Modeling E0102 with iHydra - Version IIb



This page demonstrates making a simple 3D model of the supernova
remnant E0102; the real thing is seen in a Chandra "true-color" image at
right. The model consists of concentric cylinders of emitting ions of
Oxygen, Neon, Magnesium and Silicon, surrounded by an outer "blast-wave
region" emitting a broadband shocked-plasma spectrum. An important aspect
of the model is the inclusion of Doppler shifts of the spectral lines due
to expansion of the SNR material - this is important for modeling high-
resolution data sets, e.g., from Chandra HETG, XMM-Newton RGS, or Astro-E2 XRS.


Prototype code written in IDL was used, see the main routine:

The definition of the model geometrical/plasma components, the spectra assigned to some components, and the observations (real data and their simulations generated from the model) are specified in the three files: The software makes use of "v3d" routines and other IDL code in the HAK distribution. (At MIT, in /nfs/cxc/a1/src/hak/hak_1.8/hak_code currently.)

Renderings of the System Geometry

Simple visualizations are made from the model components using the routine and are shown here:

These two images show the system geometry from a "front" view (left) and a "side" view. Note that the outer blastwave component is modelled as an ellipsoid and is "blown out" along the (lower density?) system/cylinder axis.

A more 3D-ish rendering (left) and a cross-section (right) are shown in these views:

View similar to the above left one but made using volview:

The actual X-ray emitting regions weighted by their flux are shown here rendered similarly to the full geometry above:

View similar to the above left one but made using volview:

Finally, these the X-ray emitting components are projected to the sky plane (about 15 degrees off of the cylinders' axis) and weighted by their X-ray flux to generate an approximation to the expected intensity distribution of the system seen in X-rays (by a telescope of high spatial resolution):

Quantitative Model Calculations

The volume and mass of the various components are calculated by the routine

(Calculation of the electron density, n_e, is the most difficult aspect of this, hence the routine name.) Results are given here for the model components in this example:

 O_VII:  Volume[10^57 cm^3], Mass[SM]  =        1.94572      1.59323
 O_VIII:  Volume[10^57 cm^3], Mass[SM]  =        2.11491      2.27098
 Ne_IX:  Volume[10^57 cm^3], Mass[SM]  =        2.16057     0.542617
 Ne_X:  Volume[10^57 cm^3], Mass[SM]  =        2.28410      1.03982
 Mg_XI:  Volume[10^57 cm^3], Mass[SM]  =        2.13774     0.347006
 Mg_XII:  Volume[10^57 cm^3], Mass[SM]  =        2.49358    0.0967691
 Si_XIII:  Volume[10^57 cm^3], Mass[SM]  =        2.30693     0.154251
 Blob_m:  Volume[10^57 cm^3], Mass[SM]  =      0.0214848      1.60279
 Blob_p:  Volume[10^57 cm^3], Mass[SM]  =      0.0234990      1.14052
 Blast:  Volume[10^57 cm^3], Mass[SM]  =        19.6975      164.570
 O_cont:  Volume[10^57 cm^3], Mass[SM]  =        2.75274      0.00000
 Ne_cont:  Volume[10^57 cm^3], Mass[SM]  =        3.33417      0.00000
 Mg_cont:  Volume[10^57 cm^3], Mass[SM]  =        3.73970      0.00000
 Si_cont:  Volume[10^57 cm^3], Mass[SM]  =        2.30693      0.00000
 Fe_XVII:  Volume[10^57 cm^3], Mass[SM]  =        3.52485     0.464527
 Fe_XVIII:  Volume[10^57 cm^3], Mass[SM]  =        3.01190     0.122626

These results show that the inner ejecta cylinders of the model contain about 3.9 solar-masses of Oxygen, ~ 1.6 M_solar of Neon, ~0.44 M_solar of Mg, and 0.15 M_solar of Silicon. Fe emission has also been added and suggests a mass of Fe of 0.6 M_solar in the ions Fe XVII and Fe XVIII. The outer blastwave component has a mass of ~165 M_solar of swept-up circumstellar material - assumed to be mostly H and He. Of course, these values are under the assumptions of the model and would change with other assumptions.

As mentioned, the electron density is calculated through out the whole region and can be plotted. Below is a 1-D plot of the electron density along the Y-axis, that is along the central vertical line in the cross-section images above. Note that n_e is of order 8/cm^3 in the ejecta cylinders and 0.8/cm^3 in the blast wave region.

Simulated Photons and Events

Simulations for the model are created for each desired observation (in the 'obs.rdb file) using the routine to create a simple arf-based set of events.

A file of emitted photons' X,Y,E values (for an Aperture of 100 cm^2 and exposure of 10 ks) is created by the first line of the 'obs.rdb file for use as a ray-trace input (e.g., to MARX); it is given here:

Simulated Events Compared with Real Data

The real data are loaded into internal arrays using a procedure (string) specified in the observation file - this allows quite a bit of user flexibility in getting data in. For example, to load the dispersed data sets I have made a routine which is specified in the 'obs.rdb file's "datapro" string and restores a previously saved IDL save file. In comparison, standard imaging event data is read in using a more general procedure

Output plots comparing the Model (= simulated data) and real Chandra data for E0102 were made using for non-grating and zeroth-order (e.g., obsids 3520(no HETG), 3828(zeroth-order)) and using for dispersed orders (e.g., MEG +/- 1 of obsids 120 and 3828.) The plots are given in the files:

Plots of simulated data for the Astro-E2 XRS instrument's response to the same model were created as well. These plots are given - with and without velocity the effects in E0102's model - in the two PS files:

Next up: Fitting