Image Centered on Ra.12 : 19.0 (h:m) Dec +47 : 18 (deg:m)
M106 (NGC 4258)
Information: ( from the seds online website )
Discovered by Pierre Méchain in 1781.
The bright Sb spiral galaxy M106 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
homes M108 and M109, while Tully lists it in the Coma-Sculptor cloud, and Fouque
et.al (1992) in a group called Canes Venatici II (CVn II) group or M106 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 the line of sight, many
features resemble what we know from the Andromeda galaxy M31. As Alan Sandage
mentions in the Hubble Atlas of Galaxies, this orientation explains partly why
the dust lanes are so 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
apparently end 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 million
years. 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 the radio
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
called Seyfert galaxies. Nevertheless, only few modern studies of Seyfert
galaxies include it, although its nucleus is classified as Seyfert 1.9,
according to the NED data of this galaxy.
M106 is one of Pierre Méchain's findings, which were later appended as
additional objects to Charles Messier's catalog. In case of M106, it was Helen
Sawyer Hogg who added it together with M105 and M107 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 when cataloging it on March 9,
1788.
In 1995, investigations with the Very Large Baseline Array radio telescope
equipment gave evidence that M106 is possibly the home of a massive dark
objects, which could be traced to the lowest distance from the center ever
possible up to now: 36 million solar masses apparently reside within a volume of
about 1/24 to 1/12 light year radius (27,000 to 54,000 AU). This was 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 in his PhD
thesis (Herrnstein 1997, and NRAO 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, Jon Morse,
and Patrick Shopbell in Sky & Telescope, Nov 1995 (p 20). This makes it similar
to the central "engines" in other active galaxies.
A 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").
Optics and exposure data
Telescope Celestron 9.25 SCT operating at f6.3 with a Meade focal Reducer
Mount, Losmandy G11 with Gemini control electronics
Imager, Starlite-Xpress SXV-h9 using Astronomiks RGB optical filters.
Exposure data, lum 90 minutes RGB 45 min each channel
Images acquired with Astroart and aligned then combined in Maxim Dl. Final RGB composite processed with Photoshop Cs
Images acquired from my backyard - " Dirt Clod Observatory" in Antelope California
