190, 000187, IOSA438, P00481 1 1, P0S39032, ROS9962, N002366, I0S8320, IOSA442, N00625, N001560.

The exponential drop in density for face-on galaxies and the pattern of distribution of red giants around edge-on galaxies proves that in all these cases we are seeing manifestations of thick disks.

6.4 Red giant disks and hidden mass of irregular galaxies.

Radio observations of spiral and dwarf galaxies in H1 have shown little difference in the behavior of the rotation curves of galaxies. For both types of galaxies, for explanation

119 formation of the shape of rotation curves requires the presence of significant masses of invisible matter. Could the extended disks that we have found in all irregular galaxies be the invisible matter we are looking for? The masses of the red giants themselves, which we observe in the disks, are of course completely insufficient. Using our observations of the 1C1613 galaxy, we determined the parameters of the decrease in the density of the giants towards the edge and calculated their total number and mass in the entire galaxy. It turned out that Mred/Lgal = 0.16. Those. taking into account the mass of giant branch stars slightly increases the mass of the entire galaxy. However, it should be remembered that the red giant stage is a relatively short stage in the life of a star. Therefore, significant corrections must be made to the mass of the disk, taking into account the number of less massive stars and those stars that have already passed the red giant stage. It would be interesting, based on very deep observations of nearby galaxies, to check the population of subgiant branches and calculate their contribution to the total mass of the galaxy, but this is a matter for the future.

Conclusion

Summing up the results of the work, let us dwell once again on the main results.

The 6-m telescope obtained deep multicolor images of about 100 star-resolving galaxies. A data archive has been created. These galaxies can be approached when studying stellar populations, primarily high-luminosity variable stars of the LBV type. In the studied galaxies, the colors and brightness of all visible stars were measured. Hypergiants and supergiants of the highest luminosity are identified.

A large and homogeneous array of distance measurement data was obtained for all galaxies in the northern sky with velocities less than 500 km/s. The results obtained personally by the dissertation author are very significant among the entire volume of data. The obtained distance measurements make it possible to analyze the non-Hubble motions of galaxies in the Local complex, which limits the choice of a model for the formation of the Local “pancake” galaxies.

Based on distance measurements, the composition and spatial structure of the nearest groups of galaxies in the northern sky were determined. The results of the work allow for statistical comparisons of the parameters of groups of galaxies.

A study of the distribution of galaxies in the direction of the Virgo galaxy cluster was carried out. Several relatively close galaxies have been found located between the cluster and the Local Group. Distances were determined and galaxies belonging to the cluster itself and located in different parts of the periphery and center of the cluster were identified.

The distance to the clusters in Virgo was determined, which turned out to be equal to 17.0 Mpc and Coma Berenices, equal to 90 Mpc. On this basis, the Hubble constant was calculated to be R0 = 77 ± 7 km/s/Mpc.

Based on photometry of BTA and HST images, the brightness of the brightest stars in 10 galaxies of the N001023 group, located at a distance of 10 Mpc, was measured. The distances to the galaxies were determined and the Hubble constant in this direction was calculated. It was concluded that the velocity gradient between the Local Group and the NGC1023 group is small, which can be

121 can be explained by the relatively small mass of the Virgo galaxy cluster compared to all surrounding galaxies.

Based on studies of the spatial distributions of red giants in late-type galaxies, thick and extended disks of old stars have been discovered. The dimensions of such disks are 2-3 times larger than the dimensions of the visible body of the galaxy. It was found that the boundaries of these disks have rather sharp edges, beyond which there are very few stars.

Despite large-scale studies of distances to galaxies in the northern sky, there are no fewer questions left for the future than there were before the work began. But these questions are of a different quality, since now, especially in connection with the work of space telescopes, it is possible to make precise measurements that can change our ideas about near space. This concerns the composition, structure and kinematics of nearby groups of galaxies, the distances to which are intensively determined by the TCOW method.

