APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 5430
Joined: Fri Dec 04, 2009 3:27 am

APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by APOD Robot » Sun Aug 13, 2023 4:06 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 featured 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 visible 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.

<< Previous APOD This Day in APOD Next APOD >>

JimB
Ensign
Posts: 32
Joined: Sun Aug 06, 2023 8:28 am
Location: England

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by JimB » Sun Aug 13, 2023 8:28 am

Beautiful image!

But it looks like the central region of this galaxy is pretty empty of stars - is this really the case?

User avatar
Rauf
Science Officer
Posts: 227
Joined: Tue Oct 09, 2018 3:47 pm

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by Rauf » Sun Aug 13, 2023 11:25 am

The text seems a little outdated.
APOD Robot wrote: Sun Aug 13, 2023 4:06 am Image The Sombrero Galaxy in Infrared

recently recorded by the orbiting Spitzer Space Telescope
Spitzer Space Telescope has retired, right? So it couldn't have possibly record data on this galaxy recently.

User avatar
AVAO
Commander
Posts: 587
Joined: Tue May 28, 2019 12:24 pm
AKA: multiwavelength traveller
Location: Zurich, Switzerland

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by AVAO » Sun Aug 13, 2023 12:15 pm

Rauf wrote: Sun Aug 13, 2023 11:25 am The text seems a little outdated.
APOD Robot wrote: Sun Aug 13, 2023 4:06 am Image The Sombrero Galaxy in Infrared

recently recorded by the orbiting Spitzer Space Telescope
Spitzer Space Telescope has retired, right? So it couldn't have possibly record data on this galaxy recently.
The fact that today's APOD is an evergreen or a repost from 2012 (viewtopic.php?t=27724) your question can be answered quickly. Unfortunately, it happens relatively often that the original APOD text is also adopted without making any adjustments.

By the way in this case, the title is also only 50 % correct, since the image shown is a composite of IR and the Hubble optical wavelenght.


Image
https://www.spitzer.caltech.edu/image/s ... -sombrero

User avatar
MelvzLuster
Ensign
Posts: 30
Joined: Tue Oct 18, 2022 2:16 pm
AKA: Yahweh Sabaoth

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by MelvzLuster » Sun Aug 13, 2023 12:39 pm

Great & marvelous, this Sombrero Galaxy is a sure refuge and shelter for Angels when exploring the entire Cosmos.
Cmdr. Melvyn M. Lusterio
NASA's Space Commander-Engineer
USS Victory NCC 1967

User avatar
Chris Peterson
Abominable Snowman
Posts: 18332
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by Chris Peterson » Sun Aug 13, 2023 1:14 pm

JimB wrote: Sun Aug 13, 2023 8:28 am Beautiful image!

But it looks like the central region of this galaxy is pretty empty of stars - is this really the case?
It's an illusion. The central region is nothing but stars!
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com

rwlott
Ensign
Posts: 41
Joined: Fri May 06, 2011 7:05 pm

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by rwlott » Sun Aug 13, 2023 1:18 pm

Rauf wrote: Sun Aug 13, 2023 11:25 am The text seems a little outdated.
APOD Robot wrote: Sun Aug 13, 2023 4:06 am Image The Sombrero Galaxy in Infrared

recently recorded by the orbiting Spitzer Space Telescope
Spitzer Space Telescope has retired, right? So it couldn't have possibly record data on this galaxy recently.
This APOD is a repeat, as they often are on Sundays. In fact, this entry is making its 6th appearance, going back to 11 May 2005, with only a couple of minor changes to the text along the way.

User avatar
Rauf
Science Officer
Posts: 227
Joined: Tue Oct 09, 2018 3:47 pm

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by Rauf » Sun Aug 13, 2023 2:03 pm

AVAO wrote: Sun Aug 13, 2023 12:15 pm
Rauf wrote: Sun Aug 13, 2023 11:25 am The text seems a little outdated.
APOD Robot wrote: Sun Aug 13, 2023 4:06 am Image The Sombrero Galaxy in Infrared

recently recorded by the orbiting Spitzer Space Telescope
Spitzer Space Telescope has retired, right? So it couldn't have possibly record data on this galaxy recently.
The fact that today's APOD is an evergreen or a repost from 2012 (viewtopic.php?t=27724) your question can be answered quickly. Unfortunately, it happens relatively often that the original APOD text is also adopted without making any adjustments.

