APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

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APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by APOD Robot » Sun Oct 04, 2015 4:10 am

Image The Sombrero Galaxy in Infrared

Explanation: This floating ring is the size of a galaxy. In fact, it is a galaxy -- or at least part of one: the photogenic Sombrero Galaxy, one of the largest galaxies in the nearby Virgo Cluster of Galaxies. The dark band of dust that obscures the mid-section of the Sombrero Galaxy in optical light actually glows brightly in infrared light. The above image, digitally sharpened, shows the infrared glow, recently recorded by the orbiting Spitzer Space Telescope, superposed in false-color on an existing image taken by NASA's Hubble Space Telescope in optical light. The Sombrero Galaxy, also known as M104, spans about 50,000 light years across and lies 28 million light years away. M104 can be seen with a small telescope in the direction of the constellation Virgo.

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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by sffilmstagemusic » Sun Oct 04, 2015 5:14 am

Good Evening: I like how the Owl's Eyes glow bright red in the bottom left of the picture.

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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by neufer » Sun Oct 04, 2015 1:15 pm

sffilmstagemusic wrote:
Good Evening: I like how the Owl's Eyes glow bright red in the bottom left of the picture.
Discussion of that "pair of interacting galaxies" and other good stuff: http://asterisk.apod.com/viewtopic.php?f=9&t=34422
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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by Cousin Ricky » Sun Oct 04, 2015 4:07 pm

So, is it now established that M104 is part of the Virgo Cluster, or is that still disputed?

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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by ta152h0 » Mon Oct 05, 2015 2:30 am

Disputes is what fuels science
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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by Chris Peterson » Mon Oct 05, 2015 1:55 pm

ta152h0 wrote:Disputes is what fuels science
Curiosity is what fuels science. Dispute (which isn't the same as disagreement) is fairly rare.
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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by neufer » Mon Oct 05, 2015 2:02 pm

ta152h0 wrote:
Disputes is what fuels science
Disputing whether or not M104 is part of the Virgo Cluster is like disputing whether or not Pluto is a planet.
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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by Chris Peterson » Mon Oct 05, 2015 2:43 pm

neufer wrote:Disputing whether or not M104 is part of the Virgo Cluster is like disputing whether or not Pluto is a planet.
No, it isn't. Whether or not M104 is part of the Virgo Cluster is a scientific question. Whether or not Pluto is a planet is simply a question of how we choose to define "planet". There is no disagreement about what constitutes a galaxy cluster.
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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by Cousin Ricky » Mon Oct 05, 2015 4:09 pm

neufer wrote:Disputing whether or not M104 is part of the Virgo Cluster is like disputing whether or not Pluto is a planet.
I've seen estimates of the distance to M104 vary from 25 Mly to 50 Mly. If it's only 25 Mly, then it is unambiguously not part of the cluster. But at 50 Mly, according to my math, it would still be about 20 Mly from the center of the cluster.

I never saw M104 referred to as part of the cluster until I started reading APOD.

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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by Ron-Astro Pharmacist » Mon Oct 05, 2015 5:23 pm

It is an interesting object worthy of much discussion; classroom or web / language or science. :cowboy:

Better keep up or you could get left in the dust.
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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by ta152h0 » Mon Oct 05, 2015 7:47 pm

it is like candid camera, when you least expect it there is the answer, whether borne out of discussions, disputes, and/or observations. Keep talking !
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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by neufer » Mon Oct 05, 2015 9:29 pm

Chris Peterson wrote:
neufer wrote:
Disputing whether or not M104 is part of the Virgo Cluster is like disputing whether or not Pluto is a planet.
No, it isn't. Whether or not M104 is part of the Virgo Cluster is a scientific question. Whether or not Pluto is a planet is simply a question of how we choose to define "planet". There is no disagreement about what constitutes a galaxy cluster.
  • I suppose :?
https://en.wikipedia.org/wiki/Galaxy_cluster wrote:
<<A galaxy cluster or cluster of galaxies is a structure that consists of anywhere from hundreds to thousands of galaxies bound together by gravity. They are the largest known gravitationally bound structures in the universe and were the largest known structures in the universe until the 1980s when superclusters were discovered. One of the key features of clusters is the intracluster medium or ICM. The ICM consists of heated gas between the galaxies and has a temperature on the order of 7-9 keV.>>
https://en.wikipedia.org/wiki/Virgo_Cluster wrote:
The Virgo Cluster (VC) is a cluster of galaxies whose center is 16.5 ± 0.1 Mpc away in the constellation Virgo. It is estimated that the VC's mass is 1.2×1015 M☉ out to 8 degrees of the cluster's center or a radius of about 2.2 Mpc.
M104 is ~24 degrees from the center of
the Virgo Cluster & ~7.5 Mpc closer to us
(although it is moving away from us
at about the same clip of ~1000 km/s).
  • 3 standard deviations away :!:
    Gravitationally bound :?:
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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by Chris Peterson » Mon Oct 05, 2015 10:03 pm

neufer wrote:3 standard deviations away :!:
Gravitationally bound :?:
No opinion. I don't know if M104 is a member of the Virgo Cluster, only that it's a yes/no question that is potentially answerable with a high degree of certainty (or even complete certainty).
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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by Ann » Tue Oct 06, 2015 12:50 am

