Archive for JWST

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Hubble Tension Reduced?

Posted in The Universe and Stuff with tags , , , , on August 14, 2024 by telescoper

Back in April I posted about a meeting at the Royal Society in London called Challenging the Standard Cosmological Model, some of which I attended virtually. In that post I mentioned that Wendy Freedman gave a talk related to the ongoing issue of the Hubble Tension, i.e. the discrepancy between different types of measurement of the Hubble Constant, usually characterized as local measurements (using stellar distance indicators) and larger-scale measurements (chiefly Planck). There are quite a few posts about this issue on this blog. Anyway, Wendy Freedman mention in her talk that her latest work on stellar distances suggested a value of 69.1 ± km s-1 Mpc-1, which reduces the tension with Planck significantly. At the time, however, there was no paper explaining how this number was derived.

Yesterday there appeared on arXiv a preprint by Freedman et al. which summarizes the recent results. The abstract is here:

We present the latest results from the Chicago Carnegie Hubble Program ( CCHP) to measure the Hubble constant using data from the James Webb Space Telescope (JWST). This program is based upon three independent methods: (1) Tip of the Red Giant Branch (TRGB) stars, (2) JAGB (J-Region Asymptotic Giant Branch) stars, and (3) Cepheids. Our program includes 10 nearby galaxies, each hosting Type Ia supernovae (SNe Ia), suitable for measuring the Hubble constant (H0). It also includes NGC  4258, which has a geometric distance, setting the zero point for all three methods. The JWST observations have significantly higher signal-to-noise and finer angular resolution than previous observations with the Hubble Space Telescope (HST). We find three independent values of H0 = 69.85 ± 1.75 (stat) ± 1.54 (sys) for the TRGB, H0 = 67.96 ± 1.85 (stat) ± 1.90 (sys)  km s-1 Mpc-1 for the JAGB, and H0 = 72.05 ± 1.86 (stat) ± 3.10 (sys) for Cepheids. Tying into SNe Ia, and combining these methods adopting a flat prior, yields our current estimate of H0 = 69.96 ± 1.05 (stat) ± 1.12 (sys)  km s-1 Mpc-1. The distances measured using the TRGB and the JAGB method agree at the 1% level, but differ from the Cepheid distances at the 2.5-4% level. The value of H0 based on these two methods with JWST data alone is H0 = 69.03 ± 1.75 (total error)  km s-1 Mpc-1. These numbers are consistent with the current standard ΛCDM model, without the need for the inclusion of additional new physics. Future JWST data will be required to increase the precision and accuracy of the local distance scale.

You can read the full paper on arXiv here. A summary of the summary is that of the three methods they use, two give lower values of the Hubble constant and one (Cepheids) gives a higher value but with larger errors. The number quoted in the Royal Society talk was presumably preliminary as it doesn’t match any of the numbers in the abstract, but the point remains.

You can see the reduction in scatter in the new JWST measurements in this Figure (old on the left and new on the right).

On the face of it, these results suggest that the Hubble tension is greatly reduced. I am sure, however, that advocates of a higher value will have been preparing their ripostes and it’s just a matter of time before they arrive on the arXiv too!

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SN1987A, Past and Present

Posted in Biographical, The Universe and Stuff with tags , , , , , , on February 23, 2024 by telescoper

There’s a new paper in Science featuring observations using the MIRI and NIRSpec instruments on JWST of Supernova SN1987A in the Large Magellanic Cloud. I couldn’t resist doing a short post about this result, partly because the paper features Maynooth colleague Paddy Kavanagh, and partly because I’m old enough to remember when this supernova was detected, in 1987. In fact I was doing my PhD at the time. When I started lecturing a few years later I used to use it as an example of a Type II (core-collapse) supernova. At first I would say “you will remember SN1987A” then, as the years passed, I realized that students would have been quite young in 1987 so I changed this to “some of you will remember SN1987A”. Still later, I realized that none of my students had even been born in 1987 so I forgot about the remembering bit and just talked about SN1987A. As of 2024, nobody under the age of 37 was born in 1987. Tempus has a distinct tendency to Fugit.