By the way in this case, the title is also only 50 % correct, since the image shown is a composite of IR and the Hubble optical wavelenght.


Image
https://www.spitzer.caltech.edu/image/s ... -sombrero
Yeah, I know APOD repeats itself, and quite often. But the text has been changed slightly each time. So, I guess something like this should be updated as it can be misleading to some people.

User avatar
AVAO
Commander
Posts: 587
Joined: Tue May 28, 2019 12:24 pm
AKA: multiwavelength traveller
Location: Zurich, Switzerland

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by AVAO » Sun Aug 13, 2023 2:10 pm

Chris Peterson wrote: Sun Aug 13, 2023 1:14 pm
JimB wrote: Sun Aug 13, 2023 8:28 am Beautiful image!

But it looks like the central region of this galaxy is pretty empty of stars - is this really the case?
It's an illusion. The central region is nothing but stars!
Well, basically I would definitely agree with that in terms of mass. The fine clouds of dust are then negligible.

jac berne (flickr) Original data: NASA / ESA (Closeup of the core of Messier 104 HST / PC F336W)


The fact that the star density increases towards the center can also be seen very well in the new JWST images.
Also that the resolution is drastically better than the earlier Spitzer Space Telescope (SST).
Click to view full size image 1 or image 2
jac berne (flickr) Original data: NASA / ESA / CSA (JWST)
biggg: https://live.staticflickr.com/65535/531 ... ff07_o.jpg
Overview big: https://live.staticflickr.com/65535/531 ... fe9f_k.jpg

shaileshs
Ensign
Posts: 99
Joined: Mon Mar 13, 2017 8:14 pm

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by shaileshs » Sun Aug 13, 2023 3:24 pm

Huh? It says it's only 50000 ly across.. So not that big. And it says it's one of the large galaxies in Virgo cluster. Really? Not sure and can't imagine if other galaxies in Virgo cluster (or even otherwise) would be smaller than this..

De58te
Commander
Posts: 584
Joined: Mon Sep 30, 2013 6:35 pm

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by De58te » Sun Aug 13, 2023 3:59 pm

"The Sombrero Galaxy, also known as M104, spans about 50,000 light years across."

There seems to be some discrepancy with the Wikipedia Sombrero Galaxy article. And I quote; [The Sombrero Galaxy] has a D25 isophotal diameter of approximately 29.09 kiloparsecs (94,900 light-years),[1] making it slightly BIGGER in size than the Milky Way. unquote

User avatar
orin stepanek
Plutopian
Posts: 8200
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by orin stepanek » Sun Aug 13, 2023 4:51 pm

sombrero_spitzer_1080.jpg
m104apodsub800c.jpg
Amazing how much the view changes from visible
light to infrared li9ght! I like both views! :D
You do not have the required permissions to view the files attached to this post.
Orin

Smile today; tomorrow's another day!

User avatar
Ann
4725 Å
Posts: 13553
Joined: Sat May 29, 2010 5:33 am

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by Ann » Sun Aug 13, 2023 5:35 pm

The Sombrero Galaxy is two galaxies in one! ✔️☑️
Universe Today wrote:

The Sombrero galaxy has a split personalty, according to recent observations by NASA’s Spitzer Space Telescope. Infrared imaging has revealed a hazy elliptical halo of stars enveloping a dual-structured inner disk; before this, the Sombrero galaxy was thought to be only disk-shaped.
...
Spitzer discerned that the flat disk within the galaxy is made up of two sections — an inner disk composed almost entirely of stars with no dust, and an outer ring containing both dust and stars.
Do check out the dual nature of the disk of M104, courtesy of Jac Berne:

Universe Today wrote:

“The Sombrero is more complex than previously thought,” said Dimitri Gadotti of the European Southern Observatory in Chile and lead author of the report. “The only way to understand all we know about this galaxy is to think of it as two galaxies, one inside the other.”

