Southern Virgo Deep Field - enhanced colour version added

[alpal]

That's gotta be an IOTW.

It's a superb image.

[Phil Hart]

I can see why you're pleased with this image Mike.. I sure would be. Lovely field.. holds up real nice when viewed big on screen.

If you're looking for how to squeeze the most out of it, I agree with Marcus and Paul. For sure you want to show the cirrus and you've done very well with that.. but it should be possible to have some very nearly black pixels in the image somewhere. I would be using some kind of curves adjustment to try and stretch out that dark end towards the black point a bit more.. should give even better visibilty of the cirrus (but will kill some of it for those with poor monitors).

And there is some kind of purple/magenta cast to it.. I think it's more due to the star colours than the background. Your other image that Paul linked to has a nice mix of yellow and blue stars. This image seems to have yellow and many purple stars (some blue but not so many). Don't know how you managed it but if you could fix it then it really would be a cracker!

Phil

[lazjen (Chris)]

This is a great image. Many galaxies there. Awesome.

[strongmanmike (Michael)]

Originally Posted by RB

We missed you at IISAC mate, and I had plenty of Guinness on ice for yah.

Any cigars?

Originally Posted by alpal

That's gotta be an IOTW.

It's a superb image.

Thanks a lot

Originally Posted by philiphart

I can see why you're pleased with this image Mike.. I sure would be. Lovely field.. holds up real nice when viewed big on screen.

If you're looking for how to squeeze the most out of it, I agree with Marcus and Paul. For sure you want to show the cirrus and you've done very well with that.. but it should be possible to have some very nearly black pixels in the image somewhere. I would be using some kind of curves adjustment to try and stretch out that dark end towards the black point a bit more.. should give even better visibilty of the cirrus (but will kill some of it for those with poor monitors).

And there is some kind of purple/magenta cast to it.. I think it's more due to the star colours than the background. Your other image that Paul linked to has a nice mix of yellow and blue stars. This image seems to have yellow and many purple stars (some blue but not so many). Don't know how you managed it but if you could fix it then it really would be a cracker!

Phil

Cheers for the critique Phil, Galactic Cirrus is often processed so it looks like it has been processed separately (today's APOD is a good example of this - for me the relative brightness differentials in this image are all wrong). I wanted it to look like a natural part of the image with a realistic brightness differential, so this aspect I was happy with. As for your other comments, thanks, I'll have a think

Mike

Originally Posted by lazjen

This is a great image. Many galaxies there. Awesome.

Glad you liked it, plenty of stars too

[Phil Hart]

Originally Posted by strongmanmike

today's APOD is a good example of this - for me the relative brightness differentials in this image are all wrong

I agree! I think you 'respected the light' much better than that APOD!

[ourkind (Carlos)]

What a beauty Mike! Nice to see them winds giving you a break

[lacad01 (Adam)]

Amazing how many galaxies framed, excellent stuff.

[RB (Andrew)]

Originally Posted by strongmanmike

Any cigars?

No, reducing my carbon footprint mate.

[LewisM]

Supercalifragilisticexpialidocious! !!

[strongmanmike (Michael)]

Originally Posted by LewisM

Supercalifragilisticexpialidocious! !!

Sogladyoulikedit

Mike

[strongmanmike (Michael)]

Originally Posted by ourkind

What a beauty Mike! Nice to see them winds giving you a break

Originally Posted by lacad01

Amazing how many galaxies framed, excellent stuff.

Cheers Guys

...wind...ahhhhhhh

Mike

[madbadgalaxyman (Robert)]

Hi Mike,

Thanks for pointing out your high-contrast version of your image.

As mentioned in my previous post, NGC 5084 has a very unusual appearance. This galaxy is a really excellent subject for your ultra-deep imaging/exploration project, as the peculiar-looking outer disk is of extremely low surface brightness. In fact, if this galaxy were seen face-on, I have a feeling that the faint outer structures would be undetectable.

There exist a few individual galaxies, within the population of bright galaxies to apparent Blue magnitude 13.5, where there is at least the impression of two (or more) different planar structures existing instead of a single "fundamental plane" in which the spiral structure sits. But the interpretation of more than one disk seems quite secure for NGC 5084.
(compare, for instance, the "tilted or bent" Equatorial Dust Lanes seen in NGC 5078 and NGC 3628)

It is pretty easy, in theory, and also in practice (in the real universe), for gravitational interactions with another galaxy to warp or bend the Planar Disk Structure of a Spiral galaxy or S0 galaxy away from its principal plane;
in fact, in some cases, this sort of interaction can virtually "make spaghetti" out of the disk [this is, I think, what has happened in NGC 4438, which was probably originally an ordinary-looking edge-on S0 galaxy....in fact its bulge component (its spheroid) is still normal, despite the strong distortion of its outer regions. ]

However, in NGC 5084, we seem to be looking at (at least) two moderately-well-behaved disk structures, seen edge on, at two or more position angles.

If I had to gamble on what is going on here, I would put my money on the idea that the outer extremely-faint disk, which is not very settled in its appearance, is:
- still being formed (that is, it is coalescing under the influence of gravity)
OR
- being re-formed after being disrupted.

There are a small number of galaxies in which the outermost disk has been nearly-proven be currently in the process of ongoing formation (this idea applies, probably, to M31 and our own Galaxy!). And this is a phenomenon that has been expected for a long time on theoretical grounds.

