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Lost & Found: The Fornax Dwarf Galaxy

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#1 SNH

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Posted 17 October 2020 - 11:15 PM

Hello all,
Thanks to Cloudy Nights members Keith Rivich and Love Cowboy’s encouragement, I am posting this report:

 

On the morning of October 14th, with a SQM-L reading 21.2, I tried to observe NGC 1049 (+12.6) with my 130mm f/5 reflector. It’s the brightest globular cluster that belongs to the Fornax Dwarf. I found that with 34x (1.7° TFOV), I could just see it, but I used 72x (1.3° TFOV) to confirm that sighting. I also found that keeping at 72x allowed me to nab the other member globulars Fornax 2 (+14.1), 4 (+13.6), and 5 (+13.6).

 

What was really cool was that by panning across the location of the Fornax Dwarf with 34x, I could see it! The galaxy was a roundish glow a little brighter than the background sky and brightened a little towards the center. Somewhere I’ve read that the Fornax Dwarf has been seen with a pair of 25x100 binoculars. You don’t really hear about observations of the galaxy itself, though. Especially from the Northern Hemisphere. When I made my observation, the galaxy was at an altitude of 18.5°, which is about as high as it gets for me.

 

I believe my first introduction to the Fornax Dwarf was five years ago in Phillip Harrington’s book Cosmic Challenge. In it, he wrote “The Fornax Dwarf Galaxy is a paradox. Even though the galaxy itself is beyond the range of our telescopes even from the darkest observing locations, four of its six known globular clusters are within the grasp of 10-inch, or maybe 12-inch, telescopes.” So, in January of 2016, I got to see the dwarf galaxy’s four brightest globular clusters at 132x in my 10-inch SCT. But I couldn’t see the galaxy itself – though I hadn’t expected to see it anyways from Phil’s description!

 

One of the next times I read about the Fornax Dwarf was in the November 2018 issue of Sky & Telescope, where Steve Gottlieb wrote “Our next stop is the Fornax Dwarf Spheroidal Galaxy (Fornax dSph), a Milky Way satellite at a distance of 470,000 light-years. It escaped detection until 1938, when Harlow Shapley noticed it on a 24-inch Bruce astrograph plate taken at Harvard’s Boyden Station in South Africa. Although the integrated magnitude is an impressive 8.0, don’t be misled; the light is spread out over ½° of sky and its anemic surface brightness, along with a low elevation (declination –34.5°), conspire to make the Fornax Dwarf a formidable visual target. My only convincing view was from the Southern Hemisphere when the galaxy was high overhead. Even then, I only noticed a subtle brightening confirmed by tracing around the galaxy’s periphery. The galaxy itself may be barely detectable, but four of its five globulars can be seen through a 10-inch scope (my comments are based on the view through a 13-inch).” That’s more encouraging than Phil’s description, but still not enough for me to go out of my way to try for the galaxy. He also doesn’t give any more encouragement than Phil on small telescopes seeing its globular clusters. By the way, I still don’t understand why Steve says the Fornax Dwarf only has “five globulars” when Phil says it has six.

 

The most recent write-up I’ve seen on the Fornax Dwarf was by Bob King in a December 2017 online S&T article titled “Meet the Shy Side of the Local Group”. He wrote “From my home, the Fornax Dwarf Galaxy never gets higher than 8° above the southern horizon, one of the reasons I've never seen the galaxy itself. Too much thick air and haze! But on good nights using medium and high magnifications, I've succeeded in seeing four of the galaxy's six globular clusters. Those living much farther south may be able to spot the galaxy in a 6- or 8-inch wide-field instrument by sweeping back and forth over its position until a faint haze materializes. The brightest globular, NGC 1049 at magnitude 12.9, is visible in an 8-inch, no problem. It even shows structure. In the 15-inch at 245× I can see a brighter core ringed by a fainter, diffuse halo. The other globulars — Fornax 2, 4, and 5 — appear as assorted faint puffs.” I like his write-up the best because he gave much more encouragement to the spotting of the Fornax Galaxy. And he left no doubt that NGC 1049 is a globular cluster for single digit apertures despite possibly never having seen it that way himself.

 

So I want to encourage those that have dark skies in the southern United States (and elsewhere) to try to see it this winter. And I want to encourage those with crazy awesome RFT’s like CN member Augustus to take a stab at it even though they live in the northern states. It is NOT invisible from the United States and I believe that more people can see it if they are encourage to do so. So take heart, because I saw it from 36.1 N and it didn't "break my eyes" to see it with little my Zhumell Z130!

 

Thank you,

Scott

 

(How's that, Keith Rivich and Love Cowboy?)


