RU2445641C2 - Method of tying coordinates of celestial radio sources to lipovka-kostko-lipovka (lkl) optical astrometric coordinate system - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: disclosed is a solution to the engineering problem of measuring and recording coordinates of identified celestial objects through detected radio refraction, physical characteristics of interstellar matter and intergalactic matter with high degree of reliability and accuracy compared to previously used methods.

EFFECT: high reliability and accuracy of associating radio sources with optical objects; the number radio sources identified with optical objects increased several tens of times using the method.

2 dwg, 3 tbl

Description

The invention relates to the field of scientific and technical problems studied in radio astronomy, astrophysics, astrometry, geodesy and navigation, and can be used to bind radio sky to the optical sky to create a fundamental catalog of high density reference radio sources having the correct optical identifications for space navigation purposes, for studies of the nature of celestial objects in a wide range of wavelengths, for the study of radiorefraction in outer space, to refine the received information about cosmos objects in the radio range, which is very important for understanding the evolution of the universe.

To assess the novelty and technical level of the claimed solution, we consider the technical means known to the applicant for a similar purpose, which are characterized by a combination of features similar to the claimed invention, known from information that has become publicly available before the priority date of the invention.

The currently known method of linking radio sky to optical ICRF2 (English International Celestial Reference Frame - “International Celestial Reference System”) [http://rorf.usno.navy.mil/ICRF2/] is based on a small catalog of radio sources (3414 objects) with a density of their location in the sky, approximately one object per ten square degrees for the northern sky (DEC> -37 °). First of all, we note that surveys on interferometers are performed on small sites of the order of one square degree or less, as a result of which most of the sites do not even have one reference object, while for accurate reference of the studied site, it is necessary to have at least three reference objects on the site .

The main criticism of the binding of radio sky in the ICRF2 reference directory is as follows:

1. When using the radio sky binding according to ICRF2 to the reference catalog, it turns out that the vast majority of radio sources will fall in the optical image into an empty field (Empty Field).

2. Our studies have shown that a significant part of these reference objects is radio sources that randomly coincided with optical objects, that is, not all reference objects in this catalog have reliable optical identifications.

3. In the ICRF2 reference skybinding method, nothing is mentioned about radiorefraction in the Earth’s atmosphere in the centimeter wave range, which is significant especially near the garisont and should be taken into account in radio surveys performed in azimuths and at low altitudes.

4. If a high-precision coordinate of a radio source identified with a quasar is given, then at least three radio sources with optical objects should coincide within the same lobe of the radiation pattern of the interferometer. Only in this case, it can be argued that the binding of the radio sky to the optical one is performed correctly, including the orientation of the observed site, and it can be argued that the coordinate of the radio source recommended in the reference objects is calculated correctly.

5. When using the ICRF2 method of binding a radio sky to an optical one, it is assumed that the radio waves propagate in outer space in a straight line and do not experience distortion of the trajectory when passing through interstellar space, which is not true.

The method we developed (LCL) of binding the radio sky to the optical takes into account the previously discovered and previously unknown phenomenon of the displacement of the radio coordinates of galaxies, quasars, objects such as stars and gas nebulae relative to each other due to refraction of radio waves in outer space.

Our method leads to a high degree of reliability of the binding of the vast majority of radio sources to the optical sky.

The radio refraction we discovered in outer space depends on the characteristics of Interstellar and Intergalactic media (MLM, MGS) (density, density gradient, temperature, degree of ionization), the remoteness of celestial objects, and all this must be taken into account when performing optical identifications of radio sources.

In a patent search, we discovered the only invention N 2002273 C1, author Alekseev V.A. “A method for determining the relationship of celestial coordinates established in the optical and radio ranges,” which is close in theme to the task we posed of linking the radio sky to the optical sky.

1. This method cannot be applied to ground-based measurements of the radio coordinates of celestial objects, since "radio emission is received using a radio interferometer located in outer space."

2. A significant drawback of the method Alekseev VA is the binding of two coordinate systems (optical and radio) at two points, while it is known that to determine the location of an object in the sky requires three reference objects and one control object, the coordinates of which are known with high accuracy. Thus, about 10 ⁵ -10 ⁶ reference objects are required that are evenly spaced in the northern sky in order to correctly associate the radio sky with the optical one.