I might mention the NGC 5084 case to the brilliant Dr Kenneth C. Freeman of ANU, as he is an authority on the behavior of the planar components within spiral and S0 galaxies.

Best Regards,
Robert

"Just for fun and profit", here is the g+r+i band composite image from SDSS:



It would be interesting if the outer faint disk turns out to be "in the process of being formed" rather than a result of gravitational interaction with other galaxies!

[strongmanmike (Michael)]

Originally Posted by madbadgalaxyman

Hi Mike,

Thanks for pointing out your high-contrast version of your image.

As mentioned in my previous post, NGC 5084 has a very unusual appearance. This galaxy is a really excellent subject for your ultra-deep imaging/exploration project, as the peculiar-looking outer disk is of extremely low surface brightness. In fact, if this galaxy were seen face-on, I have a feeling that the faint outer structures would be undetectable.

There exist a few individual galaxies, within the population of bright galaxies to apparent Blue magnitude 13.5, where there is at least the impression of two (or more) different planar structures existing instead of a single "fundamental plane" in which the spiral structure sits. But the interpretation of more than one disk seems quite secure for NGC 5084.
(compare, for instance, the "tilted or bent" Equatorial Dust Lanes seen in NGC 5078 and NGC 3628)

It is pretty easy, in theory, and also in practice (in the real universe), for gravitational interactions with another galaxy to warp or bend the Planar Disk Structure of a Spiral galaxy or S0 galaxy away from its principal plane;
in fact, in some cases, this sort of interaction can virtually "make spaghetti" out of the disk [this is, I think, what has happened in NGC 4438, which was probably originally an ordinary-looking edge-on S0 galaxy....in fact its bulge component (its spheroid) is still normal, despite the strong distortion of its outer regions. ]

However, in NGC 5084, we seem to be looking at (at least) two moderately-well-behaved disk structures, seen edge on, at two or more position angles.

If I had to gamble on what is going on here, I would put my money on the idea that the outer extremely-faint disk, which is not very settled in its appearance, is:
- still being formed (that is, it is coalescing under the influence of gravity)
OR
- being re-formed after being disrupted.

There are a small number of galaxies in which the outermost disk has been nearly-proven be currently in the process of ongoing formation (this idea applies, probably, to M31 and our own Galaxy!). And this is a phenomenon that has been expected for a long time on theoretical grounds.

I might mention the NGC 5084 case to the brilliant Dr Kenneth C. Freeman of ANU, as he is an authority on the behavior of the planar components within spiral and S0 galaxies.

Best Regards,
Robert

"Just for fun and profit", here is the g+r+i band composite image from SDSS:

Attachment 137167

It would be interesting if the outer faint disk turns out to be "in the process of being formed" rather than a result of gravitational interaction with other galaxies!

Thanks for posting all that Rob and the SDSS image is very revealing.

I have composed a side by side comparison HERE of that image with my data and it would seem I have gone almost as deep as there are very few stars or galaxies in the SDSS data that can not be picked out in my data. This is surprising as if I am not mistaken that SDSS composite incorporates IR data..? I assume that is what the "i" stands for in g r i..?

Mike

[madbadgalaxyman (Robert)]

Originally Posted by strongmanmike

I have composed a side by side comparison HERE of that image with my data and it would seem I have gone almost as deep as there are very few stars or galaxies in the SDSS data that can not be picked out in my data. This is surprising as if I am not mistaken that SDSS composite incorporates IR data..? I assume that is what the "i" stands for in g r i..?

Mike

Very good, Mike, considering that SDSS used a 100 inch telescope!

The SDSS i filter is essentially Deep Red to Very-near-infrared, with a central wavelength of 7480 Angstroms.
(u is blue to very-near ultraviolet)(g is 4686 Angstrom)(r is 6166 Angstrom)

They use the bandpasses called u, g, r, i, and z, as per this filter transmission curve:



The z band is their longest-wavelength filter, which is essentially an infrared filter of the sort that can be used with a standard CCD.

These ugriz filters have become as much of a standard as the Johnson-Cousins UBVRI filters, for calibrating images and for photometry. I do not know the ugriz system well, so it is giving me plenty of headaches!

Best regards,
Robert

It seems to me that I ought to be looking into this galaxy a bit more, but in typical fashion, this work could end up joining several other uncompleted projects.
(currently I am sweating on the evolutionary histories of star clusters, and their chemical enrichment with heavier elements by the ejecta of previous generations of stars.....this is just another one of the infinity of things you have to know very well, if your goal is to understand galaxies!)

P.S. The colours displayed in SDSS g+r+i composites are absolute rubbish! However, one very good thing about it is that the blue channel is very sensitive to recent star formation and OB stars.

[FlashDrive (Poppy)]

What can I say....makes our little spot in the Universe insignificant ...!!
Gosh...I feel so small ......

Flash .....

[strongmanmike (Michael)]

You bet Col cheers

Love galaxy fields, love'em

Mike

[strongmanmike (Michael)]

Originally Posted by madbadgalaxyman

Very good, Mike, considering that SDSS used a 100 inch telescope!

Cool huh?

Mike

[Ross G]

A beautiful photo Mike.

Colours, detail, sharpness.......amazing!

Great composition too.


Ross.

[strongmanmike (Michael)]

Originally Posted by Ross G

A beautiful photo Mike.

Colours, detail, sharpness.......amazing!

Great composition too.


Ross.

You're too kind Ross

Mike

[iceman (Mike)]

Stunning work Mike, artwork at its finest.