Two bright galaxies (and their neighbourhoods) in Sextans

[Martin Meredith]

NGC 3115 is a mag 10.1 E-S0 type galaxy in Sextans. It is not only bright but has a high surface brightness of 19.5. This is one of several galaxies known as the 'Spindle Galaxy'.

Just to its SW (in this image) -- but invisible in this image -- is UGCA 200, a mag 16.3 dwarf galaxy with a surface brightness of 24.5, about a 100 times less than NGC 3115. Both are at around 30 M light years so could conceivably be interacting. UGCA 200 is also incredibly faint on the DSS image. I reloaded into Jocular and in this negative, hugely-stretched, dusty image it is possible to make it out -- just about. This is what I love about astronomy, EEVA-style: the unexpected and the challenging, and UGCA 200 combined both of these. UGCA 200 is described in [1].

 

Another bright galaxy in Sextans is NGC 3044. This is type SBc (or SCd), mag 12.5 with a surface brightness of 22.2. In this relatively long exposure some of the structure of the galaxy can be seen: central condensations, some hints of higher densities towards the edge (presumably spiral arms), and a faint tilted lane at the right hand end (more clearly seen in the negative image). Reading [2] and [3] (if I'm interpreting things correctly) this is an 'extraplanar diffuse ionised gas halo' that has been blown out by supernovae (first detected in our own galaxy in 1963). Fascinating!

 

 

 

The reason I took a longer exposure was to try to capture some of the faint galaxies and no fewer than 3 quasars in this small field. I've marked the faintest galaxy detected. Details for the quasars:

q1: mag 19.3 (red filter), redshift 0.48
q2: mag 20.0, redshift 1.24
q3: mag 20.6 (photographic), redshift 1.53

As you can see, q3 escaped me on this occasion. Anyone fancy having a go?

cheers

Martin

[1] https://arxiv.org/pdf/1003.0201.pdf
[2] https://arxiv.org/pdf/astro-ph/0006301.pdf
[3] https://arxiv.org/pdf/astro-ph/0510079.pdf

 

[Mike JW]

Hi Martin,

NGC 3115 - lovely capture. Not on any of my lists - an oversight?

NGC 3044 - visited that one early in March. I did not think about checking for the quasars so not evident in my image. The tilted lane is a very nice distinguishing feature.

Until this easterly stops I cannot observe anything in the south. Hoping tonight to hunker down at the back of the house and look north.

Mike

[Marvin Jenkins]

From some one outside of EEVA with not a huge amount of Astro experience, wow, wow and wow.

I have been following this section and I have to say, in my option this is the cutting edge.

I will continue following and hopefully fall in step in the future. 
Marv

[RobertI]

Nice report Martin, some interesting objects. Also interesting to see the limiting magnitude in play, stopping you seeing q3 by just 0.6 mag. An interesting field to have a go at when I'm next out. Almost tried my first EAA session in a long time last night, but just too windy, so ended up with visual again!

[Martin Meredith]

Thanks Mike. On NGC 3115, I'm always amazed when an NGC galaxy that looks innocuous on the charts turns out to be a real beauty. Nowadays I almost never look at observing guides in advance in order to enjoy the surprise when this happens. This is an object that responds well to the interactive observing style because the appearance changes dramatically with increasing stretch from a thin lens shape to showing the extensive elliptical-style halo, fitting with its classification as E-S0. Burnham devotes 2 pages to NGC 3115, noting that it is "somewhat difficult to locate in a blank portion of the sky".

Marv, thanks for your kind words. I'm not sure about cutting edge but I think it shows that there is a lifetime's worth of interesting objects within reach even for modest equipment. I'm still using my Lodestar X2 mono which I think must be over 5 years old now and no plans to upgrade any time soon.

Thanks Rob. We've had a lot of wind here recently (these shots were taken before that arrived). I would normally (on a good moonless night) be able to just about pull out a mag 20.6 point source. Looking again on Aladin at the DSS image it appears very blue (and that magnitude estimate is in the blue filter apparently) so perhaps I'm lacking some sensitivity in that part of the spectrum. 

Martin

[Bill S]

Had quite a good session last night and started off with these two to see what I could see. Managed to make out the dwarf galaxy neighbouring NGC 3115 and the features that you (Martin) have drawn attention to in your snapshot of NGC 3044. I'm sure that the missing q3 is not to be found on my observation.

I also had a look at integral and percentage signs (new to me) and snapped them but nothing obvious to add to your (Martin and Mike's) reports. I had a look at or look for fifteen objects in total. I'll have a trawl through to see if there is anything worth sharing.

I had to call it a day when the transparency of the apparently clear sky got so poor I was not seeing much. (I was also getting rather cold.)

 

[Mike JW]

Hi,

I took a peak at NGC 3115 - what a beauty.

Next up was to have another look at NGC 3044. This is as I saw it on the screen. Not captured q2 or q3 - not really a surprise as Sextans low down for me. Spotted q1 - pleased. Also galaxy 19.6 is there as well. Thanks Martin for the challenge. I wonder if I could get q2 and q3 with the Dob on a good night. Pleased with the detail on 3044. Mike

[Bill S]

OK. I decided to post my snapshot of NGC 3044. I've oriented it the same as Martin's negative image and it's about the same field of view. I keep having a look and a tinker with the stretch etc. in Jocular and using a bit of averted wishful thinking I sometimes think I just might maybe see q3, but then again no. I reckon the total stacking time probably disqualifies it from EEVA. More like not really near real time viewing.

 

Here's my snap of NGC 3115. Using Martin's shot above as a guide it's possible to pick out the very faint fuzzy of the dwarf galaxy.

 

 

Anyway, thanks for looking.

 

[Mike JW]

Hi Bill, thanks for posting. Q3 I feel is likely to be beyond us due to its low position for GB skies. If a suitable opportunity comes along I might try the 15" Dob. Mike

[Martin Meredith]

Nice shots Bill -- always good to compare. I like how in the last image you've managed to preserve the bright central part of NGC 3115 while also showing the elliptical halo around it.

It is currently clear and the scope is outside cooling, so I may have another go at q3 with 30s subs tonight, but later on when it gets to around 45 degrees above the horizon. Before that the plan is to look at the remaining Arps in Leo (which has 27 of which I've observed 11 so far). 

Martin

[Mike JW]

Look forward to seeing your results for the Leo Arps. I am currently going through my Leo shots. We could write a guide to Leo using the EAA technique...........? Mike

[Martin Meredith]

Hi Mike

It would certainly be interesting to put together some shots of the Leo Arps. I think I have them all now. Just a matter of finding some time...

Martin

[michael.h.f.wilkinson]

Very interesting thread. Might well have a bash at imaging these galaxies, just to see what I can come up with