A possible lens in the CFHT image?
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by
Dolorous_Edd
While investigeting a CFHT image of the SDSS cluster ( posted by Jean Tate in this GZ thread )
Pic. SDSS picture of the cluster centered on the SDSS J160646.74+565139.2
I noticed a feature that could possibly be a grav lens candidate
Pic2. A CFHT R-band image (left ) and U-band image (right ) centered on the SDSS J160647.56+565201.1
The 3 galaxies on the image are SDSS J160648.41+565204.3 ( a z_sp =0.565 BCG ) / SDSS J160647.56+565201.1 / SDSS J160647.22+565155.5
They are likely members of the same galaxy group
Pic3. RGB image created by me ( CFHT R,G,U-band composite )
The arc like feature near SDSS J160647.22+565155.5 seems to have consistent color, but has 3 bright spots ( they are pointed by arrows )
Could this possibly be a lens?
If anyone is interested here is the link to download a zip file containing FITS files with CFHT image (bands: URGZ ) ~1Mb
Posted
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Capella05
moderator
It does look interesting, I gather there is no spectra available? (Sorry - I haven't checked myself).
There does not seem to be a clear counter image - the object you originally tagged on GZ as being the counter image is most likely a foreground object and not another image of the lensed background galaxy 😃
I am sure one of the project Scientists will pop along to have a peak and perhaps comment 😃
Posted
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Dolorous_Edd
in response to Capella05's comment.
There does not seem to be a clear counter image - the object you originally tagged on GZ as being the counter image is most likely a foreground object and not another image of the lensed background galaxy
Yeah, now I see it in the colored image
I gather there is no spectra available?
Only for SDSS J160648.41+565204.3 it has spectroscopic redshift of ~0.565
Other 2 galaxies have only photometric redshift, but I reckon they are the members of the same group
As for the arc - no redshifts or at least I didn't find them
Few words about the arc structure (I thought it was wierd at first ):
seems to have consistent color, but has 3 bright spots
it resemble the arc of known lens SA12, It also has 3 bright spots on the arc like this one
http://talk.spacewarps.org/#/subjects/ASW0001lqq
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Capella05
moderator
Yes, I saw that Budgie posted that comparison on GZ.
Looking at the image the one thing that concerns me is that the 'cluster' seems quite 'loose' and the single galaxy closest to the arc seem a bit light weight to do that lensing. The structure and colour is nice, but I am just not seeing where the mass is coming from to create it!
Will wait for the experts opinion 😃
Posted
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Dolorous_Edd
Will wait for the experts opinion
We all will, but in the meantime may I suggest SDSS J160647.56+565201.1 as a lensing galaxy?
Separation between arc and galaxy ~7" , big, but not something unheard of
i.e. known lens CSWA 28
Posted
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Capella05
moderator
It takes a bit more than a single person declaring it to be a candidate, for it to officially declared one 😃
Letters / papers need to be written, the candidate must be modelled, and if possible - a spectrograph taken.
Hope one of the Scientists get back to you soon 😃
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Budgieye
moderator
If the lens is a galaxy cluster rather than a single galaxy, it might explain the strange shape, and the counter image could be lost behind one of the galaxies?
http://talk.spacewarps.org/#/subjects/ASW0001lqq posted by matosa, ID by ceperman
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Dolorous_Edd
A bit of a side note:
AFAIK both SDSS and CFHT standard RGB mapping is this: i-band mapped Red, r-band mapped to Green, g-band mapped to Blue
since I-band image is missing we have 2 possible combinations
My first RGB image had following mapping: r-band mapped to Red; g-band mapped to Green; u-band mapped to Blue
Here is the same field with 2 differences
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Used HumVI to create the image ( used slightly modified CFHTLS preset )
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Used diffrent mapping this time: z-band mapped to Red; r-band mapped to Green; g-band mapped to Blue
Pic. compsite image left ZRG, right is RGU for comparison
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