Centaurus A with H alpha

[John Hothersall]

SPX350 F4.53, ATK-16HR, Astrodon filters, OAG+Mintron guidecam.

L HaRGB : L=100m Ha=120m RGB=60m each colour all in 5min subs.

This is a glorious galaxy part of M83 group and 12.2 lyrs away with bisecting dust lane from another galaxy merged 500 mil yrs ago. Some blue star burst around dust edge and some H alpha along the dust. A strange H alpha line away from galaxy on the far right with some green in it. Plenty of dusty patches seen against the wide halo.



Thanks for viewing, John.

[marc4darkskies (Marcus)]

That's a great shot John! I like that you did Ha - it does add an extra dimension. You've captured the dust and detail very well too.

Cheers, Marcus

[multiweb (Marc)]

Amazing shot. The Ha definitely adds another dimension. Looks like the jet on the top right is picked up by the Ha filter too. Top shelf.

[Ross G]

A beautiful photo John.

Sharp, detailed and amazing colours.


Thanks.


Ross.

[gregbradley]

That's a great Centaurus A image John. The Ha really does add a lot of interest to the image and you captured the jet very clearly - more than any other image I have seen of it.

Greg.

[h0ughy (David)]

great detail in that shot

[Alchemy (Clive)]

Unusual to see the Ha so well displayed..... Most impressed

[Saturn%5 (Graeme)]

Great shot John

[Stevec35 (Steve)]

Nice shot John. The H alpha certainly adds interest to this fascinating galaxy and you've captured the other features well too. If you want a jaw dropping experience check out the latest Hubble image of Centaurus A.

Cheers

Steve

[John Hothersall]

Thanks for the comments, wasn't expecting much with the Ha but thought that dust must show something and got quite a few spots as well as the Jet. Saw the Hubble effort and the core is broken up into amazing detail.

John.

[strongmanmike (Michael)]

Nice addition there John, haven't seen Ha used on Cen A too often, probably something worth investigating further... .. I remember Joe Brimacombe did a full narrowband version a couple of years ago..?

Mike

[madbadgalaxyman (Robert)]

H-alpha imaging of galaxies is still rarely practised by amateurs....still isn't fashionable. Very interesting in your image to see the distribution of HII regions so very clearly.

For comparison, I attach an Ha image from the SINGS survey:



Note that the orange channel displays the light from the H-alpha line only (essentially only one wavelength of light).
The red stellar continuum light from the raw Ha image has been subtracted out, leaving only nebular light.

The blue channel actually displays broadband red light from the target object.( technically, it displays the red light of the stellar continuum)

[Ken]

Very nice image John I am interested in how you added the Ha data to a LRGB image, I am sure it was more difficult than just adding it to the red channel?.
Clear skies Ken.

[renormalised (Carl)]

One of the few galaxies Ha actually is worth shooting in. Well done

[madbadgalaxyman (Robert)]

John,

I have some more information about the strange line of HII regions that is seen in your H-alpha channel.

There is a very strong correspondence between the H-alpha emission found in this part of your image and a line of blue knots that are seen both in optical images and UV images.

I attach two images of part of NGC 5128;

Firstly, a section of a B+V+I image (displayed as Blue+Green+Red) taken with the ESO 2.2m telescope and the WFI array of CCDs.
(At the ESO website, this is the Public Image with the Identification eso0315a)



Secondly, I attach an Far-Ultraviolet+Near-Ultraviolet composite image taken with the GALEX satellite (using its two available wavelength bands) and downloaded from the GalexView virtual telescope. FUV light is displayed as blue and NUV light is displayed as yellow.



You will note the close correspondence between the blue knots that are seen in the optical image and the Far-ultraviolet emitting knots that are seen in the GALEX image.

Now if I display your image at roughly the same scale and orientation.......



We can easily see that the line of HII regions and the line of blue knots and the line of FUV-emitting knots are exactly the same object or objects!

These objects are most likely bona fide knots of OB stars (and also lower mass stars, at least if they have a typical Initial Mass function)
This is a likely interpretation because the knots are:
- very blue in the optical regime
- very intense in FUV light
and furthermore the stars in the knots are hot enough to ionize the surrounding gas and make it emit in the H-alpha line. Only young and very luminous blue stars are hot enough to produce the ultraviolet photons necessary to make the surrounding gas glow gently in the H-alpha and [OIII] lines.

The knots of recently formed stars are believed to have been formed by an interaction of the plasma jet of N5128 with the surrounding gaseous medium, but I do not believe that this is proven yet. See attached 5GHz radio image of the two jets of N5128 together with the two inner radio lobes.

[John Hothersall]

Thanks Robert for good info on CentA, interesting to here about possibilities regarding the blue jet. This galaxy has a lot of activity going on as a result of the merger, the X-ray jets are amazing. Imaging it with IR742nm may have been interesting?

Thanks Ken, there are several ways to add Ha to red some use layers 80/20% for ha/red but I just lift the white levels up till Ha background is same or better than the brighter red, you can increase it to twice the red ADU for stronger effect although Ha addition needs to be subtle to blend well with the other colour data. Once equalized I blend red and brightened Ha together to make an Hared for the red channel in Maxim RGB col assembly. I use the LRGB with Ha+R G B as a hidden layer to jewel the galaxy with pink/red patches with opacity to taste. Ha can be blobbish sometimes so you don't want it interfering with the LRGB detail.

Regards, John.

[Paul Haese]

I really like the first image John. Great colour and fabulous detail. Well done.

[richardo (Rich)]

Yes an excellent result here John!
Great to see the HII knots in the dust lanes, and also the jet..

Very good mirrors the Orion Optics mob... this image shows this well.

Great job!

Rich