Another scientific question is how we actually measure the distance to M104. To my knowledge M104 contains no Cepheids, and I would be surprised if it did, considering its apparent lack of star formation. And if by any chance it did contain a Cepheid or two, we might miss them because of the galaxy's high inclination. And as far as I'm aware, there have been no recorded supernovas in M104. Also the galaxy is quite isolated in the sky, so we can't use any satellite galaxies and their Cepheids or supernovas to estimate the distance to M104. Do we use the tip of the red giant branch, the red clump stars or the size of the planetary nebulas? Isn't M104 too far away for that? And since M104 has so few young stars of any kind, shouldn't it have only small numbers of planetary nebulas that might be hard to find in that dust lane?

The more I think about it, the harder it seems to be to know how far away M104 is. We can of course measure its recession velocity and calculate its distance with the help of that, but M104 is close enough that its peculiar velocity might be close to the value of its recession velocity.

I have to wonder how we can really know the distance to M104. And as I said, that is a scientific question.

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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by neufer » Tue Oct 06, 2015 1:59 am

Ann wrote:
To my knowledge M104 contains no Cepheids, and I would be surprised if it did, considering its apparent lack of star formation. And if by any chance it did contain a Cepheid or two, we might miss them because of the galaxy's high inclination. And as far as I'm aware, there have been no recorded supernovas in M104. Also the galaxy is quite isolated in the sky, so we can't use any satellite galaxies and their Cepheids or supernovas to estimate the distance to M104. Do we use the tip of the red giant branch, the red clump stars or the size of the planetary nebulas? Isn't M104 too far away for that?

The more I think about it, the harder it seems to be to know how far away M104 is. We can of course measure its recession velocity and calculate its distance with the help of that, but M104 is close enough that its peculiar velocity might be close to the value of its recession velocity.

I have to wonder how we can really know the distance to M104. And as I said, that is a scientific question.
https://en.wikipedia.org/wiki/Sombrero_Galaxy#Distance_and_brightness wrote:
<<At least two methods have been used to measure the distance to the Sombrero Galaxy.
  • 1) The first method relies on comparing the measured fluxes from planetary nebulae in the Sombrero Galaxy to the known luminosities of planetary nebulae in the Milky Way. This method gave the distance to the Sombrero Galaxy as 29 ± 2 Mly (8,890 ± 610 kpc).

    2) The other method used is the surface brightness fluctuations method. This method uses the grainy appearance of the galaxy's bulge to estimate the distance to it. Nearby galaxy bulges will appear very grainy, while more distant bulges will appear smooth. Early measurements using this technique gave distances of 30.6 ± 1.3 Mly (9,380 ± 400 kpc). Later, after some refinement of the technique, a distance of 32 ± 3 Mly (9,810 ± 920 kpc) was measured. This was even further refined in 2003 to be 29.6 ± 2.5 Mly (9,080 ± 770 kpc).
The average distance measured through these two techniques is 29.3 ± 1.6 Mly (8,980 ± 490 kpc).

The absolute magnitude (in the blue) of the Sombrero Galaxy is estimated to be -21.9 at 30.6 Mly (9,400 kpc) (-21.8 at the average distance of above), that as stated above makes it the brightest galaxy within a radius of 32.6 Mly (10,000 kpc) around the Milky Way.>>
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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by Ann » Tue Oct 06, 2015 3:01 am

Thanks, Art. I should have checked Wikipedia. On the other hand, I don't entirely trust Wikipedia when it comes to the description of M104. This is what Wikipedia wrote about star formation in M104:
https://en.wikipedia.org/wiki/Sombrero_Galaxy#Dust_ring wrote:

Based on infrared spectroscopy, the dust ring is the primary site of star formation within this galaxy.[7]
So I checked source [7], http://arxiv.org/pdf/astro-ph/0603160v1.pdf.
Spitzer and JCMT Observations of the Active Galactic Nucleus in
the Sombrero Galaxy (NGC 4594) wrote:

