When run in --emission mode, CMacIonize can be used to compute line emissivities for a snapshot from a post-processing run. This assumes that you have already run a full post-processing Monte Carlo photoionization simulation and that you have a snapshot that contains accurate temperatures and ionic fractions for all cells.

In this mode, CMacIonize requires two additional command line arguments:

• --params” The name of the parameter file, as usual.
• --file: The name of the snapshot file.

The parameter file will have a completely different contents from the usual parameter file, as explained below. If the calculation of the emissivities is successful, one or more new datasets containing the result will be appended to the snapshot file.

Parameter file

Unlike the usual parameter file, the emission-mode parameter file only has one parameter block, called EmissivityValues. Currently, the following parameters are available:

EmissivityValues:
  BaHigh: false # (default value)
  BaLow: false # (default value)
  CIII_1908: false # (default value)
  CII_158mu: false # (default value)
  CII_2325: false # (default value)
  HII: false # (default value)
  Halpha: false # (default value)
  Hbeta: false # (default value)
  HeI_5876: false # (default value)
  Hrec_s: false # (default value)
  NIII_57mu: false # (default value)
  NII_122mu: false # (default value)
  NII_5755: false # (default value)
  NII_6548: false # (default value)
  NII_6584: false # (default value)
  NeIII_15mu: false # (default value)
  NeIII_3869: false # (default value)
  NeIII_3968: false # (default value)
  NeII_12mu: false # (default value)
  OIII_4363: false # (default value)
  OIII_4959: false # (default value)
  OIII_5007: false # (default value)
  OIII_52mu: false # (default value)
  OIII_88mu: false # (default value)
  OII_3727: false # (default value)
  OII_7325: false # (default value)
  OI_6300: false # (default value)
  SIII_19mu: false # (default value)
  SIII_33mu: false # (default value)
  SIII_6213: false # (default value)
  SIII_9405: false # (default value)
  SII_4072: false # (default value)
  SII_6725: false # (default value)
  SIV_10mu: false # (default value)
  WFC2_F439W: false # (default value)
  WFC2_F555W: false # (default value)
  WFC2_F675W: false # (default value)
  avg_T: false # (default value)
  avg_T_count: false # (default value)
  avg_nH_nHe: false # (default value)
  avg_nH_nHe_count: false # (default value)

As per usual, CMacIonize will read the parameter file and then generate a file called ORIGINAL_NAME.used-values (with ORIGINAL_NAME the name of the input parameter file; including extension) that contains the parameters that were actually used (including all default values).

All parameters in the file correspond to a specific line emissivity diagnostic, and the value of the parameter decides whether or not this line will be computed. By default, no lines are computed.

Below is an overview of the line diagnostics currently supported:

BaHigh, BaLow

Legacy values from Kenny Wood’s code, currently undocumented.

CIII_1908

This corresponds to the 1908 Å transition line from the (degenerate) first excited state of double ionised carbon to its ground state (see Osterbrock & Ferland, 2006; table 3.8, 3P0:3P1:3P2 to 1S0).

CII_158mu, CII_2325

These correspond to the 158 μm hyperfine transition line between the degenerate levels in the ground state of ionised carbon (2P3/2 to 2P1/2), and the 2325 Å transition from the (degenerate) first excited state to the (degenerate) ground state (see Osterbrock & Ferland, 2006; table 3.9, 4P1/2:4P3/2:4P5/2 to 2P1/2:2P3/2).

HII

Legacy values from Kenny Wood’s code, currently undocumented.

Halpha

Hα emissivity, based on the power law fit provided by Osterbrock & Ferland (2006), table 4.1.

Hbeta

Hβ emissivity, based on a power law fit to the Storey & Hummer (1995) data.

HeI_5876

5876 Å emission line from neutral helium, based on a power law fit provided by Osterbock & Ferland (2006), table 4.6.

Hrec_s

Hydrogen recombination rate, as a number of recombining ions per second, based on the fitting formula in Verner & Ferland (1996), table 1.

NIII_57mu

Corresponds to the 57 μm transition from the excited state to the ground state in double ionised nitrogen (Osterbrock & Ferland, 2006; table 3.9, 2P3/2 to 2P1/2).

