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Scientists have long been aware of the massive elliptical galaxy, M87. The galaxy was first observed in the late 18th century by Charles Messier, who cataloged objects in the sky specifically to avoid them when looking for comets. However, numerous later observations in the radio, X-ray, optical, UV, and gamma-ray bands revealed that the object is a galaxy with a prominent jet emerging from a supermassive black hole at its core. This jet is now well known for its synchrotron emission in the radio to optical wavelengths.

Although many observations have been made on M87, data had been somewhat lacking in the infrared spectrum. But now, a group of scientists have utilized new data from the James Webb Space Telescope (JWST) and its near infrared cameras (NIRCam) to resolve some previously fuzzy details about M87's jet. The work is now in the journal Astronomy & Astrophysics.

The JWST+NIRCam images were taken in four infrared bands at 0.90, 1.50, 2.77, and 3.56 µm. In order to isolate the light coming from the actual jet, the team used background subtraction methods, calibration, and galaxy modeling to remove light from stars, galactic dust, background galaxies, and globular clusters. This revealed a detailed infrared picture of the main jet, as well as the counter-jet, which points in the opposite direction coming out from the black hole.

The jet takes on a helical structure, with a slowly moving bright knot (labeled as "L") and a component called "HST-1" (after the Hubble Space Telescope used to discover it), a fast-moving superluminal feature. Both are relatively close to the center. The HST-1 component is resolved into two substructures with different spectral indices.

"The residual jet images are broadly consistent with the radio to optical spectrum. In the higher resolution, shorter wavelength images, we identified all distinct jet components up to ∼24 arcsec from the nucleus, including HST1, the more upstream knot L, and the bright shock farther downstream," the study authors write.

The counter-jet feature, which is detected ~24 arcsec from the nucleus, is typically difficult to image due to the fact that it is moving away at near the speed of light. However, the team was able to get a clearer image with the infrared data in the study.

"In the 2.77 and 3.56 µm images, the counter-jet consists of two filaments connected by a hotspot, forming a C-shape, consistent with its morphology in the radio wavelengths," the study authors say.

This study boosts the understanding of jet physics in active galactic nuclei, and provides a benchmark for future infrared studies of extragalactic jets. Additional data from JWST and other telescopes, including studies on polarimetric and multi-wavelength data could help to further discern the details of both the jet and counter-jet and reveal more about jet magnetic fields and particle acceleration.