The periphery of galaxies has received increasing attention, especially due to the search for dark matter and the history of the formation and evolution of galactic disks. It is remarkable that the first meeting on the periphery of galaxies will be held at the Lovell Observatory in the fall of 2002.

Acknowledgments

Over the many years that work was carried out on the topic of the dissertation I presented, many people, in one way or another, assisted me in my work. I am grateful to them for this support.

But I am especially pleased to express gratitude to those whose help I constantly felt. Without the highest qualifications of Galina Korotkova, work on the dissertation would have dragged on for an incredibly long time. The passion and tenacity in doing the work that Olga Galazutdinova displays allowed me to get results on a large number of objects in Virgo and N001023 in a fairly short period of time. Igor Drozdovsky, with his small service programs, provided us with great assistance in photometry of tens of thousands of stars.

I am grateful to the Russian Foundation for Basic Research, whose grants I received (95-02-05781, 97-02-17163, 00-02-16584), for financial support for eight years, which allowed me to conduct research more effectively.

List of references for dissertation research Doctor of Physical and Mathematical Sciences Tikhonov, Nikolai Aleksandrovich, 2002

1. Hubble E. 1929 Proc. Nat. Acad. Sci. 15, 168

2. Baade W. 1944 ApJ 100, 137

3. Baade W. 1963 in Evolution of Stars and Galaxies, ed. C.Payne-Gaposchkin, (Cambridge: MIT Press)

4. Sandage A. 1971 in Nuclei of Galaxies, ed. by D.J.K. O"Connel, (Amsterdam, North Holland) 601

5. Jacoby G.H., Branch V., CiarduU R., Davies R.L., Harris W.E., Pierce M.J., Pritchet C.J., Tonry J.L., Weich D.L. 1992 PASP 104, 599.

6. Minkovski R. 1964 Ann. Rev. Astr. Aph. 2, 247.7. de Jager K. 1984 Stars of the highest luminosity Mir, Moscow.

7. Gibson W.K., Stetson R.W., Freedman W.L., Mould J.R., Kennicutt R.C., Huchra G.P., Sakai S., Graham J.A., Fassett C.I., Kelson D.D., L.Ferrarese, S.M.G.Hughes, G.D.Illingworth, L.M. Maori, Madore B.F., Sebo K.M., Silbermann N.A. 2000 ApJ 529, 723

8. Zwicky F. 1936 PASP 48, 191

10. Cohen J.G. 1985 ApJ292, 9012. van den Bergh S. 1986, in Galaxy Distances and Deviations from Universal Expansion, ed. by B.F.Madore and R.B.TuUy, NATO ASI Series 80, 41

11. Hubble E. 1936 ApJ 84, 286

12. Sandage A. 1958 ApJ 127, 513

13. Sandage A., Tammann G.A. 1974 ApJ 194, 223 17] de Vaucouleurs G. 1978 ApJ224, 710

14. Humphreys R.M. 1983 ApJ269, 335

15. Karachentsev I.D., Tikhonov N.A. 1994 A&A 286, 718 20] Madore B., Freedman W. 1991 PASP 103, 93321. Gould A. 1994 AAJ426, 542