In 1987 I was in Sussex and I remember Roger Tayler getting very excited about the detection of anti-neutrinos from SN1987A at the Kamioka Observatory in Japan. There weren’t many – 12 altogether – but he wanted to do a statistical analysis of the arrival times to see if there was any evidence that might indicate the neutrinos had mass. Being rather “old-school”, he did a Monte Carlo experiment involving drawing numbers written on bits of paper out of a cardboard box. After a brief chat I suggested I could do a much better job using a random-number generator on a computer so I wrote a bit of code and did the computation. The results showed no evidence for neutrino mass.

Anyway, this type of supernova should produce a neutron star or black hole sitting inside a ring-shaped remnant. The ring has been well studied, but in 37 years of observation the central object has not been detected. The results in the latest paper (by Fransson et al.) involve a spectroscopic study of the emission lines of ionized argon from the SN1987a remnant at sufficiently high spectral resolution to map the velocity structure. The results suggest that ionizing radiation from a neutron star is illuminating gas from the inner parts of the remnant.

https://doi.org/10.1126/science.adj5796

For more details, see the paper.

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PHANGS for the galaxies…

Posted in The Universe and Stuff with tags , , , , , , , on January 31, 2024 by telescoper

I couldn’t resist sharing this wonderful set of images from JWST courtesy of the PHANGS* team showing exquisite details of 19 face-on spiral galaxies as seen in the infra-red:

More information about the remarkable structures seen in these images, as well as higher resolution versions of the images themselves, can be found on the European Space Agency website here.

*For those of you not in the know, PHANGS stands for Particularly Horrible Acronym Not Generated Sensibly Physics at High Angular resolution in Nearby GalaxieS.

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Yet more high-z galaxies from JWST…

Posted in The Universe and Stuff with tags , , , , , , , on December 19, 2023 by telescoper

I noticed a paper on arXiv yesterday, by Robertson et al., with the abstract:

You can click on this to make it larger if you find it difficult to read.

This is the latest in a number of studies by the JWST Advanced Deep Extragalactic Survey (JADES), which is aiming to detect galaxies that formed in the very early Universe; for a previous example see here. The latest batch can be seen in this figure:

There is an important caveat here, which is that these are photometric redshifts, based on the overall shape of the spectrum of the galaxy rather than on spectral lines which give a more accurate result. Follow-up spectroscopy is needed to firmly identify the redshift of the sources. Past experience suggests that some of these candidates may not actually be at as high a redshift as is claimed. If confirmed, however, the existence of large galaxies at redshifts of order 15 will put greater pressure on models of galaxy formation. A recent OJAp publication has shown that galaxies at redshift 10 are consistent with current theoretical ideas, but much larger will increase the tension on theorists. I can imagine quite a few people around the world replotting their graphs right now!

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New Publication at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , on December 12, 2023 by telescoper

I was doing some work on the Open Journal of Astrophysics site and realized that there is a paper we published last week that I haven’t advertised on here yet, so I’m remedying that now.

The paper in question is the 47th so far in Volume 6 (2023)  and it’s the 112th altogether. This one was actually published on Tuesday December 5th. Two further papers are imminent; I’m just waiting for their metadata to be registered with Crossref.

The title of this one is “The SPHINX Public Data Release: Forward Modelling High-Redshift JWST Observations with Cosmological Radiation Hydrodynamics Simulations” and it represents  public data release of Sphinx20, a full box cosmological radiation-hydrodynamics simulation that provides a statistical sample of galaxies for comparison with those observed by JWST. It is in the folder marked Astrophysics of Galaxies.

There are 10 authors: Harley Katz (Oxford, UK); Joki Rosdahl (Lyon, France); Taysun Kimm (Seoul, Korea); Jeremy Blaizot (Lyon, France);  Nicholas Choustikov (Oxford, UK); Marion Farcy  and Thibault Garel (Geneva, Switzerland);  Martin G. Haehnelt (Cambridge, UK); Leo Michel-Dansac (Lyon, France); and Pierre Ocvirk (Strasbourg, France).

