A SINFONI view of the nuclear activity and circumnuclear star formation in NGC 4303 - II. Spatially resolved stellar populations
Colina, L.; Burtscher, L.; Pastoriza, M. G.; Storchi-Bergmann, T.; Arribas, S.; Davies, R. I.; Labiano, A.; Menezes, R. B.; Riffel, R. A.; Piqueras López, J.; Riffel, R.; Dametto, Natacha Z.; Dahmer-Hahn, L. G.; Sales, D. A.
Brazil, Spain, Germany, Netherlands, Switzerland
Abstract
We present a spatially resolved stellar population study of the inner ∼200 pc radius of NGC 4303 based on near-infrared integral field spectroscopy with SINFONI/VLT at a spatial resolution of 40-80 pc and using the STARLIGHT code. We found that the distribution of the stellar populations presents a spatial variation, suggesting an age stratification. Three main structures stand out. Two nuclear blobs, one composed by young stars (t ≤ 50 Myr) and one with intermediate-age stars (50 Myr < t ≤ 2 Gyr), both shifted from the centre. The third one is an internal intermediate-age spiral arm-like structure, surrounding the blob of young stars. Our results indicate that star formation has occurred through multiple bursts in this source. Furthermore, the youngest stellar populations (t ≲ 2 Gyr) are distributed along a circumnuclear star-forming ring with r ∼ 250 pc. The ring displays star formation rates (SFRs) in the range of 0.002-0.14 M⊙yr-1, favouring the `pearls-on-a-string' scenario. The old underlying bulge stellar population component (t > 2 Gyr) is distributed outside the two blob structures. For the nuclear region (inner ∼60 pc radius) we derived an SFR of 0.43 M⊙ yr-1 and found no signatures of non-thermal featureless continuum and hot dust emission, supporting the scenario in which an LLAGN/LINER-like source is hidden in the centre of NGC 4303. Thus, our results reveal a rather complex star formation history in NGC 4303, with different stellar population components coexisting with a low efficiency accreting black hole in its centre.