APOD: A View Toward M106 (2024 Feb 22)

[APOD Robot]

A View Toward M106

Explanation: Big, bright, beautiful spiral, Messier 106 dominates this cosmic vista. The nearly two degree wide telescopic field of view looks toward the well-trained constellation Canes Venatici, near the handle of the Big Dipper. Also known as NGC 4258, M106 is about 80,000 light-years across and 23.5 million light-years away, the largest member of the Canes II galaxy group. For a far far away galaxy, the distance to M106 is well-known in part because it can be directly measured by tracking this galaxy's remarkable maser, or microwave laser emission. Very rare but naturally occurring, the maser emission is produced by water molecules in molecular clouds orbiting its active galactic nucleus. Another prominent spiral galaxy on the scene, viewed nearly edge-on, is NGC 4217 below and right of M106. The distance to NGC 4217 is much less well-known, estimated to be about 60 million light-years, but the bright spiky stars are in the foreground, well inside our own Milky Way galaxy.

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[Ann]

I've been a bit sick, so I've not felt up to making any sort of complicated post. But then, today's APOD is the sort of APOD that I, who is not only the Color Commentator but also the Galaxy Girl, really should comment on, right?

A View Toward M106. Image Credit & Copyright: Kyunghoon Lim

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This APOD is nice! It's an attractive field, containing both interesting galaxies and colorful stars. Let's start with the field around NGC 4217, shall we?

The field around NGC 4217. Credit: Marcel Drechsler.

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What I love most about this part of the field is that the blue-looking star (at 3 o'clock) really is blue for real! You don't know how unusual it is to find a truly blue star close to an NGC galaxy! The star in question is HD 106420, a fairly unreddened B-type star, of spectral class B7V, and it's as blue as Regulus. Actually, it's bluer.

Gorgeous portrait of Regulus. Note the tiny little dwarf galaxy near the bottom of the image. It's called Leo 1, if I remember correctly. Anyway, HD 106420 is similar to Regulus, except that HD 106420 is chemically peculiar. Credit: NASA?

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The other bright stars in the field are K-type stars. The brightest and most distant of them is HD 106556 (to the upper right of galaxy NGC 4217 in Marcel Drechsler's image), which shines with the luminosity of some ~700 Suns, and it is sometimes classified as a G5III star.


Let's go galaxy hunting!

NGC 4217 and background galaxy NGC 4226. What I really love about this image is the beautiful portrait of little NGC 4226. You can see its spiral arms so clearly, and it's so obvious that one arm is forming a lot of stars. Credit: Rick J of Cloudy Nights.

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A HST portrait of NGC 4217. You can clearly see that blue stars are forming in the dust lane. Also note the huge numbers of smoking dust pillars, or 'chimneys'. They are remnants of energetic events in the dust lane, such as supernovas. Credit: ESA/Hubble & NASA, Acknowledgement: R. Schoofs

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Okay, so maybe we should look at M106 itself? These are my two favorite portraits of M106:

Messier 106’s black hole is actively gobbling up material. As the gas spirals towards the black hole, it heats up and emits powerful radiation. Part of the emission from the centre of Messier 106 is produced by a process that is somewhat similar to that in a laser - although here the process produces bright microwave radiation. As well as this microwave emission from Messier 106’s heart, the galaxy has another startling feature - instead of two spiral arms, it appears to have four. The extra arms appear to be an indirect result of jets of material produced by the violent churning of matter around the black hole. As these jets travel through the galactic matter they disrupt and heat up the surrounding gas, which in turn excites the denser gas in the galactic plane and causes it to glow brightly. Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), and R. Gendler (for the Hubble Heritage Team). Acknowledgment: J. GaBany

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When M106 is viewed not only in optical light but in X-rays, radio and infrared light as well, the galaxy appears to have four extra arms. X-ray: NASA/CXC/Caltech/P.Ogle et al; Optical: NASA/STScI & R.Gendler; IR: NASA/JPL-Caltech; Radio: NSF/NRAO/VLA

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I understand that the water masers at the heart of M106 are incredibly important, and they provide an almost exact distance to this galaxy. But since I am a math idiot, I'll leave it to the math whizzes of this forum to discuss the details of the masers.

But I understand one thing. Since we have such a good grip on the distance to this galaxy, it would be just great if we found a supernova type Ia in M105, because that would help us calibrate the luminosity of these "supernova standard candles". Unfortunately, the only two supernovas that have been found in M106 have been SN type II, and their luminosities are unpredictable. Unsurprisingly, therefore, one of the SN type II that were found in M106 was more than two magnitudes brighter than the other one.

Wikipedia wrote:
Two supernovae have been observed in M106: SN 1981K (type II, mag. 17), and SN 2014bc (type II, mag. 14.8).

Let's look at a few more galaxies around M106!

Take a look at small galaxy NGC 4248. If you look at the full size of the picture, you can clearly see two pink nebulas in NGC 4248. This galaxy has virtually the same radial velocity as M106, so it is clearly a satellite of M106.

Not so interacting galaxies NGC 4231 and NGC 4232! While the distance to M106 is some 23 million light-years, the apparent radial velocity distance to these two is more than 300 million light-years.

And do you remember the small background galaxy of NGC 4217, NGC 4226 in the picture by Rick J. of Cloudy Nights? The distance to NGC 4226 also appears to be more than 300 million light-years too, just like the distance to galaxies NGC 4231 and NGC 4232! These three galaxies form a group! Note how similar they are, too. All of them are spiral galaxies with a good amount of star formation.

