I James Webb telescope calibration

[Mordred]

I understand that many of the extreme distance objects were incorrectly calibrated for their distance and subsequent age. I have been trying to track down the related articles detailing the error with the applicable mathematics. If anyone knows where I can get the related calibration papers it would be appreciated.

 

[berkeman]

Do you mean some calibration of the telescope's mirrors, or some other type of calibration?

 

[Mordred]

The calibration would also entail it's motion with regards to redshift influence much like Planck calibration for dipole anistrophy. I've seen numerous pop media articles stating the error existed on previous distance measurements were due to calibration errors and am looking for better detail.

 

[Mordred]

This article lists what needed calibrating but I haven't found which portions were in error
https://www.stsci.edu/~INS/2010CalWorkshop/mather.pdf

 

[Drakkith]

It's still unclear what you're referring to by 'calibration'. The mirrors and instruments of the telescope require physical and digital calibration, yes, but what do you mean when you say that distant objects were incorrectly calibrated? And how does that affect the calibration of the telescope?

 

[Tom.G]

It's still unclear what you're referring to by 'calibration'. The mirrors and instruments of the telescope require physical and digital calibration, yes, but what do you mean when you say that distant objects were incorrectly calibrated? And how does that affect the calibration of the telescope?

...objects were incorrectly calibrated for their distance...

 

[berkeman]

@Tom.G -- how do you calibrate an optical telescope for distance? It's not a set of binoculars with parallax rangefinder capability...

 

[Tom.G]

Don't know of any way to do that... and I did not interpret the OP as asking that (mostly due to ignoring the title and trying to parse the post).

I haven't figured out just What the post is asking about though.

@Mordred, can you re-phrase you question a bit so we can better understand just what aspect or impact you are asking about?

Cheers,
Tom

 

[Vanadium 50]

I haven't figured out what the post is about either. If it is the cosmological distance ladder, it's not JWST specific. If it's JWST specific, what is it exactly?

 

[Drakkith]

@Tom.G -- how do you calibrate an optical telescope for distance? It's not a set of binoculars with parallax rangefinder capability...

That is part of why I am confused. I understand how to calibrate a telescope. I don't understand how you calibrate an object for distance and age.

@Mordred Are you saying that we thought objects were some distance away and had some particular age, but now we've discovered that they are at a different distance and age? If so, I don't understand how this affects the JWST. The telescope will be calibrated to physically focus IR light as best it can and its instruments will be calibrated by measuring dark frames, flat frames, temperature fluctuations, accumulated sensor damage, etc. But none of these have anything to do with the distance and age of a particular object.

 

[Bandersnatch]

Context (I'm guessing; this should be the OP's job):
https://www.scientificamerican.com/...nomers-forced-to-rethink-early-jwst-findings/
Same article on the Nature website has a few references to papers detailing the calibration process.

The OP seems to be asking for papers that would show how the preliminary discoveries of early massive galaxies were corrected with the same, but recalibrated, data. Which I can't help with.

However, to be tangentially relevant, I'm aware of this paper: https://arxiv.org/pdf/2303.15431.pdf doing a follow up spectroscopy on the early jwst photometric measurements, showing how, at least in some cases, that galaxy ain't z=16, bro; you're drunk - she a 5 at best.

 

[Mordred]

Sorry for not being clear, I was looking for details such as calibration for background influences such as noise reduction, relative motion with regards to spectrographic measurements etc.

That being said the link supplied by Bandersnatch has a further link in reference 12 that includes the details I was seeking.
https://arxiv.org/abs/2211.05792

The reason I wanted to look at this with regards to background influences as often the steps needed to filter out background influences such as intervening plasma relative motion can occasionally reveal and allow fine tuning local dynamics.
An example many of us are familiar with is Planck calibration for dipole anistrophy with CMB measurements revealed details of our motion relative to the CMB background thus can be used to fine tune the movement of Earth relative to that background.
The reason I have been looking closer into the calibrations of various telescopes etc is it may reveal details for mean average density of our local group. This relates in a sense to the redshift/Hubble contention and a subsequent paper that our local group could be in a low density region.
Theoretically the steps needed to fine tune our test equipment may allow verification or at the very least how such an underdensity may or may affect spectrographic related measurements such as those involving luminosity and redshift distance calculations.

 

[Mordred]

That is part of why I am confused. I understand how to calibrate a telescope. I don't understand how you calibrate an object for distance and age.

You need to calibrate for photometric redshifts is essentially what I'm after. Which Bandersnatch posted a paper with a relevant paper I can use as it also includes the specifics on the procedures used and I should be able to further backtrack through its references as well.

Thanks all for the help I should be able to further track down the details through those references.

 

[Mordred]

A quick follow up in case others are interested. The reference 12 I linked from the article Bandersnatch provided hoes into detail on the high redshift error corrections in section 8 and also previously mentions the effect of an overdensity region at z= 8.7 roughly. Still studying the articles but I learned a ton I didn't previously consider so once again many thanks.

 

[Vanadium 50]

You need to calibrate for photometric redshifts is essentially what I'm after.

Finally!

Repeat after me: "photometric redshifts are crap." IMHO, they are useful for one and only one thing - deciding where your targets for spectroscopic redshifts will be. Because (all together now) photometric redshifts are crap

That said, every paper that uses them should cite what the are using. You can and should look up the reference. You will in most cases discover that they are being used outside their range of validity. That's because they were developed before we had as good IR data. This will get cleaned up sooner or later, but it takes time.

People got confused because a) this is not cosmology, b) this is not JWST specific, and c) is not in any way a telescope calibration.

 

[Mordred]

Another recent thread on this forum has a further related article
https://www.physicsforums.com/threads/jwst-breaks-another-redshift-record.1017252/

In particular redshift greater than 16 range and some of the filters applied. Including the absolute magnitude formula applied

 

[Bandersnatch]

Still studying the articles but I learned a ton I didn't previously consider

Give us a summary once you grok it, if you can be bothered. Ta.