Radial Profiles with srctool

[JosephHall]

Hello,

Sorry if this is the wrong place to ask this, but I am not sure which board would be better.

I am currently working on extracting radial profiles of clusters to do density fitting and I'm running into a problem when using srctool to do this. My current workflow is to use srctool to extract the spectra in annuli, which I then load into sherpa and I use that to calculate the total counts in each annulus. The problem I've found when using this method is that further from the centre of the cluster there is a sudden jump in flux that should not be there:


However, when I use the same annuli for the same cluster and extract the flux manually using Python by masking the evtool produced image, the produced profile is much closer to the expected shape (units here are cm^2 at the cluster, not the detector):


When I do the extraction with srctool, I am not providing a background region so it should not be subtracting any flux based on that. Is any additional processing done when using srctool that would explain these jumps in flux? Alternatively, I know sherpa could also be doing some additional calculations that I'm not in control of, if so I'm curious what other methods people have used to create radial profiles? Finally, I was wondering if support for radial profile generation will be added to eSASS at some point in the future?

Thanks,

Joe.

[JeremySanders]

Dear Joe

I would need to see a more complete description of how you are using srctool to understand the problem better.

However, I can give some comments:

• The exposure time given by srctool isn't the same as in exposure maps - it is more of an on-time. See the docs. I would not use the rates from spectra without spectral fitting (to get a norm or flux), as srctool modifies the ARF to account for exposure, bad pixels, etc.

• srctool does PSF correction by default. You probably want to disable this for your type of source if you're modelling the PSF externally, using psftype=NONE. You should also input an appropriate source model for the ARF calculations (e.g. top hat for an annulus).

• Make sure you are disabling the background region with backreg=NONE, as the default background may be used otherwise.

Probably srctool isn't the right tool to do this. If using the exposure maps, remember that the exposure time is for the on-axis ARF.

As far as I know, there are no plans to add code to extract profiles from sources to eSASS. You could look at MBProj2D if you want a more general method for fitting clusters (disclaimer: I am the author).

Best wishes

Jeremy

[JosephHall]

Dear Jeremy,

Thank you for your reply. I have already set the PSFTYPE=NONE and BACKREG=NONE, so I don't think it will be those which are causing the issues. However, it is likely the first point you make about using rates without fitting the spectra first. I'll have a look into both that and MBPROJ2D.

Thank you again,

Joe.