E0102 FUSE O VI Simulations

17-18 Aug. 2005 - Note: two new set of plots were added at the bottom of the page

E0102 FUSE O VI Simulations - Dan Dewey, 9/17/04

Simulated views of E0102 in O VI (left) and in Chandra-band X-rays (right).
The models include emission from eject cylinders and from a blastwave sphere.
Note that the O VI modelled ejecta emission is interior to the X-ray emission. Likewise,
the O VI blastwave emission is concentrated at the outer edge of the blastwave at the CSM interface.

Overview

Observations of SNR E0102 have been made by Sasaki et al. ( AAS HEAD 2004 ) using FUSE to get the spectrum of O VI lines at 1032A and 1038A. Using a coarse E0102 3D model ( Dewey 2004, AAS HEAD 2004 ; see also PowerPoint version ) the expected spectra of O VI at several radial and azimuthal locations of E0102 are given below for comparison with their observations. The spectra, under these model assumptions, are seen to vary dramatically with the location of the spectrometer slit giving rise to a variety of possible observed structure. In particular, because this model assume O VI emission (above left) is interior to the bright X-ray ejecta ring (above right), it is likely that further FUSE observations at more radial locations could be useful in detecting all the O VI emission.

Model creation

The O VI model was created using the same custom IDL routines that were used in the E0102 X-ray modeling, the "V3D" routines. Specifically, see the procedure v3d_e0102_fuse_simsky.pro. The result of this procedure is a structure giving photon location in Sky X,Y coordinates and each photon's corresponding energy including Doppler effects of the v~r velocity field and the line of sight. All photons were intially emitted with an assigned wavelength of 1032 A.

Renditions of the O VI emission from the simple model:
cylinder of ejecta (left) and the blastwave-CSM interface (right, cut in half to show structure.)

Observation Simulation

Using the simulated photons created above, an approximation to the FUSE instrument operation was applied for a given Roll angle and radial Offset of the 4"x20" entrance aperture. The specific steps are given in the procedure v3d_e0102_fuse_observ.pro. Output plots were created for a sample of Roll and Offset values and are given in the table below in PDF format.

-	Roll=-45 "SE"	Roll=0 "E"	Roll=45 "NE"	Roll=90 "N"
Offset=11"	- Aperture - selected - Spectrum	- Aperture - selected - Spectrum	- Aperture - selected - Spectrum	- Aperture - selected - Spectrum
Offset=14"	- Aperture - selected - Spectrum	- Aperture - selected - Spectrum	- Aperture - selected - Spectrum	- Aperture - selected - Spectrum

Outputs of the O VI observation simulation for various values of
Roll and Offset of the aperture. An offset of 11" roughly corresponds
to the peak of the modeled O VI emission, whereas the 14" offset is
closer to the peak of the observed X-ray emission.
Aperture: events in rolled sky coord.s showing the aperture region.
selected: events in det. coord.s that are in the aperture.
Spectrum: image and spectrum of the dispersed events. The solid
histogram is for "1032 A" line emission, the dashed line is an offset
and scaled version to represent the "1038 A" line flux. Note that the
Doppler velocity effects dominate instrumental effects.

Examples of simulated spectra. For the two sepctra above
the center of the aperture is along the SE radius.
In the top, Offset = 14", only a portion of the O VI ejecta
is included and the blastwave/interface is a major contributor.
In the bottom, Offset = 11", the full range of ejecta velocities
are seen with roughly uniform intensity and the bastwave/interface
level is reduced, relatively.
These spectra do not include effective area structure nor any
emission/absorption due to intervening material.

Thanks to M. Sasaki and T. Gaetz for very useful discussions.
Please send comments etc. to dd @ space.mit.edu.

Spectra (predictions) vs. Offset - 8/17-18/05

Tangential slit orientation

The model/code above was run with the location of the slit center moving from the center of the remnant to a distance of 26" toward the East; the slit is oriented along the N-S direction (PA=0). For example, the two figures below show the simulated events highlighted at the location of the slit for the cases of 0 and 14 arc seconds offset. (The slit-accepted events were 'darkened' by over-plotting them with a diamond inaddition to a ".") Note that the zero of the axes is at the slit center.

Tangential-slit Spectra

The folowing "tangential" series of spectra are for offsets of 0 to 26 arc seconds in steps of 2, as indicted in the titles.

The changes with offset show the two main model components:

(1) The growth and decrease of the O VI ejecta ring emission is seen in the 1029 to 1036 A range; it peaks around an offset of 10" where the slit intersects much of the model ring. (Note that the center of the slit is 10" from the center, but the edges of the slit are at a radial distance of ~14" so that the effective slit radial location is larger than the 10" of its center.)

(2) For low values of radial offset two peaks are seen, at 1025 and 1039 A; these are due to the front and backside O VI emission from the blastwave sphere. The +/- 7 A shifts from 1032 A correspond to roughly +/- 2000 km/s. As the offset is increased these peaks remain relativley constant in intensity and move towards each other (and 1032 A) until at about 20" offset they begin to merge.

Radial slit orientation

Simulated observed spectra are also given for the case of a radially oriented slit at various offsets - such an orientation can include nearly the full range of both the ejecta ring and the(any) blastwave emission as the slit-accepted images here show for offsets of 5, 15, and 25 arc seconds:

Radial-slit Spectra

The spectra for a series of radial offsets are given here-below for offsets of 5, 10, 15, 20, and 25 arc seconds. Note that (1) the ring of ejecta, seen from 1029 to 1035 A, is fully-included in all of these except for the last (25") one; and (2) the spherical blastwave shell contribution varies from primarilly the foreground/background contribution at high velociites (in the 5" and 10" cases) to a more uniform contribution in the 1025 to 1039 A range (offsets of 15", 20") and finally a reduced range of 1027 to 1037 A in the 25" offset case.