Multifrequency Observations of the Extended Jet of Quasar 1317+520

We have observed this quasar (redshift z = 1.06) with NASA's Chandra X-ray Observatory, the Very Large Array (VLA, an imager of radio waves operated by the National Radio Astronomy Observatory, and the Spitzer Space Telescope (a NASA infrared telescope).

The first figure displays the full radio image. The quasar core is the intense spot with the white center. To the northwest (upper right), there is a single bright spot, which is probably part of a jet whose emission is mostly beamed away from us by motion near the speed of light. There is a large radio "lobe" that is commonly seen in quasars and radio galaxies. On the souteastern side, we see a nice, knotty jet that gently curves so that the jet is eastward near the end. There is no lobe, but there is a pair of bright spots (red) and a couple of protrusions to the south. We surmise that a cloud is ramming into the jet from the north-northwest, tearing off the edges to make the prostrusions and confining the jet so that no lobe has developed. This jet must be approaching us, causing its emission to be beamed in our direction so that the jet is bright. The cloud has slowed down the progression of this side of the jet into the intergalactic medium, which is why the near jet is shorter than the far one. The opposite is usually the case, since we are seeing the far one at an earlier time (because of the time it takes for light to travel from the far side to the near side before it travels to us).

The next image shows thet jet at both radio (contours) and X-ray (false color) wavelengths. Notice that the X-ray emission becomes bright at the brightest radio knot. Our Spitzer Space Telescope observations indicate that this region is also a source of infrared light.

With the VLA, we can examine the linear polarization of the jet. The next image shows the polarization as sticks that show the direction of the magnetic field in the jet.

 

Here's a close-up of the region with the X-ray emission:

From the oblique angle of the magnetic field on the northern side of the brightest spot, we think that an oblique standing shock wave exists there, caused by the ramming of the gas cloud into the jet from the north-northeast. A bit downstream (to the east, or left on the figure), the magnetic field becomes perpendicular to the jet. We think that this is the so-called "working surface" - a strong standing shock that slows down the jet as it runs into the intergalactic medium.

Most of the energization of electrons that causes the emission occurs at the oblique shock. The infrared emission indicates that the electrons need to be heated up to very high energies - greater than 1 million TeV (about 1 erg). We can't figure out how nature seems to do this so easily. Maybe the obliqueness of the shock front allows electrons to skid along the shock front, gaining energy every time they pass across it.

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