Y. Kamata, K. Tachihara, A. Hara, Y. Fukui

Abstract

X-ray shadowing e ffects by the nearby dark clouds in our galaxy have mainly been studied by ROSAT observations in the1/4 - 3/4 keV energy band. However, the cutoff energy of these energy bands are equivalent to Log (NH[cm-2]) of <=21 anddense core e quivalent to Log (NH[cm-2])~22can not easily identified. We have analyzed th e X-ray attenuation of Cosmic X-ray Background radiation by the Lupusmolecul ar clouds using the data obtained by the Japanese X-ray Astronomy satellite ASCA . Because of the absence ofintense X-ray sources in this region, we could cl early see the X-ray extinction core in the Lupus 1 north region. Theposition al coincidence of X-ray shadows in the Lupus 1 north region is nearlyconsist ent with CO cloud core, far infrared emission (IRAS 100μm) and visual extinct ion. The peak equivalent Log(NH[cm-2]) is estimated to be 21.5 from the X-ra y intensity ratio between 0.7-1.8keV and 1.8-3.5keV energy bands, whichis co nsistent with the value expected from the observations of C18O, IRAS 100μm an d star counts (visual extinction).