16. Feast M. 1998 MNRAS 293L, 27

17. Madore B., Freedman W. 1998 ApJ492, 110

18. Mould J., Kristian J. 1986 ApJ 305, 591

19. Lee M., Freedman W., Madore B. 1993 ApJ417, 533

20. Da Costa G., Armandroff T. 1990 AJlOO, 162

21. Salaris M., Cassisi S. 1997 MNRAS 289, 406

22. Salaris M., Cassisi S. 1998 MNRAS298, 166

23. Bellazzini M., Ferraro F., Pancino E. 2001 ApJ 556, 635

24. Gratton R., Fusi Pecci F., Carretta E., Clementini G., Corsi C., Lattanzi M. 1997 ApJ491, 749

25. Fernley J., Barnes T., Skillen L, Hawley S., Hanley C, Evans D., Solono E., Garrido R. 1998 A&A 330, 515

26. Groenewegen M., Salaris M. 1999 A&A 348L, 3335. Jacoby G. 1980 ApJS 42, 1

27. Bottinelli L., Gouguenheim L., Paturel C., Teerikorpi P., 1991 A&A 252, 550

28. Jacoby G., Ciardullo R. 1999 ApJ 515, 169

29. Harris W. 1991 Ann. Rev. Astr. Ap. 29, 543

30. Harris W. 1996 AJ 112, 1487

31. Blakeslee J., Vazdekis A., Ajhar E., 2001 MNRAS S20, 193

32. Tonry J., Schneider B. 1988 AJ 96, 807

33. Tonry J., Blakeslee J., Ajhar E., Dressier A. 2000 ApJ530, 625

34. Ajhar E., Lauer T., Tonry J., Blakeslee J., Dressier A., Holtzman J., Postman M., 1997 AJ 114, 626

35. Tonry J., Blakeslee J., Ajhar E., Dressier A. 1997 ApJ475, 399

36. Tully R., Fisher J. 1977 A&A 54, 661

37. Russell D. 2002 ApJ 565, 681

38. Sandage A. 1994 ApJ 430, 13

39. Faber S., Jackson R. 1976 ApJ 204, 668

40. Faber S., Wegner G., Burstain B., Davies R., Dressier A., Lynden-Bell D., Terlevich R. 1989 ApJS 69, 763

41. Panagia N., Gilmozzi R., Macchetto F., Adorf H., Kirshner R. 1991 ApJ 380, L23

42. Salaris M., Groenewegen M. 2002 A&A 3 81, 440

43. McHardy J., Stewart G., Edge A., Cooke B., Yamashita K., Hatsukade I. 1990 MNRAS 242, 215

44. Bahle H., Maddox S. Lilje P. 1994 ApJ 435, L79

45. Freedman W., Madore B., Gibson B., Ferrarese L., Kelson B., Sakai S., Mould R., Kennicutt R., Ford H., Graham J., Huchra J., Hughes S., Illingworth G., Macri L., Stetson P. 2001 ApJ553, 47

46. Lee M., Kim M., Sarajedini A., Geisler D., Gieren W. 2002ApJ565, 959

47. Kim M., Kim E., Lee M., Sarajedini A., Geisler D. 2002 AJ123, 244

48. Maeder A., Conti P. 1994 Ann. Rev. Astron. Astroph. 32, 227

49. Bertelli G., Bessan A., Chiosi C., Fagotto F., Nasi E. 1994 A&A 106, 271

50. Greggio L. 1986 A&A 160, 111

51. Shild H., Maeder A. A&A 127, 238.

52. Linga G. Catalog of Open Cluster Data, 5th edn, Stellar Data Center, Observatoire de Strasbourg, France.

53. Massey P. 1998 ApJ 501, 153

54. Makarova L. 1999 A&A 139, 491

55. Rozanski R., Rowan-Robinson M. 1994 MNRAS 271, 530

56. Makarova L., Karachentsev I., Takolo L. et al. 1998 A&A 128, 459

57. Crone M., Shulte-Ladbeck R., Hopp U., Greggio L. 2000 545L, 31

58. Tikhonov N., Karachentsev I., Bilkina V., Sharina M. 1992 A&A Trans 1, 269

59. Georgiev Ts, 1996 Doctoral dissertation Nizhny Arkhyz, CAO RAS 72] Karachentsev L, Kopylov A., Kopylova F. 1994 Bull. SAO 38.5