Such a number of reference objects can be provided only by the Fundamental catalogs of reference stars of the FK6 type and UCAC catalog [http://ad.usno.navy.mil/UCAC/].

3. The author does not take into account radiorefraction in outer space, which even at high galactic latitudes is ± 3 min of the arc, which will significantly affect the accuracy of the measured coordinates.

The present invention is based on the solution of the technical problem of measuring and recording radio coordinates and physical characteristics of celestial objects in the radio range, as well as the physical characteristics of the MZS, MGS with a high degree of reliability and accuracy compared to the above methods.

Currently, the generally accepted point of view is the assertion that at high galactic latitudes (b> 2) only extragalactic objects, which are active galaxies and quasars ("Nearly all discrete radio sources more than 1 or 2 from the Galactic plane are extragalactic") emit radio waves. P.1694. The NRAO VLA SKY SURVEY, JJCondon, WDCotton, EWGreisen, QFYin, RAPerley, GBTaylor, JJBroderick. The Astronomical Journal, 115, 1693-1716, 1998 May).

We maintain that this view is erroneous.

In 1985, we performed optical identifications using a blink comparator at the National Institute of Astrophysics of Optics and Electronics (Tonantsintla, Mexico) using glass copies of the Palomar sky atlas. The reference stars of the Pulkovo catalogs were used as reference stars for the binding of radio coordinates. Even then, a poor coincidence of the coordinates of radio sources with optical objects such as galaxies and quasars was discovered, as well as the fact that there is radio emission from star-shaped objects [Preprint N37 l, USSR Academy of Sciences, Special Astrophysical Observatory, Leningrad Branch, 1986, Lipovka NM , E. Chavira - Navarrete “Optical Identification of Weak Radio Sources”]. [Preprint N 81 of the St. Petersburg Special Astrophysical Observatory of the Russian Academy of Sciences, E. Chavira-Navarrete, O. V. Kiyaeva, N. M. Lipovka, A. A. Lipovka, “Methodology for Optical Identification Using Blink-Comparator Devices”]. [Preprint N88 of the St. Petersburg Special Astrophysical Observatory of the Russian Academy of Sciences, E. Chavira-Navarrete, N. M. Lipovka, A. A. Lipovka, “Optical positions of 748 weak diffuse objects and galaxies in the vicinity of radio sources of the RC catalog”, 1993].

The fallacy of the above statement that only extragalactic objects emit radio is also confirmed by our recent studies on the optical identification of radio sources made by the LCL method. It turned out that some of the radio sources are identified with galaxies and quasars, but a significant part of radio sources are identified with stars. The brightest stars belong to the local spiral arm of the Galaxy, in which our solar system is located.

The objective of the proposed method is to increase the reliability and accuracy of the binding of radio sources to optical objects by using the following sequence of operations in calculating the astrometric equatorial coordinates of radio sources and determining the true physical characteristics of celestial objects, as well as the characteristics of the MLM, the MGS in a wide range of wavelengths.

The essence of the claimed invention as a technical solution is expressed in the following combination and sequence of essential features sufficient to achieve the above technical result provided by the invention.

The method of binding the coordinates of celestial radio sources to the optical astrometric coordinate system Lipovka-Kostko-Lipovka (LKL, English LKL)

The method of binding the coordinates of radio sources to optical luminaries, proposed by us (LCL), differs in that the coordinates are coordinated according to the following rules:

radio sky binding is performed directly to the optical sky;

optical identifications are performed on the site, the size of which does not exceed the size of the sky, defined by the petals of the diagram of the interferometer;

determine the totality of radio sources and the adequate totality of optical celestial objects;

identify the morphological affiliation of radio sources (galaxies, quasars, nebulae, nearby stars and distant stars);

identify radio sources and optical objects in compliance with their spectral characteristics inherent in this type of object;

comply with the principle of configurational coincidence of at least three objects on the site, the size of which is determined by the petals of the interferometer diagram

comply with the principle of brightness matching of objects of radio optics, characteristic of a given morphological type of objects;

take into account the presence of radiorefraction in (MOH, MGS) [Lipovka A.A., Lipovka N.M. The end of the "Empty Field" epoch in optical identifications. "Molecules in Space and Laboratory", the meeting held in Paris, France, May 14-18, 2007. Editors: J.L. Lemaire, F. Combes. Publisher: S. Diana, p. 26.].

