INTERSTELLAR MEDIUM AND DECAMETER RADIO SPECTROSCOPY

DOI: https://doi.org/10.15407/rpra26.04.314

S. V. Stepkin, O. O. Konovalenko, Y. V. Vasylkivskyi, D. V. Mukha

Abstract


Purpose: The analytical review of the main results of research in the new direction of the low-frequency radio astronomy, the interstellar medium radio spectroscopy at decameter waves, which had led to astrophysical discovery, recording of the radio recombination lines in absorption for highly excited states of interstellar carbon atoms (more than 600).

Design/methodology/approach: The UTR-2 world-largest broadband radio telescope of decameter waves optimally connected with the digital correlation spectrum analyzers has been used. Continuous modernization of antenna system and devices allowed increasing the analysis band from 100 kHzto 24 MHz and a number of channels from 32 to 8192. The radio telescope and receiving equipment with appropriate software allowed to have a long efficient integration time enough for a large line series simultaneously with high resolution, noise immunity and relative sensitivity.

Findings: A new type of interstellar spectral lines has been discovered and studied, the interstellar carbon radio recombination lines in absorption for the record high excited atoms with principal quantum numbers greater than 1000. The line parameters (intensity, shape, width, radial velocity) and their relation ship with the interstellar medium physical parameters have been determined. The temperature of line forming regions is about 100 K, the electron concentration up to 0.1 cm–3 and the size of a line forming region is about 10 pc. For the first time, radio recombination lines were observed in absorption. They have significant broadening and are amplified by the dielectronic-like recombination mechanism and are also the lowest frequency lines in atomic spectroscopy.

Conclusions: The detected low-frequency carbon radio recombination lines and their observations have become a new highly effective tool for the cold partially ionized interstellar plasma diagnostics. Using them allows obtaining the information which is not available with the other astrophysical methods. For almost half a century of their research, a large amount of hardware-methodical and astrophysical results have been obtained including a record number of Galaxy objects, where there levant lines have been recorded. The domestic achievements have stimulated many theoretical and experimental studies in other countries, but the scientific achievements of Ukrainian scientists prove the best prospects for further development of this very important area of astronomical science.

Key words: low-frequency radio astronomy; radio telescope; interstellar medium; radio recombination lines; carbon; hydrogen; spectral analyzer

Manuscript submitted 01.09.2021

Radio phys. radio astron. 2021, 26(4): 314-325

REFERENCES

1. KAPLAN, S. A. and PIKELNER, S. B., 1979. Physics of theInterstellar Medium. Moscow, Russia: Nauka Publ. (in Russian).

2. SPITZER, L., 1978. Physical Processes in the Interstellar Medium. New York: Wiley. DOI: https://doi.org/10.1063/1.2995108

3. SHKLOVSKII, I. S., 1956. Cosmic Radio Emission. Moscow, Russia: Gostekhizdat Publ. (in Russian).

4. KARDASHEV, N. S., 1959. On the Possibility of Detection of Allowed Lines of Atomic Hydrogen in the Radio-Frequency Spectrum. Sov. Astron. vol. 3, pp. 813–820.

5. GORDON, M. A. and SOROCHENKO, R. L., 2002. Radio Recombination Lines: Their Physics and Astronomical Applications. Dordreht, Boston, London: Kluver Academic Publ. DOI: https://doi.org/10.1007/978-94-010-0261-5

6. KONOVALENKO, A. A. and SODIN, L. G., 1980. Neutral 14N in the interstellar medium. Nature. vol. 283, pp. 360–361. DOI: https://doi.org/10.1038/283360a0

7. BLAKE, D. H., CRUTCHER, R. M. and WATSON, W. D.,1980. Identifi cation of the anomalous 26.131-MHz nitrogenline observed towards Cas A. Nature. vol. 287, pp. 707–708. DOI: https://doi.org/10.1038/287707a0

8. KONOVALENKO, A. A. and SODIN, L. G., 1981. The 26.13 MHz absorption line in the direction of Cassiopeia A. Nature. vol. 294, pp. 135–136. DOI: https://doi.org/10.1038/294135a0

9. KONOVALENKO, A. A., 1990. Review of decameter recombination lines: Problems and Methods. In: M. A. GORDON and R. L. SOROCHENKO, eds. Radio Recombination Lines: 25 Years of Investigation. Proceedingsof IAU Colloq. Dordrecht: Springer, pp. 175–189. DOI:https://doi.org/10.1007/978-94-009-0625-9_17

10. KONOVALENKO, A. A., STEPKIN, S. V. and SHALUNOV,D. V., 2001. Low-Frequency Carbon RecombinationLines. Radio Phys. Radio Astron. vol. 6, no. 1, pp. 21–31.

