Thermal X-ray radiation (PDF) - SRON

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• In older supernova remnants, emission is dominated by swept-up Interstellar matter. This offers a unique opportunity to sample the ISM of for instance metal-poor galaxies like the LMC and SMC, by observing their old supernova remnants. • In clusters of galaxies, the hot gas is a fair sample of the chemical composition of the Universe as a whole, which differs from the Solar composition. • One of the poorest known environments is the cosmic web between clusters of galaxies. depending upon the galacitic evolution scenario of the galaxies in that web, one predicts models with low metallicity (say 0.1 time Solar), or models with strongly varying abundances, ranging from 0.001 to 1 times Solar. • Active Galactic Nuclei sample the composition of galactic cores, which due to higher stellar birth rates in those environments is higher than in the Solar neighbourhood. 23
3.6 Basic processes In order to be able to calculate X-<strong>ray</strong> spectra, it is necessary to determine first the concentrations of the various ions. There are several ionisation and recombination processes that are important for determining these concentrations. Some of these processes also play directly a role in spectral line formation processes. We will first introduce the basic processes in some detail, then we will discuss how the ion concentrations can be determined, and then we return to the continuum and line formation processes. The relevant basic processes that we discuss here are: 1. excitation processes: (a) collisional excitation (b) collisional de-excitation (c) radiative excitation 2. Radiative transitions 3. Auger processes and fluorescence 4. ionisation processes: (a) collisional (direct) ionisation (b) Excitation-Autoionisation (c) Photoionisation (d) Compton ionisation 5. recombination processes: (a) Radiative recombination (b) Dielectronic recombination 6. charge transfer processes: (a) Charge Transfer ionisation (b) Charge Transfer recombination All these processes will be treated below. 24
Page 1 and 2: High Energy Astrophysics Jelle Kaas
Page 3 and 4: 3.1 Introduction Thermal X-ray radi
Page 5 and 6: Figure 3.2: The observed X-ray spec
Page 7 and 8: Figure 3.6: X-ray spectrum of the S
Page 9 and 10: series of alkaline spectra). The no
Page 11 and 12: • The first atomic shell (n = 1)
Page 13 and 14: Z El 1s 2s 2p 3s 3p 3d 4s Ground te
Page 15 and 16: m l1 s 1 m l2 s 2 M L M S +1 + +1
Page 17 and 18: 3.3 Energy levels We have seen the
Page 19 and 20: 3.4 Transitions between different l
Page 21 and 22: Figure 3.10: Transitions between a
Page 23: 3.5 Abundances of the elements With
Page 27 and 28: leading to Here the constant S 0 is
Page 29: 3.6.3 Radiative transition probabil
Page 32 and 33: Figure 3.12: Fluorescence yield as
Page 34 and 35: The formula of Younger While the Lo
Page 36 and 37: 3.6.6 Excitation-Autoionisation In
Page 38 and 39: 3.6.7 Photoionisation Figure 3.20:
Page 40 and 41: 3.6.9 Radiative recombination Radia
Page 42 and 43: 3.6.10 Dielectronic recombination T
Page 44 and 45: 3.7 The ionisation balance In order
Page 46 and 47: of computing time. Therefore one us
Page 48 and 49: 3.8 Continuum emission processes Af
Page 50 and 51: decays back to the 1s orbit by a ra
Page 52 and 53: Inner-shell ionisation The third li
Page 54 and 55: 3.9.3 Line width For most X-ray spe
Page 56 and 57: Table 3.6: The strongest emission l
Page 58 and 59: Table 3.8: Some important iron line
Page 60 and 61: with τ(λ) = τ 0 ϕ(λ) (3.83) wh
Page 62 and 63: Table 3.9: The most important X-ray
Page 64 and 65: where the hydrogen column density N
Page 66 and 67: source itself. Fortunately, with hi
Page 68 and 69: Figure 3.35: Stability for the ioni
Page 70: Table 3.10: Wavelengths in Å of th

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