Astrophys. J., 869, 61-61 (2018/December-2)
Jet-related excitation of the [C II] emission in the active galaxy NGC 4258 with SOFIA.
APPLETON P.N., DIAZ-SANTOS T., FADDA D., OGLE P., TOGI A., LANZ L., ALATALO K., FISCHER C., RICH J. and GUILLARD P.
Abstract (from CDS):
We detect widespread [C II] 157.7 µm emission from the inner 5 kpc of the active galaxy NGC 4258 with the SOFIA integral field spectrometer FIFI-LS. The emission is found to be associated with warm H2, distributed along and beyond the end of the southern jet, in a zone known to contain shock-excited optical filaments. It is also associated with soft X-ray hotspots, which are the counterparts of the "anomalous radio arms" of NGC 4258, and a 1 kpc long filament on the minor axis of the galaxy that contains young star clusters. Palomar CWI Hα integral field spectroscopy shows that the filament exhibits non-circular motions within NGC 4258. Many of the [C II] profiles are very broad, with the greatest line width, 455 km s–1, observed at the position of the southern jet bow-shock. Abnormally high ratios of L([C II])/L(FIR) and L([C II])/L(PAH 7.7 µm) are found along and beyond the southern jet and in the X-ray hotspots. These are the same regions that exhibit unusually large intrinsic [C II] line widths. This suggests that the [C II] traces warm molecular gas in shocks and turbulence associated with the jet. We estimate that as much as 40% (3.8 x 1039 erg s–1) of the total [C II] luminosity from the inner 5 kpc of NGC 4258 arises in shocks and turbulence (<1% bolometric luminosity from the active nucleus), the rest being consistent with [C II] excitation associated with star formation. We propose that the highly inclined jet is colliding with, and being deflected around, dense irregularities in a thick disk, leading to significant energy dissipation over a wide area of the galaxy.
© 2018. The American Astronomical Society. All rights reserved.
galaxies: active - galaxies: jets - galaxies: ISM - infrared: galaxies
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