Although it might seem that the Sombrero is the result of a collision between two separate galaxies, that’s actually not thought to be the case. Such an event would have destroyed the disk structure that’s seen today; instead, it’s thought that the Sombrero accumulated a lot of extra gas billions of years ago when the Universe was populated with large clouds of gas and dust. The extra gas fell into orbit around the galaxy, eventually spinning into a flattened disk and forming new stars.
But the Sombrero Galaxy has not formed any new stars in a long time, and it is a very yellow galaxy. Let's compare the (blurry) GALEX picture of M104 with a somewhat less blurry GALEX picture of the Andromeda Galaxy. In these pictures, blue means hot stars that radiate far ultraviolet light, like B- och O-type stars, and yellow means cool stars that radiate near ultraviolet light, like F, G, K and M-type stars.

M104 GALEX.png
M104 in ultraviolet light by GALEX.
Andromeda Galaxy GALEX.png
The Andromeda Galaxy in ultraviolet light by GALEX.

Even though Andromeda is a quite yellow galaxy, its blue population of hot OB stars shows up very clearly in the GALEX image. In the GALEX picture of M104, however, we strain to see any traces of blue. It is safe to say that if there are any hot OB stars in M104, they are very few and far between.

Ann
You do not have the required permissions to view the files attached to this post.
Color Commentator

User avatar
AVAO
Commander
Posts: 587
Joined: Tue May 28, 2019 12:24 pm
AKA: multiwavelength traveller
Location: Zurich, Switzerland

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by AVAO » Sun Aug 13, 2023 8:12 pm

Ann wrote: Sun Aug 13, 2023 5:35 pm ...
"Although it might seem that the Sombrero is the result of a collision between two separate galaxies, that’s actually not thought to be the case. Such an event would have destroyed the disk structure that’s seen today; instead, it’s thought that the Sombrero accumulated a lot of extra gas billions of years ago when the Universe was populated with large clouds of gas and dust. The extra gas fell into orbit around the galaxy, eventually spinning into a flattened disk and forming new stars."
...

Ann
[/quote]

ThanX Ann

.. as always, for your wonderful explanations and the link to my picture comparison...

The explanation you quoted about the origin doesn't really seem plausible to me. As is clearly visible in NGC 3607, for example, the dust disk is "wrapped" line by line from the inside. This line pattern is also very visible in the Sombrero Galaxy. In the case of the Sombrero galaxy, however, the dust "umbilical cord" is currently interrupted, since it seems that the central "winding motor" has run out of fuel ;-)


NGC 3607 jac berne (flickr) Cerdit original data NASA /ESA (HST)
NGC 383 jac berne (flickr) Credit original data NASA /ESA (HST/VLA)

User avatar
johnnydeep
Commodore
Posts: 2977
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by johnnydeep » Sun Aug 13, 2023 8:31 pm

De58te wrote: Sun Aug 13, 2023 3:59 pm "The Sombrero Galaxy, also known as M104, spans about 50,000 light years across."

There seems to be some discrepancy with the Wikipedia Sombrero Galaxy article. And I quote; [The Sombrero Galaxy] has a D25 isophotal diameter of approximately 29.09 kiloparsecs (94,900 light-years),[1] making it slightly BIGGER in size than the Milky Way. unquote
You beat me to it. I'll chalk it up to a repeat APOD and (hopefully) a more accurate recent reference for the diameter in Wikepedia (*). But if the Sombrero Galaxy really IS only 50 Kly in diameter, it makes it much less impressive in my view.