In the above method (LKL, Eng. LKL) of radio-sky linking to optical, there is a combination and sequence of features that ensure the receipt of the correct technical result in all cases to which the requested amount of legal protection applies to intellectual property.

Our proposed method of linking the radio sky to the optical one is free from the disadvantages of the ICRF2 system of reference objects and has shown very good results. The number of radio sources identified with optical objects increased by several dozen times.

The applicants did not identify sources containing information about the technical solutions for linking the radio sky to the optical one, both by individual characteristics and by the totality of features that match the totality of features claimed in our invention. This allows us to conclude that the present invention meets the condition of "novelty."

Information confirming the real possibility of carrying out the invention

An example of the use of the proposed method (LCL) for binding a radio sky to an optical one is the identification made by us in the area of radio emission associated with the galaxy A1716 cluster.

Radio-sky binding made in the review [The NRAO VLA SKY SURVEY, J.J. London, W. D. Cotton, E.W. Greisen, Q. F. Yin, R. A. Perley, G. B. Taylor, J. J. Broderick. The Astronomical Journal, 115, 1693-1716, 1998, May] (NVSS), according to a small list of reference objects (419 reference objects for the northern sky), showed that only one radio source coincided with an optical object on a site measuring one square degree. Moreover, in the nearest vicinity of the Galaxy IC883, no radio source was identified anymore.

The binding of the same sky area, performed by our proposed method (LCL), showed a coincidence of 90% of the radio sources with optical objects.

Moreover, by performing optical identifications according to the proposed method (LCL), we found that the stars also emit radio, but their radio coordinate system is shifted relative to the radio coordinate system for objects associated with a galaxy cluster.

Figure 1a shows an optical image of the sky in the vicinity of the Galaxy IC883 (G) (http://cadcwww.dao.nrc.ca/cadcbin/getdss/, Palomar Atlas). Figure 1b shows a radio image of the same sky in accordance with the NVSS survey [The NRAO VLA SKY SURVEY, J.J. London, W. D. Cotton, E. W. Greisen, Q. F. Yin, R. A. Perley, G. B. Taylor, J. J. Broderick. The Astronomical Journal, 115, 1693-1716, 1998 May, http://www.cv.nrao.edu/NVSS]. The binding in this review was performed using 419 reference radio sources, the density of which was one reference object per 80 square degrees.

Thus, it turned out that only one site of 80 sites has a reference object, and there is no reference object on the site under consideration (Fig. 1b). When comparing figa and figb it is seen that two bright radio sources "a" and "c" fall into an empty field in the optical image when the positional combination of the source "G" on the optical map (figa) and the object (G?) on the radio card (figb) according to the binding according to the NVSS measurements.

We doubted the correspondence of radio and optical objects proposed in the NVSS review, since, as it turned out, the radio spectrum of the object (G?), Combined with the Galaxy IC883, did not correspond to the spectrum of the active Galaxy, which is Galaxy IC883.

If the proposed in NVSS identification of IC883 with the specified radio source (fig.1b) is questioned and try to re-identify this area using our proposed method (LCL), then it turns out that in the nearest vicinity of the Galaxy IC883 there is a radio source (G, fig.2b) with the spectrum typical of radio galaxies.

The detected radio source (Fig.2b) in the optical image of the sky falls into an empty field according to the equatorial coordinates given in the NVSS survey, i.e. does not have an optical object with which it could be identified. Moreover, in the immediate vicinity of this radio source nothing else was identified with optical objects.

