ismabs: A high resolution ISM absorption model with variable columns for individual ions

This is an X-ray photoabsorption model for the interstellar medium that takes into account both neutral and ionized species from H, He, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni and Zn. This model has been developed by Efrain Gatuzz in collaboration with Javier Garcia, Tim Kallman, Claudio Mendoza, and Tom Gorczyca. A complete description of the science behind the model is described in Gatuzz et al. (2015).

Note that the He I column density is not included as a free parameter in the model, due to an inherent degeneracy between the relative columns of H, He I, He II. Instead, the He I column is assumed to be one tenth that of the H column.

The sources of the cross-sections are as follows:

• Neutral states of Si, S, Ar and Ca from Verner et al. (1995)
• Singly and doubly ionized states of Si, S, Ar and Ca from Witthoeft et al. (2009) and Witthoeft et al. (2011)
• Neutral, singly and doubly ionized states of N from Garcia et al. (2009)
• Neutral states of O from Gorczyca et al. (2013)
• Singly and doubly ionized states of O from Garcia et al. (2005), including corrections applied by Gatuzz et al. (2013)
• Neutral state of Ne from Gorczyca et al. (2000)
• Singly and doubly ionized states of Ne from Gorczyca et al. (2005)
• For the Fe-L edge region we use the measurement of metallic iron by Kortright & Kim (2000)
• Neutral, singly and doubly ionized states of Mg from Hasoglu et al. (2014).

The parameters are:

par1	H column (in units of $10^{22}$ cm$^-2$)
par2	He II column (in units of $10^{16}$ cm$^-2$)
par3	C I column (in units of $10^{16}$ cm$^-2$)
par4	C II column (in units of $10^{16}$ cm$^-2$)
par5	C III column (in units of $10^{16}$ cm$^-2$)
par6	N I column (in units of $10^{16}$ cm$^-2$)
par7	N II column (in units of $10^{16}$ cm$^-2$)
par8	N III column (in units of $10^{16}$ cm$^-2$)
par9	O I column (in units of $10^{16}$ cm$^-2$)
par10	O II column (in units of $10^{16}$ cm$^-2$)
par11	O III column (in units of $10^{16}$ cm$^-2$)
par12	Ne I column (in units of $10^{16}$ cm$^-2$)
par13	Ne II column (in units of $10^{16}$ cm$^-2$)
par14	Ne III column (in units of $10^{16}$ cm$^-2$)
par15	Mg I column (in units of $10^{16}$ cm$^-2$)
par16	Mg II column (in units of $10^{16}$ cm$^-2$)
par17	Mg III column (in units of $10^{16}$ cm$^-2$)
par18	Si I column (in units of $10^{16}$ cm$^-2$)
par19	Si II column (in units of $10^{16}$ cm$^-2$)
par20	Si III column (in units of $10^{16}$ cm$^-2$)
par21	S I column (in units of $10^{16}$ cm$^-2$)
par22	S II column (in units of $10^{16}$ cm$^-2$)
par23	S III column (in units of $10^{16}$ cm$^-2$)
par24	Ar I column (in units of $10^{16}$ cm$^-2$)
par25	Ar II column (in units of $10^{16}$ cm$^-2$)
par26	Ar III column (in units of $10^{16}$ cm$^-2$)
par27	Ca I column (in units of $10^{16}$ cm$^-2$)
par28	Ca II column (in units of $10^{16}$ cm$^-2$)
par29	Ca III column (in units of $10^{16}$ cm$^-2$)
par30	Fe column (in units of $10^{16}$ cm$^-2$)
par31	Redshift, z