60. Kelson D., lUingworth G. et al. 1996 ApJ 463, 26

61. Saha A., Sandage A., et al. 1996ApJS 107, 693

62. Iben I., Renzini A. 1983 Ann. Rev. Astron. Astroph. 21, 271

63. Kholonov P. 1985 Star clusters. Mir, Moscow

64. Sakai S., Madore V., Freedman W., Laver T., Ajhar E., Baum W. 1997 ApJ478, 49

65. Aparicio A., Tikhonov N., Karachentsev I. 2000 AJ 119, 177.

66. Aparicio A., Tikhonov N. 2000 AJ 119, 2183

67. Madore V., Freedman W. 1995 AJ 109, 1645

68. Velorosova T., Merman., Sosnina M. 1975 Izv. RAO 193, 175 82] Tikhonov N. 1983 Communication. JSC 39, 40

69. Ziener R. 1979 Astron. Nachr. 300, 127

70. Tikhonov N., Georgiev T., Bilkina B. 1991 SoobiL. CAO 67, 114

71. Karachentsev L, Tikhonov N. 1993 A&A 100, 227 87] Tikhonov N., Karachentsev I. 1993 A&A 275, 39 88] Landolt A. 1992 AJ 104, 340

72. Treffers R.R., Richmond M.W. 1989, PASP 101, 725

73. Georgiev Ts.B. 1990 Astrophiz. Issled. (Izv.SAO) 30, 127

74. Sharina M., Karachentsev I., Tikhonov N. 1996 A&A 119, 499

75. Tikhonov N., Makarova L. 1996 Astr. Nachr. 317, 179

76. Tikhonov N., Karachentsev I. 1998 A&A 128, 325

77. Stetson P. 1993 User's Manual for SHORYOT I (Victoria: Dominion Astrophys. Obs.)

78. Drozdovsky I. 1999 Candidate's thesis of St. Petersburg State University, St. Petersburg

79. Holtzman J, Burrows C, Casertano S, et al. 1995 PASP 107, 1065 97] Aparicio A., Cepa J., Gallart C. et al. 1995 AJ 110, 212

80. Sharina M., Karachentsev I., Tikhonov I., Letters to AJ, 1997 23, 430

81. Abies N. 1971 Publ.U.S.Naval Obs. 20, part IV, 1

82. Karachentsev I. 1993 Preprint CAO 100, 1

83. Tolstoy E. 2001 Local Group in Microlensing 2000: A New Era of Microlensing Astrophysics, Cape Town, ASP Conf. Ser eds. J.W. Menzies and P.D. Sackett

84. Jacoby G., Lesser M. 1981 L J 86, 185

85. Hunter D. 2001 ApJ 559, 225

86. Karachentseva V. 1976 Communication. GAG 18, 42

87. Aparicio A., Gall art K., Bertelli G. 1997 AJ 114, 680112. Lee M. 1995 AJ 110, 1129.

88. Miller V., Dolphin A. et. al. 2001 ApJ 562, 713 114] Fisher J., TuUy R. 1975 A&A 44, 151

89. Greggio L., Marconi G. et al. 1993 AJ 105, 894

90. Lee M., Aparicio A., Tikhonov N. et al. 1999 AJ 118, 853

91. Armandroff T. et al. 1998 AJ 116, 2287

92. Karachentsev L, Karachentseva V. 1998 A&A 127, 409

93. Tikhonov N., Karachentsev I. 1999 PAGE 25, 391

94. Sandage A. 1984 AJ 89, 621

95. Humphreys R., Aaronson M. et al. 1986 AJ 93, 808

96. Georgiev Ts., Bilkina V., Tikhonov N. 1992 A&A 95, 581

97. Georgiev Ts. V., Tikhonov N.A., Karachentsev I.D., Bilkina B.I. 1991 A&AS 89, 529

98. Karachentsev ID., Tikhonov N.A. Georgiev Ts.B., Bilkina B.I. 1991 A&AS 91, 503

99. Freedman W., Hughes S. et al. 1994 ApJ427, 628

100. Sandage A., Tammann G. 1974 ApJ 191, 559 134] Sandage A., Tammann G. 1974 ApJ 191, 603

101. NASA/IP AC Extragalactic Database http://nedwww.ipac.caltech.edu 136] Karachentsev I., Tikhonov N., Sazonova L. 1994 PAGE 20, 84

