X-ray absorption of cold gas: Simulating interstellar molecular clouds in the laboratory

Itay Gissis; Amnon Fisher; Ehud Behar

doi:10.1103/PhysRevE.104.015205

paper

X-ray absorption of cold gas: Simulating interstellar molecular clouds in the laboratory

arXiv:2106.09266 · doi:10.1103/PhysRevE.104.015205

Abstract

Galactic and extra-galactic sources produce X-rays that are often absorbed by molecules and atoms in giant molecular clouds (GMCs), which provides valuable information about their composition and physical state. We mimic this phenomenon with a laboratory Z-pinch X-ray source, which is impinged on neutral molecular gas. The novel technique produces a soft X-ray pseudo continuum using a pulsed-current generator. The absorbing gas is injected from a 1 cm long planar gas-puff without any window or vessel along the line of sight. An X-ray spectrometer with a resolving power of $λ /Δ λ \sim$ 420, comparable to that of astrophysical space instruments, records the absorbed spectra. This resolution clearly resolves the molecular lines from the atomic lines; therefore, motivating the search of molecular signature in astrophysical X-ray spectra. The experimental setup enables different gas compositions and column densities. K-shell spectra of CO $_{2}$ , N $_{2}$ and O $_{2}$ reveal a plethora of absorption lines and photo-electric edges measured at molecular column densities between $\sim$ 10 $^{16}$ cm $^{- 2}$ -- 10 $^{18}$ cm $^{- 2}$ typical of GMCs. We find that the population of excited-states, contributing to the edge, increases with gas density.

arXiv commentAccepted for publication in PRE ref: LC18406E

X-ray absorption of cold gas: Simulating interstellar molecular clouds in the laboratory

Abstract

References in corpus (9)