Cool, eh? Wait - you don't think so?

Well, I do!

Ann

[mostly cloudy]

As always, thank you Ann. Get well!

[Ann]

As always, thank you Ann. Get well!

Thank you!

Ann

[johnnydeep]

Two questions for Ann based on her post above:

1. Don't "jets" from central black holes in galaxies get directed perpendicular to the galactic plane, and if so why would they help to form arms in the galaxy disk?
2. Why do we "have such a good grip on the distance" to M106?

[ EDIT: never mind answering 2. It's because of the maser! Serves me right for reading the comments before the main text. ]

[AVAO]

Two questions for Ann based on her post above:

1. Don't "jets" from central black holes in galaxies get directed perpendicular to the galactic plane, and if so why would they help to form arms in the galaxy disk?
2. Why do we "have such a good grip on the distance" to M106?

Somehow it looks like the galaxy is already in its second iteration. The external shape can be seen very well in HERSCHEL images in the submillimeter range. The inner, practically analogous form is then very clearly visible in IR with SPITZER and JWST. The red X-Ray arms look as if they were freshly generated (newborn) and need to cool down a bit until they are transformed into normal spiral arms. But that's just a subjective interpretation of what I think I see. In reality, I have no idea what is really going on...

Click to view full size image 1 or image 2

Opt / Microwave

Click to view full size image 1 or image 2

Microwave / IR and X-ray

[Ann]

Two questions for Ann based on her post above:

1. Don't "jets" from central black holes in galaxies get directed perpendicular to the galactic plane, and if so why would they help to form arms in the galaxy disk?
2. Why do we "have such a good grip on the distance" to M106?

[ EDIT: never mind answering 1. It's because of the maser! Serves me right for reading the comments before the main text. ]

I'll try to answer your question #1 anyway, by quoting parts of the caption from Wikipedia:

Unlike the normal arms, these two extra arms are made up of hot gas rather than stars, and their origin remained unexplained until recently. Astronomers think that these, like the microwave emission from the galactic centre, are caused by the black hole at Messier 106’s heart, and so are a totally different phenomenon from the galaxy’s normal, star-filled arms.

The extra arms appear to be an indirect result of jets of material produced by the violent churning of matter around the black hole.

As these jets travel through the galactic matter they disrupt and heat up the surrounding gas, which in turn excites the denser gas in the galactic plane and causes it to glow brightly.

This denser gas closer to the centre of the galaxy is tightly-bound, and so the arms appear to be straight. However, the looser disc gas further out is blown above or below the disc in the opposite direction from the jet, so that the gas curves out of the disc — producing the arching red arms seen here.

As for how we have such a good grip on the distance to M106, you may want to read this text from arXiv:

J. R. Herrnstein et al. wrote:

The water maser in the mildly active nucleus in the nearby galaxy NGC4258 traces a thin, nearly edge-on, subparsec-scale Keplerian disk. Using the technique of very long baseline interferometry, we have detected the proper motions of these masers as they sweep in front of the central black hole at an orbital velocity of about 1100 km/s. The average maser proper motion of 31.5 microarcseconds per year is used in conjunction with the observed acceleration of the masers to derive a purely geometric distance to the galaxy of 7.2 +- 0.3 Mpc. This is the most precise extragalactic distance measured to date, and, being independent of all other distance indicators, is likely to play an important role in calibrating the extragalactic distance scale.

Ann

[johnnydeep]

Thanks Ann, and AVAO. I still find it strange that the central black hole could produce "jets" in the plane of the galaxy disc.

And I still have no idea how a maser makes it easy to accurately determine distance. The most I can understand from the Wikipedia quote is that the masers (why are there more than one?) is like a lighthouse beacon in the plane of the galaxy disc and either the microwaves from the maser(s) and/or the maser sources themselves "sweep by" the central blackhole. But this might be totally wrong, and it only gets worse from there.

[Chris Peterson]

Thanks Ann, and AVAO. I still find it strange that the central black hole could produce "jets" in the plane of the galaxy disc.

And I still have no idea how a maser makes it easy to accurately determine distance. The most I can understand from the Wikipedia quote is that the masers (why are there more than one?) is like a lighthouse beacon in the plane of the galaxy disc and either the microwaves from the maser(s) and/or the maser sources themselves "sweep by" the central blackhole. But this might be totally wrong, and it only gets worse from there.

A black hole that is consuming material and producing jets directs them along its rotational axis. Why do you assume that axis must be perpendicular to the plane of the galaxy?

[johnnydeep]

Thanks Ann, and AVAO. I still find it strange that the central black hole could produce "jets" in the plane of the galaxy disc.

And I still have no idea how a maser makes it easy to accurately determine distance. The most I can understand from the Wikipedia quote is that the masers (why are there more than one?) is like a lighthouse beacon in the plane of the galaxy disc and either the microwaves from the maser(s) and/or the maser sources themselves "sweep by" the central blackhole. But this might be totally wrong, and it only gets worse from there.

A black hole that is consuming material and producing jets directs them along its rotational axis. Why do you assume that axis must be perpendicular to the plane of the galaxy?

Ah, I see where I screwed up: the central black hole's axis of rotation does NOT have to be perpendicular to the galaxy disk itself! D'oh! Seems like it would be unusual though. Are there other instances of this?