[ (*) EDIT: the reference for the diameter in Wikipedia is rather old:
"NASA/IPAC Extragalactic Database". Results for M104. Retrieved 2008-07-09." ]

Some more info: from https://esahubble.org/images/opo0328a/, the FOV of the image below is 9.57 x 5.36 arcminutes, which, assuming the distance of 30 Mly is correct, makes the real extent of the image at that distance out to be 87500 x 46700 ly. (I used the calculator at https://www.1728.org/angsize.htm.) So, the diameter of the bulk of what we can see here a lot closer to 50000 ly than it is to 100000 ly. There goes the majesty of the otherwise totally awesome Sombrero! <sigh> :ssmile:

--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

User avatar
Ann
4725 Å
Posts: 13553
Joined: Sat May 29, 2010 5:33 am

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by Ann » Mon Aug 14, 2023 5:04 am

johnnydeep wrote: Sun Aug 13, 2023 8:31 pm
De58te wrote: Sun Aug 13, 2023 3:59 pm "The Sombrero Galaxy, also known as M104, spans about 50,000 light years across."

There seems to be some discrepancy with the Wikipedia Sombrero Galaxy article. And I quote; [The Sombrero Galaxy] has a D25 isophotal diameter of approximately 29.09 kiloparsecs (94,900 light-years),[1] making it slightly BIGGER in size than the Milky Way. unquote
You beat me to it. I'll chalk it up to a repeat APOD and (hopefully) a more accurate recent reference for the diameter in Wikepedia (*). But if the Sombrero Galaxy really IS only 50 Kly in diameter, it makes it much less impressive in my view.

[ (*) EDIT: the reference for the diameter in Wikipedia is rather old:
"NASA/IPAC Extragalactic Database". Results for M104. Retrieved 2008-07-09." ]

Some more info: from https://esahubble.org/images/opo0328a/, the FOV of the image below is 9.57 x 5.36 arcminutes, which, assuming the distance of 30 Mly is correct, makes the real extent of the image at that distance out to be 87500 x 46700 ly. (I used the calculator at https://www.1728.org/angsize.htm.) So, the diameter of the bulk of what we can see here a lot closer to 50000 ly than it is to 100000 ly. There goes the majesty of the otherwise totally awesome Sombrero! <sigh> :ssmile:

Thanks, Johnny! Interestingly, a 2003 Hubblesite caption of a portrait of M104 claims that the diameter of this galaxy is 50,000 ly, but a recent (2021) NASA caption says nothing about the diameter of M104.

I was going to ask someone to calculate the size of M104 based on its apparent size on the sky and its distance. Let's see, Johnny, you calculated the diameter of the APOD at a distance of 30 million light-years, not the size of the visible diameter of the galaxy?

Okay. According to Wikipedia, the apparent size of M104 is 9′ × 4′ — I assume that means 9 x 4 arcminutes? How big is a thing whose apparent diameter is 9 x 4 arcminutes at a distance of 30 million light-years?

Wikipedia talks about the isophotal diameter of M104. This apparently refers to the distance at which the surface brightness of a galaxy drops below a certain value. But take a look at this ESA/Hubble portrait of M104:


We see no signs that the galaxy, so to speak, gradually drops off beyond the well-defined dust lane. M104 appears to end abruptly at the outer edge of the dust lane, as if this dust lane was a piece of string keeping the contents of a parcel safe inside its wrapping. So to find the diameter of M104, it should be enough to calculate the size of the dust lane.

Unless, of course, James Webb is going to show us that M104 is much, much wider than the dust lane fooled us to believe. And indeed, even the old Spitzer Telescope showed us that the the old stellar population of M104 extended beyond the dust lane. Note that the false color blue haze of starlight extends slightly beyond the red-colored dust lane in the APOD:


I'd like to add that Wikipedia says that the isophotal diameter of the Milky Way is smaller than that of M104, corresponding to 26.8 ± 1.1 kiloparsecs (87,400 ± 3,590 light-years) versus 29.09 kiloparsecs (94,900 light-years) for M104.

Okay!! I have found the source for the claim that the diameter of M104 is almost 100.000 light-years. It's the NED database. If you scroll down almost to the bottom, you will find QUICK-LOOK ANGULAR & PHYSICAL DIAMETERS for MESSIER 104.

Here it says that the K (infrared) diameter of M104 is 32.32 kiloparsecs. That does indeed correspond to about 100,000 light-years. And the B diameter for M104 is 29.09 kiloparsecs (or 94,900 light-years), according to NED.

