摘要
We present the most comprehensive catalog of 12.2 GHz methanol maser sources within the Milky Way to date,consisting of 45712.2 GHz methanol masers associated with 10856.7 GHz methanol masers,resulting in a detection rate of 42%.Distances to these sources are derived from the Bar and Spiral Structure Legacy Survey project Distance Calculator.Our analysis shows that both 6.7 and 12.2 GHz methanol masers are more likely to be excited near galactocentric distances of 5–6 kpc,with the detection rate of 12.2 GHz methanol masers decreasing as the galactocentric distance increases.There are no significant differences in the detection rates of 12.2 GHz masers across the four spiral arms,which consistently range between 40%and 50%.However,the detection rate of12.2 GHz methanol masers tends to be higher in the heads of the spiral arms compared to the tails.Analysis of data from the APEX Telescope Large Area Survey of the Galaxy(ATLASGAL)indicates that the luminosity of6.7 GHz masers peaks at a clump dust temperature of about 30 K,while that of 12.2 GHz masers grows with increasing dust temperature.Clumps associated with 12.2 GHz methanol masers generally have higher dust temperatures,bolometric luminosities,and hydrogen densities than those associated only with 6.7 GHz methanol masers or without either maser.Furthermore,clumps in the HⅡregion stage exhibit a higher detection rate of12.2 GHz masers compared to those in other stages,as indicated by the evolutionary stages derived from the ATLASGAL survey results.
基金
supported by the National Key R&D Program of China(2022YFA1603102)
the National Natural Science Foundation of China(11873002,12011530065,and 11590781)
China Postdoctoral Science Foundation(2023M740803)。
