APOD: NGC 4414: A Flocculent Spiral Galaxy (2016 Nov 20)

[APOD Robot]

NGC 4414: A Flocculent Spiral Galaxy

Explanation: How much mass do flocculent spirals hide? The featured true color image of flocculent spiral galaxy NGC 4414 was taken with the Hubble Space Telescope to help answer this question. The featured image was augmented with data from the Sloan Digital Sky Survey (SDSS). Flocculent spirals -- galaxies without well-defined spiral arms -- are a quite common form of galaxy, and NGC 4414 is one of the closest. Stars and gas near the visible edge of spiral galaxies orbit the center so fast that the gravity from a large amount of unseen dark matter must be present to hold them together. Understanding the matter and dark matter distribution of NGC 4414 helps humanity calibrate the rest of the galaxy and, by deduction, flocculent spirals in general. Further, calibrating the distance to NGC 4414 helps humanity calibrate the cosmological distance scale of the entire visible universe.

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[Ann]

Good work, NASA, ESA, Wendy Freedman et al., and Judy!

Click to view full size image

NGC 4414. Photo: Adam Block.

Click to view full size image

NGC 3521. Photo: NGC 3521. Photo: R Jay GaBany, David Martinez-Delgado et al.

I have to post my favorite photo of NGC 4414, which is by Adam Block. His photo, at left, shows the enormous starry halo surrounding this galaxy. Other flocculent galaxies also sport stellar huge halos, such as NGC 3521 at right.

Click to view full size image

NGC 3923. Photo: David Malin.

Click to view full size image

I think it was David Malin who first discovered extended shells around galaxies, but he discovered shells surrounding ellipticals. The explanation he gave, if I understood him correctly, was that elliptical galaxies have undergone many mergers, which have all sent some sort of shock waves through the galaxy. In response, tidal waves of stars have flown outwards and then stopped and receded, not entirely unlike waves washing up on a beach and then receding. But not all the stars that were washed out have receded afterwards. Some of them have stayed in their new position, marking the edge(s) of the shell(s).

I find it interesting to think of flocculent spirals in a similar way. These spirals have undergone some sort of upheavals, which have stirred up and broken their spiral symmetry, and at the same time waves of stars have washed out from them and then (mostly) receded.

The shells of NGC 3923 seem to have been lapping very gently, as has the huge shell of NGC 4414. NGC 3521, by contrast, still seems to be torn by forces ravaging it.

And of course, as I said, in flocculent galaxies the same forces that made the shells would have broken up the spiral arms, making them short and disordered.

Ann

[geckzilla]

This picture ended up being emergently replaced earlier today. A couple of days ago I noticed the original in the queue before it went up and decided (rather on a whim) to reprocess it. I was a little surprised RJN agreed to replace it. Should I have gone and done that? What do you guys think?

This was the image originally set to run:
http://imgsrc.hubblesite.org/hu/db/imag ... ll_jpg.jpg

Here's a link to the APOD image for quick access:
http://apod.nasa.gov/apod/image/1611/ng ... s_2069.jpg

[Ann]

I've never liked that original Hubble image. In my opinion, yours looks so much better.

Ann

[Case]

The Hubble image doesn't look as sharp, a bit puffy and whooly. On the other hand, the big bright center is a bit lost in the reprocessed image.

[heehaw]

What's the story on the black hole at the center? Also, what fee did Alamy Stock Photo charge for use of their image? (Don't you usually get from them a copy without the watermark, once you've paid their fee?) Is the fee larger for broadcast use, such as this one, as compared with just for personal use?

[Ann]

The Hubble image doesn't look as sharp, a bit puffy and whooly. On the other hand, the big bright center is a bit lost in the reprocessed image.

Click to view full size image

Spiral galaxy. Photo: Jeff Bryant.

Let's not forget that almost all spiral galaxies have bright centers and comparatively faint arms. So in order to bring out the spiral arms, almost all astrophotographers suppress the brilliant light from the center.

Take a look at the well-known, nearby galaxy at left. What, don't you recognize it? Isn't it obvious that it is M81 (pictured here by evansg)?

I think it's okay to suppress the brightness of the center of a galaxy to bring out its arms. But we should be aware that the center of a galaxy is usually way, way brighter than the arms.

And by the way... If you want to see more of Jeff Bryant's galaxy pictures and learn a little about Jeff's astrophotography, you can visit this page.

Ann

[tmulcahy]

When I first saw flocculent, an oddly rarely seen word, I thought instead of flatulent. That's just my brain making associations, but, lo! and behold! the description says that in this and similar galxies, dark matter must be holding a lot of orbiting stars and gas together to keep them from being thrown out. I'll admit it's a juvenile reaction to a serious scientific discussion, but, well, throw out a word like flocculent, and that's what happens.

[Fred the Cat]

It looks to me that you've teased out much more "fluffy" than the original Geck.

[Ann]

It looks to me that you've teased out much more "fluffy" than the original Geck.

Teasing Fluffy.jpg

Fluffy is right.

Click to play embedded YouTube video.

Ann

[geckzilla]

The Hubble image doesn't look as sharp, a bit puffy and whooly. On the other hand, the big bright center is a bit lost in the reprocessed image.

Funny enough, the APOD version has had the contrast increased. The galaxy is even fluffier without the high pass filter applied. In reality, it really is a kind of fluffy, hazily glowing galaxy, like most galaxies. Sometimes people really crank up the contrast and sharpness of the dust and super saturate the colors. I personally think that's gilding the lily, but a lot of people probably disagree.