Ann
Color Commentator

User avatar
johnnydeep
Commodore
Posts: 2977
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by johnnydeep » Mon Aug 14, 2023 12:19 pm

Ann wrote: Mon Aug 14, 2023 5:04 am
johnnydeep wrote: Sun Aug 13, 2023 8:31 pm
De58te wrote: Sun Aug 13, 2023 3:59 pm "The Sombrero Galaxy, also known as M104, spans about 50,000 light years across."

There seems to be some discrepancy with the Wikipedia Sombrero Galaxy article. And I quote; [The Sombrero Galaxy] has a D25 isophotal diameter of approximately 29.09 kiloparsecs (94,900 light-years),[1] making it slightly BIGGER in size than the Milky Way. unquote
You beat me to it. I'll chalk it up to a repeat APOD and (hopefully) a more accurate recent reference for the diameter in Wikepedia (*). But if the Sombrero Galaxy really IS only 50 Kly in diameter, it makes it much less impressive in my view.

[ (*) EDIT: the reference for the diameter in Wikipedia is rather old:
"NASA/IPAC Extragalactic Database". Results for M104. Retrieved 2008-07-09." ]

Some more info: from https://esahubble.org/images/opo0328a/, the FOV of the image below is 9.57 x 5.36 arcminutes, which, assuming the distance of 30 Mly is correct, makes the real extent of the image at that distance out to be 87500 x 46700 ly. (I used the calculator at https://www.1728.org/angsize.htm.) So, the diameter of the bulk of what we can see here a lot closer to 50000 ly than it is to 100000 ly. There goes the majesty of the otherwise totally awesome Sombrero! <sigh> :ssmile:

Thanks, Johnny! Interestingly, a 2003 Hubblesite caption of a portrait of M104 claims that the diameter of this galaxy is 50,000 ly, but a recent (2021) NASA caption says nothing about the diameter of M104.

I was going to ask someone to calculate the size of M104 based on its apparent size on the sky and its distance. Let's see, Johnny, you calculated the diameter of the APOD at a distance of 30 million light-years, not the size of the visible diameter of the galaxy?

Okay. According to Wikipedia, the apparent size of M104 is 9′ × 4′ — I assume that means 9 x 4 arcminutes? How big is a thing whose apparent diameter is 9 x 4 arcminutes at a distance of 30 million light-years?

Wikipedia talks about the isophotal diameter of M104. This apparently refers to the distance at which the surface brightness of a galaxy drops below a certain value. But take a look at this ESA/Hubble portrait of M104:


We see no signs that the galaxy, so to speak, gradually drops off beyond the well-defined dust lane. M104 appears to end abruptly at the outer edge of the dust lane, as if this dust lane was a piece of string keeping the contents of a parcel safe inside its wrapping. So to find the diameter of M104, it should be enough to calculate the size of the dust lane.

Unless, of course, James Webb is going to show us that M104 is much, much wider than the dust lane fooled us to believe. And indeed, even the old Spitzer Telescope showed us that the the old stellar population of M104 extended beyond the dust lane. Note that the false color blue haze of starlight extends slightly beyond the red-colored dust lane in the APOD:


I'd like to add that Wikipedia says that the isophotal diameter of the Milky Way is smaller than that of M104, corresponding to 26.8 ± 1.1 kiloparsecs (87,400 ± 3,590 light-years) versus 29.09 kiloparsecs (94,900 light-years) for M104.

Okay!! I have found the source for the claim that the diameter of M104 is almost 100.000 light-years. It's the NED database. If you scroll down almost to the bottom, you will find QUICK-LOOK ANGULAR & PHYSICAL DIAMETERS for MESSIER 104.

Here it says that the K (infrared) diameter of M104 is 32.32 kiloparsecs. That does indeed correspond to about 100,000 light-years. And the B diameter for M104 is 29.09 kiloparsecs (or 94,900 light-years), according to NED.