Edited by SNH, 17 October 2020 - 11:20 PM.

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#2 ShaulaB

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Posted 18 October 2020 - 12:00 AM

Great post!

 

I spent some time with Stellarium just now. The Fornax Dward PGC 10074 will be on the Meridian at 17 degrees altitude at 10pm on December 1st for me at 38.6 degrees latitude. Now if the skies cooperate and I can remember to look, it will be fun.


Edited by ShaulaB, 18 October 2020 - 12:01 AM.


#3 Redbetter

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Posted 18 October 2020 - 04:34 AM

There has historically been some doubt as to whether Fornax 6 is a globular or something else.  Its somewhat distorted/elliptical shape, diffuse nature, and some unresolved stars mistaken for background galaxies all contributed to rejecting it as a GC for some years.  The most recent paper (2019, here) identifies it as a "bona fide star cluster."   This unfortunately isn't very clear...open cluster or globular?  However, the rest of the thrust of the paper and its title is about it being a GC.   I guess the presumption is that it couldn't be an ancient open cluster within the dwarf based on the properties observed.

 

The main problem I have with the Fornax Dwarf is that I only have one dark site with a clear and dark southern horizon, and it is closed by snows sometime in fall through winter and sometimes up until early summer.   (Fires have had it closed in recent months.)  So while I have studied the Fornax dwarf and its globulars with the 20", it isn't a frequent target.  

 

Good job on seeing it with the 130.  The main obstacle I have seen to observing Fornax and Sculptor dwarf galaxies is getting a dark and transparent southern horizon.  I have been able to see the Sculptor Dwarf in the 80mm f/5 when I specifically tried to, but can't remember if I have succeeded with it on Fornax.  With large scopes I expect to see these galaxies when I target them, despite their low elevations.  The problem is getting good opportunities to do so.  

 

The two that are a real handful are:  Draco Dwarf and Ursa Minor Dwarf.  Fortunately, both are high in the sky, but they are of much lower actual surface brightness.  The impressions I have had of them have been weak.  I have gone after UMi Dwarf several times over the years and have consistently had the same subtle hint of its shape and orientation.   



#4 SNH

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Posted 19 October 2020 - 07:05 AM

Thanks Redbetter, I'll have to read up on Fornax 6 now!

 

I've heard that both the Draco Dwarf (UGC 10822) and the Ursa Minor Dwarf (UGC 9749) have been seen with a 4.3-inch telescope. But the more realistic sighting I have is from the late Steve Coe, who saw the UMD with a 6--inch f/6 Mak-Newt and a 6-inch f/8 refractor.

 

I've tried for the UMD galaxy myself earlier in the year, but to no avail. So the UMD and Draco Dwarf will continue to "haunt" me for a while it seems!

 

I have already seen Leo I and IC 1316 with my 130mm and will be going after the Sculptor Dwarf soon (already seen it in the 10-inch).

 

Keep up the good work, all.

Scott



#5 sgottlieb

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Posted 19 October 2020 - 12:00 PM

By the way, I still don’t understand why Steve says the Fornax Dwarf only has “five globulars” when Phil says it has six.

 

Redbetter really answered this question, but when I wrote the Sky & Tel article in 2018, Fornax 6 wasn't considered a globular.  So although I had previously observed Fornax 6, I decided to not include it.

 

For example, See section 3.6 in this paper includes the following quote... "nearly half of the "stars" in cluster 6 appear to us to be nonstellar and seem to constitute a very faint compact group of galaxies."

 

The paper "Rediscovery of the Sixth Star Cluster in the Fornax Dwarf Spheroidal Galaxy" was posted on astro-ph in February 2019, so I just missed out on the announcement!

 

-- Steve



#6 Keith Rivich

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Posted 19 October 2020 - 07:08 PM

Hello all,
Thanks to Cloudy Nights members Keith Rivich and Love Cowboy’s encouragement, I am posting this report:

 

On the morning of October 14th, with a SQM-L reading 21.2, I tried to observe NGC 1049 (+12.6) with my 130mm f/5 reflector. It’s the brightest globular cluster that belongs to the Fornax Dwarf. I found that with 34x (1.7° TFOV), I could just see it, but I used 72x (1.3° TFOV) to confirm that sighting. I also found that keeping at 72x allowed me to nab the other member globulars Fornax 2 (+14.1), 4 (+13.6), and 5 (+13.6).

