Examples of Extended Sources


All boxes have Flag #3 set ('Within extended'), while all circles are considered to lie outside of the extended emission.
 

 

Smooth extended sources:

Bright emission, with core: few real sources, many spurious detections:

[000381-PN] [000381-PN] [000381-PN]
 EPIC PN image (netscape)  EPIC PN image (ds9)  EPIC PN image with sources overlaid (ds9): cyan sources are flagged as false with the source comment 'False in extended'. Green sources are real and have the comment 'In extended', except for the fat green box which has the comment 'Near OOT events' instead (it is considered to be the more important effect here). The fat red box has the source comment 'Core of ext emission'.
 
 

Bright emission, shallow core: many real sources, few spurious detections

[000817-PN] [000817-PN] [000817-PN]
 EPIC PN image (netscape)  EPIC PN image (ds9)  EPIC PN image with sources overlaid (ds9): cyan sources are flagged as false with the source comment 'False in extended', while green sources are real. There are many real sources in this example, while the patch of spurious detections is only small. There might be one or two faint real sources within this patch, but we cannot easily determine this (sometimes a comparison with detections in another camera is helpful, depending on the depth of the exposures). The core has not been detected. The example also shows the extent of this extended source (boxes versus circles).
 
 

Faint emission, no core: no real sources

[000480-M2] [000480-M2] [000480-M2]
 EPIC M2 image (netscape)  EPIC M2 image with contours (ds9)  EPIC M2 image with sources overlaid (ds9): cyan sources are flagged as false with the source comment 'False in extended'. This small and shallow extended source has no apparent core.
 
 

Bright emission, with structure:

[001458-M1] [001458-M1] [001458-M1]
 EPIC M1 image (netscape)  EPIC M1 image with contours (ds9)  EPIC M1 image with sources overlaid (ds9): cyan sources are flagged as false with the source comment 'False in extended', while green sources are real and have the comment 'In extended'. This is a Supernova remnant and there is no peaked core. However, the fat magenta source is the brightest of the central ones and has therefore the source comment 'Poss core of ext em'. It is flagged as false, though, since it is not clear without further checks how much of the central part has been included in this source measurement; it might also be the measurement of the local clump only (='Part of extended').
 
with a different contrast:
[001458-M1]
 EPIC M1 image with sources overlaid (ds9)

 

Clumpy extended sources:

In case of doubt use the source comment 'Poss false in extended', but use it as little as possible.
 

Filamentary emission:

[001150-PN] [001150-PN] [001150-PN]
 EPIC PN image (netscape)  EPIC PN image with contours (ds9)  EPIC PN image with sources overlaid (ds9): cyan sources are flagged as false with the source comment 'False in extended'. In a case like this it is difficult to distinguish between real and spurious detections. The extended emission is clumpy which in itself causes detections (these can also be called 'Part of extended'), on the other hand, the brighter background generates, as usual, spurious detections. In this case only pointlike sources and detections that lie outside of the obvious patches are considered to be real (green boxes).
 
  

Compact emission with clumps and core:

[001272-M1] [001272-M1] [001272-M1]
 EPIC M1 image (netscape)  EPIC M1 image (ds9)  EPIC M1 image with sources overlaid (ds9): cyan sources are flagged as false with the source comment 'False in extended' for the thin boxes and 'Part of extended' for the fat boxes. The fat red box has the source comment 'Core of ext emission'. This example is a spiral galaxy with point-like sources (stars etc) mixed with the filamentary arms and clumps therein. A distinction between spurious detections or part of the extended emission (cyan) and real detections (green) becomes difficult.
 
 

Compact emission with real sources, spurious detections and clumps mixed

[000843-PN] [000843-PN] [000843-PN]
 EPIC PN image (netscape)  EPIC PN image (ds9)  EPIC PN image with sources overlaid (ds9): cyan sources are flagged as false with the source comment 'False in extended' for the thin boxes and 'Part of extended' for the fat boxes. This example is Centaurus A, and a jet and a shock front can be clearly distinguished. Both are considered to be part of the extended emission and are flagged as false detection, since they are no clearly defined point-like sources, like a star or a compact nebula, as in the galaxy above. The large number of real sources among the spurious detection makes screening difficult. A comparison with the other cameras can be of help. The fat red box has the source comment 'Core of ext emission'.
 
  

irregular and clumpy emission:

[001079-M2] [001079-M2] [001079-M2]
 EPIC M2 image (netscape)  EPIC M2 image (ds9)  EPIC M2 image with sources overlaid (ds9): cyan sources are flagged as false with the source comment 'False in extended' for the thin boxes and 'Part of extended' for the fat boxes. A comparison with the M1 detections (blue small circles) identifies the clumps in this supernova remnant.


Screening Notes Example: Version 29.05.2003