Here is the overlay of the paper containing the abstract:

 

 

You can click on the image of the overlay to make it larger should you wish to do so. You can find the officially accepted version of the paper on the arXiv here.

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New Views of the Orion Nebula

Posted in The Universe and Stuff with tags , , on October 3, 2023 by telescoper

The Orion Nebula, a stellar nursery about 400 pc away from Earth, is a much-studied object that has yielded considerable insights into the processes of star formation. If you thought that there wasn’t much more to be learned about this object, though, you’d be very wrong. A set of JWST images has been released by the European Space Agency and they are amazing. You can see them all here, but here’s a taster in the form of a detail from one of the pictures. The following image is entitled “Explosion fingers from the BN-KL region in Orion” but to me it looks like demons rising up from the Underworld, like in the last act of Don Giovanni…

Here’s the blurb:

This cutout from the new NASA/ESA/CSA James Webb Space Telescope short-wavelength infrared image of the Orion Nebula shows bright ‘fingers’ of gas racing away from an explosion that occurred roughly 500 to 1000 years ago in the heart of a dense molecular cloud behind the nebula, perhaps as two young massive stars collided. The dense cloud is called Orion Molecular Cloud 1 and lies to the northwest of the visible Trapezium stars in Orion.

The fingers are predominantly red, indicating emission from molecular hydrogen gas that has been shocked by the immense energy pouring out from the explosion site. Near the tips of some of the fingers, the emission turns green due to hot iron gas and even white in some cases where the gas is at its hottest. Further down, the fingers seem mostly turbulent, but in some places, the flow appears laminar.

The Orion Nebula lies roughly 1300 light-years from Earth in the so-called ‘sword’ of the constellation of Orion the Hunter, and the image shows a region that is 4 by 2.75 light-years in size.

Image description: The image shows a series of red fingers of shocked molecular gas expanding from the bottom of the image towards the top and top right. Each of the fingers comprises a series of bright arcs of emission like bow waves, expanding behind tips, the latter often appearing green. There are many stars spread across the image with the characteristic eight spikes due to diffraction in the optics of Webb, and there is a foreground haze of wisp blue clouds due to the Orion Nebula, which lies in front of the fingers.

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Two Views of the Ring Nebula

Posted in Cardiff, Maynooth, The Universe and Stuff with tags , , , , , , , , , on August 22, 2023 by telescoper

It’s very nice to have an opportunity, courtesy of JWST, to congratulate astronomers from my current institution (Maynooth, Ireland) and my previous one (Cardiff, UK) – as well as many others – or their involvement in stunning new observations of the Ring Nebula (aka M57 and NGC 6720), a planetary nebula. There is a full story on the Maynooth University website here detailing the involvement of Dr Patrick Kavanagh in the processing of the images and another on the Cardiff University website here about Dr Roger Wesson, who led the programme. Not surprisingly there has been a lot of news coverage about these wonderful images obtained with the NIRCam and MIRI instruments on JWST here in Ireland and in Wales and elsewhere.

A particular excuse for reproducing the pictures here is to try out the fancy “image comparison” tool on WordPress, which allows the reader – that’s you – to slide one picture over the other. Have a go!

This groovy visual shows two images side by side of the Ring Nebula. The image on the left shows the NIRCam view and the image on the right shows the MIRI image. The left image shows the planetary nebula as a distorted doughnut with a rainbow of colours with a blue/green inner cavity and clear filamentary structure in the inner region. The right image shows the nebula with a red/orange central cavity with a ring structure that transitions from colours of yellow to purple/blue. Picture credits ESA/Webb, NASA, CSA, M. Barlow, N. Cox, R. Wesson

The full paper describing these observations can be found on the arXiv here.

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A proto-cluster at z ~ 8!

Posted in The Universe and Stuff with tags , , , , on April 26, 2023 by telescoper
Blow-ups of the seven galaxies with spectroscopic redshifts, shown together with their positions near the line of sight to a foreground cluster.

I missed the paper containing this impressive picture when it first appeared on the arXiv, the primary source for astrophysics and cosmology research, but fortunately it has now been published on a secondary site, Astrophysical Journal Letters, with an accompanying press release so I can now do a quick post about it.

