APOD: MACS0647: Gravitational Lensing of... (2023 Jan 18)

[APOD Robot]

MACS0647: Gravitational Lensing of the Early Universe by Webb

Explanation: Gravitational lensing by the galaxy cluster MACS0647 -- in which the massive foreground cluster distorts and lenses the light emitted by distant background galaxies along the line of sight — is on vivid display here in this recent multi-color infrared image from the James Webb Space Telescope (JWST). In particular, the background source MACS0647-JD is seen to be lensed three times by the cluster. When first discovered with the Hubble Space Telescope, MACS0647-JD was observed as an amorphous blob. With Webb though, this single source is revealed to be a pair or small group of galaxies. The colors of the MACS0647-JD objects are different as well -- indicating differences potentially in the age or dust content of these galaxies. These new images provide rare examples of galaxies in an era only a few 100 million years after the Big Bang.

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[Ann]

A Hubble image of cluster MACS0647 and the lensed background galaxy, MACS0647-JD. Credit: NASA, ESA, and M. Postman and D. Coe

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Cluster MACS0647 and three versions of lensed background galaxy MACS0647-JD by JWST. mage Credit: NASA, ESA, CSA, Dan Coe (STScI), Rebecca Larson (UT), Yu-Yang Hsiao (JHU); Processing: Alyssa Pagan (STScI); Text: Michael Rutkowski (Minn. St. U. Mankato)

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There can be no doubt that JWST is doing a better job than Hubble when it comes to resolving the extremely early and distant background galaxy, MACS0647-JD. JWST showed us three lensed versions of this galaxy, too.

(And by the way, why were the three lensed versions not labeled in the order that they appeared on the sky, which was, anti-clockwise: 3, 1, 2? Oh, wait, is the numbering of the lensed galaxies a right ascension thing?)

Back to Hubble's and JWST's portraits of cluster MACS0647. Overall, I prefer Hubble. The diffraction spikes from the bright stars are not so distracting in the Hubble image. I like the colors better, too, and I think Hubble does a better job than JWST at singling out blue starforming galaxies versus yellow ellipticals. But obviously JWST is resolving many more distant galaxies than Hubble.

Ann

[De58te]

A question. In the close-up of JD 3 there is a small totally green galaxy that's even smaller than JD 3 at the bottom right corner. Could this be an even younger galaxy and why is it green? Was it really green, or that it was red shifted to green because of its distance and it was really some other color?

[JohnD]

Gosh! That is most impressive, not just of the Webb's capability, but of the astronomers' (Larson, Hsiao? There's no credit for the pic) dedication in searching the image.

To my eye there are signs of lensing, especially on the left with 'smeared' galaxies, but to search for and find THREE images of the same galaxy!
John

[bystander]

...
There can be no doubt that JWST is doing a better job than Hubble when it comes to resolving the extremely early and distant background galaxy, MACS0647-JD. JWST showed us three lensed versions of this galaxy, too.
...

Let's see. The Webb image is totally infrared (near (blue), mid (green), and far (red)). It is, after all, an infrared telescope.

The Hubble image was originally visible wavelengths (blue) with near infrared added on (green), and then some more (near) infrared (green and red) added with a later observation. Remember, Hubble is primarily a conventional telescope with some IR and UV capabilities.

Since the further objects are, the more they are red-shifted, Webb is doing exactly what it was designed to do. Give us a better look at the distant universe.

...
(And by the way, why were the three lensed versions not labeled in the order that they appeared on the sky, which was, anti-clockwise: 3, 1, 2? Oh, wait, is the numbering of the lensed galaxies a right ascension thing?)
...

I think it has to do with magnification JD1 (8x), JD2 (5x), & JD3 (2x) (Dan Coe).

[johnnydeep]

Two questions:

1 - In the original Hubble image of this cluster, distant and ancient background galaxy MACS0647-JD was detected and "observed as an amorphous blob". Were the other two lensed versions of this background galaxy that JWST detected also detected by Hubble? (aside: all three images of MACS0647-JD are technically being "lensed" are they not?) If Hubble didn't detect the other two, why not?

2 - How in blazes was it determined that all three lensed images of this galaxy were of the same object?! And

[JohnD]

Spectral lines?

[Cousin Ricky]

A question. In the close-up of JD 3 there is a small totally green galaxy that's even smaller than JD 3 at the bottom right corner. Could this be an even younger galaxy and why is it green? Was it really green, or that it was red shifted to green because of its distance and it was really some other color?

The short answer is that green is what fell out of the color assignments to the filters. JWST does not work with visible light, and these galaxies are all drastically red-shifted anyway.

[johnnydeep]

Spectral lines?

Was that in answer to my second question above?