Ann
Not to belabor this much longer, but I said:
Some more info: from https://esahubble.org/images/opo0328a/, the FOV of the image below is 9.57 x 5.36 arcminutes, which, assuming the distance of 30 Mly is correct, makes the real extent of the image at that distance out to be 87500 x 46700 ly.
To which you replied:
I was going to ask someone to calculate the size of M104 based on its apparent size on the sky and its distance. Let's see, Johnny, you calculated the diameter of the APOD at a distance of 30 million light-years, not the size of the visible diameter of the galaxy?

Okay. According to Wikipedia, the apparent size of M104 is 9′ × 4′ — I assume that means 9 x 4 arcminutes? How big is a thing whose apparent diameter is 9 x 4 arcminutes at a distance of 30 million light-years?
So, yes, I assumed the FOV data at the esahubble.org link was for the square extent of the image, not for the galaxy that happens to be in it. Here's how it presented that data:
Coordinates
Position (RA): 12 39 59.29
Position (Dec): -11° 37' 21.89"
Field of view: 9.57 x 5.36 arcminutes
Orientation: North is 5.0° right of vertical
So, what's the correct interpretation here? Is the angular FOV measurement of the image rectangle as I took it to be, or is it of the galaxy shown in it? I had assumed that unless otherwise stated, the FOV of a particular image from a particular telescope is always of the total rectangular extent of it, since that is presumably precisely known, and independent of distance.
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

User avatar
Chris Peterson
Abominable Snowman
Posts: 18332
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by Chris Peterson » Mon Aug 14, 2023 1:35 pm

johnnydeep wrote: Mon Aug 14, 2023 12:19 pm
So, yes, I assumed the FOV data at the esahubble.org link was for the square extent of the image, not for the galaxy that happens to be in it. Here's how it presented that data:
Coordinates
Position (RA): 12 39 59.29
Position (Dec): -11° 37' 21.89"
Field of view: 9.57 x 5.36 arcminutes
Orientation: North is 5.0° right of vertical
So, what's the correct interpretation here? Is the angular FOV measurement of the image rectangle as I took it to be, or is it of the galaxy shown in it? I had assumed that unless otherwise stated, the FOV of a particular image from a particular telescope is always of the total rectangular extent of it, since that is presumably precisely known, and independent of distance.
I've never seen FOV refer to anything other than the physical extents of the image. Not any structure within the image. (The angular extent of anything in the image is also precisely known and independent of distance, of course... but that isn't reasonably labeled "FOV".)
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com

User avatar
johnnydeep
Commodore
Posts: 2977
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by johnnydeep » Mon Aug 14, 2023 1:40 pm

Chris Peterson wrote: Mon Aug 14, 2023 1:35 pm
johnnydeep wrote: Mon Aug 14, 2023 12:19 pm
So, yes, I assumed the FOV data at the esahubble.org link was for the square extent of the image, not for the galaxy that happens to be in it. Here's how it presented that data:
Coordinates
Position (RA): 12 39 59.29
Position (Dec): -11° 37' 21.89"
Field of view: 9.57 x 5.36 arcminutes
Orientation: North is 5.0° right of vertical
So, what's the correct interpretation here? Is the angular FOV measurement of the image rectangle as I took it to be, or is it of the galaxy shown in it? I had assumed that unless otherwise stated, the FOV of a particular image from a particular telescope is always of the total rectangular extent of it, since that is presumably precisely known, and independent of distance.
I've never seen FOV refer to anything other than the physical extents of the image. Not any structure within the image. (The angular extent of anything in the image is also precisely known and independent of distance, of course... but that isn't reasonably labeled "FOV".)
Thanks. That's what I thought. So, the conclusion here is that the Sombrero galaxy, at least with respect to the well defined dust ring that seems to circumscribe it, is closer in diameter to 50 Kly than it is to 100 Kly.
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

User avatar
MarkBour
Subtle Signal
Posts: 1377
Joined: Mon Aug 26, 2013 2:44 pm
Location: Illinois, USA

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by MarkBour » Tue Aug 15, 2023 12:02 am

Chris Peterson wrote: Sun Aug 13, 2023 1:14 pm
JimB wrote: Sun Aug 13, 2023 8:28 am Beautiful image!

