From The European Southern Observatory
Due to its particular shape Messier 104 is widely known as the "Sombrero" (the Mexican hat). A great amount of fine detail is revealed, from the structures in the pronounced dust band in the equatorial plane, to many faint background galaxies that shine through the outer regions. It is located in the constellation Virgo at a distance of about 50 million light-years. The overall "sharpness" of this color image corresponds to about 0.7 arcsec which translates into a resolution of about 170 light-years at that distance. This galaxy is notable for its dominant nuclear bulge, composed primarily of mature stars, and its nearly edge-on disk composed of stars, gas, and intricately structured dust. The complexity of this dust, and the high resolution of this image, is most apparent directly in front of the bright nucleus, but is also very evident as dark absorbing lanes throughout the disk. A significant fraction of the galaxy disk is even visible on the far side of the source, despite its massive bulge. This image of Messier 104 is a composite of three exposures in different wavebands.: V (central wavelength 554 nm; 112 nm Full Width Half Maximum (FWHM); exposure time 120 sec; here rendered as blue), R-band (657 nm; 150 nm FWHM; 120 sec; green) and I-band (768 nm; 138 nm FWHM, 240 sec; red). North is up and East is left..
A large number of small and slightly diffuse sources can be seen as a swarm in the halo of Messier 104. Most are globular clusters, similar to those found in our own Galaxy. Measurements reveal a steep increase in the mass-to-light ratio and increasing stellar speeds near the nucleus of Messier 104. This is indicative of the presence of a massive black hole at the center, estimated at about 109 solar masses.
The radio properties of Messier 104 are unusual for a spiral galaxy - it has a variable core. The optical spectrum of the central region displays emission lines from hot gas (of the "LINER" type - Low Ionization Nuclear Emission line Region). This points to Messier 104 harboring a weak Active Galactic Nucleus (AGN). Although more commonly known from the much more luminous and distant quasars and powerful radio galaxies, the weak AGN in this galaxy lies at the opposite extreme: the most likely explanation being a central black hole accreting circumnuclear matter at a slow pace.
Based on press release with ESO PR Photo 07a/00
Catalog #: Photo 07a/00
Target Name: Fine Shades of a Sombrero: A New Look at an Unusual Galaxy
Last Modified On: Sunday, December 17, 2000