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##

wdem, vwdem, vvwdem: plasma emission, multi-temperature with
power-law distribution of emission measure.

A multi-temperature plasma emission model built on top of the apec or
mekal codes. The emission measure distribution is a
powerlaw:

where is the emission measure and is chosen so that the total
emission measure equals the normalization parameter
(Kaastra et al. 2004).
The `switch` parameter determines whether the apec or mekal
codes will be used. For the mekal code there are also the options to
run the code for each temperature or interpolate from a pre-calculated
table. The former is slower but more accurate. The mekal options are
now obsolete and are only included for historical purposes. See the
documentation on the apec model for additional information
on using different AtomDB versions or applying thermal or velocity
broadening.

For the wdem version, the abundance ratios are set by the
abund command. The vwdem variant allows the user to
define abundances for the more common elements while vvwdem has
parameters for abundances of all elements up to Zn. See the documentation
on the apec model for further information.

The parameters for wdem are:

par1 |
Maximum temperature for power-law emission measure distribution |

par2 |
Ratio of minimum to maximum temperature (
) |

par3 |
Inverse slope () |

par3 |
nH (cm). Fixed at 1 for most applications. |

par4 |
abundance relative to Solar |

par5 |
redshift z |

par6 |
switch (0 = calculate using MEKAL model; 1 = interpolate using
MEKAL model; 2 = interpolate using APEC model) |

norm |
Normalization |

For the vwdem variant the parameters are:

par1 |
Maximum temperature for power-law emission measure distribution |

par2 |
Ratio of minimum to maximum temperature (
) |

par3 |
Inverse slope () |

par4 |
nH (cm) |

par5-18 |
abundance for He, C, N, O, Ne,
Na, Mg, Al, Si, S,Ar, Ca, Fe, Ni wrt Solar (defined by the abund
command) |

par19 |
redshift z |

par20 |
switch (0 = calculate using MEKAL model; 1 = interpolate using
MEKAL model; 2 = interpolate using APEC model) |

norm |
Normalization |

For the vvwdem variant the parameters are:

par1 |
Maximum temperature for power-law emission measure distribution |

par2 |
Ratio of minimum to maximum temperature (
) |

par3 |
Inverse slope () |

par4 |
nH (cm) |

par5-34 |
abundance for H to Zn wrt Solar (defined by the abund
command) |

par35 |
redshift z |

par36 |
switch (0 = calculate using MEKAL model; 1 = interpolate using
MEKAL model; 2 = interpolate using APEC model) |

norm |
Normalization |

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