Hubble: Clumps of New Stars in Distant Galaxy

[bystander]

Hubble Pushed Beyond Limits to Spot Clumps of New Stars in Distant Galaxy
NASA | GSFC | STScI | HubbleSite | 2017 Jul 06

[c][attachment=0]hubblestscihp1727af.jpg[/attachment][/c][hr][/hr]

When it comes to the distant universe, even the keen vision of NASA’s Hubble Space Telescope can only go so far. Teasing out finer details requires clever thinking and a little help from a cosmic alignment with a gravitational lens.

By applying a new computational analysis to a galaxy magnified by a gravitational lens, astronomers have obtained images 10 times sharper than what Hubble could achieve on its own. The results show an edge-on disk galaxy studded with brilliant patches of newly formed stars.

“When we saw the reconstructed image we said, ‘Wow, it looks like fireworks are going off everywhere,’” said astronomer Jane Rigby of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

The galaxy in question is so far away that we see it as it appeared 11 billion years ago, only 2.7 billion years after the big bang. It is one of more than 70 strongly lensed galaxies studied by the Hubble Space Telescope, following up targets selected by the Sloan Giant Arcs Survey, which discovered hundreds of strongly lensed galaxies by searching Sloan Digital Sky Survey imaging data covering one-fourth of the sky. ...

Star Formation at z=2.481 in the Lensed Galaxy SDSS J1110+6459:
Star Formation down to 30 parsec scales - Traci L. Johnson et al

• Astrophysical Journal Letters 843(2):L21 (2017 Jul 10) DOI: 10.3847/2041-8213/aa7516
  arXiv.org > astro-ph > arXiv:1707.00706 > 03 Jul 2017

Star Formation at z=2.481 in the Lensed Galaxy SDSS J1110+6459:
I. Lens Modeling and Source Reconstruction - Traci L. Johnson et al

• Astrophysical Journal 843(2):L21 (2017 Jul 10) DOI: 10.3847/1538-4357/aa7756
  arXiv.org > astro-ph > arXiv:1707.00707 > 03 Jul 2017

Star Formation at z=2.481 in the Lensed Galaxy SDSS J1110+6459:
II: What is missed at the normal resolution of the Hubble Space Telescope? - J. R. Rigby et al

• Astrophysical Journal 843(2):79 (2017 Jul 10) DOI: 10.3847/1538-4357/aa775e
  arXiv.org > astro-ph > arXiv:1707.00704 > 03 Jul 2017

[Ann]

So, an ancient blue arc, whose color likely corresponds to redshifted ultraviolet light, has been transformed by Hubble into a relatively fat grayscale disk galaxy with white clumps of star formation?

Ann

[geckzilla]

So, an ancient blue arc, whose color likely corresponds to redshifted ultraviolet light, has been transformed by Hubble into a relatively fat grayscale disk galaxy with white clumps of star formation?

Surely you understand by now that science is done on those grayscale images (or, more specifically, the numbers represented by those images), and that the color ones are almost exclusively used for outreach. The reconstruction is probably pulled straight from the research while the color image is likely something outreach made.

[Chris Peterson]

So, an ancient blue arc, whose color likely corresponds to redshifted ultraviolet light, has been transformed by Hubble into a relatively fat grayscale disk galaxy with white clumps of star formation?

Surely you understand by now that science is done on those grayscale images (or, more specifically, the numbers represented by those images), and that the color ones are almost exclusively used for outreach. The reconstruction is probably pulled straight from the research while the color image is likely something outreach made.

FWIW, it's common with scientific grants for there to be an outreach component, usually funded at a few percent of the total grant. That's one of the things that helps make many of these images available (although as more amateur image processors discover the raw data and develop techniques, we're seeing a lot more processed Hubble images coming from outside the professional community).

[Ann]

So, an ancient blue arc, whose color likely corresponds to redshifted ultraviolet light, has been transformed by Hubble into a relatively fat grayscale disk galaxy with white clumps of star formation?

Surely you understand by now that science is done on those grayscale images (or, more specifically, the numbers represented by those images), and that the color ones are almost exclusively used for outreach. The reconstruction is probably pulled straight from the research while the color image is likely something outreach made.

NASA wrote:

In this Hubble photograph of a distant galaxy cluster, a spotty blue arc stands out against a background of red galaxies. That arc is actually three separate images of the same background galaxy. The background galaxy has been gravitationally lensed, its light magnified and distorted by the intervening galaxy cluster. On the right: How the galaxy would look to Hubble without distortions.

Yes, I do understand that science is done with grayscales (or numbers), but I thought it wasn't a good idea to show a picture of variously colored galaxies, and then tell the general public that the blue arc would really look like a a black and white galaxy if it could be seen up close.

Click to view full size image

Brilliantly starforming galaxy NGC 4631.
Photo: Johannes Schedler.

I think that, if nothing else, NASA could have asked one of the great amateur astrophotographers if they could borrow a picture of an edge-on brilliantly star forming disk galaxy to stand in for the distant lensed one. I think NGC 4631 would have made a very fine substitute.

Ann

[geckzilla]

No, they couldn't have put any random galaxy in there, because then it would not be about the research anymore? It's a reconstruction of a real galaxy and the best image we have of that exact galaxy. Putting in a different one just because it's colorful wouldn't make sense.

[bystander]

[c]
This artist's illustration portrays what the gravitationally lensed galaxy
SDSS J1110+6459 might look like up close. A sea of young, blue stars is
streaked with dark dust lanes and studded with bright pink patches that
mark sites of star formation. The patches' signature glow comes from
ionized hydrogen, like we see in the Orion Nebula in our own galaxy.
Credits: NASA, ESA, and Z. Levay (STScI)[/c][hr][/hr]

[geckzilla]

They could, however, provide a supplementary illustration... apparently.

[Ann]

No, they couldn't have put any random galaxy in there, because then it would not be about the research anymore? It's a reconstruction of a real galaxy and the best image we have of that exact galaxy. Putting in a different one just because it's colorful wouldn't make sense.

I agree with you, but I have seen it done before. That is, I've seen NASA using an existing galaxy to illustrate the appearance of galaxy whose true appearance can't be shown. In particular, I have seen them pick another (often well-known) galaxy to illustrate the appearance of the Milky Way. I wouldn't mind them doing this, as long as they point out that they are using another galaxy as an illustration, and preferably they should name the galaxy that they are using as a substitute.

Oh, and thanks for posting that illustration of the lensed galaxy, bystander!

Ann

[Chris Peterson]

Yes, I do understand that science is done with grayscales (or numbers), but I thought it wasn't a good idea to show a picture of variously colored galaxies, and then tell the general public that the blue arc would really look like a a black and white galaxy if it could be seen up close.

They didn't say that. I think your obsession with color is distorting how you read it. Color is completely irrelevant here. What they're saying is that's what the galaxy would look like if you removed the distortion caused by the gravitational lensing. The entire purpose of the illustration centers around morphology. Color isn't discussed and isn't important. The story is the ability to mathematically unwrap the gravitational lensing to reveal actual physical structure inside lensed galaxies.

[Ann]

Yes, I do understand that science is done with grayscales (or numbers), but I thought it wasn't a good idea to show a picture of variously colored galaxies, and then tell the general public that the blue arc would really look like a a black and white galaxy if it could be seen up close.

They didn't say that.

I know. In my initial response to the NASA illustration, I made it clear that it was possible to think that NASA said that the blue arc was really a black-and-white galaxy, not that they actually said that it was. But then I wanted a snappier and shorter description, and I thought that the only ones who read this forum are the ones that won't be fooled by my post.

Color isn't discussed and isn't important.

I disagree. It is important that the lensed galaxy is forming huge numbers of stars.

In a black-and-white image, an edge-on galaxy may look patchy because of the distribution of its dust, not because it is forming many stars. I have seen black-and-white images of M104 that might lead you to believe that there is a respectable amount of star formation going on in its dust lane, even though the picture in the link isn't the best example of this patchiness.

The story is the ability to mathematically unwrap the gravitational lensing to reveal actual physical structure inside lensed galaxies.

I can see that that is the main object here.

Ann

[geckzilla]

The reconstruction doesn't have any color, though. If the goal is to show the reconstruction, that's probably the most truthful way to do it. It would be trivial to add a blue tint to the galaxy, but then people might think the reconstruction contained that information. Anyway, it's probably not that important to warrant this long discussion.

[Chris Peterson]

Color isn't discussed and isn't important.

I disagree. It is important that the lensed galaxy is forming huge numbers of stars.

It is important to you. But not to the story that's being told, which is about morphology and optical resolution. What they can learn from color is essentially the same whether or not they remove the distortion from lensing.

[Ann]

The reconstruction doesn't have any color, though. If the goal is to show the reconstruction, that's probably the most truthful way to do it. It would be trivial to add a blue tint to the galaxy, but then people might think the reconstruction contained that information. Anyway, it's probably not that important to warrant this long discussion.

Point taken, but I'm still sticking my neck out to add one more thing. Suppose this galaxy wasn't forming a lot of stars at all. Suppose it was actually a red and dead galaxy, a blob, similar in appearance to many elliptical galaxies.

Being so far away and so redshifted, wouldn't it be very hard to see such a distant elliptical galaxy? Isn't all the star formation and the ultraviolet brightness that comes with it almost a prerequisite to easily see a galaxy that has been so redshift-reddened?

If the galaxy was just a roundish, featureless blob, what would its lensed appearance look like?

EDIT: As I read the press release again, I got the impression that it was the resolution of the starforming knots and the determination of their sizes that was the main object of this particular research, not the "overall shape" of the galaxy.

I will shut up now.

Ann

[geckzilla]

Like this?
http://hubblesite.org/news_release/news/2017-26

This previous news release features a reconstruction with color. I take it to mean that the reconstruction itself was done using at least two of the filters instead of just one, and so a color version was provided. I could be wrong. Probably I could be wrong about the other one, too. I'm too tired to look at the actual papers right now.