APOD: The Perseus Cluster Waves (2017 May 04)

[APOD Robot]

The Perseus Cluster Waves

Explanation: The cosmic swirl and slosh of giant waves in an enormous reservoir of glowing hot gas are traced in this enhanced X-ray image from the Chandra Observatory. The frame spans over 1 million light-years across the center of the nearby Perseus Galaxy Cluster, some 240 million light-years distant. Like other clusters of galaxies, most of the observable mass in the Perseus cluster is in the form of the cluster-filling gas. With temperatures in the tens of millions of degrees, the gas glows brightly in X-rays. Computer simulations can reproduce details of the structures sloshing through the Perseus cluster's X-ray hot gas, including the remarkable concave bay seen below and left of center. About 200,000 light-years across, twice the size of the Milky Way, the bay's formation indicates that Perseus itself was likely grazed by a smaller galaxy cluster billions of years ago.

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[geckzilla]

Holy processing artifacts, Batman.

[RocketRon]

Precisely.

It is spectacular though, innit ?

It would be interesting - maybe even should be mandatory - to include some detail of HOW this was processed.
What do the red & yellow colours represent, and what are they overlaid onto - some sort of visible image from
say a regular telescopic view ? - or maybe an artists conception..... ??

[Ann]

Holy processing artifacts, Batman.

Click to view full size image

What... you want me to be a bit more specific?

Ann

[xiox]

The algorithm and image are described in our paper: https://arxiv.org/abs/1605.02911

It basically measures the gradient of the image on various scales using a Gaussian gradient magnitude filter. This filter convolves the image with the gradient of a Gaussian (i.e. normal) function, in X and Y, then the total gradient is calculated from these. These gradient images on different scales are then weighted together.

[Boomer12k]

I have a hard time comparing it to the visible light cluster image linked in the description... I would not have guessed at a "Target" like spiral and waves... it is hard to relate the two... interesting though it is. Should there not be a "small galactic cluster" some where fairly close, It should not have gone that far in so "short" a time.... right???

:---[===] *

[JohnD]

Batman? Schmatman!

All together now! Dee-de-dee, dum-de-dum, ah-eeee-ah! This is pure Dr.Who.

At least, the later ones:

Click to play embedded YouTube video.

John

[neufer]

Click to play embedded YouTube video.

Batman? Schmatman! All together now!
Dee-de-dee, dum-de-dum, ah-eeee-ah!
This is pure Dr.Who.

Doo-de-loo-doo:

SLOSH (v.) "to splash about in mud or wet," 1844, from slosh (n.) 1814, "slush, sludge, a watery mess," probably a blend of slush and slop.

[De58te]

To put this size in perspective. The Milky Way is only half the size of the bay wave at the bottom. But to imagine there are some 1,000 galaxies in the Perseus Cluster. The Apod link to the May 20009 image says the cluster is some 1.5 million light years across. So today's image is just some two thirds the size. Still for an observer in one galaxy in the Perseus cluster they must see hundreds of galaxies in their night sky at any given time.
Consider that the Andromeda galaxy is some 2.3 million light years away from the Milky Way. (Although there are some dozen minor galaxies within that distance.) That means if the Milky Way was on the left frame of this image, Andromeda would be more than double the width of this image off the right frame. And Andromeda is our closest large galaxy! Looks like the Local Group is much less as packed as Perseus.
A question comes to my notice. Today's information says that the Perseus cluster is some 240 million light-years distant. In the May 2009 Apod link they said the Perseus cluster is nearly 250 million light-years away. Does that mean that in just 8 years the Perseus Cluster has come nearly 10 million light years closer to us? That's a speed of about 1.25 million light years in one year? Of course if the Milky Way was also closing in at the same speed, both galaxy groups would only be traveling at 625,000 light years a year.

[Fred the Cat]

...indicates that Perseus itself was likely grazed by a smaller galaxy cluster'''...

Click to play embedded YouTube video.

[BDanielMayfield]

Holy processing artifacts, Batman.

The algorithm and image are described in our paper: https://arxiv.org/abs/1605.02911

It basically measures the gradient of the image on various scales using a Gaussian gradient magnitude filter. This filter convolves the image with the gradient of a Gaussian (i.e. normal) function, in X and Y, then the total gradient is calculated from these. These gradient images on different scales are then weighted together.

