Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Absorption Measure Distribution of the Outflow in IRAS 13349+2438:
  Direct Observation of Thermal Instability?   We analyze the Chandra X-ray spectrum obtained with the HETGS grating
spectrometer of IRAS 13349+2438, which has one of the richest absorption
spectra of a quasar outflow. Absorption from almost all charge states of Fe is
detected. This allows for a detailed reconstruction of the absorption measure
distribution (AMD), which we define as the continuous distribution of column
density as a function of ionization parameter. We find a double peaked AMD for
IRAS 13349+2438 with a total (ionized) column density of N_H = (1.2 +- 0.3)*
10^{22} cm^-2} assuming solar iron abundance. For comparison, we perform a
similar analysis on the well studied HETGS spectrum of NGC 3783. Both sources
feature a deep minimum in column density consistent with no absorption from gas
at temperatures of 4.5 < log T < 5 (K). We interpret the minima as
observational evidence for thermal instability in this temperature regime.

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The categories of this paper are: nucl-ex
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The categories of this paper are: stat
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The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: funct-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: physics
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The categories of this paper are: hep-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int
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The categories of this paper are: q-alg