Pressure Balance and Energy Budget of the Nuclear Superbubble of NGC 3079
The Astrophysical Journal(2024)
摘要
Superbubbles in the nuclear region of galaxies could be produced by the AGN
or nuclear starburst via different driving forces. We report analysis of the
multi-wavelength data of the kpc-scale nuclear superbubble in NGC 3079, in
order to probe the mechanisms driving the expansion of the superbubble. Based
on the Chandra X-ray observations, we derive the hot gas thermal pressure
inside the bubble, which is about one order of magnitude higher than that of
the warm ionized gas traced by optical lines. We derive a [C II]-based star
formation rate of SFR∼1.3 M_⊙ yr^-1 from the nuclear
region using the SOFIA/FIFI-LS observation. This SFR infers a radiation
pressure toward the bubble shells much lower than the thermal pressure of the
gases. The VLA radio image infers a magnetic pressure at the northeast cap
above the superbubble less than the thermal pressure of the hot gas enclosed in
the bubble, but has a clearly larger extension. The magnetic field may thus
still help to reconcile the expansion of the bubble. The observed thermal
energy of the hot gas enclosed in the bubble requires an energy injection rate
of ≳10^42 ergs s^-1 within the bubble's dynamical age, which is
probably larger than the power provided by the current nuclear starburst and
the parsec-scale jet. If this is true, stronger past AGN activity may provide
an alternative energy source to drive the observed bubble expansion.
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关键词
Superbubbles,Cosmic rays,Active galaxies,Starburst galaxies
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