The virus-p exploration of nearby galaxies (venga): radial gas inflow andshock excitation in ngc 1042

Abstract

NGC 1042 is a late-type bulgeless disk galaxy that hosts low-luminosity active galactic nuclei (AGNs) coincident with a massive nuclear star cluster. In this paper, we present the integral field spectroscopy studies of this galaxy, based on the data obtained with the Mitchell spectrograph on the 2.7 m 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 this 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 similar to 32 +/- 10 km s(-1), and the estimated mass-inflow rate is similar to 1.1 +/- 0.3 x 10(-3) M-circle dot yr(-1). The mass-inflow rate is about one hundred times the black hole's mass-accretion rate (similar to 1.4 x 10(-5) M-circle dot yr(-1)) and slightly larger than the star-formation rate in the nuclear star cluster (7.94 x 10(-4) M-circle dot yr(-1)), implying that the inflow material is enough to feed both the AGN activity and star formation in the nuclear star cluster. Our study highlights that secular evolution can be important in late-type unbarred galaxies like NGC 1042.