NII_122mu, NII_5755, NII_6548, NII_6584

These correspond to transitions between excited states of ionised nitrogen (Osterbrock & Ferland, 2006; table 3.12):

• the 122 μm hyperfine transition between the degenerate levels of the first excited state (3P2 to 3P1)
• the 5755 Å transition between the third and second excited state (1S0 to 1D2)
• the 6548 Å transition between the second excited state and the lower level of the (degenerate) first excited state (1D2 to 3P1)
• the 6584 Å transition between the second excited state and the higher level of the (degenerate) first excited state (1D2 to 3P2)

NeIII_15mu, NeIII_3869, NeIII_3968

These correspond to transitions between excited states of double ionised neon (Osterbrock & Ferland, 2006; table 3.14):

• the 15 μm hyperfine transition between the first and second level in the degenerate ground state (3P1 to 3P2)
• the 3869 Å transition between first excited state and the lowest level of the (degenerate) ground state (1D2 to 3P2)
• the 3968 Å transition between the first excited state and the second level of the (denegerate) ground state (1D2 to 3P1)

NeII_12mu

12 μm hyperfine transition between the two levels in the ground state of ionised neon (Osterbrock & Ferland, 2006; table 3.11, 2P1/2 to 2P3/2).

OIII_4363, OIII_4959, OIII_5007, OIII_52mu, OIII_88mu

These correspond to transitions between excited states of double ionised oxygen (Osterbrock & Ferland, 2006; table 3.12):

• the 4363 Å transition between the second and first excited state (1S0 to 1D2)
• the 4959 Å transition between the first excited state and the second level of the (degenerate) ground state (1D2 to 3P1)
• the 5007 Å transition between the first excited state and the highest level of the (degenerate) ground state (1D2 to 3P2)
• the 52 μm hyperfine transition between the third and second level in the degenerate ground state (3P2 to 3P1)
• the 88 μm hyperfine transition between the second and first level in the degenerate ground state (3P1 to 3P0)

OII_3727, OII_7325

These correspond to transitions between excited state of ionised oxygen (Osterbrock & Ferland, 2006; table 3.13):

• the sum of the 3726 and 3728.8 Å transition lines between the (degenerate) first excited state and the ground level (2D5/2:2D3/2 to 4S3/2)
• the sum of the 7319.9, 7330.7, 7318.8 and 7329.6 Å transition lines between the (degenerate) second and first excited states (2P3/2:2P1/2 to 2D5/2:2D3/2)

OI_6300

Sum of the 6300.3 and 6363.8 Å transition lines between the first excited level of neutral oxygen and its (degenerate) ground state (Osterbrock & Ferland, 2006; table 3.14, 1D2 to 3P2:3P1).

SIII_19mu, SIII_33mu, SIII_6213, SIII_9405

These correspond to transitions between excited levels of double ionised sulphur (Osterbrock & Ferland, 2006; table 3.12):

• the 19 μm hyperfine transition between the third and second level of the (degenerate) ground state (3P2 to 3P1)
• the 33 μm hyperfine transition between the second and first level of the (degenerate) ground state (3P1 to 3P0)
• the 6213 Å transition between second and first excited state (1S0 to 1D2)
• the sum of the 9531 and 9068.9 Å transitions between the first excited state and the (degenerate) ground state (1D2 to 2P1:3P2)

SII_4072, SII_6725

These correspond to transitions between excited levels of ionised sulphur (Osterbrock & Ferland, 2006; table 3.13):

• the sum of the 4068.6 and 4076.4 Å transitions between the (degenerate) second excited level and the ground state (2P1/1:2P3/2 to 4S3/2)
• the 6725 Å transition between the (degenerate) first excited level and the ground state (2D3/2:2D5/2 to 4S3/2)

SIV_10mu

Transition between the first excited state and the ground state in triple ionised sulphur (Osterbrock & Ferland, 2016; table 3.10; 2P3/2 to 2P1/2).

WFC2_F439W, WFC2_F555W, WFC2_F675W

Sums of all the lines that fall within the wavelength ranges of the HST WFC2 filters F439W, F555W and F675W, useful to make synthetic HST images.

avg_T, avg_T_count

Variables required to compute the density weighted average temperature of the ionised particles in each cell.

avg_nH_nHe, avg_nH_nHe_count

Variables required to compute the average product of the hydrogen and helium ionised densities.