Description
In recent decades, the modelling of increasingly high quality photometry and spectroscopy have led to significant progress in understanding galaxy formation and evolution up to early cosmic epochs. The resolving of the data into sub-kpc scales within galaxies is expected to incur further advances. We present a new hierarchical Bayesian SED fitting method that fits data from all pixels in resolved galaxy observations simultaneously, demonstrated on three local quenched galaxies. It provides joint estimations of both the local resolved star-formation histories, and the spatial distribution of stellar/dust/chemical properties. The hierarchical approach extends regions with high-confidence estimates into lower SNR outskirts, expanding our probe into galaxies formation into fainter ends.
Upon applying this to three massive local recently quenched galaxies from the SDSS MaNGA IFU survey, we found all three showed two clear periods of increased recent star formation that are spatially distinct: A weaker, more metal-poor and slower quenching starburst located mainly in the outskirts is followed ≈1Gyr later by a stronger, more metal-rich and quicker quenching starburst located primarily in the centre. Combined with asymmetric dust distributions found in 2/3, our results are consistent with the effects of galaxy mergers as shown by hydrodynamic simulations in the literature, where the first starburst is tied to the first pericentre passage, while the second (central) starburst is tied to the second passage/final coalescence. This work greatly strengthens the idea that galaxy mergers strongly influence the spatial distribution of star formation and metallicity, and can effectively quench local massive galaxies.
