The Space Telescope Imaging Spectrograph (STIS) simultaneously records, in unprecedented detail, the velocities of hundreds of gas knots streaming at hundreds of thousands of miles per hour from the nucleus of NGC 4151, thought to house a supermassive black hole.
This is the first time the velocity structure in the heart of this object, or similar objects, has been mapped so vividly this close to its central black hole.
The twin cones of gas emission are powered by the energy released from the supermassive black hole believed to reside at the heart of this Seyfert galaxy. The STIS data clearly show that the gas knots illuminated by one of these cones is rapidly moving towards us, while the gas knots illuminated by the other cone are rapidly receding.
The images have been rotated to show the same orientation of NGC 4151. The figures show:
WFPC2 (upper left) – A Hubble Wide Field Planetary Camera 2 image of the oxygen emission (5007 Angstroms) from the gas at the heart of NGC 4151. Though the twin cone structure can be seen, the image does not provide any information about the motion of the oxygen gas.
STIS OPTICAL (upper right) – In this STIS spectral image of the oxygen gas, the velocities of the knots are determined by comparing the knots of gas in the stationary WFPC2 image to the horizontal location of the knots in the STIS image.
STIS OPTICAL (lower right) – In this false color image the two emission lines of oxygen gas (the weaker one at 4959 Angstroms and the stronger one at 5007 Angstroms) are clearly visible. The horizontal line passing through the image is from the light generated by the powerful black hole at the center of NGC 4151.
STIS ULTRAVIOLET (lower left) – This STIS spectral image shows the velocity distribution of the carbon emission from the gas in the core of NGC 4151. It requires more energy to make the carbon gas glow (CIV at 1549 Angstroms) than it does to ionize the oxygen gas seen in the other images. This means we expect that the carbon emitting gas is closer to the heart of the energy source.
Credit: John Hutchings (Dominion Astrophysical Observatory), Bruce Woodgate (GSFC/NASA), Mary Beth Kaiser (Johns Hopkins University), Steven Kraemer (Catholic University of America), the STIS Team., and NASA