Contains calculations and fitting codes (ISIS table models and XSPEC models) from Corrales et. al. (2016)

http://arxiv.org/abs/1602.01100

To download, use git to create an ismdust folder:

    git clone https://github.com/eblur/ismdust.git ismdust

The following models are provided

• ISMdust
• OlivineAbs
• ISMdust_sca (ISIS only)
• ISMdust_abs (ISIS only)
• FeLedge (ISIS only)

This model provides the extinction (= absorption + scattering) properties for a power law distribution of dust grains using the optical properties for dust provided in Draine (2003).

sil_md : dust mass column for Silicate in units of 1.e-4
  default = 0.6

gra_md : dust mass column for Graphite in units of 1.e-4
  default = 0.4

redshift : redshift of the obscuring dust (XSPEC only)
  default = 0.0

The default mixture of 60% / 40% silicate / graphite is described in Corrales et al. (2016). Please cite this paper if you use this model.

A model for olivine absorption that uses the silicate absorption model from ISMdust with the Rogantini et al. (2018) cross-section for the Fe K edge incorporated.

olv_md : dust mass column for Olivine grains in units of 1.e-4
  default = 1.0

redshift : redshift of the obscuring dust (XSPEC only)
  default = 0.0

Please cite both Corrales et al. (2016) and Rogantini et al. (2018) if you use this model.

Each model returns exp(-tau md), where tau is the path-integrated absorption, scattering, or extinction optical depth and md is the dust mass column in units of 10^-4 g cm^-2.

To estimate the appropriate dust mass column for a given ISM column (NH), one must choose a dust-to-gas mass ratio. For for the Milky Way ISM, this value is typically ~0.01.

For example, NH = 10^22 cm^-2 corresponds to NH * m_p (proton mass) * 0.01 = 1.67e-4 g cm^-2. One can then set, for example, the md_sil parameter in ISMdust to 1.67.

Enter the ismdust directory and start XSPEC

XSPEC12> initpackage ismdust lmodel_ismdust.dat .
XSPEC12> exit

Finally, set an environment variable to point to location of ismdust, e.g.

export ISMDUSTROOT=/path/to/ismdust/

Now, when you want to load the ISMDUST model in XSPEC, load the correct library. The following example loads ismdust and then applies the extinction model to a power law component:

XSPEC12> lmod ismdust $::env(ISMDUSTROOT)
XSPEC12> mo ismdust*pow

Note: You can omit the $::env(ISMDUSTROOT) portion if you have the LMODDIR environment variable set to the location where ISMdust is installed.

Try the test file to make sure it's working.

XSPEC12> @test.xcm

Follow the instructions above to set your ISMDUSTROOT environment variable (and LMODDIR, if you choose).

Now install the local model

XSPEC12> initpackage olivineabs lmodel_olivineabs.dat .

To load the model in XSPEC:

XSPEC12> lmod olivineabs $::env(ISMDUSTROOT)
XSPEC12> mo olivineabs*pow

Try the test file to make sure it's working.

XSPEC12> @test_olivine.xcm

Add a line to your .isisrc file

add_to_isis_load_path("/path/to/ismdust/ismdust_isis");

Set an environment variable (same way you would for the XSPEC model)

export ISMDUSTROOT=/path/to/ismdust/

When you want to invoke the model, use the require function in ISIS to load ismdust

isis> require("ismdust");

To set up the model extinction model with a power law continuum, for example, do:

isis> require("ismdust");
isis> fit_fun("ismdust(1) * powerlaw(1)");

For absorption component only

isis> require("ismdust");
isis> fit_fun("ismdust_abs(1) * powerlaw(1)");

For scattering component only

isis> require("ismdust");
isis> fit_fun("ismdust_sca(1) * powerlaw(1)");

See ismdust_isis/test_ismdust.sl

Use the same set up instructions as above.

To run the model with a power law continuum, for example, do:

isis> require("olivineabs");
isis> fit_fun("olivineabs(1) * powerlaw(1)");

See also ismdust_isis/test_olivine.sl

Set an environment variable to point to the location of the Fe-L edge templates:

export FEPATH=/path/to/ismdust/ismdust_isis/

To invoke the model:

isis> require("FeLedge");
isis> fit_fun("FeLedge(1) * powerlaw(1)");