![]() ![]() In Fig.2, the open squares mark 17 OSCs with | l |. Hence, theprojections of the objects with l close to zero have large deviations and large errors. (5), the division by sin l is made in the second term. à â / (Murray 1986).Figure 1 shows the coordinates of the objects being analyzed in projection onto theGalactic XY plane.Figure 2 shows the Galactic rotation curve constructed from parameters (9) the OSCcircular velocity projections were calculated only from radial velocities using Eq. Based on parameters (9), we estimated the circular rotation velocity of the solar neigh-borhood to be V = | R Ï | = 208 ± â and the period of its revolution around theGalactic center to be T = 2 Ï/ ( γ Ï ) = 221 Myr, where the coeï¬cient γ = 1. As a result, taking into account all constraints, we used the data for 140 young OSCs(including S269) with a mean age of 18 Myr, 89 radial velocities of the HII regions (Russeil2003), 135 radial velocities for the tangential points (CO) from Clemens (1985), and 133radial velocities for the tangential points (H I) from Burton and Gordon (1978). ![]() Ħ4) km s â, and the parameters of the an-gular velocity of Galactic rotation, Ï = â. RESULTSĪt a ï¬xed Galactocentric distance of the Sun ( R = 7. 4 that the points rejected by this criterionhave large residuals). Inthis paper, we use only 89 HII regions selected according to the following criteria:(i) the relative random errors in the distances to the objects do not exceed 20% (ii) the regions are located outside the zone with the Galactic centerâanticenter direction | l | | l |. We also used the CO radio observations bythe tangential point method from Clemens (1985).We took the data on star-forming (H II) regions mainly from the catalog by Russeil(2003), which contains the radial velocities and photometric distances for 204 regions. (1989), where the 21-cm hydrogen radio observations described in Burton andGordon (1978) are presented in tabular form. We took the radial velocities of HI clouds obtained by the tangential point method fromFich et al. Our objective is to determine the Galactic rotation curve in a widerange of distances, R >. R without dividing it into segments, but this rotation curve was given in tabular form, whichcomplicates its use. In addition, there are signiï¬cant radial motions of gas at R. Therefore, the entire R range is diï¬cult to describe by asmooth curve. This approach is usedmainly because there is a segment of solid-body rotation in the inner Galaxy that passesinto a fairly ï¬at curve further out. Stepanishchev,Ĭentral (Pulkovo) Astronomical Observatory of RAS, St-PetersburgÄ«ased on currently available data on the three-dimensional ï¬eld of space ve-locities of young ( â¤Ä¥0 Myr) open star clusters and the radial velocities of HI clouds andstar-forming (HII) regions, we have found the Galactic rotation curve in the range of Galac-tocentric distances 3 kpc R ) regionsof the Galaxy, as was done by Burton (1971) and Clemens (1985). Galactic Rotation Curve and the Eï¬ect of Density Wavesfrom Data on Young Objects Stepanishchev, 2008, published in Pisâmav Astronomicheski Ë Ä± Zhurnal, 2008, Vol. c (cid:13) Pleiades Publishing, Inc.,2008. It shows that the phase of the Sun in the density wave is close to -90 degrees and the Sun is located in the interarm space near the outer edge of the Carina-Sagittarius arm.Īa r X i v. A spectral analysis of the radial velocities of young open star clusters has confirmed the presence of periodic perturbations with an amplitude of 5.9+-1.1 km/s and a wavelength 1.7+-0.5 kpc. The amplitude of the density wave perturbations is largest in the inner part of the Galaxy, about 9 km/s, and decreases to approximately 1 km/s in its outer part. These have allowed us to estimate the distances between the density wave peaks, 1.9, 2.4, and 3.2 kpc as R increases, in agreement with the description of the density weave as a logarithmic spiral. ![]() A Fourier spectral analysis of the velocity residuals from the derived rotation curve attributable to density waves reveals three dominant peaks with wavelengths of 2.5, 1.4, and 0.9 kpc and amplitudes of 4.7, 2.6, and 3.6 km/s, respectively. We have established that the centroid of the sample moves relative to the local standard of rest along the Galactic Y axis with a velocity of -6.2+-0.8 km/s. Based on currently available data on the three-dimensional field of space velocities of young (<50 Myr) open star clusters and the radial velocities of HI clouds and star-forming (HII) regions, we have found the Galactic rotation curve in the range of Galactocentric distances 3 kpc ![]()
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