[Chris Peterson]

A question. In the close-up of JD 3 there is a small totally green galaxy that's even smaller than JD 3 at the bottom right corner. Could this be an even younger galaxy and why is it green? Was it really green, or that it was red shifted to green because of its distance and it was really some other color?

The short answer is that green is what fell out of the color assignments to the filters. JWST does not work with visible light, and these galaxies are all drastically red-shifted anyway.

And FWIW, given a redshift of z=10.7, the two IR filters mapped to green represent a source wavelength range of about 150-250 nm, or middle ultraviolet.

[moconnor]

As was pointed out, the three images of the same cluster look different. Does that mean that the lensing shows them at different times (or ages), although they are captured at the same time from our viewpoint on Earth? For example, does JD-1 show the object at age Big Bang + 300 million years, whereas JD-2 shows it at age BB + 320 million years and JD-3 show it at BB + 390 million years? Can the lensing have that degree of difference that depends on which side of the foreground cluster we see it?

[Chris Peterson]

As was pointed out, the three images of the same cluster look different. Does that mean that the lensing shows them at different times (or ages), although they are captured at the same time from our viewpoint on Earth? For example, does JD-1 show the object at age Big Bang + 300 million years, whereas JD-2 shows it at age BB + 320 million years and JD-3 show it at BB + 390 million years? Can the lensing have that degree of difference that depends on which side of the foreground cluster we see it?

I think you misunderstand. All three images show the same colors. The observation is that the two or three individual sources that make up each image are different colors. We are seeing them all at very nearly the same time, because the light path lengths are nearly identical.

[johnnydeep]

As was pointed out, the three images of the same cluster look different. Does that mean that the lensing shows them at different times (or ages), although they are captured at the same time from our viewpoint on Earth? For example, does JD-1 show the object at age Big Bang + 300 million years, whereas JD-2 shows it at age BB + 320 million years and JD-3 show it at BB + 390 million years? Can the lensing have that degree of difference that depends on which side of the foreground cluster we see it?

I think you misunderstand. All three images show the same colors. The observation is that the two or three individual sources that make up each image are different colors. We are seeing them all at very nearly the same time, because the light path lengths are nearly identical.

Well, what does this statement in the text mean, specifically, "these galaxies"? There's only one galaxy being imaged here, right?:

The colors of the MACS0647-JD objects are different as well -- indicating differences potentially in the age or dust content of these galaxies.

[Chris Peterson]

As was pointed out, the three images of the same cluster look different. Does that mean that the lensing shows them at different times (or ages), although they are captured at the same time from our viewpoint on Earth? For example, does JD-1 show the object at age Big Bang + 300 million years, whereas JD-2 shows it at age BB + 320 million years and JD-3 show it at BB + 390 million years? Can the lensing have that degree of difference that depends on which side of the foreground cluster we see it?

I think you misunderstand. All three images show the same colors. The observation is that the two or three individual sources that make up each image are different colors. We are seeing them all at very nearly the same time, because the light path lengths are nearly identical.

Well, what does this statement in the text mean, specifically, "these galaxies"? There's only one galaxy being imaged here, right?:

The colors of the MACS0647-JD objects are different as well -- indicating differences potentially in the age or dust content of these galaxies.

No. The lensed images show two or three different galaxies. With different colors.

[johnnydeep]

I think you misunderstand. All three images show the same colors. The observation is that the two or three individual sources that make up each image are different colors. We are seeing them all at very nearly the same time, because the light path lengths are nearly identical.

Well, what does this statement in the text mean, specifically, "these galaxies"? There's only one galaxy being imaged here, right?:

The colors of the MACS0647-JD objects are different as well -- indicating differences potentially in the age or dust content of these galaxies.

No. The lensed images show two or three different galaxies. With different colors.

But the text says "In particular, the background source MACS0647-JD is seen to be lensed three times by the cluster."

To me, that means that the same MACS0647-JD galaxy is shown in all three outset images.

[Chris Peterson]

Well, what does this statement in the text mean, specifically, "these galaxies"? There's only one galaxy being imaged here, right?:

No. The lensed images show two or three different galaxies. With different colors.

But the text says "In particular, the background source MACS0647-JD is seen to be lensed three times by the cluster."

To me, that means that the same MACS0647-JD galaxy is shown in all three outset images.

But MACS0647-JD isn't a galaxy. It's a cluster of two or more galaxies. Did you miss this in the caption: "When first discovered with the Hubble Space Telescope, MACS0647-JD was observed as an amorphous blob. With Webb though, this single source is revealed to be a pair or small group of galaxies."

So we're seeing three images of the same group of galaxies.

[johnnydeep]

No. The lensed images show two or three different galaxies. With different colors.

But the text says "In particular, the background source MACS0647-JD is seen to be lensed three times by the cluster."

