MEGs residual
MEGs model
MEGs DATA

HEGs DATA
HEGs model
HEGs residual
2D dispersed images of Pollock-II model and combined MEG and HEG datasets. The wavelength range shown is from 3 A (left) to 23 A (right). The upper and lower panels are the Data-Model residual images, color-coded so that red indicates Data > Model, blue indicates Model > Data, and green/black is Data ~ Model within 1 sigma.

E0102: HETG and Pollock-II model comparison

6,16 Sept. 2007 - dd

Summary

A model for the spectrum of E0102 based on XMM-Newton RGS data was produced and provided by Andy Pollock ("Pollock-II" from 28 April 2007.) The purpose here is to compare that model spectrum with actual Chandra HETG data. Because of the extended nature of E0102, the HETG dispersed data are effectively 2-dimensional: with axes of wavelength and cross-dispersion direction. The highest information comparison therefore requires comparing 2D dispersed images of the data to similar 2D images created from a spatial-spectral model. That comparison is carried out here.

In the MEG band, 5-23A, the agreement between model and data is very good: the data/model count rate ratio is ~ 1.03 averaged over the 4 MEG spectra used. This is without any free spectral parameters, being adjusted, including the norms.

K-S plots of the MEG and HEG data-model events also shows that the distribution of counts with wavelength is very similar between HETG data and the Pollock-II model. There is a slight indication that the ~ 13.5 A lines in the model are a bit too strong.

At higher energy (shorter wavelengths), looking at the 2D images one can see some hints of a few missing lines, and perhaps some additional continuum (though some of this may be background events.)

Two regions are also looked at in better detail: the "Ne IX - Ne X" and the "Fe XVII" regions: Pollock's RGS spectrum plots are compared with the HETG combined data in these regions at the bottom of this page.

The purpose here was to compare the Pollock-II spectral model with HETG data. A next step will be to extend that model to better agree with the HETG data and to use the proposed Galactic/SMC 2-component NH model.


Note: "click" any image on this page to see the actual size graphic: plots are larger when clicked, 2D images are smaller.

Spectral Model

The spectral model is from Pollock, 28 April 2007 and has been entered into ISIS .par format using an ISIS/ S-Lang routine:

The model consists of a continuum times a wabs absorption plus many discete Gaussian lines. Note that the line widths have been set to 0.01 times their Pollock-given values: Doppler broadening will be added in the modeling process. The spectrum is plotted here:


Spatial Model and Non-Dispersed Data

A crude geometriuc model was created to roughly have many of the main features of the E0102 image for use in modeling. Below are images of data and modelled zeroth-order events from HETG Obsid 3828 showing that the rough image agreement is OK.

Data Residual Model

At right are K-S tests of the RADIUS of the data and model events from the zeroth-order of obsid 3828 (dataset 11, the same data and model as the images pictured above) and obsid 3520 (dataset 13, a non-grating observation.)
At right are K-S tests between the ENERGY of the data and model for the zeroth-order Obsid 3828 (dataset 11) and the non-grating ACIS observation Obsid 3520 (dataset 13).


The Data sets

HETG data from Obsids 120 and 3828 were reprocessed and corresponding arfs created. This gives a total of 4 MEG spectra and 4 HEG spectra. The data, model, and residuals for these 8 data sets are given below. Note that the Monte Carlo model is "over-simulated" with 3 [5] times as many simulated events as in the real MEG [HEG] data; beacause of this the models look less grainy than the data images here.

All 4 MEG and all 4 HEG datasets were combined to create the data/model images at the top of this web page. Because the roll angles are different for the 4 sets being combined, the remnant image is washed out a bit but retains its ring-like character and it may be easier to detect weak lines this way.


MEG data from Obsid 120, 5 A to 23 A:
residual
model
m = -1, DATA

m = +1, DATA
model
residual

MEG data from Obsid 3828, 5 A to 23 A:
residual
model
m = -1, DATA

m = +1, DATA
model
residual


K-S tests are given for the 4 MEG spectra and also for the combined MEG data - the agreement is very good all-in-all.

Combined MEG datasets:


HEG data from Obsid 120, 3 A to 20 A:
residual
model
m = -1, DATA

m = +1, DATA
model
residual

HEG data from Obsid 3828, 3 A to 20 A:
residual
model
m = -1, DATA

m = +1, DATA
model
residual

K-S tests are given for the 4 HEG spectra and also for the combined HEG data - the need for some additional flux in the model at shorter wavelengths is clear.

Combined HEG datasets:


Close-ups of two spectral regions

Ne IX - Ne X : 9A to 14A

MEG
HEG
Pollock

Fe XVII : 14A - 18A

HEG
MEG
Pollock


Software for reference

The plots here were created using ISIS and the Event-2D software with these specific files: