Supernova in NGC 1365

[Bernard Heathcote]

Terry,
It is always comforting when different instruments, observers. locations and conditions give supporting results

Christian,
I thought my urban imaging conditions were poor but when I see (top photo) the amount of street light you are subject to then I don't feel so bad ... and, also considering the low altitude, your results are remarkable!

I think it is interesting to examine the 'bonus' spectra of the NGC1365 core, an AGN galaxy with some useful emission lines, around 60M ly distant.

NGC1365 core.jpg (45.03 KiB) Viewed 8178 times

With only the two nebular [OIII] and Hb lines it is possible to determine the galaxy's distance, nebular excitation class and interstellar extinction.

Even though I've been taking spectra for a few years it never ceases to amaze and impress me that spectra from 'simple' backyard equipment can reveal so much about such distant worlds.

Cheers, Bernard

[Martin Dubs]

Hi Bernard,

very nice spectrum. Your caption is somewhat ambiguous. On one hand you write that the spectrum is not instrument response corrected, on the other hand you calculate interstellar extinction. As far as I know interstellar extinction is calculated from the Balmer decrement (ratio of H-alpha to H-beta) using an instrument response and atmospheric extinction corrected spectrum. How did you calculate it? I agree with you, an interesting object.

Regards, Martin

[Bernard Heathcote]

Hi Martin,

I'm sorry about the confusion. The reason the displayed spectra isn't corrected is that the instrumental response curve I have stops just before Ha and if used then that emission line doesn't appear. I didn't realise this at the time and need to make a new one. To calculate the Balmer Decrement I certainly did make manual corrections for the instrumental response, which is flat in the Ha zone. Atmospheric corrections also applied.

Cheers, Bernard

[Terry Bohlsen]

Bernard.
I agree the "bonus" spectrum is interesting. I have't graphed it but interestingly on the raw images the Ha line is clearly distorted and shifted depending on how far from the centre of the galaxy it is measured. I will post a pic later when I'm at home.
Cheers
Terry

[Bernard Heathcote]

Hi Terry,

Unfortunately I was only able to capture the Ha emission very close to the edge of my image (below), but I do see a small degree of curvature towards the blue each side of the main spectral line.

H alpha.jpg (7.73 KiB) Viewed 8175 times

If this is what you are referring to then I guess one explanation could be that the hydrogen emitted from the two galactic arms are at a slightly higher RV than the core, which I find hard to understand as the galaxy is virtually face-on to us.

NGC1365.jpg (43.56 KiB) Viewed 8175 times

Cheers, Bernard

[Terry Bohlsen]

I had better success last night and was able to take about 80 minutes of spectra with my LISA.
A comparison spectra is here

_sninngc1365_20121031_469_TBohlsen.png (6.8 KiB) Viewed 8170 times

Bernard.
Below is a crop of the region around Ha of the raw spectra of the core of the galaxy. There is certainly some asymmetry. I agree that this is strange as it is a face on galaxy. Any suggestions?

Terry

NGC1365crop.png (111.36 KiB) Viewed 8170 times

[Robin Leadbeater]

NGC 1365 is a Seyfert Galaxy so out of plane jets perhaps?

Robin

[Bernard Heathcote]

Hi Robin,

It wasn't that obvious in my 'off the edge' image of Ha, which looks more symmetrical, but in Terry's it is clearly asymmetrical with a blue shift on one side of the main spectra and maybe a small redshift on the other. Based on this I think you are right in suggesting an off-axis jet, possibly a Seyfert 2 rather than a Seyfert 1 or Blazar galaxy, as the black-hole/jet axis doesn't have to be normal to the galactic plane.

I came across the following ATT 6df spectra, which also shows the [NII] 6584A emission close to Ha.

AAT 6dF NGC1365.png (10.71 KiB) Viewed 8169 times

Interesting stuff.

Cheers, Bernard

[Christian Buil]

Terry, Bernard, ...

I propose to centralize NGC 1365 SN spectra in a special page on ARAS.
The object is peculiar (very fast change of color index) and can evolve to
a bright object (V=12 for the moment). Intensive spectra collection by
southern observer is welcome. Send your FITS processed spectra to my
personnal e-mail adress (christian.buil-at-wanadoo.fr).

Christian

[Terry Bohlsen]

OK, Ill send you the spectra directly.
cheers

Terry