A statistical approach to polarimetric and photometric investigation of the intermediate-age open cluster NGC 1912

Abstract

This paper presents a comprehensive multiwavelength investigation of the intermediate-age open cluster NGC 1912. We identified 401 member stars for NGC 1912 using K-nearest neighbour and Gaussian Mixture Model machine learning techniques. The fundamental parameters determined for the cluster are metallicity (z) = 0.0141 $\pm$ 0.0006, log(age) = 8.519 $\pm$ 0.040, binary fraction ($b_{\text{frac}}$) = 0.445 $\pm$ 0.035, visual extinction ($A_V$) = 0.864 $\pm$ 0.033 mag, total-to-selective extinction ratio ($R_V$) = 3.007 $\pm$ 0.096, distance = 1096 $\pm$ 15 pc. The central density ($\rho _o$), core radius ($r_c$), tidal radius ($r_t$), and background density ($\rho _{\mathrm{bg}}$) for the cluster are obtained as 0.643 $\pm$ 0.067 stars arcmin$^{-2}$, 7.743 $\pm$ 0.784 arcmin, 84.633 $\pm$ 7.188 arcmin, and 0.001 $\pm$ 0.000 stars arcmin$^{-2}$, respectively. Dynamical mass segregation study revealed a concentration of some apparently massive stars towards the cluster centre. Polarimetric analysis of 90 stars in $BVR_cI_c$ wavelength bands revealed that the observed polarization in NGC 1912 is not solely attributed to interstellar dust. The Galactic magnetic field is dominant in this region. Dust grain sizes within the intracluster region are found to be relatively smaller than that of the general ISM. The extinction map revealed the existence of a potential ‘interstellar bubble’ located close to the cluster region. Towards the periphery of the probable bubble region, which displays an ovoid-like geometry, 16 probable young stellar objects have been detected, suggesting the ongoing triggering of secondary star formation events in this region.