tbabs, ztbabs, tbgrain, tbvarabs: ISM grain absorption
The Tuebingen-Boulder ISM absorption model. This model calculates the cross section for X-ray absorption by the ISM as the sum of the cross sections for X-ray absorption due to the gas-phase ISM, the grain-phase ISM, and the molecules in the ISM. In the grain-phase ISM, the effect of shielding by the grains is accounted for, but is extremely small. In the molecular contribution to the ISM cross section, only molecular hydrogen is considered. In the gas-phase ISM, the cross section is the sum of the photoionization cross sections of the different elements, weighted by abundance and taking into account depletion onto grains.
In addition to the updates to the photoionization cross sections, the gas-phase cross section differs from previous values as a result of updates to the ISM abundances. These updated abundances are available through the abund wilm command. Details of updates to the photoionization cross sections as well as to abundances can be found in Wilms, Allen and McCray (2000, ApJ 542, 914).
tbabs allows the user to vary just the molecular hydrogen column.
par1 equivalent hydrogen column (in units of 1022 atoms/cm–2)
ztbabs is similar, but allows the user to set a fixed redshift parameter
par1 equivalent hydrogen column (in units of 1022 atoms/cm–2)
z redshift
tbgrain allows the user to vary the molecular hydrogen column and the grain distribution parameters.
|
par1 |
equivalent hydrogen column (in units of 1022 atoms cm–2) |
|
par2 |
molecular hydrogen column (in units of 1022 atoms cm–2) |
|
par3 |
grain density (in gm/cm-3) |
|
par4 |
grain minimum size (in mm) |
|
par5 |
grain maximum size (in mm) |
|
par6 |
power-law index of grain sizes |
tbvarabs additionally allows the user to vary the elemental abundances and the redshift
|
par1 |
equivalent hydrogen column (in units of 1022 atoms cm–2) |
|
par2 -par18 |
abundance (relative to Solar) of He, C, N, O, Ne, Na, Mg, Al, Si, S, Cl, Ar, Ca, Cr, Fe, Co, Ni |
|
par19 |
molecular hydrogen column (in units of 1022 atoms cm–2) |
|
par20 |
grain density (in gm/cm-3) |
|
par21 |
grain minimum size (in mm) |
|
par22 |
grain maximum size (in mm) |
|
par23 |
power-law index of grain sizes |
|
par24 -par41 |
grain depletion fractions of He, C, N, O, Ne, Na, Mg, Al, Si, S, Cl, Ar, Ca, Cr, Fe, Co, Ni} |
|
par42 |
redshift |