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I have an external data file data which contains the position of stars of a galaxy simulations and it looks like this

data = Import["NGC_1566.out", "Table"];
L0 = ListPlot[data, Frame -> True, Axes -> False, 
     PlotStyle -> {Darker[Green], PointSize[0.001]}, 
     PlotRange -> {{-60, 60}, {-60, 60}}, AspectRatio -> 1]

enter image description here

and here is a real image of the NGC 1566

enter image description here

Now I would like to plot and fit my data on top of the real image. Any suggestions?

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ImageCompose and some adjustments to the size and aspectratio of your plot should get you there. – Karsten 7. Aug 4 '14 at 15:03
@Karsten7. Great thanks! BTW, could you elaborate a little bit more your suggestions in a short answer, so I could accept it? – Vaggelis_Z Aug 4 '14 at 15:15
up vote 3 down vote accepted

With the image of your plot

graph = With[{grImp = Import[""]},
            ColorReplace[grImp, First@DominantColors@grImp -> Transparent]

and the image

img = Import[""];

One can prepare a composition interactively using

  irGra = ImageResize[graph, {s1, s2}];
  ImageCompose[img, irGra, Scaled[{p1, p2}]]
 {{p1, 0.448}, 0.3, 0.8}, {{p2, 0.495}, 0.3, 0.8}, {{s1, 347.5}, 200, 500}, {{s2, 298.}, 200, 500}


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ImageCorrelate like, e.g. in the answers to this question, could be used to find the correct position. – Karsten 7. Aug 4 '14 at 15:56
Just a minor question: at the end, how can I export the joined plot in a .jpg format without showing the Manipulation controls? – Vaggelis_Z Aug 4 '14 at 16:17
@Vaggelis_Z Right click -> Save Image As... . If you want to use the composed image later in your notebook, e.g. for Export, than you can simply Set (=) it to a global symbol inside of Manipulate, e.g. ic = ImageCompose[img, irGra, Scaled[{p1, p2}]]. – Karsten 7. Aug 4 '14 at 16:48

Not an excellent fit, but close:

L0 = ListPlot[data, Frame->True, Axes->False, PlotStyle -> {Darker[Green],PointSize[0.001]},
  PlotRange -> 1.9 * {{-60,60},{-60,60}}, AspectRatio -> 1]

and, with im as the JPEG :

ImageCompose[im, L0, {270, 290}]

but the credit goes to Karsten, not me!

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One more way will be to use Prolog option with ListPlot. In that case we can use your image as a texture in the background too!

image = Import[""];
plotRange={{-60, 60}, {-60, 60}};
bdbox = Flatten[MapAt[Reverse, Outer[List, ##], 2], 1] & @@ plotRange;
back = {Texture[image], EdgeForm[],Polygon[bdbox, 
VertexTextureCoordinates -> {{1/5.5, 1/5.5}, {1/5.5,4.4/5.5},
{4.4/5.5, 4.4/5.5}, {4.4/5.5, 1/5.5}}]};

Then we can call your ListPlot. You can play with the VertexTextureCoordinates using Manipulate for example to hit the right zoom you need. I set the numbers above from my visual judgement only.

data = Import["NGC_1566.out", "Table"];
L0 = ListPlot[data, Frame -> True, FrameStyle -> Darker[Green],Axes -> False,
PlotStyle -> {Darker[Green], PointSize[0.001]},PlotRange ->plotRange,
AspectRatio -> 1,ImageSize -> 600, Prolog -> back, PlotRangeClipping -> False]

enter image description here

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