Messier 65 (M65) in the Leo Triplett
Spiral Galaxy, (NGC 3623), type Sa
Right Ascension 11:18.9
Declination +13:05
Distance 35000 (kly)
Visual Brightness - 9.3 (mag)
Apparent Dimension -8x1.5 (arc min)
Background description
Messier 65 (M65, NGC 3623), together with its neighbors M66 and NGC 3628, forms
a most conspicuous triplet of galaxies, the Leo Triplett or M66 group, located at a distance of
about 35 million light years so that light recorded today left after the fall of the dinosaurs but
when many land mammals were just evolving on Earth.
Although it is close to and thus under the gravitational influence of its neighbors, M65
looks like a very "normal" Sa type spiral and seems to have felt little influence. It has a
prominent central lens and tightly wound spiral arms, plus a prominent dust lane marking the
facing edge. The luminous disk is dominated by a smooth old stellar population. Near the
lane, some knots are visible, which, according to J.D. Wray, may be associated with star
forming regions. The lane may hide regions of star formation usually associated with such
features in spiral galaxies.
M65, together with its neighbor, M66, has been discovered by Charles Messier, who
cataloged it on March 1, 1780, describes it as "very faint nebula without stars." Because of a
dubious error, Admiral Smyth has assigned this discovery of M65 and M66 (and M68) to
Pierre Méchain, a view which was adopted by Kenneth Glyn Jones some when in the 1960s,
and consequently, in many sources, despite the fact that Messier doesn't acknowledge such a
prior sighting, which he did in all other cases.
Halton Arp includes M65 in his entry number 317 of his Catalogue of Peculiar
Galaxies, which denotes the Leo Triplett.
Multiwavelength observations
X-Ray image: ROSAT
The x-ray image reveals very little emission. The core of M65 is faintly seen, but there is no
significant x-ray emission from the rest of the galaxy disk.
Visible image: DSS
Color image: AOO
The DSS visible-light photograph is probably (we think) over-exposed in the central
regions, and most of the galaxy's structural details are lost in the saturated light. Nonetheless,
can be see a vertical lane of dust in the eastern (left-side) edge of the galaxy. The dust lane is
much more prominent in the color image from the Anglo-Australian Observatory. In this
photograph, dust can easily be seen throughout the entire disk of the galaxy.
Near-Infrared image: 2MASS
Mid-Infrared image: IRAS
Far-Infrared image: IRAS
Near-infrared light is ideal for tracing the old stellar population in galaxies, and hence
the 2MASS image reveals an impressive degree of structure within the galaxy disk, despite its
short exposure time of 7.8 seconds. The dark lane of dust running north-south along the left
edge of the galaxy.
Messier 65 is barely seen at a wavelength of 25 microns. Newborn stars normally
appear bright at this mid-infrared wavelength, and we are left to conclude that the rate of star
formation in M65 is rather low.
The far-infrared image is of relatively poor. The central core of M65 is clearly the
brightest region in the far-infrared, corresponding to the region of highest stellar density.
Overall, the long-wavelength IR emission from M65 is rather modest, due to relatively low
rates of ongoing star formation.
Radio image: NVSS
The radio image reveals emission along the vertical extent of the galaxy. From the
description of this image we know if, the brightest source of radio emission near the galaxy is
not at the center, but is located (yellow/orange peak) about 2 arcminutes to the southsoutheast, at approximately the 7 o'clock position. It is not clear what is the source of this
emission. A search of the exhaustive NASA Extragalactic Database (NED) fails to find any
cataloged astronomical object outside our Galaxy corresponding to the position of the modest
radio peak. A similar search of the SIMBAD database of stellar objects fails to reveal the
source of the emission. Meanwhile, the bright source of radio emission to the northwest
(upper right corner) is probably associated with a background object, such as a distant and
uncataloged quasar.
This report were done by:
Malgorzata Mergo (teacher),
Pawel Kosiński, Bartłomiej Krysa, Dawid Rodzik
Zespol Szkol im. Mikolaja Kopernika
Bełżyce
Poland