Kinematical and dynamical properties of recently discovered bulge and disc star clusters with WINERED

Abstract

Context. Galactic globular clusters are a very important tool in explaining the characteristics of the Milky Way. Therefore it is essential to determine the kinematical and dynamical properties of the new star cluster candidates, especially at the low-latitude regions that suffer from heavy extinction and crowding. Aims. In this work, we report the first spectroscopic analysis for seven recently identified star cluster candidates: CWNU 4193, FSR 1700, Garro 02, Patchick 98, FSR 1767, Mercer 08, and BH 140. Our aim is to determine the kinematical properties, such as the mean cluster radial velocity, and the dynamical properties, such as the orbital parameters and the global dynamical mass, of these clusters in order to spectroscopically confirm the nature of these seven stellar systems. Methods. We collected the high-resolution infrared spectra of 33 candidate members of these clusters using the WINERED spectrograph mounted on the Magellan Clay 6.5 m telescope. Using the WINERED spectra, we measured the radial velocity of each individual star to confirm its membership in the clusters. From the confirmed members, we derived the mean cluster radial velocity of each cluster. In addition, for these clusters, we computed the orbital elements using the GravPot16 model and estimated their global dynamical masses based on the virial theorem. Results. As a result, we confirmed enough member stars (from three to seven stars per cluster) to reliably derive the mean cluster radial velocity and compute the orbital parameters of the clusters CWNU 4193, FSR 1700, Garro 02, and BH 140. For clusters CWNU 4193, FSR 1700, and BH 140, the number of confirmed members also allowed us to estimate their global dynamical masses. Therefore, we successfully derived key kinematical and dynamical properties for four of the most obscured star clusters in the Milky Way.

Figures (8)

• Figure 1: WINERED spectra at the 54th echelle order of star 5534905976200827776 (black line). The dark cyan line is the synthetic spectrum, creating with the same atmospheric parameters as Arcturus and adopting for the cross-correlation to derive the RV.
• Figure 2: WINERED spectra of the three member stars of Garro 02 (top) and of the seven member stars of BH 140 (bottom). In the plots, we have shifted the relative flux scale of the stars vertically with additive constants, and we show zoomed spectra between 1058 nm and 1064 nm in the Y-band (53th echelle order). The spectra without corrections are presented, and they show that member stars have lines at the same wavelengths, thus indicating similar $\mathrm{RVs}$.
• Figure 3: Ensemble of one million orbits in the frame corotating with the bar for the CWNU 4193 cluster, projected on the equatorial (top) and meridional (bottom) Galactic planes in the non-inertial reference frame with a $\Omega_{\rm bar}$ of 31 (left), 41 (middle), and 51 (right) km s$^{-1}$ kpc$^{-1}$ and time-integrated backwards over 2 Gyr. The yellow and orange colours correspond to more probable regions of the space, which are most frequently crossed by the simulated orbits. The solid inner white circle and the dashed outer circle in the top panels show the locations of the CR (see text) and the solar orbit, respectively. The white dots mark the positions of the Lagrange points of the Galactic bar, $L_4$ and $L_5$, and the current position of the Sun, respectively. The horizontal solid white line shows the extension of the bar Robin2012 in our model. The black-filled and unfilled star symbols indicate the initial and final positions of the cluster in our simulations, respectively. The solid black line shows the orbital path of the CWNU 4193 cluster from the observables without error bars.
• Figure 4: Same as in Figure \ref{['fig:orbit4193']}, but for the FSR 1700 cluster.
• Figure 5: Same as in Figure \ref{['fig:orbit4193']}, but for the Garro 02 cluster.