A SINFONI view of the nuclear activity and circumnuclear star formation in NGC 4303

Rogemar A. Riffel, L. Colina, T. Storchi-Bergmann, J. Piqueras Lopez, S. Arribas, R. Riffel, M. Pastoriza, Dinalva A. Sales, N. Z. Dametto, A. Labiano, R. I. Davies. 2016. A SINFONI view of the nuclear activity and circum-nuclear star formation in NGC 4303. Monthly Notices of the Royal Astronomical Society 461, 4, 4192-4205 DOI: 10.1093/mnras/stw1609

We present new maps of emission-line flux distributions and kinematics in both ionized (traced by HI and [Fe II] lines) and molecular (H-2) gas of the inner 0.7 x 0.7 kpc(2) of the galaxy NGC 4303, with a spatial resolution 40-80 pc and velocity resolution 90-150 km s(-1) obtained from near-IR integral field spectroscopy using the Very Large Telescope instrument SINFONI. The most prominent feature is a 200-250 pc ring of circumnuclear star-forming regions. The emission from ionized and molecular gas shows distinct flux distributions: while the strongest HI and [Fe II] emission comes from regions in the west side of the ring (ages similar to 4 Myr), the H-2 emission is strongest at the nucleus and in the east side of the ring (ages > 10 Myr). We find that regions of enhanced hot H-2 emission are anti-correlated with those of enhanced [Fe II] and HI emission, which can be attributed to post-starburst regions that do not have ionizing photons anymore but still are hot enough (approximate to 2000 K) to excite the H-2 molecule. The line ratios are consistent with the presence of an active galactic nucleus at the nucleus. The youngest regions have stellar masses in the range 0.3-1.5 x 10(5) M-circle dot and ionized and hot molecular gas masses of similar to 0.25-1.2 x 10(4) M-circle dot and similar to 2.5-5 M-circle dot, respectively. The stellar and gas velocity fields show a rotation pattern, with the gas presenting larger velocity amplitudes than the stars, with a deviation observed for the H-2 along the nuclear bar, where increased velocity dispersion is also observed, possibly associated with non-circular motions along the bar. The stars in the ring show smaller velocity dispersion than the surroundings, which can be attributed to a cooler dynamics due to their recent formation from cool gas.

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