New images taken by the James Webb Space Telescope[1], reveal in exquisite detail the infrared view of the internal region of the Seyfert 2 galaxy NGC 1433.
When this galaxy was first observed, its bar-like region glowing beyond the center, gave it its classification as a spiral barred galaxy (SBnl); with the "nl" referring to its lens-like nucleus. Later on, it gained its new extended classification as a SB (R’1, nl) galaxy because of its arms emerging from each end of the bar and making a 180° turn to return to the opposite side in a winding-like structure. In 1986 it was also classified as Seyfert 2 galaxy because of its strong nuclear emission lines and high [NII]/Hα ratio [2], although other authors preferred to classify it as a LINER, because of its [OIII]/Hβ ratio, which is just at the limit between Seyfert and LINERs [3].
Seyfert galaxies are also known as Starburst galaxies. These are quite interesting to radio astronomers, who look to investigate the morphology and dynamics of the gas inside the central regions and to probe what is fueling the burst of star formation. With this objective in mind, a group of radio astronomers observed the center of this galaxy using the radio observatory ALMA[4]. These observations revealed not a lens like a nucleus but rather a spiral structure embedded in the large-scale primary bar, rotating inside the nuclear ring that encircles a nuclear stellar bar. The astronomers also found a jet of material flowing away from the central black hole, extending only a distance of 150 light-years. With this size, this is the smallest of such molecular outflows ever observed in a galaxy beyond our own.
This gaseous central spiral, seen in the observations made by the Hubble Space Telescope (HST), also shows dust fingers extending from this central region to the outer ring, where pink and bluish patches reveal regions of star formation. The new James Webb Space Telescope (JWST) observations made with the Mid-infrared (MIRI) detector and Near Infrared Camera (NIRCam) reveal another striking view of this galaxy. Central arms of cold gas, previously identified by ALMA, are now clearly defined in this image. The dark dust fingers in the HST observations are now extended clouds of dust that emit back the light absorbed from forming stars. Similarly, the regions of star formation appear to cover a wider area than those observed with HST.
The JWST fine-scale observations contain a great deal of information. These, along with those obtained by ALMA and HST, will allow astronomers to better understand Seyfert galaxies and how these evolve over time.
For more information about the James Webb image go to:
https://webbtelescope.org/contents/news-releases/2023/news-2023-104
References:
[1] https://webbtelescope.org/contents/news-releases/2023/news-2023-104
[2] Veron-Cetty & Veron 1986, A&AS , 66, 335
[3] Sosa-Brito et al. 2001, ApJS, 136, 61
Images
https://cgs.obs.carnegiescience.edu/CGS/object_html_pages/NGC1433.html
https://esawebb.org/images/weic2306a/
https://ui.adsabs.harvard.edu/abs/2013A%26A...558A.124C/abstract