The article concerned, with lead author Takahiro Morishita of the California Institute of Technology (Caltech) et al. describes the detection using JWST of an apparent proto-cluster – seven galaxies in close proximity – at redshift z = 7.88. Here is the abstract:

Although only seven galaxies are identified, this does look like the very early stages of formation of an object that will grow into a giant galaxy cluster by the present epoch. The redshift of this progenitor corresponds to a stage of the Universe just 650 million years or so after the Big Bang, compared with the current age of about 14 billion years. As the abstract says, we would need to know more about other possible constituent galaxies and their motions to be sure, but it looks like a baby destined to grow into a monster…

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Spectroscopy of High Redshift Galaxies

Posted in The Universe and Stuff with tags , , , , , on March 28, 2023 by telescoper

The tentative identifications of a number of galaxies at high redshift using JWST on the basis of photometric measurements (see, e.g., here and here) have initiated a huge amount of activity in the extragalactic community trying to establish spectroscopic redshifts for these galaxies. Results of this endeavour have started to appear on the arXiv here with this abstract:

During the first 500 million years of cosmic history, the first stars and galaxies formed and seeded the cosmos with heavy elements. These early galaxies illuminated the transition from the cosmic “dark ages” to the reionization of the intergalactic medium. This transitional period has been largely inaccessible to direct observation until the recent commissioning of JWST, which has extended our observational reach into that epoch. Excitingly, the first JWST science observations uncovered a surprisingly high abundance of early star-forming galaxies. However, the distances (redshifts) of these galaxies were, by necessity, estimated from multi-band photometry. Photometric redshifts, while generally robust, can suffer from uncertainties and/or degeneracies. Spectroscopic measurements of the precise redshifts are required to validate these sources and to reliably quantify their space densities, stellar masses, and star formation rates, which provide powerful constraints on galaxy formation models and cosmology. Here we present the results of JWST follow-up spectroscopy of a small sample of galaxies suspected to be amongst the most distant yet observed. We confirm redshifts z > 10 for two galaxies, including one of the first bright JWST-discovered candidates with z = 11.4, and show that another galaxy with suggested z ~ 16 instead has z = 4.9, with strong emission lines that mimic the expected colors of more distant objects. These results reinforce the evidence for the rapid production of luminous galaxies in the very young Universe, while also highlighting the necessity of spectroscopic verification for remarkable candidates.

arXiv:2303.15431

As the abstract explains, the spectroscopic measurements confirm some – but not all – of the galaxies studied to be at high redshift. One galaxy – the one discussed here (known to its friends as 93316) which appeared to have a redshift of 16.6 ± 0.1 now seems to have a much lower redshift of 4.91. Here’s an image of this object:

The redshift 16.6 object was of some interest to cosmologists because an object of large stellar mass at such a large distance is difficult to reconcile with the standard theory of galaxy formation. That is now apparently out of the way, and the remaining high-z galaxies are not as extreme as this one and pose less of a problem.

While this result may disappoint some, and indeed delight others, it is also interesting to note that there are three similar objects at much the same redshift, which may indicate the presence of some sort of group or cluster:

Fascinating!

P.S. It struck me, after writing this, that waiting for spectroscopic confirmation of photometric redshifts is a lot like waiting for VAR to check whether or not to rule out a goal for offside…

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A 13-billion-year-old Galaxy Spectrum

Posted in The Universe and Stuff with tags , , , , , on February 16, 2023 by telescoper

The Galaxy GN-z11 has been known for some time to have a very high redshift z~11 (hence the name) but you can now feast your eyes on the exquisite infrared spectrum of this object recently obtained using JWST:

It’s incredible to see so many clear emission lines for an object at such an enormous distance. The light from this galaxy set out towards us over 13 billion years in the past, when the Universe was less than 400 million years old, so it provides clues about the very early stages of cosmic structure formation. The spectral lines can not only be used to establish the redshift with great precision – it is z = 10.603 – but also to probe the physical properties of this source and its environment. The progress in this field is truly remarkable thanks to superb advances in observational technology.

For more details of this amazing result see the paper by Bunker et al now on the arXiv.

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