A SINFONI view of the nuclear activity and circumnuclear star formation in NGC 4303 – II. Spatially resolved stellar populations

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 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 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 , favoring 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 a 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 a 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.

The multiphase gas structure and kinematics in the circumnuclear region of NGC 5728

“…These rings of young nuclear star formation associated with low velocity dispersions seem to be a common characteristic of local Seyfert galaxies as many studies using IFU data have found them within the central kpc (e.g. Riffel et al 2010Riffel et al , 2011Diniz et al 2017;Dametto et al 2019)…”

A comparison between X-shooter spectra and PHOENIX models across the HR-diagram

“…Attempts to match the colors of large samples of galaxies from the near-ultraviolet (near-UV) to the near-IR have been found to leave significant residuals, sometimes leading authors to discard near-IR data in part of their analysis (Taylor et al 2011). Star formation histories derived from optical and near-IR data separately, or from a given data set with different population synthesis models, still differ significantly (Powalka et al 2017;Baldwin et al 2018;Dahmer-Hahn et al 2018;Dametto et al 2019;Riffel et al 2019). A part of the problem certainly lies in the theoretical modeling of advanced phases of stellar evolution, but it is also worth questioning the stellar spectral libraries.…”

Time-slicing spiral galaxies with SDSS-IV MaNGA

“…Most low-redshift disc galaxies host non-axisymmetric structures such as spiral arms and bars (Knapen et al 2000;Eskridge et al 2000;Masters et al 2011) which are likely to affect different stellar populations in different ways. It is known that azimuthal variation in the current star formation rate can arise as a result of the presence of bars (Martin & Friedli 1997;Verley et al 2007) and spiral arms (Gonzalez & Graham 1996;Puerari & Dottori 1997;Dametto et al 2019). Additionally, bars are associated with stable orbits (Contopoulos & Papayannopoulos 1980;Athanassoula 1992) and hence flattened stellar population gradients (Sánchez-Blázquez et al 2014, Fraser-McKelvie et al in prep.…”