To me, that means that the same MACS0647-JD galaxy is shown in all three outset images.

But MACS0647-JD isn't a galaxy. It's a cluster of two or more galaxies. Did you miss this in the caption: "When first discovered with the Hubble Space Telescope, MACS0647-JD was observed as an amorphous blob. With Webb though, this single source is revealed to be a pair or small group of galaxies."

So we're seeing three images of the same group of galaxies.

Ah. Indeed I did miss that, although it did first register with me when I read it!

[Evenstar]

Won't say much because I am just amazed and don't understand how one ends up here with the same image lensed 3 times all of which look different to me (JD1, JD2, JD3).

[Chris Peterson]

Won't say much because I am just amazed and don't understand how one ends up here with the same image lensed 3 times all of which look different to me (JD1, JD2, JD3). :ssmile:

They look different because gravitational lensing produces distorted images, and the distortion depends upon the path the light takes through the lensing gravitational field.

[bystander]

...
1 - In the original Hubble image of this cluster, distant and ancient background galaxy MACS0647-JD was detected and "observed as an amorphous blob". Were the other two lensed versions of this background galaxy that JWST detected also detected by Hubble? (aside: all three images of MACS0647-JD are technically being "lensed" are they not?) If Hubble didn't detect the other two, why not?
...

The Hubble image is visible light and near infrared. The JWST image is all infrared (near, mid, and far) and much more sensitive.

[Ann]

...
There can be no doubt that JWST is doing a better job than Hubble when it comes to resolving the extremely early and distant background galaxy, MACS0647-JD. JWST showed us three lensed versions of this galaxy, too.
...

Let's see. The Webb image is totally infrared (near (blue), mid (green), and far (red)). It is, after all, an infrared telescope.

The Hubble image was originally visible wavelengths (blue) with near infrared added on (green), and then some more (near) infrared (green and red) added with a later observation. Remember, Hubble is primarily a conventional telescope with some IR and UV capabilities.

Since the further objects are, the more they are red-shifted, Webb is doing exactly what it was designed to do. Give us a better look at the distant universe.

Certainly, bystander. I know what you mean, and you know what I mean. JWST is an amazing instrument that is teaching us more than we ever knew before about the Universe. For myself though, I like the visual aspects of the Hubble picture of this galaxy cluster better than I like the overall visual impression of the JWST picture of the same galaxy cluster. That's all I'm saying.

...
(And by the way, why were the three lensed versions not labeled in the order that they appeared on the sky, which was, anti-clockwise: 3, 1, 2? Oh, wait, is the numbering of the lensed galaxies a right ascension thing?)
...

I think it has to do with magnification JD1 (8x), JD2 (5x), & JD3 (2x) (Dan Coe).

Thanks!

Ann

[JohnD]

Spectral lines?

Was that in answer to my second question above?

Yes, Johnny. That's a guess, no doubt Chris could confirm or tell us how.
John

[Francesca]

I see in the picture (also in that by Hubble) two identical images of a galaxy. My question is whether this has been already noted. To see the first one, look at the star at the left of the center of the picture. It has six blue rays. Prolong the ray pointing up-right till a small red galaxy. The second image is approximately on the vertical line at the middle of the picture, just at the end of the left blue ray of another star, a bit less brilliant than that considered above.
There are two more objects that seem to be distorted mirror images one of the other.

[johnnydeep]

I see in the picture (also in that by Hubble) two identical images of a galaxy. My question is whether this has been already noted. To see the first one, look at the star at the left of the center of the picture. It has six blue rays. Prolong the ray pointing up-right till a small red galaxy. The second image is approximately on the vertical line at the middle of the picture, just at the end of the left blue ray of another star, a bit less brilliant than that considered above.
There are two more objects that seem to be distorted mirror images one of the other.

I'm not sure I'm following your directions correctly. Can you post a pic with the two galaxies indicated? This are the two galaxies that I think you are referring to:

[ EDIT: nah, that can't be right. I give up. I need a pic! ]

[Chris Peterson]

I see in the picture (also in that by Hubble) two identical images of a galaxy. My question is whether this has been already noted. To see the first one, look at the star at the left of the center of the picture. It has six blue rays. Prolong the ray pointing up-right till a small red galaxy. The second image is approximately on the vertical line at the middle of the picture, just at the end of the left blue ray of another star, a bit less brilliant than that considered above.
There are two more objects that seem to be distorted mirror images one of the other.

Interesting catch. While the two objects appear very similar- really, too much for a coincidence IMO (and not mirrored)- I don't think they can be lensed images. You'd never have a pair of lensed images that look the same, given the nature of gravitational lensing distortion. Some kind of processing and stacking anomaly, maybe?
_