The Most Interesting Galaxies in the Universe by Joel L Schiff

Author:Joel L Schiff
Language: eng
Format: epub
ISBN: 9781643270043
Publisher: IOP Publishing
Published: 2018-09-03T16:00:00+00:00

Figure 7.34. Radio image of the five recently appearing intense outbursts seen near the core of NGC 660 and thought to be from relativistic jets arising from a supermassive black hole hitting material in the nuclear region. Credit: Minchin et al, NRAO/AUI/NSF (HSA); Travis Rector, Gemini Observatory, AURA (optical).

Color analysis (that has been corrected since the original studies) of the ring gives the age at 1 billion years but there has been continual star formation as the ring contains some very young stars 7–9 million years old.

One of the main interests in studying polar ring galaxies is that by measuring the rotational velocities of both the disk and ring, it allows for the determination of the shape and mass of the dark matter halo around the system. In this instance, it was found that the rotational velocities are compatible with a spherical dark matter halo (as also determined for NGC 4650A) and that its mass is comparable to that of the disk (+bulge) component: 21 billion solar masses, representing about 60% of the mass of the visible system.

A fortuitous event happened sometime between 2008 and 2012 while NGC 660 and a number of other galaxies were under long term study. It was noticed that during that period, NGC 660 started to give out a very violent outburst near the galaxy’s core. Utilizing a global array of radio telescopes, sufficient resolution was obtained to pin down the location of the source of the eruption. Rather surprisingly, the strong emissions were coming from five separate sites of radio emission with one close to the core of the galaxy and two on either side (see figure 7.34). They are now thought to arise from relativistic jets of particles from the galaxy’s supermassive black hole colliding with material around the nuclear region.

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