Changes between Version 14 and Version 15 of Durham_MDS_Testing

Timestamp:

Jul 15, 2009, 12:17:18 AM (17 years ago)

Author:

shaun.cole@…

Comment:

--

Durham_MDS_Testing

@@ -16 +16 @@
 More worrying: here is an example of a comparison of g and r-band stacks of skycell 030. Something seems to have gone quite badly wrong - especially with g. I suspect this is a masking issue - looks like something from a bright star has infected the image?
 
-[[Image(g_and_r.jpg, 600px, align=center)]]
+[[Image(g_and_r.jpg, 600px)]]
 
 
 Finally, just looking at a few of the z-band warped images, there might still be an issue with correlated readnoise:
 
-[[Image(readnoise.jpg, 600px, align=center)]]
-
-
+[[Image(readnoise.jpg, 600px)]]
 
 Not yet clear to me how much of an issue this is with the other filters, until we look at all of the data. Will do that in the next few days.
 
 
+== Object detection == 
+
+The .cmf catalogue seems only to contain fairly bright (and mainly point-like sources). I ran Sextractor on the frame with a very simple 3-sigma / 5-pixel threshold (quite low, I admit - but I wanted to push it to see what came up). I got the following (red circles are Sextracted and green boxes are from the supplied cmf catalogue). Note - should the cmf catalogue have extended / faint sources in it? There might be some de-blending going on, because some of the big bright things have been split into two.
+
+[[Image(MD07_r_056_jeg_extract_with_PS1_extract.jpg, 600px)]] 
 
 
-Object detection the .cmf catalogue seems only to contain fairly bright (and mainly point-like sources). I ran Sextractor on the frame with a very simple 3-sigma / 5-pixel threshold (quite low, I admit - but I wanted to push it to see what came up). I got the following (red circles are Sextracted and green boxes are from the supplied cmf catalogue). Note - should the cmf catalogue have extended / faint sources in it? There might be some de-blending going on, because some of the big bright things have been split into two.
+== Depth/photometry and comparison to existing deep optical images == 
+
+Here is an example of a side-by-side view of an r-band image of MD07, compared with the CFHTLS (MegaCam) image. I've overlaid the positions and photometry from the CFHTLS so you can compare depths:
+
+[[mds_cfhtls_rcomp.jpg, 600px)]] 
+
+... and the same for MD08, compared to Subaru SuprimeCam (i-band):
+
+[[en1_iband_comparison.ti.jpg, 600px)]] 
+
+Of course, we don't expect the current MDS data to be as deep as these comparison frames yet (in fact, it looks like we're hitting r~24 at 5-sigma)... but the image quality should be something to aim for in order to be competitive in extragalactic studies.
+
+You can see that (roughly) a 5-sigma detection is at about r=24 mag. Here is a plot showing the MDS instrumental mag (I’ve bootstrapped the z.p. from the CFHTLS  deep catalogue) compared to the Megacam magnitude (note that the CFHTLS catalogue should be going down to r=28 mag). You can see where the scatter blows up at about r = 24 mags (I’ve shown two versions of the plot). This was only rough, I need to do something a bit more rigourous to work out the true depth. Also, this is for just one cell:
 
 
-Depth/photometry I have overlaid objects with their r (Megacam) magnitudes (in yellow boxes) on two zoom-ins of skycell.056 here and here. This gives you a rough impression of what the faint blips correspond to in a deeper image - getting the CFHTLS image to compare to now... will update this later with a new figure.
 
-
-You can see that (roughly) a 5-sigma detection is at about r=24 mag. Here is a plot showing the MDS instrumental mag (I’ve bootstrapped the z.p. from the CFHTLS  deep catalogue) compared to the Megacam magnitude (note that the CFHTLS catalogue should be going down to r=28 mag). You can see where the scatter blows up at about r = 24 mags (I’ve shown two versions of the plot). This was only rough, I need to do something a bit more rigourous to work out the true depth. Also, this is for just one cell.          
+.