But it looks like the central region of this galaxy is pretty empty of stars - is this really the case?
It's an illusion. The central region is nothing but stars!
Thanks, Chris. When I look at this flat image, a 2-dimensional elliptical region, or oval, appears to be the main illuminated area. And you're pointing out that what we might mistake for a "glow" in empty space, is actually the effect of a vast number of stars that are too far away to be distinguished into points. And what seems the almost obvious mental interpretation is that these stars actually inhabit a 3-D ellipsoid, or somewhat "squashed sphere" shape in space. I think the overall shape is what about everyone would have guessed immediately, but it's very interesting to imagine the vast number of stars that fill this region and together create the "glow". Perhaps one can even determine the number of stars from measurements of this overall glow, though I am not thinking of trying that.

What I am most curious about today is the dark ring -- the galaxy's singular dust lane. I have a basic question about it. When we see such a dust lane, can we surmise much about its origin? Is it the debris from one or more prior generations of stars that have exploded? If so, why would it be in this position for this galaxy? Why wouldn't it form the same shape as the distribution of stars, and be all over the place?
Mark Goldfain

User avatar
Ann
4725 Å
Posts: 13553
Joined: Sat May 29, 2010 5:33 am

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by Ann » Tue Aug 15, 2023 7:23 am

Ann wrote: Sun Aug 13, 2023 5:35 pm
But the Sombrero Galaxy has not formed any new stars in a long time, and it is a very yellow galaxy. Let's compare the (blurry) GALEX picture of M104 with a somewhat less blurry GALEX picture of the Andromeda Galaxy. In these pictures, blue means hot stars that radiate far ultraviolet light, like B- och O-type stars, and yellow means cool stars that radiate near ultraviolet light, like F, G, K and M-type stars.

M104 GALEX.png
M104 in ultraviolet light by GALEX.
Andromeda Galaxy GALEX.png
The Andromeda Galaxy in ultraviolet light by GALEX.

Even though Andromeda is a quite yellow galaxy, its blue population of hot OB stars shows up very clearly in the GALEX image. In the GALEX picture of M104, however, we strain to see any traces of blue. It is safe to say that if there are any hot OB stars in M104, they are very few and far between.

Ann
Sorry to quote myself, but I have to take back what I said. No: M-type stars do not emit any appreciable amounts of near ultraviolet light. M-type stars barely emit any blue light, let alone near ultraviolet light.


Why do you think M-type red supergiant Antares is surrounded by a yellow nebula? It is because the dust in this area scatters light from Antares, and such nebulas, reflection nebulas, typically scatter blue light. But in the case of Antares, there is no blue light there to scatter, so the reflection nebula surrounding Antares is yellow. Note however the typically blue reflection nebula surrounding Rho Ophiuchi (to the upper right of Antares).

No, the near ultraviolet light detected by GALEX was preferentially emitted by stars of spectral classes F and G, and to some extent by early K-type stars like Pollux. But mostly by stars of spectral classes F and G. As for A-type stars, I guess that an early A-type star like Vega emits an appreciable amount of far ultraviolet light, whereas a late A-type star like Altair undoubtedly emits a lot of near ultraviolet light.

Okay, one more correction. Highly evolved supergiant M-type stars may actually emit ultraviolet light of ionized iron, FeII. Antares, in fact, does so. Also a much more modest M-type star, Mirach, Beta Andromedae, also does so. Perhaps this is a typical feature of M-type giants.

And I found an extremely interesting spectrum of a very cool Mira-type variable, SS Virginis. You can see from its spectrum that it emits barely any blue light at all (between 380 and 470 nm), but at far left, at near ultraviolet, its emission goes up.


Well, that's amazing. Maybe GALEX can detect these very red stars after all! It could sure detect circa M7-type star Mira itself as it rushes through space, periodically casting off parts of its outer layers which then interact with the surrounding medium, creating ultraviolet light.


So, yeah. Maybe I didn't need to correct myself about the near ultraviolet emission of M-type stars after all.

