The VIRUS-P Exploration of Nearby Galaxies (VENGA): Radial Gas Inflow and Shock Excitation in NGC 1042
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Abstract:
- NGC 1042 is a late type bulgeless disk galaxy which hosts a low luminosity Active Galactic Nuclei (AGN) coincident with a massive nuclear star cluster. We present the integral-field-spectroscopy (IFS) studies of this galaxy, based on the data obtained with the Mitchell spectrograph on the 2.7 meter Harlan J. Smith telescope. In the central 100-300 pc region of NGC 1042, we find a circumnuclear ring structure of gas with enhanced ionization, which we suggest is mainly induced by shocks. Combining with the harmonic decomposition analysis of the velocity field of the ionized gas, we propose that the shocked gas is the result of gas inflow driven by the inner spiral arms. The inflow velocity is ～ 32±10 km s^-1 and the estimated mass inflow rate is ～ 1.1±0.3×10^-3 M⊙ yr^-1 . The inflow rate is about one hundred times the blackhole’s mass accretion rate (～ 1.4×10^-5 M⊙ yr^-1), and slightly larger than the star formation rate in the nuclear star cluster (7.94 × 10^-4 M⊙ yr^-1). The inflow rate is large enough to feed both the AGN activity and the star formation in the nuclear star cluster. Our studies highlights the contribution of spiral arms in transferring gas inwards, especially for the late-type unbarred galaxies like NGC 1042.
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