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

[APOD Robot]

Galaxy Cluster Magnifies Distant Supernova

Explanation: How do you calibrate a huge gravitational lens? In this case the lens is the galaxy cluster Abell 383, a massive conglomeration of galaxies, hot gas, and dark matter that lies about 2.5 billion light years away (redshift z=0.187). What needs calibrating is the mass of the cluster, in particular the amount and distribution of dark matter. A new calibration technique has been tested recently that consists of waiting for supernovas of a very specific type to occur behind a galaxy cluster, and then figuring out how much the cluster must have magnified these supernovas through gravitational lensing. This technique complements other measures including computing the dark matter needed to contain internal galaxy motions, to confine cluster hot gas, and to create the gravitational lens image distortions. Pictured above from the Hubble Space Telescope, galaxy cluster A383 shows its gravitational lens capabilities on the right by highly distorting background galaxies behind the cluster center. On the left is a distant galaxy shown both before and after a recent revealing supernova. To date, calibration-quality supernovas of Type Ia have been found behind two other galaxy clusters by the Cluster Lensing And Supernova survey with Hubble (CLASH) project.

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[bystander]

http://asterisk.apod.com/viewtopic.php?t=33339

[Ann]

I find it remarkable that the supernova is so very red, and much redder than its apparent host galaxy. Even though it's very red, the supernova still appears very bright compared with its host galaxy.

Remarkable. Perhaps the supernova is only bright in infrared light, however.

Ann

[BDanielMayfield]

I find it remarkable that the supernova is so very red, and much redder than its apparent host galaxy. Even though it's very red, the supernova still appears very bright compared with its host galaxy.

Remarkable. Perhaps the supernova is only bright in infrared light, however.

Ann

They must have caught this SN at close to it's peak brightness when a SN can breifly outshine an entire galaxy. Also it must be behind a great deal of dust to make it look so red Ann.

Bruce

[Chris Peterson]

They must have caught this SN at close to it's peak brightness when a SN can breifly outshine an entire galaxy. Also it must be behind a great deal of dust to make it look so red Ann.

It would be a mistake to make any casual inferences about the color, given that this is a composite generated from almost UV through near infrared, using 12 different band passes, narrow and wide, mapped with unknown weights to just three channels. As if that weren't complicated enough, at z=0.187 the entire spectrum is shifted by about 100 nm (which is enough alone to move blue to red). And finally, the object isn't really red, but magenta, with high red and blue signal, and low green.

You could look at the raw data and learn a lot. You can't look at this image and get much information from the apparent colors.

[geckzilla]

Haha, two-thirds of that dataset is infrared. There's so much to see in the redshifted universe. Oh, how I am looking forward to JWST...

[Ann]

Haha, two-thirds of that dataset is infrared. There's so much to see in the redshifted universe. Oh, how I am looking forward to JWST...

Well then, most of the signal is in the infrared. That's what I thought.

Ann

[starsurfer]

Also it appears so red due to it being many billions of light years away, so I'm guessing that high redshift partly contributes to its red colour.

[BDanielMayfield]

Also it appears so red due to it being many billions of light years away, so I'm guessing that high redshift partly contributes to its red colour.

But, per how Chris answered me starsurfer, this redshift is only enough to shift the spectra by about 100nm. I'm trying to understand this in view of the fact that the visible spectrum ranges from about 380nm to 760nm. 100nm isn't a massive amount of shift and the z number isn't that large, so is this cluster really "many" billions of lys away? After all, our entire range of view is only about 12 billion lys.

P.S. the description says 2.5 billion light years.

[Nitpicker]

The supernova is a lot further away than the cluster. That's the point, I think.

[BDanielMayfield]

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?

[BDanielMayfield]

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.

[Chris Peterson]

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.

[Chris Peterson]

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).

[Ron-Astro Pharmacist]

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

[Ann]

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

[CygnusOB2]

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

[Chris Peterson]

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 (9.97 KiB) Viewed 6898 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.

[geckzilla]

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

[ta152h0]

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

[Chris Peterson]

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.

[ta152h0]

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

[southern cross]

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?

[Chris Peterson]

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.

[MarkBour]

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 ?