So it ain't no artifact, it's the fact Jack. How they did it may be difficult to understand, but Sanders et. al. seem to have found a new tool for extracting real signal from noisy data. Congrats. Spectacular Image!

The great temperature of this extra galactic plasma reminds me of the mysteriously hot solar corona. Could these temps come from similar causes?

Bruce

[geckzilla]

Holy processing artifacts, Batman.

The algorithm and image are described in our paper: https://arxiv.org/abs/1605.02911

It basically measures the gradient of the image on various scales using a Gaussian gradient magnitude filter. This filter convolves the image with the gradient of a Gaussian (i.e. normal) function, in X and Y, then the total gradient is calculated from these. These gradient images on different scales are then weighted together.

So it ain't no artifact, it's the fact Jack. How they did it may be difficult to understand, but Sanders et. al. seem to have found a new tool for extracting real signal from noisy data. Congrats. Spectacular Image!

It's not an either-or thing. It's both fact and artifact, and it takes a trained eye to interpret.

[Jean Bosseler]

The frame spans over 1 million light-years across..

Should this not 1 Billion?

[Jean Bosseler]

Sorry, it is 1 Million!

[neufer]

Click to play embedded YouTube video.

<<In 2003 a team of astronomers led by Dr. Andrew Fabian at Cambridge University discovered one of the deepest notes ever detected, a B♭, after 53 hours of Chandra observations. No human will actually hear the note, because its time period between oscillations is 9.6 million years, which is 57 octaves below the keys in the middle of a piano. The sound waves appear to be generated by the inflation of bubbles of relativistic plasma by the central active galactic nucleus in NGC 1275. The bubbles are visible as ripples in the X-ray band since the X-ray brightness of the intracluster medium that fills the cluster is strongly dependent on the density of the plasma. A similar case also happens in the nearby Virgo Cluster, generated by an even larger supermassive black hole in the galaxy Messier 87, also detected by Chandra. Like the former, no human will hear the note. The tone is variable, and even lower than those generated by NGC 1275, from 56 octaves below middle C on minor eruptions, to as low as 59 octaves below middle C on major eruptions.>>

[klaskinaragingwind]

so does anybody see the white nine (digit only, ie: [9]) in the centre of the image?

Is this someone labelling the picture.... or is it really there? There appear to be two letters partially obscured to the right of the nine, about eight point type as well.

KGB

[bystander]

http://asterisk.apod.com/viewtopic.php?t=37138

[xiox]

It's not an either-or thing. It's both fact and artifact, and it takes a trained eye to interpret.

Yes - there is noise. It gives rise to some of the wiggly lines in the output image (see paper). The number of photons in the input image isn't massive, so we can only apply this to deep observations of bright clusters. I plan in the future to investigate how to reduce the noise optimally, but it's mainly a visualisation technique to see where interesting things are. The "bay" feature is extremely obvious in the raw data.

[Chris Peterson]

It's not an either-or thing. It's both fact and artifact, and it takes a trained eye to interpret.

I wouldn't say the image as a whole could be classified as an artifact in any way. "Artifact" in imaging generally means some kind of structure which isn't related to the underlying data. Of course, there's noise in this image as there is in all images, and noise is often amplified by processing into artifacts. But the image as a whole is showing shock waves and other structure in the intracluster medium around NGC 1275 (the central galaxy in the Perseus Cluster) made apparent by removing the much more luminous glow of the galaxy itself. By flattening that, the otherwise obscured fine x-ray structure becomes visible.

A trained eye can always extract more information from an astronomical image. But this image does not require a trained eye in order to extract the most salient features that the processing was designed to reveal- the large scale wave pattern in the hot medium surrounding this galaxy.

[Guest]

Would it be possible to overlay the 2009 visible light image over this one? What is the actual source of the energy on this image?

