Distance to the Tarantula Nebula

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Where should the Tarantula Nebula (30 Dor) be in relation to LMC's central bar?

In front of (closer to the Sun than) the LMC's central bar
2
29%
Behind (farther away from the Sun than) the LMC's central bar
3
43%
The same distance as LMC's central bar, or unknown
2
29%
 
Total votes: 7

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LukeCEL
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Distance to the Tarantula Nebula

Post #1by LukeCEL » 06.04.2020, 04:19

I'm working on an update to the LMC for my LMC/SMC stars add-on. In it, the stars will be distributed as to form a "central bar", but there will also be a clump of stars where the Tarantula Nebula (30 Doradus) would be.

Do we know enough about the Tarantula Nebula to know its distance, particularly in relation to LMC's central bar? I always thought most objects don't have distances known to more precision than the LMC itself. However, I'm willing to move the Tarantula stars' position if it's demonstrated otherwise.

Bringing up references is welcome :)

Thanks,
Luke

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Lafuente_Astronomy
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Post #2by Lafuente_Astronomy » 06.04.2020, 04:32

Actually, I don't think we know much about the Nebula to determine its distance and placement. But its known distance is 49 kpc or 160,000 light years away, which is a bit ahead distance from the LMC, since its distance(And I have to assume it's the center) would be around 163,000 light years or 50 kpc.

Overall, based on those things, I'll vote on in front of the Bar until more research proves otherwise Definitely corrected to behind now
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Post #3by SevenSpheres » 06.04.2020, 17:08

Wikipedia puts the Tarantula Nebula at 49 kpc (160,000 ly), citing this paper, and the LMC at 50 kpc (163,000 ly), citing this paper. I'm not sure if the first paper's distance is supposed to be the distance to the nebula or to the galaxy, but I think the discrepancy is probably just due to the first paper being older. I vote same distance, or unknown.

Added after 5 hours 54 minutes:
Turns out I was right that the difference is only due to one estimate being older; this is the original source for the 49 kpc distance, and it says (my bold):

[...]we obtained a distance modulus of (m-M)0 = 18.45 ± 0.15 for 30 Doradus in excellent agreement with the best estimate for distance to the LMC, (m-M)0 = 18.50.

Added after 30 minutes 9 seconds:
Just to be clear: the 49 kpc distance to the Tarantula Nebula is from a 1999 paper that says it is "in excellent agreement" with the distance to the LMC. This has been superseded by a more accurate distance to the LMC of 50 kpc from 2013 (which is also very close to the distance in Celestia). No paper actually says that the Tarantula Nebula is closer than the LMC's central bar, and that conclusion can only be reached by assuming that an older distance estimate is just as accurate as a newer one.
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Post #4by Fafers_br » 07.04.2020, 02:35

I found two papers on the structure of the LMC.
The one I found most "didatic" was Koerwer 2009.
It provides a good 3D schematics in figure 6.

The other is Subramanian 2013.
Both seem to agree that 30 Dor is slightly behind the plane of the disc of LMC.

Refer to section 5 from first source and section 8.1 of the second one.

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Post #5by Lafuente_Astronomy » 07.04.2020, 03:46

In light of the papers that Fafers_br presented, I have now changed my vote to Behind. Also, it's pretty much the correct answer anyways
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Post #6by LukeCEL » 08.04.2020, 22:00

Thank you everyone for participating in the poll. I've decided to put to take a closer look at the two papers that Fafers_br gave.


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