However, when combining IC883 (G, fig. 2a) with a radio object (G, fig. 2b), we identified with good accuracy another 8 objects on a site measuring 15 ′ × 15 ′. The identification accuracy was ΔRA = -0.12 ^s ± 0.5 ^s and ΔDEC = -4 ″ ± 10 ″

The true equatorial coordinates of the radio source that we identified with the Galaxy IC883 turned out to be shifted in right ascension by ΔRA = -01 ^m 32 ^s and in declination ΔDEC = + 15′28 ″ (object G). It should be noted that at the same site we also detected radiorefraction in the interstellar medium, which, depending on the remoteness of the studied region from the observer and the parameters of the interstellar medium, shifts the coordinates of radio objects in the sky [Lipovka AA, Lipovka NM The end of the "Empty Field" epoch in optical identifications. // "Molecules in Space and Laboratory", the meeting held in Paris, France, May 14-18, (2007). Editors: JLLemaire, F. Combes. Publisher: S. Diana., P. 26].

In FIG. 2b, the letters L, M, N, and K mark four bright radio sources that, when combined with IC883 and the radio source (G), fall into an empty field. However, they are all identified with optical objects (which are very few in this area), if we take into account radiorefraction in outer space, having displaced them (L, M, N, and K) for 3 seconds in right ascension towards increasing right ascension.

Moreover, on a site of one square degree in the vicinity of IC883, we were able to identify with good accuracy 9 weak radio sources with stars 10 ^m -17 ^m (see table 3). It turned out that due to radio refraction in outer space, the coordinate system of radio stars in the sky is shifted relative to the coordinate system of optical stars in right ascension by ΔRA = -01 ^m 09 ^s and in declination ΔDEC = + 15′37 ″. On fig.2b two objects are indicated, such as ST (star).

We performed further optical identifications in the vicinity of IC883 on a site measuring one square degree by the method (LCL) and calculated the coordinates of objects in the optical range of the AWP [Irvin M., 1998 (http://www.ast.cam.ac.uk/ ~ mike / apmcat /)] and in the radio band [The NRAO VLA SKY SURVEY, JJCondon, WDCotton, EWGreisen, QFYin, RAPerley, GBTaylor, JJBroderick, The Astronomical Journal, 115, 1693-1716, 1998, May, NVSS (http://www.cv.nrao.edu/NVSS/)], which are shown in tables 1-3.

Two sites were considered: one in the optical range in the vicinity of IC883 (optical field) and the second in the radio range in the vicinity of a relatively bright radio source with a non-thermal spectrum (α = -1.0, object N14, table 1) with coordinates for the epoch 2000.0 along the right ascension RA ( J) = 13 ^h 19 ^m 03.1 ^s and according to the declination DEC (J) = + 34 ° 23′52.2 ″.

As mentioned above, when the combination of the radio source with the radio coordinates RA (J) = 13 ^h 20 ^m 35.38 ^s and DEC (J) = + 34 ° 08′22.5 ″ was proposed with NVSS data, the galaxy IC883 in the immediate vicinity of the galaxy no longer coincided not a single radio source with an optical object. A similar picture is observed with optical identifications in the vicinity of a bright radio source with the proposed identification according to NVSS data (object N14). In this area, a bright radio source (object N14) fell into an empty field (Empty Field), and in the immediate vicinity of one square degree in size, not a single radio source was identified with an optical object.

A survey of these two sites showed that between them there is a good similarity in the configurational arrangement of objects and the brightness correspondence in both optics and radio. Accordingly, we assumed that the true radio image is shifted relative to the optical in right ascension by ΔRA = 01 ^m 32 ^s and in declination by ΔDEC = -15′32 ″. After taking into account the above correction (linking the radio sky to the optical), the combination of a bright radio source (object N14) with Galaxy IC883 showed a perfect coincidence of a large number of radio objects with optical ones.

Table 1 shows the source (according to NVSS) and radio coordinates given for our correction obtained by linking a bright radio source with coordinates RA (J) = 13 ^h 19 ^m 03.1 ^s and DEC (j) = + 34 ° 23′52.0 ″ to Galaxy IC883.

The coordinates of the radio sources (columns 2, 3), presented in table 1, were obtained from files in Fits format according to NVSS.

Column 4 shows the measured flux density according to NVSS. For objects whose radio flux density is less than 2.5 mJy, a dash is worth it, since these objects are not listed in the NVSS catalog.

Columns 5 and 6 show the corrected ΔRA = 01 ^m 32 ^s and ΔDEC = -15′32 ″ coordinates of the radio sources corrected for the correction (the amendment is added to columns 2, 3 of Table 1).

