Movatterモバイル変換

Discovered by Pierre Méchain in 1781.

The bright Sb spiral galaxy Messier 106 (M106, NGC 4258) is perhaps about 21 to 25 million light years distant. It is receding at 537 km/sec. Sandage suspects it may be a member of the Ursa Major cloud, a loose agglomeration of galaxies which probably also homesM108 andM109, while Tully lists it in the Coma-Sculptor cloud, andFouqueet.al (1992) in a groupcalled Canes Venatici II (CVn II) group orM106 group of galaxies. While M106 is usually classified as peculiar "normal" spiral of type Sb (or Sbp), Tully classifies it as SABbc, i.e., intermediate between Sb and Sc, and intermediate between normal and barred spirals.

As its equatorial plane is similarly inclined to theline of sight, many features resemble what we know from the Andromeda galaxyM31. As Alan Sandage mentions in the HubbleAtlas of Galaxies, this orientation explains partly why the dust lanes areso prominent in this galaxy. They form a spiral pattern which can be traced well into its bright central region to the core. The spiral arms apparentlyend in bright blue knots. These knots are most probably young star clusters which are dominated by their very hot, brightest and most massive stars;the occurance of these hot stars indictes that these clusters cannot be very old, as such massive stars have only a short lifetime of a few millionyears. So the blue knots show us the regions of very recent star formation!

Following the spiral arms in the sense of rotation, and most conspicuous on the right of our image, is the yellowish remnant of an older spiral arm. The color of this arm indicates that its more massive stars have ceased to shine long ago, the color of the remaining ones sums up to the yellow-greenish appearance. The age of the stellar population in this fossil spiral arm is estimated by J.D. Wray to amount several hundred million years.

Since the 1950s, M106 has been known to have a much larger extent in theradio radiation than in visual light. In 1943,Carl K. Seyfert had listed this galaxy among the galaxies with emission line spectra from their nuclei,which are now calledSeyfert galaxies. Nevertheless, only few modern studies of Seyfert galaxies include it, although its nucleus is classified as Seyfert 1.9, according to theNED data of this galaxy.

M106 is one ofPierre Méchain'sfindings, which were later appended asadditional objects toCharles Messier'scatalog. In case of M106, it wasHelen Sawyer Hogg who added ittogether withM105 andM107 in 1947, but it appears reasonable to assume that already Méchain had intended to add it to a future edition.William Herschel had numbered it H V.43 whencataloging it on March 9, 1788.

In 1995,investigations with the Very Large Baseline Array radio telescopeequipment gave evidence that M106 is possibly the home of a massive darkobjects, which could be traced to the lowest distance from the center everpossible up to now: 36 million solar masses apparently reside within avolume of about 1/24 to 1/12 light year radius (27,000 to 54,000 AU). Thiswas then the densest matter concentration ever detected.

The dense disk around this object works as a maser (Microwave Amplifier by Stimulated Emission of Radiation, i.e. a microwave laser). Thus nuclear maser ring allows a geometric distance measurement, independent of other distance indicators such as Cepheid variables, given by James Herrnstein inhis PhD thesis (Herrnstein 1997, andNRAO Press Release).He obtained a distance value of 7.3 +/- 0.4 Mpc (23.8 +/- 1.3 Mly), stated to fit with available Cepheid data.

The active center also emits jets, as was described by Brent Tully, JonMorse, and Patrick Shopbell inSky & Telescope, Nov 1995 (p 20).This makes it similar to the central "engines" in other active galaxies.

Two supernovae have been found in M106:

• The first supernova (1981K) occured im M106 in August 1981 and reached 16th magnitude (Kenneth Glyn Jones's book, in the table on page 32, misprints "1931K").
• Supernova 2014bc was found in M106 by Lick Observatory Supernova Search (LOSS) on May 20, 2014 when it was already 40 days old and at mag 14.8; this one was classified as of Supernova Type II.

NGC Online data for M106

References:

• P. Fouque, E. Gourgoulhon, P. Chamaraux and G. Paturel, 1992. Groups of Galaxies within 80 Mpc. II. The catalogue of groups and group members. Astronomy and Astrophysics Supplement Series, Vol. 93, No. 2, p. 211-233 (May 1992) [ADS: 1992A&AS...93..211F]
• James Rezso Herrnstein, 1997. Observations of the Sub-Parsec Maser Disk in NGC 4258. PhD thesis, Harvard University (08/1997) [ADS: 1997PhDT........10H] - thanks to Bill Keel for pointing to this reference.
• NRAO, 1997. Radio Astronomers Set New Standard for Accurate Cosmic Distance Measurement.NRAO Press Release of June 1, 1999.

---

Hartmut Frommert
Christine Kronberg
[contact]

Last Modification: May 26, 2014

---

[8]ページ先頭

---

©2009-2025 Movatter.jp