Ann
Color Commentator

User avatar
VictorBorun
Captain
Posts: 1072
Joined: Fri Oct 16, 2020 10:25 pm

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by VictorBorun » Wed Aug 16, 2023 11:54 pm

MarkBour wrote: Tue Aug 15, 2023 12:02 am
Chris Peterson wrote: Sun Aug 13, 2023 1:14 pm
JimB wrote: Sun Aug 13, 2023 8:28 am Beautiful image!

But it looks like the central region of this galaxy is pretty empty of stars - is this really the case?
It's an illusion. The central region is nothing but stars!
Thanks, Chris. When I look at this flat image, a 2-dimensional elliptical region, or oval, appears to be the main illuminated area. And you're pointing out that what we might mistake for a "glow" in empty space, is actually the effect of a vast number of stars that are too far away to be distinguished into points. And what seems the almost obvious mental interpretation is that these stars actually inhabit a 3-D ellipsoid, or somewhat "squashed sphere" shape in space. I think the overall shape is what about everyone would have guessed immediately, but it's very interesting to imagine the vast number of stars that fill this region and together create the "glow". Perhaps one can even determine the number of stars from measurements of this overall glow, though I am not thinking of trying that.

What I am most curious about today is the dark ring -- the galaxy's singular dust lane. I have a basic question about it. When we see such a dust lane, can we surmise much about its origin? Is it the debris from one or more prior generations of stars that have exploded? If so, why would it be in this position for this galaxy? Why wouldn't it form the same shape as the distribution of stars, and be all over the place?
A short-lived accretion ring like Saturn's one comes to mind.
Neither dark matter halo no stellar population feels any friction or viscosity; this fact is proved by all the old elliptic galaxies.
For stars and dust to form a flat ring you need a dense, viscous gas/plasma ring in the first place, and for that you need a peaceful time with no tsunami from the central black hole: so the gas/plasma, coming in to a peaceful galaxy, get to go round the core a several times and be shaped by the friction into a flat ring.

It seems to me logical that a disk galaxy with a large core is a result of 10 billion years old galaxy with a violent past (now the core) later attracting cluster media and dwarf galaxies to form a short-lived ring for 1 billion years.

A random minor pair of jets from the central black hole will not blow up the disk altogether and only create a pair of radial arms that will differentially rotate and become spiral arms. Then again there can be no minor jets and no arms in the accretion ring.

What stars and dust we can see in the flat ring just marks the densest part of the ring; the gas/plasma ring can be not so flat and not so distinct as the visible part of it suggests to our eyes.

Inner parts of a short-lived flat ring should be first to disappear. They will be first to create their own supernovas and kilonovas, that will blow away the gas/plasma of the ring. Then after a while the long-lived stellar population will evaporate from the plane and join the elliptic stellar cloud, and there will be too little gas/plasma left to form new stars in the plane.

User avatar
Ann
4725 Å
Posts: 13553
Joined: Sat May 29, 2010 5:33 am

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by Ann » Thu Aug 17, 2023 3:18 pm

MarkBour wrote: Tue Aug 15, 2023 12:02 am
What I am most curious about today is the dark ring -- the galaxy's singular dust lane. I have a basic question about it. When we see such a dust lane, can we surmise much about its origin? Is it the debris from one or more prior generations of stars that have exploded? If so, why would it be in this position for this galaxy? Why wouldn't it form the same shape as the distribution of stars, and be all over the place?
Universe Today claimed that M104 formed in, basically, this way:

Formation of galaxy M104.png

Or, in other words: The galaxy that would become M104 was originally an elliptical galaxy. But there were large gas clouds in the vicinity of this elliptical galaxy. The gas fell into orbit around the galaxy, eventually creating the dust lane that we can see today.

Ann
You do not have the required permissions to view the files attached to this post.
Color Commentator

User avatar
MarkBour
Subtle Signal
Posts: 1377
Joined: Mon Aug 26, 2013 2:44 pm
Location: Illinois, USA

Re: APOD: The Sombrero Galaxy in Infrared (2023 Aug 13)

Post by MarkBour » Wed Aug 30, 2023 4:14 pm

Thanks, Victor and Ann.
Mark Goldfain