 

What was really cool was that by panning across the location of the Fornax Dwarf with 34x, I could see it! The galaxy was a roundish glow a little brighter than the background sky and brightened a little towards the center. Somewhere I’ve read that the Fornax Dwarf has been seen with a pair of 25x100 binoculars. You don’t really hear about observations of the galaxy itself, though. Especially from the Northern Hemisphere. When I made my observation, the galaxy was at an altitude of 18.5°, which is about as high as it gets for me.

 

I believe my first introduction to the Fornax Dwarf was five years ago in Phillip Harrington’s book Cosmic Challenge. In it, he wrote “The Fornax Dwarf Galaxy is a paradox. Even though the galaxy itself is beyond the range of our telescopes even from the darkest observing locations, four of its six known globular clusters are within the grasp of 10-inch, or maybe 12-inch, telescopes.” So, in January of 2016, I got to see the dwarf galaxy’s four brightest globular clusters at 132x in my 10-inch SCT. But I couldn’t see the galaxy itself – though I hadn’t expected to see it anyways from Phil’s description!

 

One of the next times I read about the Fornax Dwarf was in the November 2018 issue of Sky & Telescope, where Steve Gottlieb wrote “Our next stop is the Fornax Dwarf Spheroidal Galaxy (Fornax dSph), a Milky Way satellite at a distance of 470,000 light-years. It escaped detection until 1938, when Harlow Shapley noticed it on a 24-inch Bruce astrograph plate taken at Harvard’s Boyden Station in South Africa. Although the integrated magnitude is an impressive 8.0, don’t be misled; the light is spread out over ½° of sky and its anemic surface brightness, along with a low elevation (declination –34.5°), conspire to make the Fornax Dwarf a formidable visual target. My only convincing view was from the Southern Hemisphere when the galaxy was high overhead. Even then, I only noticed a subtle brightening confirmed by tracing around the galaxy’s periphery. The galaxy itself may be barely detectable, but four of its five globulars can be seen through a 10-inch scope (my comments are based on the view through a 13-inch).” That’s more encouraging than Phil’s description, but still not enough for me to go out of my way to try for the galaxy. He also doesn’t give any more encouragement than Phil on small telescopes seeing its globular clusters. By the way, I still don’t understand why Steve says the Fornax Dwarf only has “five globulars” when Phil says it has six.

 

The most recent write-up I’ve seen on the Fornax Dwarf was by Bob King in a December 2017 online S&T article titled “Meet the Shy Side of the Local Group”. He wrote “From my home, the Fornax Dwarf Galaxy never gets higher than 8° above the southern horizon, one of the reasons I've never seen the galaxy itself. Too much thick air and haze! But on good nights using medium and high magnifications, I've succeeded in seeing four of the galaxy's six globular clusters. Those living much farther south may be able to spot the galaxy in a 6- or 8-inch wide-field instrument by sweeping back and forth over its position until a faint haze materializes. The brightest globular, NGC 1049 at magnitude 12.9, is visible in an 8-inch, no problem. It even shows structure. In the 15-inch at 245× I can see a brighter core ringed by a fainter, diffuse halo. The other globulars — Fornax 2, 4, and 5 — appear as assorted faint puffs.” I like his write-up the best because he gave much more encouragement to the spotting of the Fornax Galaxy. And he left no doubt that NGC 1049 is a globular cluster for single digit apertures despite possibly never having seen it that way himself.

 

So I want to encourage those that have dark skies in the southern United States (and elsewhere) to try to see it this winter. And I want to encourage those with crazy awesome RFT’s like CN member Augustus to take a stab at it even though they live in the northern states. It is NOT invisible from the United States and I believe that more people can see it if they are encourage to do so. So take heart, because I saw it from 36.1 N and it didn't "break my eyes" to see it with little my Zhumell Z130!

 

Thank you,

Scott

 

(How's that, Keith Rivich and Love Cowboy?)

waytogo.gif

 

Now I have a reason to go back to the Fornax dwarf!


Edited by Keith Rivich, 19 October 2020 - 07:09 PM.

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#7 SNH

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Posted 19 October 2020 - 07:16 PM

Thanks Steve! I read the 2019 paper that you and Redbetter mentioned and see that they believe 100% that Fornax 6 is a star cluster. What kind of star cluster is still up to debate it seems, though they are leaning towards a unique low-mass globular cluster. Good to know!

 

Scott


Edited by SNH, 19 October 2020 - 07:21 PM.


#8 Migwan

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Posted 19 October 2020 - 11:17 PM

waytogo.gif waytogo.gif  Scott

 

Saw NGC 1049 while trying to catch as much of the local group as I could.  I panned around and that's all I could spot up here.   Will have to give it another look.  Especially next time I get out to the SW. 

 

jd




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