naa a22 4500 510790577 CHVBK 20180411083318.0 cr unu---uuuuu 180411e20131101xx s 000 0 eng 10.1134/S1063773713110017 doi (NATIONALLICENCE)springer-10.1134/S1063773713110017 Estimation of the pitch angle of the Galactic spiral pattern [Elektronische Daten] [V. Bobylev, A. Bajkova] To estimate the pitch angle i of the Galactic spiral arms, we have used data on Galactic masers with known trigonometric parallaxes. These masers are associated with very young objects located in active star-forming regions. The well-knownmethod of analyzing the "position angle-distance logarithm” diagram has been applied. Our estimates of the angle i obtained from four segments of different arms belonging to the grand-design structure are in satisfactory agreement between themselves and are close to i = −13°. The segment of the outer arm is of greatest interest. It contains only three masers, but we have additionally invoked data on 12 very young star clusters with their distances estimated by Camargo et al. from infrared photometry. Using such a combination of data, we have found i = −13.3° ± 1.3°. Comparison of this value with other spiral density wave parameters obtained from a kinematic analysis of masers leads us to conclude that the model of a four-armed spiral pattern is most likely realized in our Galaxy. Pleiades Publishing, Inc., 2013 Galactic structure nationallicence outer arm nationallicence spiral density waves nationallicence masers nationallicence open star clusters nationallicence Bobylev V. Pulkovo Astronomical Observatory, Russian Academy of Sciences, Pulkovskoe sh. 65, 196140, St. Petersburg, Russia aut Bajkova A. Pulkovo Astronomical Observatory, Russian Academy of Sciences, Pulkovskoe sh. 65, 196140, St. Petersburg, Russia aut Astronomy Letters Springer US; http://www.springer-ny.com 39/11(2013-11-01), 759-764 1063-7737 39:11<759 2013 39 11443 https://doi.org/10.1134/S1063773713110017 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1134/S1063773713110017 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Bobylev V. Pulkovo Astronomical Observatory, Russian Academy of Sciences, Pulkovskoe sh. 65, 196140, St. Petersburg, Russia aut NATIONALLICENCE 700 1- Bajkova A. Pulkovo Astronomical Observatory, Russian Academy of Sciences, Pulkovskoe sh. 65, 196140, St. Petersburg, Russia aut NATIONALLICENCE 773 0- Astronomy Letters Springer US; http://www.springer-ny.com 39/11(2013-11-01), 759-764 1063-7737 39:11<759 2013 39 11443 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer