APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

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Expand view Topic review: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by southern cross » Tue May 06, 2014 9:04 pm

Thanks Chris, for the insight, especially about the impact of ccds.

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by geckzilla » Tue May 06, 2014 5:39 am

Chris Peterson wrote:
geckzilla wrote:I think maybe if when processing a galaxy cluster you could balance the colors for the lensed z-depth only and they would look more normal. I probably need to try this myself at some point. In fact, I will make it a point to look at the CLASH data and pick one to do soon.
Try it with this one. Map the 1050 filter to blue, the 1100 filter to green, and the 1250, 1400, and 1600 filters to red. That will be quite close to the emitted ranges for z=1.14. Then you'll just have to play around with color balance.
Ok, not all of the filters covered that particular area. There's a problem! The 1100 filter did not reach so I was forced to use the next one up. They are not separated far enough for a pleasing range of color, but you can already see that actually, this supernova is not leaning toward red at all. It's slightly blue-green assuming I didn't do this incorrectly. Also it is very apparent this is a merger. The two cores are plain as day. The western one is slightly yellower. I left the two smaller nearby galaxies for context. They're probably all interacting.
Supernova behind Abell 383. North is up, east is left.
Supernova behind Abell 383. North is up, east is left.
Here's a link to the overall image at 50% size, ~2MB file. This is minimally processed. Colors were balanced and seams were made less apparent. Some egregious anomalies were removed.
http://www.geckzilla.com/astro/Abell_383.jpg

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by alter-ego » Tue May 06, 2014 5:36 am

Chris Peterson wrote: No, gravitational lenses are nothing like our optical lenses. An optical lens has no power through its optical center, and increases in power as you move towards its edge. A gravitational lens has its maximum power in the center, and the power drops off with radial distance. If you were to make an optical equivalent of a gravitational lens, it would look something like the base of a wine glass, with the maximum curvature in the center and the minimum at the edges (and a singularity at the very center).

Gravitational lenses can't bring a distant object to focus; optically, they have no focal plane.
A good visual helps with this analogy:
Click to play embedded YouTube video.

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by NGC3314 » Tue May 06, 2014 3:00 am

On the discovery of gravitational lensing - the popular-level book The Sky at Einstein's Feet devoted 2 chapters to the discovery and exploitation of gravitational lensing. I think it's now print-on-demand, but most of it can be found from Google Books here. There were, as so often happens, a lot of twists and turns along the way.

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by geckzilla » Tue May 06, 2014 12:40 am

JuanAustin wrote:I've noticed thru the years of being an avid fan of APOD that photos that appear in their original format and sources are often opposite when they appear in APOD. I guess it doesn't matter in the grander scheme of life, but it's kinda annoying and i have to wonder why go thru the trouble of flipping and reorientating the originals? Not a big deal, just saying. thanks
To me it seems it's just an aesthetic choice by one of the editors and other times it's to bring the subject into focus. I've never seen any flipping done but sometimes things are rotated, stretched, or cropped and they are almost invariably resized.

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by JuanAustin » Tue May 06, 2014 12:28 am

I've noticed thru the years of being an avid fan of APOD that photos that appear in their original format and sources are often opposite when they appear in APOD. I guess it doesn't matter in the grander scheme of life, but it's kinda annoying and i have to wonder why go thru the trouble of flipping and reorientating the originals? Not a big deal, just saying. thanks

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by Chris Peterson » Mon May 05, 2014 11:30 pm

MarkBour wrote:I'm thinking that when we make our own lenses, we make them in a shape that is convenient, to produce good optical results. However, these natural gravitational lenses are not shaped for our purposes. So, I'm wondering if that produces the kind of "optics" you are reporting. Are most gravitational lenses of a similar "shape", perhaps like looking at something through a spherical crystal ?
No, gravitational lenses are nothing like our optical lenses. An optical lens has no power through its optical center, and increases in power as you move towards its edge. A gravitational lens has its maximum power in the center, and the power drops off with radial distance. If you were to make an optical equivalent of a gravitational lens, it would look something like the base of a wine glass, with the maximum curvature in the center and the minimum at the edges (and a singularity at the very center).

Gravitational lenses can't bring a distant object to focus; optically, they have no focal plane.

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by Chris Peterson » Mon May 05, 2014 11:26 pm

geckzilla wrote:I think maybe if when processing a galaxy cluster you could balance the colors for the lensed z-depth only and they would look more normal. I probably need to try this myself at some point. In fact, I will make it a point to look at the CLASH data and pick one to do soon.
Try it with this one. Map the 1050 filter to blue, the 1100 filter to green, and the 1250, 1400, and 1600 filters to red. That will be quite close to the emitted ranges for z=1.14. Then you'll just have to play around with color balance.

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by Ann » Mon May 05, 2014 10:50 pm

Chris Peterson wrote:
Ann wrote:Judging from how I read the caption, the host galaxy can actually be seen in this picture, and it appears to be much less red (or magenta) than the supernova. The best explanation I can think of is that the supernova created an incredible amount of either infrared or redshifted visible light, but not very much UV light. The galaxy, on the other hand, emits a lot of UV light, which is seen as blue, yellow and orange light in today's APOD.
Here's a careful enlargement from the color managed original:
tiberius.jpg
The supernova itself shows 46% of its total energy emitted from 491-748 nm, 25% of its total energy emitted from 362-397 nm, and 29% of its total energy emitted from 203-292 nm. That makes the UV component a little high, perhaps, but this seems largely consistent with most supernovas.

The galaxy itself is a little harder to figure. Most of it is highly red biased, which is absolutely normal, meaning that the emitted light was substantially white (as is the case with virtually all galaxies). The blue edge, however, has most of its energy emitted in UV. Perhaps this galaxy is actually a pair in collision, or something else is going on producing a front of intense star formation. Even so, I'd expect more intensity in the visible than the IR, so something odd is happening there.
Thanks, Chris. The supernova is not at all UV deficient, then, but a large part of the galaxy is strangely UV bright.

Ann

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by geckzilla » Mon May 05, 2014 10:23 pm

MarkBour wrote:
geckzilla wrote:It's something about the way they get lensed. There are always often oddly red cores with oddly blue arms for lensed galaxies. . . .
I'm thinking that when we make our own lenses, we make them in a shape that is convenient, to produce good optical results. However, these natural gravitational lenses are not shaped for our purposes. So, I'm wondering if that produces the kind of "optics" you are reporting. Are most gravitational lenses of a similar "shape", perhaps like looking at something through a spherical crystal ?
It's like a magnifying glass as far as I know. Hubble is being used to look at them because they let us see farther than we normally would. I have absolutely no idea how but it also seems to reduce the redshift. I could be completely misunderstanding it, though. Lensed galaxies always look pretty strange because of the distortion they go through. I think maybe if when processing a galaxy cluster you could balance the colors for the lensed z-depth only and they would look more normal. I probably need to try this myself at some point. In fact, I will make it a point to look at the CLASH data and pick one to do soon.

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by MarkBour » Mon May 05, 2014 10:03 pm

geckzilla wrote:It's something about the way they get lensed. There are always often oddly red cores with oddly blue arms for lensed galaxies. . . .
I'm thinking that when we make our own lenses, we make them in a shape that is convenient, to produce good optical results. However, these natural gravitational lenses are not shaped for our purposes. So, I'm wondering if that produces the kind of "optics" you are reporting. Are most gravitational lenses of a similar "shape", perhaps like looking at something through a spherical crystal ?

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by Chris Peterson » Mon May 05, 2014 9:13 pm

southern cross wrote:I find this such a remarkable image. The supernova itself is amazing to see, but aside from this, the way the light from the background galaxy/galaxies is smeared around the big foreground galaxy in concentric rings - wow! I wonder if Abell saw this in his original survey? And this leads to the next question that springs into my mind... when was the gravitational lensing effect first noticed?
Gravitational lensing was proposed in the early 20th century by Einstein and others, as an obvious consequence of GR. None was actually observed until 1979. Recording them really requires CCD cameras- film simply lacks the resolution and sensitivity. Abell lacked the technology to detect gravitational lensing while he was conducting his galaxy cluster surveys.

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by southern cross » Mon May 05, 2014 9:00 pm

I find this such a remarkable image. The supernova itself is amazing to see, but aside from this, the way the light from the background galaxy/galaxies is smeared around the big foreground galaxy in concentric rings - wow! I wonder if Abell saw this in his original survey? And this leads to the next question that springs into my mind... when was the gravitational lensing effect first noticed?

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by ta152h0 » Mon May 05, 2014 8:32 pm

I live in the Pacific Northwest, land where the mere mention of telescopes is cloubait

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by Chris Peterson » Mon May 05, 2014 8:29 pm

ta152h0 wrote:as I look out my kitchen window at night ( facing south ) I am in awe of astronomers actually finding these things
The finding is easy. You simply aim telescopes at things as much as possible. Much more impressive is the analysis and the ability to reasonably explain what are, in the end, just observations.

You'd find a great many things like this yourself if you had a five meter telescope in your kitchen.

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by ta152h0 » Mon May 05, 2014 8:21 pm

as I look out my kitchen window at night ( facing south ) I am in awe of astronomers actually finding these things

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by geckzilla » Mon May 05, 2014 5:40 pm

It's something about the way they get lensed. There are always often oddly red cores with oddly blue arms for lensed galaxies. Keep in mind that the two instruments used (ACS and WFC3) produced images of differing resolutions. I can't remember the specifics off hand but I want to say that it is the farther infrared data which are of lower resolution... I guess if you shrink the higher resolution image to match the lower resolution one then it will not make a big difference but if the lower resolution data were sampled up then things get weird.

Quick reference for single filter images is available here: (scroll down below the color pictures)
http://archive.stsci.edu/prepds/clash/a383_display.html

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by Chris Peterson » Mon May 05, 2014 5:06 pm

Ann wrote:Judging from how I read the caption, the host galaxy can actually be seen in this picture, and it appears to be much less red (or magenta) than the supernova. The best explanation I can think of is that the supernova created an incredible amount of either infrared or redshifted visible light, but not very much UV light. The galaxy, on the other hand, emits a lot of UV light, which is seen as blue, yellow and orange light in today's APOD.
Here's a careful enlargement from the color managed original:
tiberius.jpg
tiberius.jpg (9.97 KiB) Viewed 6947 times
The supernova itself shows 46% of its total energy emitted from 491-748 nm, 25% of its total energy emitted from 362-397 nm, and 29% of its total energy emitted from 203-292 nm. That makes the UV component a little high, perhaps, but this seems largely consistent with most supernovas.

The galaxy itself is a little harder to figure. Most of it is highly red biased, which is absolutely normal, meaning that the emitted light was substantially white (as is the case with virtually all galaxies). The blue edge, however, has most of its energy emitted in UV. Perhaps this galaxy is actually a pair in collision, or something else is going on producing a front of intense star formation. Even so, I'd expect more intensity in the visible than the IR, so something odd is happening there.

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by CygnusOB2 » Mon May 05, 2014 4:51 pm

We are able watch the death of a star even though this event occurred billions of years before our sun and planet existed.. Wow ! :shock:

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by Ann » Mon May 05, 2014 4:32 pm

Judging from how I read the caption, the host galaxy can actually be seen in this picture, and it appears to be much less red (or magenta) than the supernova. The best explanation I can think of is that the supernova created an incredible amount of either infrared or redshifted visible light, but not very much UV light. The galaxy, on the other hand, emits a lot of UV light, which is seen as blue, yellow and orange light in today's APOD.

Ann

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by Ron-Astro Pharmacist » Mon May 05, 2014 3:34 pm

How do you calibrate a huge gravitational lens? The Very Large Contact :lol2:

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by Chris Peterson » Mon May 05, 2014 2:03 pm

BDanielMayfield wrote:
Nitpicker wrote:The supernova is a lot further away than the cluster. That's the point, I think.
You're right. Is the SN's distance known then, I wonder?
The redshift is z=1.14. That makes the comoving distance 11.9 billion ly, or the light travel time 8.3 billion ly (i.e. the light was emitted when the Universe was 5.4 billion years old).

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by Chris Peterson » Mon May 05, 2014 2:00 pm

Nitpicker wrote:The supernova is a lot further away than the cluster. That's the point, I think.
You're right. I read the redshift as applying to the supernova, but it actually refers to the lensing cluster. Of course, even a redshift of 0.187 is enough to change blue to red- 100 nm will move 500 nm (strong in a blue star) to 600 nm (strong in a red star). But in this case, the actual supernova is z=1.14, so what we're seeing in the blue channel was emitted from 203-292 nm (UV), in the green channel was emitted from 362-397 nm (UV), and in the red channel from 491-748 nm (pretty much the entire visible light range). So I'm not surprised we see a color containing a strong red component.

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by BDanielMayfield » Mon May 05, 2014 1:49 pm

Ann wrote:I find it remarkable that the supernova is so very red, and much redder than its apparent host galaxy.
Is it safe to assume that this SN is even part of the "apparent host galaxy"?

Edit: But I should add that from the inset detail images it certainly looks like it is. I should have just deleted this post. Never mind. Please forget I wrote this dumb question. :oops:

Re: APOD: Galaxy Cluster Magnifies Distant... (2014 May 05)

by BDanielMayfield » Mon May 05, 2014 1:27 pm

Nitpicker wrote:The supernova is a lot further away than the cluster. That's the point, I think.
You're right. Is the SN's distance known then, I wonder?

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