The spectrum of the ring is more consistent with star formation activity than the nucleus.
PAH emission from the ring, especially in the 11.3 µm band, is much stronger. Qualitatively,
the stronger PAH features would shift this galaxy into the star formation regime in the
diagnostic diagrams of Genzel et al. (1998), Peeters et al. (2004), and D. A. Dale et al.
(2006, in preparation). Unfortunately, the observations are too limited to show that the
spectrum of the ring is consistent with star formation.
The long-high observations, which
are needed to measure the 25.9 µm [O IV] line, do not adequately cover the ring. The signalto-noise
ratio is too low for the low-resolution spectrum between 5 and 8 µm for accurate
measurement of the 6.2 and 7.7 µm PAH features. Finally, because of the limitations of
the spatial resolution, a significant fraction of the flux at wavelengths greater than 20 µm
may include emission from the AGN, thus making measurements of the 25.9 µm [O IV] and
34.8 µm [Si II] lines suspect.
So the paper that is used to say that most of the star formation in M104 is in the dust ring of M104, does not conclusively say that there is any star formation in M104. (Although an infrared image taken in the 24 µm bandpass does show a weak knot in the dust ring, which might indeed be an embedded site of star formation.)

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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by neufer » Tue Oct 06, 2015 4:12 am

Ann wrote:
http://arxiv.org/pdf/astro-ph/0603160v1.pdf wrote:Spitzer and JCMT Observations of the Active Galactic Nucleus in
the Sombrero Galaxy (NGC 4594) wrote:

The spectrum of the ring is more consistent with star formation activity than the nucleus.

Unfortunately, the observations are too limited to show that the
spectrum of the ring is consistent with star formation.
So the paper that is used to say that most of the star formation in M104 is in the dust ring of M104, does not conclusively say that there is any star formation in M104. (Although an infrared image taken in the 24 µm bandpass does show a weak knot in the dust ring, which might indeed be an embedded site of star formation.)
  • `Take some more tea,’ the March Hare said to Alice, very earnestly.

    `I’ve had nothing yet,’ Alice replied in an offended tone, `so I can’t take more.

    `You mean you can’t take LESS,’ said the Hatter: `it’s very easy to take MORE than nothing.
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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by Ann » Wed Oct 07, 2015 5:20 am

neufer wrote:
  • `Take some more tea,’ the March Hare said to Alice, very earnestly.

    `I’ve had nothing yet,’ Alice replied in an offended tone, `so I can’t take more.

    `You mean you can’t take LESS,’ said the Hatter: `it’s very easy to take MORE than nothing.
Thanks for that lovely Alice in Wonderland quote, Art! (Or is it Alice Through the Looking Glass?)

Anyway. I am on record here at Starship Asterisk* for saying that there is no star formation in M104, but I take it back. The reason is that almost any really substantial dust lane in a galaxy will produce some new stars. Take a look at this APOD from May 3, 2010, which portrayed galaxy NGC 3190. At first glance, you would be forgiven for thinking that NGC 3190 contains no young stars at all, but at full resolution you can see several little blue dots in the dust lane, which may be small clusters of young stars, or even individual young stars. So there are young stars in NGC 3190, and there is probably some ongoing star formation too, although none is visible in the APOD in question. For the same reason, we should assume that there really are a few - a few!! - young stars in M104, and probably some ongoing star formation.

So let's return to Alice. Had she really had no tea at all at the time when the March Hare offered her more? But she had gone into the room where the tea party was taking place, and the tea that the others were drinking might have been hot and steaming. Little droplets of tea mixed with the air, and Alice could undoubtedly smell the tea. If she smelled it, she must have breathed it, and since she breathed it, she must have ingested some minute quantities of it. So had Alice had no tea? I beg to differ.

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Re: APOD: The Sombrero Galaxy in Infrared (2015 Oct 04)

Post by neufer » Wed Oct 07, 2015 11:28 am

Ann wrote:
neufer wrote:
  • `Take some more tea,’ the March Hare said to Alice, very earnestly.

    `I’ve had nothing yet,’ Alice replied in an offended tone, `so I can’t take more.

    `You mean you can’t take LESS,’ said the Hatter: `it’s very easy to take MORE than nothing.
Thanks for that lovely Alice in Wonderland quote, Art! ...Had she really had no tea at all at the time when the March Hare offered her more? But she had gone into the room where the tea party was taking place, and the tea that the others were drinking might have been hot and steaming. Little droplets of tea mixed with the air, and Alice could undoubtedly smell the tea. If she smelled it, she must have breathed it, and since she breathed it, she must have ingested some minute quantities of it. So had Alice had no tea? I beg to differ.
  • But, at most, Alice only dreamt that she smelled tea:
`Oh, I’ve had such a curious dream!’ said Alice, and she told her sister, as well as she could remember them, all these strange Adventures of hers that you have just been reading about; and when she had finished, her sister kissed her, and said, `It WAS a curious dream, dear, certainly: but now run in to your tea; it’s getting late.’ So Alice got up and ran off, thinking while she ran, as well she might, what a wonderful dream it had been.
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