11. KONOVALENKO, A. A. and STEPKIN, S. V., 2005. RadioRecombination Lines. In: L. I. GURVITS, S. FREY and S. RAWLINGS, eds. Radio Astronomy from Karl Jansky to Microjansky – JENAM’03. EAS Publication Series. vol. 15, pp. 271–295. DOI: https://doi.org/10.1051/eas:2005158

12. STEPKIN, S. V., KONOVALENKO, A. A., KANTHARIA,N. G. and UDAYA SHANKAR, N., 2007. Radio recombination lines from the largest bound atoms in space.Mon. Not. R. Astron. Soc. vol. 374, is. 3, pp. 852–856.DOI:https://doi.org/10.1111/j.1365-2966.2006.11190.x

13. GEE, C. S., PERCIVAL, L. C., LODGE, J. G. and RICHARDS, D., 1976 Theoretical Rates for Electron Excitationof Highly-Excited Atoms. Mon. Not. R. Astron. Soc.vol. 176, is. 1, pp. 209–215. DOI: https://doi.org/10.1093/mnras/175.1.209

14. SHAVER, P. A., 1975. Theoretical intensities of low-frequency recombination lines. Pramana – J. Phys. vol. 5, is. 1,pp. 1–28. DOI: https://doi.org/10.1007/BF02875147

15. WALMSLEY, C. M. and WATSON, W. D., 1982. The influence of dielectronic-like recombination at low temperatureson the interpretation of interstellar, radio recombination lines of carbon. Astrophys. J. vol. 260, pp. 317–325. DOI:https://doi.org/10.1086/160256

16. KONOVALENKO, A. A., 1984. Decameter-wavelength carbonrecombination lines toward Cassiopeia A. Sov. Astron. Lett. vol. 10, is. 11, pp. 353–356.

17. KONOVALENKO, A. A., 1984. Decameter excited-carbonlines in certain galactic objects. Sov. Astron. Lett. vol. 10,is. 12, pp. 384–386.

18. KANTHARIA, N. G., ANANTHARAMAIAH, K. R. and PAYNE, H. E., 1998. Carbon Recombination Lines between 34.5 and 770 MHz toward Cassiopeia A. Astrophys. J.vol. 506, is. 2, pp. 758–772. DOI: https://doi.org/10.1086/306266

19. KONOVALENKO, O. O., ZAKHARENKO, V. V., LYTVYNENKO, L. M., ULYANOV, O. M., SIDORCHUK, M. A., STEPKIN, S. V., SHEPELEV, V. A., ZARKA, P., RUCKER,H. O., LECACHEUX, A., PANCHENKO, M., BRUCK, YU. M., TOKARSKY, P. L., BUBNOV, I. M.,YERIN, S. M., KOLIADIN, V. L., MELNIK, V. M., KALINICHENKO,M. M., STANISLAVSKY, O. O., DOROVSKYY,V. V., KHRISTENKO, O. D., SHEVCHENKO,V. V., BELOV, O. S., GRIDIN, A. O., ANTONOV, O. V., BOVKUN, V. P., REZNICHENKO, O. M., BORTSOV, V. M., KVASOV, G. V., OSTAPCHENKO, L. M., SHEVCHUK, M. V., SHEVCHENKO, V. A., YATSKIV, YA. S., VAVILOVA, I. B., BRAUDE, I. S., SHKURATOV, Y. G., RYABOV, V. B.,PIDGORNY, G. I., TYMOSHEVSKY, A. G., LYTVYNENKO,O. O., GALANIN, V. V., RYABOV, M. I., BRAZHENKO,A. I., VASHCHISHIN, R. V., FRANTSUZENKO, A. V., KOSHOVYY, V. V., IVANTYSHYN, O. L., LOZINSKY,A. B., KHARCHENKO, B. S., VASYLIEVA, I. Y., KRAVTSOV, I. P., VASYLKIVSKY, Y. V., LITVINENKO,G. V., MUKHA, D. V., VASYLENKO, N. V., SHEVTSOVA, A. I., MIROSHNICHENKO, A. P., KUHAI, N. V.,SOBOLEV, YA. M. and TSVYK, N. O., 2021. The Founderof the Decameter Radio Astronomy in Ukraine Academicianof NAS of Ukraine Semen Yakovych Braude is 110 Years Old: History of Creation and Development of the National Experimental Base for the Last Half Century. Radio Phys.Radio Astron. vol. 26, no. 1, pp. 5–73. (in Ukrainian). DOI:https://doi.org/10.15407/rpra26.01.005

20. ZAKHARENKO, V., KONOVALENKO, A., ZARKA, P., ULYANOV, O., SIDORCHUK, M., STEPKIN, S., KOLIADIN,V., KALINICHENKO, N., STANISLAVSKY, A., DOROVSKYY, V., SHEPELEV, V., BUBNOV, I., YERIN,S., MELNIK, V., KOVAL, A., SHEVCHUK, N.,VASYLIEVA, I., MYLOSTNA, K., SHEVTSOVA, A., SKORYK,A., KRAVTSOV, I., VOLVACH, Y., PLAKHOV, M., VASILENKO, N., VASYLKIVSKYI, Y., VAVRIV, D.,VINOGRADOV, V., KOZHIN, R., KRAVTSOV, A., BULAKH,E., KUZIN, A., VASILYEV, A., RYABOV, V., REZNICHENKO, A., BORTSOV, V., LISACHENKO, V., KVASOV, G., MUKHA, D., LITVINENKO, G., BRAZHENKO,A., VASHCHISHIN, R., PYLAEV, O., KOSHOVYY,V., LOZINSKY, A., IVANTYSHYN, O., RUCKER,H. O., PANCHENKO, M., FISCHER, G., LECACHEUX,A., DENIS, L., COFFRE, A. and GRIEß-MEIER, J.-M., 2016. Digital Receivers for Low-Frequency Radio Telescopes UTR-2, URAN, GURT. J. Astron. Instrum.vol. 5, is. 4, id. 1641010. DOI: https://doi.org/10.1142/S2251171716410105

