Silicon isotopic abundance ratio along different galactocentric distance

ABSTRACT The abundance ratios of $^{28}$Si, $^{29}$Si, and $^{30}$Si provide valuable constraints for Galactic Chemical Evolution models. We report simultaneous observations of the $^{28}$SiO, $^{29}$SiO, and $^{30}$SiO 4–3 lines toward 51 massive star-forming regions, conducted with the IRAM 30 m telescope. Detections were achieved in 46, 25, and 24 sources for $^{28}$SiO, $^{29}$SiO, and $^{30}$SiO, respectively. Based on the largest sample of silicon isotope ratios to date, the relationships between $^{28}$Si/$^{30}$Si, $^{28}$Si/$^{29}$Si, and $^{29}$Si/$^{30}$Si ratios, and Galactocentric distance ($D_{\mathrm{GC}}$), are presented. No clear trend between these ratios and ($D_{\mathrm{GC}}$) is found. On the other hand, the abundance ratios of $^{28}$Si/$^{30}$Si and $^{29}$Si/$^{30}$Si, show a positive correlation, which implies that nucleosynthesis of $^{29}$Si and $^{30}$Si is closely related.