Archive for Lyman Break

A Cosmic Miracle?

Posted in OJAp Papers, The Universe and Stuff with tags , , , , , on January 30, 2026 by telescoper

A while ago (last May, in fact) I posted an article about a galaxy with an apparent spectroscopic redshift of 14.44. The paper to which that post related had been submitted to the Open Journal of Astrophysics and I haven’t mentioned that paper again until now as the paper was then, so to speak, sub judice. Well, as of today, the paper is now published and will feature in tomorrow’s traditional Saturday roundup of publications at the journal.

This paper was in fact accepted for publication before Christmas, but it took until this morning for the final accepted article to reach the arXiv. Rather awkwardly, the Space Telescope Science Institute issued a press release about this paper on 28th January 2026 stating that the paper was published in the Open Journal of Astrophysics, when that statement was not accurate. As Editor-in Chief of the Open Journal of Astrophysics, I was subsequently contacted by a number of journalists asking where they could find the paper on the OJAp platform. Since it hadn’t been published then I had to say they couldn’t, so a number of pieces (including, for example, this one in Scientific American) have appeared based on the STSCi press release without links to the final version of the paper. It would have been far better, in my opinion, to have delayed the press release until the paper was actually published. It’s better to wait until the ball is in the back of the net before you start celebrating!

Anyway, thanks to me getting up at 6am today, it’s now published so there’s no real harm done.

The fediscience announcement is here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "A Cosmic Miracle: A Remarkably Luminous Galaxy at $z_{rm spec} = 14.44$ Confirmed with JWST" by Rohan Naidu (MIT Kavli Institute) and 45 others.

doi.org/10.33232/001c.156033

January 30, 2026, 7:20 am 1 boosts 0 favorites

For reference, here is the key plot showing the spectrum from which the galaxy’s redshift is determined. It is rather noisy, but the Lyman break seems convincing and there are some emission lines that offer corroborative evidence:

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A galaxy at redshift z=14.44?

Posted in OJAp Papers, The Universe and Stuff with tags , , , , , on May 19, 2025 by telescoper

This morning’s arXiv mailing presented me with a distraction from examination marking in the form of a paper by Naidu et al. with this abstract:

This paper has been submitted to the Open Journal of Astrophysics. In the relatively recent past, papers like this about record-breaking galaxies would normally be submitted to Nature so perhaps we’re at last starting to see a change of culture?

I usually feel a bit conflicted in situations when a paper has been submitted for editorial review there. In this case I am posting it here for two reasons: one is that I am not the Editor responsible for this paper; the other is that the arXiv submission specifically says

Submitted to the Open Journal of Astrophysics. Comments greatly appreciated and warmly welcomed!

In order to generate flagging it here to encourage people to comment, either through the box below or by contacting the authors.

For reference, here is the key plot showing the spectrum from which the redshift is determined. It is rather noisy, but the Lyman break seems reasonably convincing and there are some emission lines that appear to offer corroborative evidence:

You might want to read this article (another OJAp paper) which contains this plot showing how galaxies at redshift z>10 challenge the standard model:

Please read the paper and comment if you wish!

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Now a Galaxy at z>16?

Posted in The Universe and Stuff with tags , , , , , , on July 26, 2022 by telescoper

It’s less than a week since I posted an item about an object which is possibly the highest redshift galaxy ever observed (with z ~13) and now along comes a paper describing an object that may be of even higher redshift (with z~16.7). The abstract of the new paper – lead author of which is Callum Donnan of the University of Edinburgh – is here:

As with the previous object the redshift of this one is not obtained via spectroscopy (which usually involves the identification of spectral lines) but via fitting a spectral profile to photometric imaging data seen in different bands. The process for this galaxy is illustrated by this diagram from the paper:

There are 7 images along the top showing the source through various broad band filters. Suitably calibrated these can be converted to the flux measurements shown on the graph. Notice the first three images are significantly fainter than the others, so the first three points on the left of the graph are lower.

If this is a galaxy its spectrum is expected to possess a Lyman Break resulting from the fact that radiation of shorter wavelength than the Lyman Limit (912 Å) is absorbed by neutral gas surrounding the regions where stars are formed in the galaxy. In the rest frame of a galaxy this break is the ultraviolet region of the spectrum but because of the cosmological redshift it is observed in the infrared part of the spectrum for very distant galaxies. In this case the best fit is obtained if the break is positioned as shown, with the first three fainter points to the left of the break and the rest to the right. The break itself is straddled by two observational bands. Employing a number of different estimates the authors conclude that the redshift of this galaxy is z=16.7 or thereabouts.

There is no direct evidence for the sharp edge associated with the Lyman Break – and no spectral lines are observed either – so this all depends on the object being correctly identified as a high-redshift galaxy and not some other object at lower redshift. You have to assume this to get a redshift, but then all inferences are based on assumed models so there’s nothing unusual about this approach. The authors discuss other possibilities and conclude that there is no plausible alternative source. Take away the green template spectrum and you just see a spectrum that rises to a peak and falls again. The authors claim that there is no plausible low-redshift source with such a spectrum.

Anyway, here is a composite colour image of the source:

So is this now the earliest galaxy ever observed? And what object will I be asking this question about next week? One thing I can predict is that there are going to be many more such objects in the very near future!

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