21. KONOVALENKO, A., SODIN, L., ZAKHARENKO, V., ZARKA, P., ULYANOV, O., SIDORCHUK, M., STEPKIN,S., TOKARSKY, P., MELNIK, V., KALINICHENKO,N., STANISLAVSKY, A., KOLIADIN, V., SHEPELEV,V., DOROVSKYY, V., RYABOV, V., KOVAL, A., BUBNOV, I., YERIN, S., GRIDIN, A., KULISHENKO,V., REZNICHENKO, A., BORTSOV, V., LISACHENKO,V., REZNIK, A., KVASOV, G., MUKHA, D., LITVINENKO,G., KHRISTENKO, A., SHEVCHENKO, V. V., SHEVCHENKO, V. A., BELOV, A., RUDAVIN, E., VASYLIEVA,I., MIROSHNICHENKO, A., VASILENKO, N., OLYAK, M., MYLOSTNA, K., SKORYK, A., SHEVTSOVA,A., PLAKHOV, M., KRAVTSOV, I., VOLVACH, Y., LYTVINENKO, O., SHEVCHUK, N., ZHOUK, I., BOVKUN,V., ANTONOV, A., VAVRIV, D., VINOGRADOV,V., KOZHIN, R., KRAVTSOV, A., BULAKH, E., KUZIN, A., VASILYEV, A., BRAZHENKO, A., VASHCHISHIN,R., PYLAEV, O., KOSHOVYY, V., LOZINSKY, A., IVANTYSHIN, O., RUCKER, H. O., PANCHENKO, M., FISCHER, G., LECACHEUX, A., DENIS, L., COFFRE, A.,GRIEßMEIER, J.-M., TAGGER, M., GIRARD, J., CHARRIER,D., BRIAND, C. and MANN, G., 2016. The modern radio astronomy network in Ukraine: UTR-2, URAN and GURT. Exp. Astron. vol. 42, is. 1, pp. 11–48. DOI: https://doi.org/10.1007/s10686-016-9498-x

22. OONK, J. B. R., VAN WEEREN, R. J., SALAS, P., SALGADO,F., MORABITO, L. K., TORIBIO, M. C., TIELENS,A. G. G. M. and RÖTTGERING, H. J. A., 2017. Carbon and hydrogen radio recombination lines from the cold clouds towards Cassiopeia A. Mon. Not. R. Astron. Soc.vol. 465, is. 1, pp. 1066–1088. DOI: https://doi.org/10.1093/mnras/stw2818

23. SALGADO, F., MORABITO, L. K., OONK, J. B. R., SALAS,P., TORIBIO, M. C., RÖTTGERING, H. J. A. and TIELENS, A. G. G. M., 2017. Low-frequency Carbon Radio Recombination Lines. II. The Diffuse Interstellar Medium. Astrophys. J. vol. 837, is. 2, id. 142. DOI: https://doi.org/10.3847/1538-4357/aa5d9a

24. SALAS, P., OONK, J. B. R., VAN WEEREN, R. J., SALGADO,F., MORABITO, L. K., TORIBIO, M. C., EMIG, K., RÖTTGERING, H. J. A. and TIELENS, A. G. G. M., 2017. LOFAR observations of decameter carbon radiorecombination lines towards Cassiopeia A. Mon. Not. R. Astron. Soc. vol. 467, is. 2, pp. 2274–2287. DOI: https://doi.org/10.1093/mnras/stx239

25. PETERS, W. M., LAZIO, T. J. W., CLARKE, T. E., ERICKSON,W. C. and KASSIM, N. E., 2011. Radio recombinationlines at decametre wavelengths. Prospects for the future. Astron. Astrophys. vol. 525, id. A128. DOI: https://doi.org/10.1051/0004-6361/201014707

26. KONOVALENKO, O. O., ZAKHARENKO, V. V., KALINICHENKO, M. M., MELNIK, V. M., SIDORCHUK, M. A.,STANISLAVSKY, A. A., STEPKIN, S. V. and ULYANOV, O. M., 2019. The Universe Radio Emission at Decameter Wavelengths. Radio Phys. Radio Astron. vol. 24, no.1,pp. 3–43. (in Ukrainian). DOI: https://doi.org/10.15407/rpra24.01.003


Keywords


low-frequency radio astronomy; radio telescope; interstellar medium; radio recombination lines; carbon; hydrogen; spectral analyzer

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