Possible AGN ?
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by suelaine
The brilliant white centre in this either disc or elliptical, might it be an AGN?
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that particular thing is an artifact caused by the center being so bright that the images make it dimmer. #ukidssring
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by JeanTate in response to suelaine's comment.
It's a disk galaxy - it has pointy ends! - and yes, the extremely bright center means it's almost certainly an AGN.
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by JeanTate in response to JeanTate's comment.
Well, astronomy is full of surprises! 😄
Here's this galaxy as seen by SDSS:
Very bright nucleus/bulge, no surprise there. However, look at the spectrum!
It'd be very cool if an astronomer (a SCIENTIST) could weigh in, but I think this shows a quite 'dead and red' stellar population - without even the slightest hint of an AGN - and very little dust either. If so, how come the bulge is so bright?
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Well, there's a small OIII spike in its different emission lines, and the hydrogen emission line appears to support the red-and-dead elliptical. It appears to be that the center just has a dense cluster of stars.
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by JeanTate in response to planetaryscience's comment.
Well, there's a small OIII spike in its different emission lines
It certainly looks like that in the png version I copy/pasted; however, if you use the interactive spectrum, you'll see that there's no [OIII] emission
It appears to be that the center just has a dense cluster of stars.
Yes. I wonder how easy it would be to estimate the surface brightness, and compare that with the core of a big globular cluster (like Omega Cen)?
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S = m + 2.5 * log10 A.
m: 14.43
14.43 + 2.5 = 16.93
A= ~2.5 arcseconds
0.39794
16.93 * 0.39794 = surface brightness of +6.7
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Omega Centauri's surface brightness:
S = m + 2.5 * log10 A
m: 3.9
3.9 + 2.5 = 7.4
A= 2178 arcseconds
3.33806
7.4 * 3.33806 = surface brightness of +24.7
That means that this galaxy has a surface brightness of almost 4x as much as Omega Centauri.
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by JeanTate in response to planetaryscience's comment.
Good start, planetaryscience! 😃
m: 14.43
A= ~2.5 arcseconds
Where did you get these values from, may I ask?
Also, A is an area, so it will have units of square arcsecs (or similar), not arcsecs.
16.93 * 0.39794 =
The default precedence order for operators in an equation like "S = m + 2.5 * log10 A" is multiplication then addition, so you first need to calculate "log10 A", then "2.5 * log10 A", and finally "m + 2.5 * log10 A".
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I got the magnitude value from finding the average of the different values from SDSS (ugriz)
I got the area from visually measuring the galaxy.
Here is the corrected calculation:
S = m + 2.5 * log10 A
A= 135 arcsecs (15 x 9)
2.13033
4.63033
surface brightness= 19.06033
Omega Centauri:
A= 4743684 😮
6.67611
9.17611
surface brightness= 16.57611
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