Characteristics
NGC 1553 is an early type galaxy with a luminosity of 4×1010 L⊙. It has been detected in H I but has an H I mass to B-band luminosity ratio (MHI/LB) of less than 0.01. NGC 1553's ultraviolet spectrum shows weak flux under the main-sequence turn off at around 2,400 A°. This is characteristic of old intermediate populations of quiescent lenticular galaxies.
NGC 1553 has an especially well developed lens (~36″) component of nearly constant surface brightness that is found between the bulge and the exponential disk. Its lens is similar to what is found in NGC 3945 and its inner parts are very hot.
NGC 1553 has associated with itself cool gas and dust. It can also be seen in infrared and is a weak radio source. Hubble observations in 2000 revealed an inner torus-like dust lane about 3″ across at the galaxy's center.
Chandra X-ray imaging of NGC 1553 show diffuse hot gas making up 70% of the emissions, dotted with many point-like sources (low-mass X-ray binaries) making up the rest. Similarly to NGC 4697 and Messier 60, these bright spots are due to binary star systems of black holes and neutron stars most of which are located in globular clusters and reflect this old galaxy's very active past. In these systems, material pulled off a regular star is heated and gives off X-rays as it falls toward the accompanying black hole or neutron star. The brightest of the point sources is coincident with the galaxy's optical nucleus. Its luminosity and spectrum suggest its being an obscured central active galactic nucleus (AGN). This source is visible in the center of the X-ray image of NGC 1553 shown above.
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