HII regions in M81

[Ivan Maly]

In the spirit of some recent material here, a deeper dive into one of the most observed objects. Last night I was able to hunt down a few of the small HII regions in M81, from the 1983 Hodge-Kennicutt catalog. 20", 250x, SQM 21.6. It's a bit hard to match HK's coordinates to the broadband image. Most identifications are from the Stoyan Atlas of the Messier Objects and two more (305 and 435) are my best attempt using Aladin. Most of these presented a nonstellar or "unstellar" appearance, and the putative foreground star on the N edge of region 746 was also seen, as was the extended object immediately WNW of 652. I'd be interested to hear about other observations of these, and about a method of identification that others use for such objects.

[Howard B]

Hi Ivan,

I used Aladin to identify HII regions in M81, and the regions I've seen are shown here: http://www.skyandtelescope.com/wp-co...82-Details.pdf

[Ivan Maly]

Thanks, that's a great approach. I remember your observations now. Incidentally, I saw your region G last night but thought it was a star. Will get back to it.

[yapo]

Hi Ivan,

Incidentally I was writing an article about Holmberg IX so the HII regions weren't too far from that.

I use NASA's NED for HII regions, or SIMBAD, as well as the ADS to get to the professional articles about them.

I have recorded 7 HII regions (or groups of HII regions)/stellar associations with my 17.5" at 271x.

In the hook of the northern arm : (PSK 139), (PSK 170 + PSK 178 + PSK 177) and (PSK 97 + PSK 72)
In the prolongation of this arm, west of the main core and going south : (PSK 15 + [l92b] 6), ([ZH91] M 81 394 + PSK 17 + PSK 16 + PSK 26) and (PSK 29 +
HK NGC 3031 741 + PSK 30)
In the south arm going E and reaching north, around a mag.14 star, the HII regions are not separated but they enhance the arm locally : PSK 414 + PSK 416 +PSK 417 + [l92b] 153 + 155 + 156

clear skies,
Yann

[Bertrand Laville]

Hi All,

Looking back along the «*off the beatten path*», I noticed a recent thread about the HII regions in M 81.
It seemed to me intresting to retrieve the HII regions I was able to see during a detailed observation of the galaxy, some years ago, but without knowing them, and of course without looking for them,
Here is my drawing, with my 25'' Obsession*:

M 81 T635 BL 2013 01 09.jpg

And the HII regions retrieved on the drawing*:

M 81 T635 BL 2013 01 09 HII.jpg

There are four small patches, labelled D, E, F, and J, and 6 larger zones, where HII regions are not individualized, but where their density is such that they enhanced the brightness of the area. They are A, B, C, G, H, and I.
HII regions of patches and zones are identified according two catalogs*:

[HK83]: Kennicutt, R. C., Hodge P. W., 1980ApJ, 241, 573K
PSK: Petit, H., Sivan, J.-P, & Karachentsev, I.D., 1988A&AS, 74, 475P
All details of the labelling at*: http://www.deepsky-drawings.com/m-081-t635/dsdlang/en

Clear skies
Bertrand
http://www.deepsky-drawings.com/dsdlang/en/

[Ivan Maly]

Great stuff, Bertrand. The brighter "star" between H and G may be an HII region, too - I am writing from memory.

[Bertrand Laville]

You're right, Ivan, but more or less !
The hereunder crop of a large image of Nasa shows that the "brighter" star in a real star, but surrounded by a weak HII region on the left, and a stronger one on the right;

M 81 Nasa large.jpg

The PSK catalogue labels the left one 444, and the bright one 416.
I have pointed in blue the three stars which can be easely seen on the Nasa image, in order to well identify the area.

M 81 HII regions PSK cat.jpg

Regards
Bertrand
http://www.deepsky-drawings.com/dsdlang/en/

[Ivan Maly]

Actually, the "star" is one of the nonstellar objects in M81, identified in the survey of globular cluster candidates by Perelmuter and Racine (1995), NED name MESSIER 081:[PR95] 50739. Another one, which I have seen in 20", is 51072 in the northern part of the galaxy.