Clouds of Centaurus A

[matlud (Mathew)]

Originally Posted by AdamJL

Oh I love your posts, Mat You're always doing something unique and I love the science behind everything.
That said, I'd also be hesitant to call these emissions around Centaurus. I mean, they're incredibly bright if so. I know this is a massive amount of integration, but thinking of the Inverse-square law (the Intensity of the radiation is inversely proportional to the square of the distance) that hydrogen would have to be almost half as bright as a black hole's accretion disk to be picked up at this distance, and what would cause it to be that bright?

edit: Peter's said as much above as well

Thanks Adam, really appreciate that! I did mask the central galaxy in that so everything could be visible and not blown out, as the outer Ha emission is very faint 👍. I discussed some of the brightness and feasibility of detecting the Ha in my reply to Peter - I agree it is most likely Milky Way gas but certainly possible that some of it is associated with CenA 😀. Cheers, Mat

[alpal]

Originally Posted by matlud

Thanks Marc!

As Allan has mentioned RBA published his fantastic image of the Ha clouds around M31,
and Vicet Peris from Pixinsight also did a great monochrome M31 recently 👍

Hi Mathew,
as the article says -
https://www.deepskycolors.com/archiv...Andromeda.html

Along with all the bright emission and reflection nebula we usually see in photographs, our night sky is filled with a much fainter type of clouds that goes by different names: High Galactic Cirrus, Integrated Flux Nebula (IFN), Translucent Clouds, High Latitude Clouds and so on... (Low et al., 1984)
IFN is usually visible in infrared, and can also be - barely - captured under dark skies in "visible light" because it's mostly dust (not gas) that manages to reflect the light of our own galaxy as a whole. It, however, can also emit some light in the Extended Red Emission or ERE (Witt et al. 2008), a wide spectral range that covers all red visible light all the way to the near infrared. This is one reason IFN usually appears brownish in color when captured with broadband filters: it's a mix of reflected blue light and some emitted ERE (red) light.

It's fairly certain that you have picked up emissions from the Milky Way.

cheers
Allan

[AdamJL]

Gosh I'd love to capture the IFN around the SCP. There's a kiwi photographer working on that right now. Need to live in a B1 site for a month though

[alpal]

Originally Posted by AdamJL

Gosh I'd love to capture the IFN around the SCP. There's a kiwi photographer working on that right now.
Need to live in a B1 site for a month though

The South Celestial Pole -



I found this:
https://i.redd.it/ix77q2x2oao81.jpg


and Annotated:
https://media.discordapp.net/attachm.../Annotated.jpg


cheers
Allan

[AdamJL]

ha, yeah that's the photographer and his earlier shot.
He's working on more detailed IFN now as well.

Though I think Mat takes the cake here with his in-or-out-of-the-Milky Way Hydrogen shot
Not only is it great to see these fainter objects, Mat always frames his shots beautifully as well. Not just data, it's art.

[alpal]

Originally Posted by AdamJL

ha, yeah that's the photographer and his earlier shot.
He's working on more detailed IFN now as well.

Though I think Mat takes the cake here with his in-or-out-of-the-Milky Way Hydrogen shot
Not only is it great to see these fainter objects, Mat always frames his shots beautifully as well. Not just data, it's art.

Good - so who is the Photographer? -
that shot was just on reddit and I couldn't find who took it.
Does he have a website link?

[alpal]

I felt all scientific this morning so I decided to see if an Ha filter
would work properly with Centaurus A, NGC 5128, given
that it has a red shift - would that put it outside the
band pass of a narrowband filter?


http://simbad.u-strasbg.fr/simbad/si...=SIMBAD+search

V(km/s) 547 z(~) 0.001826

Ha wavelength is = 656.281 nm

Ha = 656.281nm * 0.001826 = 1.1983691 nm

So the Ha emission line is shifted to the Red by 1.19nm = 657.48 nm

That's only a tiny amount.
Mathew has used a Chroma H-alpha 5nm Bandpass filter
so the 1.19 nm red shift is OK - well inside.


It's interesting though to see what an Astrodon 3nm filter would have done?
https://astronomyplus.com/product/as...-alpha-filter/

It's right on the edge at 80% pass so
20% of the light would have been lost!


cheers
Allan

[multiweb (Marc)]

Originally Posted by matlud

Thanks Marc! As Allan has mentioned RBA published his fantastic image of the Ha clouds around M31, and Vicet Peris from Pixinsight also did a great monochrome M31 recently 👍

Yes the mono shot from Peris at PI is the one I was referring to. It's a great shot and I was surprised to see how much details he got in the bright core.

[Paul Haese]

Now that is something I have not seen before. An interesting image of the surrounds of Cent A.

I suspect there is an element of some gas nearby to us and some near to the galaxy. As suggested, write an paper on the idea and submit that.

Well done with the image.

[N1 (Mirko)]

Interesting discussion, based on an awesome image!

Originally Posted by alpal

I felt all scientific this morning so I decided to see if an Ha filter
would work properly with Centaurus A, NGC 5128, given
that it has a red shift - would that put it outside the
band pass of a narrowband filter?


http://simbad.u-strasbg.fr/simbad/si...=SIMBAD+search

V(km/s) 547 z(~) 0.001826

Ha wavelength is = 656.281 nm

Ha = 656.281nm * 0.001826 = 1.1983691 nm

So the Ha emission line is shifted to the Red by 1.19nm = 657.48 nm

That's only a tiny amount.
Mathew has used a Chroma H-alpha 5nm Bandpass filter
so the 1.19 nm red shift is OK - well inside.


It's interesting though to see what an Astrodon 3nm filter would have done?
https://astronomyplus.com/product/as...-alpha-filter/

It's right on the edge at 80% pass so
20% of the light would have been lost!


cheers
Allan

This is an important point, since it outlines how, by using narrower filtering, one could obtain a better understanding of what nebulosity might be associated with Cen A (assuming it shares its red shift), and what's part of the foreground.

[alpal]

Originally Posted by N1

Interesting discussion, based on an awesome image!

This is an important point, since it outlines how, by using narrower filtering, one could obtain a better understanding of what nebulosity might be associated with Cen A (assuming it shares its red shift), and what's part of the foreground.

But in this case I just wanted to know if a Ha filter would work properly with Centaurus A.