Diffuse Interstellar Bands With The Physical And Chemical Environment

In addition to stars in the universe we know,there are still a lot of gas and dust between stars.These gases and dusts are collectively referred to as interstellar matter,also known as interstellar medium(ISM).They are both the material produced by the death of a star and one of the necessary conditions for the birth of a star.Their scale and contained quality has reached the level of galaxies.It is now customary to call an interstellar matter cluster with a density of more than 10 atoms per cubic centimeter(or ions,molecules)as an interstellar cloud.The chemical composition of gaseous atoms,molecules and ions in interstellar gas can be measured by various electromagnetic wave lines.They have narrow absorption characteristics on the extinction curve.Many broad absorption characteristics have also been observed,and these absorption characteristics are called Diffuse Interstellar Bands(DIBs).Since the first two DIBs were observed in the 1920s,the carriers of interstellar diffusion bands(DIBs)are still uncertain.In recent years,a large number of DIBs have been detected in the intergalactic environment of the Milky Way and the river.The nature of DIBs has been reemphasized in connection with the physical and chemical conditions of the interstellar cloud.Of particular interest now is whether the carrier of the DIBs will have an effect on ultraviolet(UV)radiation and how it reacts to UV radiation.If they are certain molecules or ions,ultraviolet radiation may destroy the DIBs carrier by photodissociation or generate more DIBs carriers by photoionization.To shed light on the nature and origin of the DIBs carriers,we investigate the relation between the DIBs strength and RV,the total-to-selective extinction ratio,which characterizes how the extinction varies with wavelength(i.e.,the extinction curve)and measures the extent to which the interstellar UV radiation would be attenuated by interstellar dust.We find that the DIBs strength and R_V are not related,in contrast to the earlier finding of an anticorrelation.We argue that the UV radiation has complex effects of interplay between photodestruction and photoionization on the DIBs carriers and thus there is no simple relation between the DIBs strength and the shape of the interstellar UV extinction curve.