Optical identifications were performed for the coordinates of the radio sources (columns 5, 6, table 1) obtained after binding the radio sky to Galaxy IC883.

Table 2 presents optical identifications according to AWP data (Irvin M., 1998, http://www.ast.cam.ac.uk/~mike/apmcat) for those objects from table 1 for which the coordinates turned out to be close to optical:

column 1 - serial number according to table 1;

column 2 - right ascension of an optical object according to AWP data;

column 3 - declination of the optical object according to AWP;

columns 4, 6 - magnitude in blue and red rays according to AWP;

columns 5, 7 — size in pixels and ellipticity of an optical object according to AWP data;

When combining the radio coordinates of a bright radio source (object N14, table 1, columns 5, 6) and Galaxy IC883 (RA (J) = 13 ^h 20 ^m 35.38 ^s , DEC (J) = + 34 ° 08′22.5 ″ (object N14, table 2, columns 2, 3), 17 radio sources were identified with optical objects.The accuracy of the optical identification was Δ = -0.12 ^s ± 0.5 ^s and the declination Δ = -4.4 ″ ± 11.5 ″ according to the right ascension.

It should be emphasized that Table 1 includes several weak radio sources projected onto the A1716 Galaxy cluster, which do not have an optical pair at the shift of the radio sky coordinates proposed above by ΔRA = + 01 ^m 32 ^s and ΔDEC = -15′32 ″. We found that these radio sources have their own coordinate system and are shifted relative to their optical image by ΔRA = + 01 ^m 09 ^s and ΔDEC = -15′28 ″.

Table 3 presents the corrected coordinates of the radio catalog (table 1, columns 2, 3), taking into account the amendments to right ascension (ΔRA = + 01 ^m 09 ^s ) and declination (ΔDEC = -15′28 ″):

column 1 - serial number according to table 1;

column 2 - right ascension of the radio source, taking into account the corrections for the stellar component (ΔRA = + 01 ^m 09 ^s );

column 3 - the declination of the radio source, taking into account the above amendments for the stellar component (ΔDEC = -15′28 ″);

column 4 - right ascension of the optical object (AWP);

column 5 - declination of the optical object (AWP);

columns 6, 8 - magnitude by optical identifications (AWS);

columns 7, 9 are the size in pixels and the ellipticity of the optical object (AWP).

As a result of the optical identification performed (Table 3), it turned out that 9 weak radio sources coincided with 10 ^m -19 ^m stars. The identification error for the right ascension was Δ = 0.02 ^s ± 0.64 ^s and for the declination Δ = 5 ″ ± 10. ″.

We suggested that the observed effect (a shift in the coordinate system of radio stars relative to the coordinate system of radio objects associated with the Galaxy A1716 cluster) may be due to radiorefraction in the interstellar medium.

In total, in our sample of 29 objects located on the site in one square degree, 26 radio sources (90%) were identified, while in the case of the NVSS proposed linking of the radio sky to the optical coordinate coordinate combination of the radio sky, only one radio source was identified on the site two square degrees.

Based on the foregoing, according to the applicants, it can be concluded that the claimed technical solution “Method of linking the coordinates of celestial radio sources to the optical astrometric coordinate system Lipovka-Kostko-Lipovka (LKL, English LKL), meets the condition of“ inventive step ”.

Claims (1)

The method of linking the coordinates of celestial radio sources to an optical astrometric coordinate system by using reference objects, characterized in that the following sequence of operations is used to solve the reliability problem of binding the coordinates of a radio source to an optical object:
radio sky binding is performed directly to the optical sky;
optical identifications are performed on the site, the size of which does not exceed the size determined by the petals of the interferometer;
identify the morphological affiliation of radio sources (galaxies, quasars, nebulae, nearby stars and distant stars);
identify radio sources and optical objects with observance of their spectral characteristics inherent in this morphological type of objects;
comply with the principle of configuration match for at least three objects on the site, the size of which is determined by the petals of the diagram of the interferometer;
comply with the principle of brightness matching of objects of radio optics,
characteristic for this morphological type of object;
take into account the presence of radiorefraction in interstellar and intergalactic environments.

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