by Ann » Fri Mar 12, 2021 6:14 am
I'm glad to see a picture by Wissam Ayoub become an APOD!
Wissam has recently started posting pictures at Starship Asterisk*, and he has posted some really fine images here!
The most interesting aspect of Wissam Ayoub's image, in my opinion, is the little blue satellite galaxy, Holmberg IX (bottom). Undoubtedly this galaxy has formed as a result of the interaction between M81 and its two relatively large neighbors,
M82 and
NGC 3077.
If you check out the neutral hydrogen radio data picture at right by de Blok et al, you can see how neutral hydrogen flows between these three galaxies. Obviously this gas has accumulated in certain places and helped give rise to Holmberg IX. In the picture by de Blok et al, Holmberg IX is located to the left of M81 (where the gas, shown in blue, is "thicker").
There is another obvious blue gaseous "concentration" in the de Blok et al image, and it is located above the position of Holmberg IX in the picture by de Blok et al. That other concentration is (a part of) Arp's Loop. Bernard Miller has taken a fine picture of M81 with both Holmberg IX and Arp's Loop.
In Bernard Miller's image, Holmberg IX is located above M81 and Arp's Loop is to the right of Holmberg IX. As you can see in Bernard Miller's image, the gas in Holmberg IX has given birth to a good number of young stars, but there are not many young stars in Arp's Loop. But there are indeed a few young stars there.
If anyone is interested in reading about dwarf galaxies in the M81 Group, I recommend the paper
Stellar Population and Structural Properties of Dwarf Galaxies and Young Stellar Systems in the M81 Group by Sakurako Okamoto et al.
Ann
I'm glad to see a picture by Wissam Ayoub become an APOD! 😀 Wissam has recently started posting pictures at Starship Asterisk*, and he has posted some really fine images here! 😀
[float=left][img3="M81 with its small blue satellite galaxy, Holmberg IX. Photo: Wissam Ayoub."]https://apod.nasa.gov/apod/image/2103/BodesGalaxyM81_1024.jpg[/img3][/float] [float=right][img3="Interaction between M81, M82 and NGC 3077 as seen in neutral hydrogen radio emission. Source: HI data of the M81 Triplet (M81, M82, NGC3077),
de Blok et al. 2018, Astrophysical Journal, 865, 26"]https://www.astron.nl/~blok/M81data/_Media/m81robsdss_med_hr.jpeg[/img3][/float]
The most interesting aspect of Wissam Ayoub's image, in my opinion, is the little blue satellite galaxy, Holmberg IX (bottom). Undoubtedly this galaxy has formed as a result of the interaction between M81 and its two relatively large neighbors, [url=https://www.nasa.gov/feature/goddard/2017/messier-82-the-cigar-galaxy]M82[/url] and [url=https://en.wikipedia.org/wiki/NGC_3077#/media/File:NGC_3077_Hubble.jpg]NGC 3077[/url].
If you check out the neutral hydrogen radio data picture at right by de Blok et al, you can see how neutral hydrogen flows between these three galaxies. Obviously this gas has accumulated in certain places and helped give rise to Holmberg IX. In the picture by de Blok et al, Holmberg IX is located to the left of M81 (where the gas, shown in blue, is "thicker").
[float=left][img3="M81 with Holmberg IX (top) and Arp's Loop (top right). Photo: Bernard Miller."]https://www.starobserver.org/image/1304/m81loop_miller_960.jpg[/img3][/float]
[clear][/clear]
There is another obvious blue gaseous "concentration" in the de Blok et al image, and it is located above the position of Holmberg IX in the picture by de Blok et al. That other concentration is (a part of) Arp's Loop. Bernard Miller has taken a fine picture of M81 with both Holmberg IX and Arp's Loop.
In Bernard Miller's image, Holmberg IX is located above M81 and Arp's Loop is to the right of Holmberg IX. As you can see in Bernard Miller's image, the gas in Holmberg IX has given birth to a good number of young stars, but there are not many young stars in Arp's Loop. But there are indeed a few young stars there.
If anyone is interested in reading about dwarf galaxies in the M81 Group, I recommend the paper [url=https://iopscience.iop.org/article/10.3847/1538-4357/ab44a7]Stellar Population and Structural Properties of Dwarf Galaxies and Young Stellar Systems in the M81 Group[/url] by Sakurako Okamoto et al.
Ann