银河系星际消光空间分布的研究进展

The Spatial Distribution of the Galactic Intersteller Extinction:Current Status

银河系中星际尘埃的存在使观测到的天体的亮度和颜色发生改变。银河系尘埃消光改正不止是河内/外天体观测性质研究的必要步骤,也是银河系自身性质研究的重要课题。从三个方面对银河系消光的研究进展进行了综述,包括银河系的整体消光、银河系内天体消光的测量和银河系消光曲线。最后进行了总结和展望。

Dust extinction in the Milky Way affects the observed luminosity and colors of all astronomical objects.The knowledge of Galactic extinction is not only an essential correction to all astronomical measurements in the ultraviolet,optical,and near infrared bands,but also constrains the properties of intersteller dust which is a key ingredient in understanding the structure and evolution of the Milky Way.This paper reviews the basic framework and recent developments of the Galactic extinction studies from three aspects.For the integral Galactic extinction,the SFD extinction map derived from the farinfrared emission is the most widely used technique in extra-galactic studies,while the more recent Planck maps provide even better spatial resolution.On the other hand,the statistical approaches,including galaxy number counts and color excess determinations provide independent measurements of the integral Galactic extinction.For the extinction measurements of intergalactic objects,different methods are also reviewed,and each has its advantages and disadvantages.The statistical methods,star number counts and statistical color excess,are mainly for the extinction measurement of stars behind molecular clouds.For individual stars,the RJCE method is mainly used in the near-infrared,while the star-pair method requires an exact spectral type match which is often difficult.With the extinction measured for a large sample of individual stars,the 3D extinction maps with respect to the solar position can be built with the stellar population synthesis method,where a Bayesian approach has been recently developed to break the model degeneracy.On the basis of 3D extinction maps,the overall physical distribution of the Galactic dust can be further modeled.An exponential dust disk and the Gould belt around the solar neighborhood are the main structures of the dust distribution seen in the 3D extinction map.The variation of the Galactic extinction with wavelength,i.e.the Galactic extinction curve,can be described by a family of curves parameterized by the only RV parameter from ultraviolet to near-infrared band.The shape of the Galactic extinction curve is mainly determined by the size and chemical composition of the dust particles,and therefore is expected to vary from the diffuse intersteller medium to more dense environments.However,recent studies have shown that the spatial variation of RV parameter occurs on a scale larger than individual molecular clouds,suggesting the physical cause for a larger RV may not just be grain growth.