102. Aloisi A., Clampin M., et al. 2001 AJ 121, 1425

103. Luppino G., Tonry J. 1993 ApJ410, 81

104. Tikhonov N., Karachentsev I. 1994 Bull. SAO 38, 32

105. Valtonen M., Byrd G., et al. 1993 AJ 105, 886 141] Zheng J., Valtonen M., Byrd G. 1991 A&A 247 20

106. Karachentsev I., Kopylov A., Kopylova F. 1994 Bnll SAO 38, 5 144] Georgiev Ts., Karachentsev I., Tikhonov N. 1997 YALZH 23, 586

107. Makarova L., Karachentsev I., Georgiev Ts. 1997 PAGE 23, 435

108. Makarova L., Karachentsev I., et al. 1998 A&A 133, 181

109. Karachentsev L, Makarov D. 1996 AJ 111, 535

110. Makarov D. 2001 PhD thesis

111. Freedman W., Madore V. et al. 1994 Nature 371, 757

112. Ferrarese L., Freedman W. et al. 1996 ApJ4Q4 568

113. Graham J., Ferrarese L. et al. 1999 ApJ51Q, 626 152] Maori L., Huchra J. et al. 1999 ApJ 521, 155

114. Fouque P., Solanes J. et al. 2001 Preprint ESO, 1431

115. BingeUi B. 1993 Halitati onsschrift, Univ. Basel

116. Aaronson M., Huchra J., Mould J. at al. 1982 ApJ 258, 64

117. BingeUi V., Sandage A., Tammann G. 1995 AJ 90, 1681157. Reaves G. 1956 AIJai, 69

118. Tolstoy E., Saha A. et al. 1995 AJ 109, 579

119. Dohm-Palmer R., Skillman E. et al. 1998 A J116, 1227 160] Saha A., Sandage A. et al. 1996ApJS 107, 693

120. Shanks T., Tanvir N. et al. 1992 MNRAS 256, 29

121. PierceM., McClure R., Racine R. 1992ApJ393, 523

122. Schoniger F., Sofue Y. 1997 A&A 323, 14

123. Federspiel M., Tammann G., Sandage A. 1998 ApJ495, 115

124. Whitemore W., Sparks W., et al. 1995 ApJ454L, 173 167] Onofrio M., Capaccioli M., et al. 1997 MNRAS 289, 847 168] van den Bergh S. 1996 PASF 108, 1091

125. Ferrarese L., Gibson B., Kelson D. et al. 1999 astroph/9909134

126. Saha A., Sandage A. et al. 2001 ApJ562, 314

127. Tikhonov N., Galazutdinova 0., Drozdovsky I., 2000 Astrophysics 43,

128. Humason M., Mayall N., Sandage A. 1956 AJ 61, 97173. TuUy R. 1980 ApJ 237, 390

129. TuUy R., Fisher J. 1977 A&A 54, 661

130. Pisano D., Wilcots E. 2000 AJ 120, 763

131. Pisano V., Wilcots E., Elmegreen B. 1998 AJ 115, 975

132. Davies R., Kinman T. 1984 MNRAS 207, 173

133. Capaccioli M., Lorenz H., Afanasjev V. 1986 A&A 169, 54 179] Silbermann N., Harding P., Madore B. et al. 1996 ApJ470, 1180. Pierce M. 1994 ApJ430, 53

134. Holzman J.A. , Hester J.J., Casertano S. et al. 1995 PASP 107, 156

135. CiarduUo R., Jacjby J., Harris W. 1991 ApJ383, 487 183] Ferrarese L., Mould J. et al. 2000 ApJ529, 745

136. Schmidt W., Kitshner R., Eastman R. 1992 ApJ 395, 366

137. Neistein E., Maoz D. 1999 AJ117, 2666186. Arp H. 1966 ApJS 14, 1

138. Elholm T., Lanoix P., Teerikorpi P., Fouque P., Paturel G. 2000 A&A 355, 835

139. Klypin A., Hoffman Y., Kravtsov A. 2002 astro-ph 0107104

140. Gallart C., Aparicio A. et al. 1996 AJ 112, 2596

141. Aparicio A., Gallart C. et al. 1996 Mem.S.A.It 67, 4

142. Holtsman J., Gallagher A. et al. 1999 AJ 118, 2262

143. Sandage A. Hubble Atlas of Galaxies Washington193. de Vaucouleurs G. 1959 Handb. Physik 53, 295194. van den Bergh S. 1960 Publ. Obs. Dunlap 11, 6

