HI gas in higher density regions of the intergalactic medium

概要

論文の詳細を見る
Using H I absorption alone, we attempt to separate H I absorption lines in quasar spectra into two categories: higher density lines (HDLs) and lower density lines (LDLs), and we discuss the difference in their physical properties. We deblend and fit all H I lines with Voigt profiles and make an unbiased sample of H I lines covering a wide column density range (12<log N-H I [cm(-2)]<19). To reduce the influence of line blending, we simultaneously fit several Lyman series lines. As a result of a two-point correlation analysis, we found that higher column density H I lines are clustering at Deltav<200 km s(-1), whereas lower ones cluster at &UDelta;v<100 km s(-1). We define HDLs as H I lines with 15<log N-H I<19 and all H I lines within 200 km s(-1) of a line with log N-H I>15 and LDLs as all others with 12<log N-H I<15. We found that the HDLs have smaller minimum b-values for a given column density than the LDLs. This difference is successfully reproduced by our hydrodynamic simulation. The LDLs seem to be cool or shock-heated diffuse intergalactic medium gas, whereas the HDLs are likely to be cooler dense gas near to galaxies.
UNIV CHICAGO PRESSの論文