What's the story on the black hole at the center? Also, what fee did Alamy Stock Photo charge for use of their image? (Don't you usually get from them a copy without the watermark, once you've paid their fee?) Is the fee larger for broadcast use, such as this one, as compared with just for personal use?

I'm guessing this is a joke. The fact that Alamy downloads images from the Hubble website where everyone can get the same high quality image for free and then sells them is rather unscrupulous, isn't it?

[heehaw]

I'm guessing this is a joke. The fact that Alamy downloads images from the Hubble website where everyone can get the same high quality image for free and then sells them is rather unscrupulous, isn't it?

It was not a Hubble image, it was an image of sea froth. (It's not a matter for the FBI, but it is unethical, or actually, I think, illegal. Or possibly it is OK if you leave the watermark on it, which was done.)

[geckzilla]

I'm guessing this is a joke. The fact that Alamy downloads images from the Hubble website where everyone can get the same high quality image for free and then sells them is rather unscrupulous, isn't it?

It was not a Hubble image, it was an image of sea froth. (It's not a matter for the FBI, but it is unethical, or actually, I think, illegal. Or possibly it is OK if you leave the watermark on it, which was done.)

Oh, you were talking about Ann's post. I thought you were talking about the galaxy itself. Incidentally, they DO have an image of the galaxy for sale. They've horked most of the freebie public domain NASA images and put them up for sale on their website. Anyway, It's not illegal (or even unethical) to share an image like Ann has done at that size for educational or illustrative purposes without commercial intent.

[ta152h0]

Now I have to look up the word " Flocculent "

[Chris Peterson]

Anyway, It's not illegal (or even unethical) to share an image like Ann has done at that size for educational or illustrative purposes without commercial intent.

Especially as the watermark has been left in place. Stock photo sites benefit from that kind of advertising.

[starsurfer]

This picture ended up being emergently replaced earlier today. A couple of days ago I noticed the original in the queue before it went up and decided (rather on a whim) to reprocess it. I was a little surprised RJN agreed to replace it. Should I have gone and done that? What do you guys think?

This was the image originally set to run:
http://imgsrc.hubblesite.org/hu/db/imag ... ll_jpg.jpg

Here's a link to the APOD image for quick access:
http://apod.nasa.gov/apod/image/1611/ng ... s_2069.jpg

The reprocessed version is light years better! It goes to show how much new information can be gleaned out of old data with new processing techniques and tools. I've always loved your processing, it'd be awesome if you had your own remote observatory in Chile! If you did have a 32 inch telescope in Chile, what targets would you go after?

[starsurfer]

Good work, NASA, ESA, Wendy Freedman et al., and Judy!

Click to view full size image

NGC 4414. Photo: Adam Block.

Click to view full size image

NGC 3521. Photo: NGC 3521. Photo: R Jay GaBany, David Martinez-Delgado et al.

I have to post my favorite photo of NGC 4414, which is by Adam Block. His photo, at left, shows the enormous starry halo surrounding this galaxy. Other flocculent galaxies also sport stellar huge halos, such as NGC 3521 at right.

Click to view full size image

NGC 3923. Photo: David Malin.

Click to view full size image

I think it was David Malin who first discovered extended shells around galaxies, but he discovered shells surrounding ellipticals. The explanation he gave, if I understood him correctly, was that elliptical galaxies have undergone many mergers, which have all sent some sort of shock waves through the galaxy. In response, tidal waves of stars have flown outwards and then stopped and receded, not entirely unlike waves washing up on a beach and then receding. But not all the stars that were washed out have receded afterwards. Some of them have stayed in their new position, marking the edge(s) of the shell(s).

I find it interesting to think of flocculent spirals in a similar way. These spirals have undergone some sort of upheavals, which have stirred up and broken their spiral symmetry, and at the same time waves of stars have washed out from them and then (mostly) receded.

The shells of NGC 3923 seem to have been lapping very gently, as has the huge shell of NGC 4414. NGC 3521, by contrast, still seems to be torn by forces ravaging it.

And of course, as I said, in flocculent galaxies the same forces that made the shells would have broken up the spiral arms, making them short and disordered.

Ann

Thanks for including Adam Block's image, which I don't have to link to anymore! Also extra thanks for including NGC 3923, one of the best shell elliptical galaxies that still doesn't have a deep amateur image, would be perfect for Rolf Olsen! There is a recent paper about it here.

David Malin wasn't the first to discover shells around galaxies but he (along with David Carter) were the first to definite the class of galaxy known as shell ellipticals. Check out their 1983 paper here. Also you might like this archive of deep galaxy images.

I think shells were first observed around galaxies by Halton Arp and also Boris Vorontsov-Velyaminov but they just included them in the category of peculiar galaxies.

[geckzilla]

If you did have a 32 inch telescope in Chile, what targets would you go after?

There are a number of times when I'd like to be able to fill in some missing data, just like I did with SDSS on this one, but I am perfectly content to have astronomers image things that are of scientific interest to them that I can then also make use of it to create pretty pictures. I've got a little thing I'd love for JWST to look at (sorry it's only in tweet form right now)
https://twitter.com/SpaceGeck/status/800584099626946560

It really stands out compared to a lot of other nebulas I've seen at that wavelength. It's got this odd, curly structure to it. It sits almost right on top of the galactic nucleus though. Tough to see in visual wavelengths.

[neufer]

Click to play embedded YouTube video.

[ta152h0]

like a fluffy cotton ball