144. Morgan W. 1958 PASP 70, 364

145. Wilcots E., Miller B. 1998 AJXIQ, 2363

146. Pushe D., Westphahl D., et al. 1992 A J103, 1841

147. Walter P., Brinks E. 1999 AJ 118, 273

148. Jarrett T. 2000 PASP 112, 1008

149. Roberts M., Hyanes M. 1994 in Dwarf Galaxies ed. by Meylan G. and Prugniel P. 197

150. Bosma A. 1981 R J 86, 1791

151. Skrutskie M. 1987 Ph.D. Cornell University

152. Bergstrom J. 1990 Ph.D. University of Minnesota

153. Heller A., Brosch N., et al. 2000 MNRAS 316, 569

154. Hunter D., 1997 PASP 109, 937

155. Bremens T., Bingelli B, Prugniel P. 1998 A&AS 129, 313 208] Bremens T., Bingelli B, Prugniel P. 1998 A&AS 137, 337

156. Paturel P. et al. 1996 Catalog of Principal Galaxies PRC-ROM

157. Harris J., Harris W., Poole 0. 1999 AJ 117, 855

158. Swaters R. 1999 Ph.D. Rijksuniversiteit, Groningen

159. Tikhonov N., 1998 in lAU Symp. 192, The Stellar Content of Local Group Galaxies, ed. Whitelock P., and Cannon R., 15.

160. Minniti D., Zijlstra A. 1997 AJ 114, 147

161. Minniti D., Zijlstra A., Alonso V. 1999 AJ 117, 881

162. Lynds R., Tolstoy E. et al. 1998 AJ 116, 146

163. Drozdovsky I., Schulte-Ladbeck R. et al. 2001 ApJL 551, 135

164. James P., Casali M. 1998 MNRAS 3Q1, 280

165. Lequeux J., Combes F. et al. 1998 A&A 334L, 9

166. Zheng Z., Shang Z. 1999 AJ 117, 2757

167. Aparicio A., Gallart K. 1995 AJ 110, 2105

168. Bizyaev D. 1997 Candidate's dissertation, Moscow State University, SAI

169. Ferguson A, Clarke S. 2001 MNRAS32b, 781

170. Chiba M., Beers T. 2000 AJ 119, 2843

171. Cuillandre J., Lequeux J., Loinard L. 1998 in lAU Symp. 192, The Stellar Content of Group Galaxies, ed. Whitelock P., and Cannon R., 27

172. Fig. 1: Images of galaxies in the Virgo cluster taken by us with the BTA. To highlight the structure of galaxies, median filtering of images was carried out143

173. Fig. 3: Images of galaxies in the KSS1023 group obtained with the BTA and N8T (end)

Please note that the scientific texts presented above are posted for informational purposes only and were obtained through original dissertation text recognition (OCR). Therefore, they may contain errors associated with imperfect recognition algorithms. There are no such errors in the PDF files of dissertations and abstracts that we deliver.

Rice. 12.1. Spatial distribution of galaxies according to SDSS data. Green dots indicate all galaxies (in a given solid angle) with brightness exceeding a certain value. The red dots indicate the most luminous galaxies from distant clusters, forming a fairly homogeneous population; in the corresponding reference frame, their spectrum is redshifted compared to ordinary galaxies. The light blue and blue dots show the locations of regular quasars. The h parameter is approximately equal to 0.7.