[xiox]

Here's a comparison of visible light with the X-ray emission: https://www.researchgate.net/figure/518 ... orth-Lower

The X-ray image is thermal emission from the hot plasma which fills up most of a galaxy cluster. It has temperatures of around 10 million K, heated as the material which formed the cluster collapsed. The energy source is the thermal energy (i.e. it cools in the absence of heat sources). The emission mechanism is thermal bremsstrahlung, if you're interested. Most of the baryonic matter (not dark matter, but normal electrons, protons, neutrons, etc), is in the form of this hot atmosphere. The atmosphere is supported by its pressure.

[geckzilla]

It's not an either-or thing. It's both fact and artifact, and it takes a trained eye to interpret.

I wouldn't say the image as a whole could be classified as an artifact in any way. "Artifact" in imaging generally means some kind of structure which isn't related to the underlying data. Of course, there's noise in this image as there is in all images, and noise is often amplified by processing into artifacts. But the image as a whole is showing shock waves and other structure in the intracluster medium around NGC 1275 (the central galaxy in the Perseus Cluster) made apparent by removing the much more luminous glow of the galaxy itself. By flattening that, the otherwise obscured fine x-ray structure becomes visible.

A trained eye can always extract more information from an astronomical image. But this image does not require a trained eye in order to extract the most salient features that the processing was designed to reveal- the large scale wave pattern in the hot medium surrounding this galaxy.

...Ok, I definitely did not mean to infer that the entire image is a single artifact. I don't think the audience here is going to instantly understand what they are looking at with a paragraph or two of information explaining it. I think most people get the general idea, though. It just struck me, personally, as having a lot more artifacting than I am used to when seeing image releases from Chandra. Something different, for sure. And I was a little terse. I apologize. Thank you xiox and all for your wonderful work, and also for taking the time to come and talk with us here at the forum.

[neufer]

What is the actual source of the energy on this image?

[b][color=#0000FF]Hubble Space Telescope image of galaxy NGC 1275. The red filaments are composed of cool gas being suspended by a magnetic field, and are surrounded by the 100-million-degree Fahrenheit hot gas in the center of the Perseus galaxy cluster. The filaments are dramatic markers of the feedback process through which energy is transferred from the central massive black hole to the surrounding gas. The filaments originate when cool gas is transported from the center of the galaxy by radio bubbles that rise in the hot interstellar gas. NGC 1275 is one of the closest giant elliptical galaxies.[/color][/b]

---

<<NGC 1275 corresponds to the radio galaxy Perseus A and is situated near the center of the large Perseus Cluster of galaxies. NGC 1275 contains 13 billion solar masses of molecular hydrogen that seems to be infalling from Perseus' intracluster medium in a cooling flow, both feeding its active nucleus and fueling significant amounts of star formation. A supermassive black hole with a mass 340 million times that the Sun may be present in NGC 1275's center.

NGC 1275 consists of two galaxies, a central type-cD galaxy in the Perseus Cluster, and a so-called "high velocity system" (HVS) which lies in front of it. The HVS is moving at 3000 km/s towards the dominant system, and is believed to be merging with the Perseus Cluster. The HVS is not affecting the cD galaxy as it lies at least 200 thousand light years from it.; however tidal interactions are disrupting it and ram-pressure stripping produced by its interaction with the intracluster medium of Perseus is stripping its gas as well as producing large amounts of star formation within it.

The central cluster galaxy contains a massive network of spectral line emitting filaments, which apparently are being dragged out by rising bubbles of relativistic plasma generated by the central active galactic nucleus. Long gaseous filaments made up of threads of gas stretch out beyond the galaxy, into the multimillion-degree, X-ray–emitting gas that fills the cluster. The amount of gas contained in a typical thread is approximately one million times the mass of the Sun. They are only 200 light-years wide, are often very straight, and extend for up to 20,000 light-years.>>

[Ann]

Like you said, Art. The energy and outbursts of the Perseus Cluster are centered on Perseus A, NGC 1275. That includes the special energy and the spiral wave seen in today's APOD.

Ann

[LMPR8R]

so does anybody see the white nine (digit only, ie: [9]) in the centre of the image?

Is this someone labelling the picture.... or is it really there? There appear to be two letters partially obscured to the right of the nine, about eight point type as well.

KGB

I actually see a scribbled figure of a person singing, arms held out in front as if belting out opera....