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[sr #110649] Clumps with S/N smaller than threshold consider as a true c
From: |
Sepideh Eskandarlou |
Subject: |
[sr #110649] Clumps with S/N smaller than threshold consider as a true clumps |
Date: |
Thu, 12 May 2022 11:20:35 -0400 (EDT) |
URL:
<https://savannah.gnu.org/support/?110649>
Summary: Clumps with S/N smaller than threshold consider as a
true clumps
Project: GNU Astronomy Utilities
Submitted by: sepideh
Submitted on: Thu 12 May 2022 03:20:33 PM UTC
Category: Segment
Priority: 5 - Normal
Severity: 3 - Normal
Item Group: Output not reasonable
Status: None
Privacy: Public
Assigned to: None
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Operating System: GNU/Linux
_______________________________________________________
Details:
I was attempting to make catalog for one of the Frontier-fields cluster. But I
realized some faint objects are not in my catalog.
I checked Segmentation map and realized this object did not consider as true
clump, while, the fainter objects considered as a clump.
I expected the S/N of main object (which did not consider as a clump) became
smaller the S/N threshold and S/N of faint objects (which considered as clump)
was larger than S/N threshold. While S/N of both of them were smaller than the
S/N threshold.
But why the fainter objects considered as clump, they should be ignored
because the S/N of these objects were smaller than S/N threshold. I think this
is a bug and it should be solved.
For producing this problem I put all the command use for making this segment
below.
At first, I downloaded a frontier-fields cluster by below command:
wget
https://archive.stsci.edu/pub/hlsp/frontier/abell2744/images/hst/v1.0/hlsp_frontier_hst_wfc3-60mas_abell2744_f160w_v1.0_drz.fits
-Oabell2744-f160w.fits
Secondly, based on the below command I crop the deeper part:
astcrop abell2744-f160w.fits -h0
--polygon="3.6034055,-30.4165889:3.5655321,-30.4135259:3.5722988,-30.3765434:3.6103451,-30.3816284"
--mode=wcs --output=crop.fits
Then I run NiseChisel on output of the astcrop:
astnoisechisel crop.fits --output=nc.fits
Finally, I have make a flat(3*3) kernel and based on this kernel Segment was
built.
astconvert flat.txt --output=kernel.fits
astsegment nc.fits --kernel=kernel.fits --snquant=0.99 --gthresh=1000
--grownclumps --output=seg.fits
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- [sr #110649] Clumps with S/N smaller than threshold consider as a true clumps,
Sepideh Eskandarlou <=