Spherical galaxy clusters are more compact than open clusters and have spherical symmetry. Their members are noticeably concentrated towards the center. An example of a spherical cluster is the galaxy cluster in the constellation Coma Berenices, which contains many elliptical and lenticular galaxies (242). Its diameter is almost 12 degrees. It contains about 30,000 galaxies brighter than photographic magnitude 19. The distance to the cluster center is about 70 Mpc. Many rich galaxy clusters are associated with powerful, extended sources of X-ray radiation, the nature of which is most likely associated with the presence of hot intergalactic gas, similar to the coronas of individual galaxies.
There is reason to believe that galaxy clusters, in turn, are also unevenly distributed. According to some studies, the clusters and groups of galaxies surrounding us form a grandiose system - a Supergalaxy. In this case, individual galaxies apparently concentrate towards a certain plane, which can be called the equatorial plane of the Supergalaxy. The cluster of galaxies just discussed in the constellation Virgo is at the center of such a giant system. The mass of our Supergalaxy should be about 1015 solar masses, and its diameter should be about 50 Mpc. However, the reality of the existence of such second-order galaxy clusters currently remains controversial. If they exist, then only as a weakly expressed inhomogeneity in the distribution of galaxies in the Universe, since the distances between them can slightly exceed their sizes.

You look at the article (abstract): “ Spatial distribution of galaxies"from discipline" Astrophysics»

Abstracts and publications on other topics :

Typically, galaxies occur in small groups containing a dozen members, often combining into vast clusters of hundreds and thousands of galaxies. Our Galaxy is part of the so-called Local Group, which includes three giant spiral galaxies (our Galaxy, the Andromeda nebula and the Triangulum nebula), as well as more than 15 dwarf elliptical and irregular galaxies, the largest of which are the Magellanic Clouds. On average, the sizes of galaxy clusters are about 3 Mpc. In some cases, their diameter can exceed 10−20 Mpc. They are divided into open (irregular) and spherical (regular) clusters. Open clusters do not have a regular shape and have blurred outlines. The galaxies in them are very weakly concentrated towards the center. An example of a giant open cluster is the closest cluster of galaxies to us in the constellation Virgo (241). In the sky it occupies approximately 120 square meters. degrees and contains several thousand mostly spiral galaxies. The distance to the center of this cluster is about 11 Mpc. Spherical galaxy clusters are more compact than open clusters and have spherical symmetry. Their members are noticeably concentrated towards the center. An example of a spherical cluster is the galaxy cluster in the constellation Coma Berenices, which contains many elliptical and lenticular galaxies (242). Its diameter is almost 12 degrees. It contains about 30,000 galaxies brighter than photographic magnitude 19. The distance to the cluster center is about 70 Mpc. Many rich galaxy clusters are associated with powerful, extended sources of X-ray radiation, the nature of which is most likely associated with the presence of hot intergalactic gas, similar to the coronas of individual galaxies. There is reason to believe that galaxy clusters, in turn, are also unevenly distributed. According to some studies, the clusters and groups of galaxies surrounding us form a grandiose system - a Supergalaxy. In this case, individual galaxies apparently concentrate towards a certain plane, which can be called the equatorial plane of the Supergalaxy. The cluster of galaxies just discussed in the constellation Virgo is at the center of such a giant system. The mass of our Supergalaxy should be about 1015 solar masses, and its diameter should be about 50 Mpc. However, the reality of the existence of such second-order galaxy clusters currently remains controversial. If they exist, then only as a weakly expressed inhomogeneity in the distribution of galaxies in the Universe, since the distances between them can slightly exceed their sizes.

The most striking feature of the spatial distribution of globular clusters in the Galaxy is a strong concentration towards its center. In Fig. Figure 8-8 shows the distribution of globular clusters throughout the celestial sphere, here the center of the Galaxy is in the center of the figure, the north pole of the Galaxy is at the top. There is no noticeable zone of avoidance along the Galactic plane, so interstellar absorption in the disk does not hide a significant number of clusters from us.

In Fig. Figures 8-9 show the distribution of globular clusters along the distance from the Galactic center. There is a strong concentration towards the center - most globular clusters are located in a sphere with a radius of ≈ 10 kpc. It is within this radius that almost all globular clusters formed from matter are located single protogalactic cloud and formed subsystems of the thick disk (clusters with > -1.0) and their own halo (less metallic clusters with extremely blue horizontal branches). Metal-poor clusters with horizontal branches that are anomalously red for their metallicity form a spheroidal subsystem accreted halo radius ≈ 20 kpc. About one and a half dozen more distant clusters belong to the same subsystem (see Fig. 8-9), among which there are several objects with anomalously high metal contents.

Accreted halo clusters are believed to be selected from satellite galaxies by the Galaxy's gravitational field. In Fig. 8-10 schematically shows this structure according to Borkova and Marsakov from the Southern Federal University. Here the letter C denotes the center of the Galaxy, S is the approximate position of the Sun. In this case, clusters with a high content of metals belong to the oblate subsystem. We will dwell on a more detailed justification for the division of globular clusters into subsystems in § 11.3 and § 14.3.

Globular clusters are also common in other galaxies, and their spatial distribution in spiral galaxies resembles that in our Galaxy. The Magellanic Clouds are noticeably different from the Galactic clusters. The main difference is that, along with old objects, the same as in our Galaxy, young clusters are also observed in the Magellanic Clouds - the so-called blue globular clusters. It is likely that in the Magellanic Clouds the era of globular cluster formation either continues or ended relatively recently. In our Galaxy, there appear to be no young globular clusters similar to the blue clusters of the Magellanic Clouds, so the era of the formation of globular clusters in our Galaxy ended a long time ago.

Globular clusters are evolving objects that gradually lose stars in the process. dynamic evolution . Thus, all clusters for which it was possible to obtain a high-quality optical image showed traces of tidal interaction with the Galaxy in the form of extensive deformations (tidal tails). Currently, such lost stars are also observed in the form of increases in stellar density along the galactic orbits of clusters. Some clusters whose orbits pass near the galactic center are destroyed by its tidal influence. At the same time, galactic orbits of clusters also evolve due to dynamic friction.

In Fig. 8-11 shows the dependence diagram globular cluster masses from their galactocentric positions. The dashed lines delineate the region of slow evolution of globular clusters. The upper line corresponds to the critical value of the mass that is stable for dynamic friction effects , leading to the slowdown of a massive star cluster and its fall into the center of the Galaxy, and the lower one - for dissipation effects taking into account tidal effects during the passage of clusters through the galactic plane. The reason for dynamic friction is external: a massive globular cluster moving through the stars of the field attracts the stars it meets on its way and forces them to fly around behind it along a hyperbolic trajectory, which is why an increased density of stars forms behind it, creating a decelerating acceleration. As a result, the cluster slows down and begins to approach the galactic center along a spiral trajectory until it falls onto it in a finite time. The greater the mass of the cluster, the shorter this time. Dissipation (evaporation) of globular clusters occurs due to the internal mechanism of stellar-stellar relaxation constantly operating in the cluster, which distributes stars according to their velocities according to Maxwell’s law. As a result, the stars that received the largest velocity increases leave the system. This process is significantly accelerated by the passage of a cluster near the galactic core and through the galactic disk. Thus, with a high probability we can say that the clusters lying on the diagram outside the area bounded by these two lines are already finishing their life path.

I wonder what accreted globular clusters discover the dependence of their masses on their position in the Galaxy. The solid lines in the figure represent direct regressions performed on genetically associated (black dots) and accreted (open circles) globular clusters. It can be seen that genetically related clusters do not show changes in their average mass with increasing distance from the galactic center. But for accreted clusters there is a clear anticorrelation. So the question that needs to be answered is why is there an increasing deficit of massive globular clusters in the outer halo with increasing galactocentric distance (the almost empty upper right corner of the diagram)?