Insights into the Evolution of Five Isolated Galaxies

Abstract

Abstract Galaxy evolution is believed to be conditioned by the environment. Isolated galaxies or galaxies in poor groups are an excellent laboratory to study evolutionary mechanisms where effects of the environment are minimal. We present new Swift-UVOT data in six filters, three in the ultraviolet (UV), of five isolated galaxies aiming at shedding light into their evolution. For all of our targets, we present new UV integrated fluxes, and for some of them also new UBV magnitudes. Our observations allow us to improve their multiwavelength spectral energy distributions, extending them over about three orders of magnitude in wavelength. We exploit our smooth particle hydrodynamical simulations with chemo-photometric implementation anchored, a posteriori, to the global multiwavelength properties of our targets, to give insight into their evolution. Then we compare their evolutionary properties with those previously derived for several galaxies in groups. The evolution of our targets is driven by a merger that occurred several gigayears ago, in the redshift range 0.5 ≤ z ≤ 4.5, not unlike what we have already found for galaxies in groups. The merger shapes the potential well where the gas is accreting, driving the star formation rate and the galaxy evolution. Isolated galaxies should not have suffered from interactions for at least 3 Gyr. However, the initial merger is still leaving its signature on the properties of our targets. Several rejuvenation episodes, triggered by in situ accretion, are highlighted. Moreover, jellyfish morphologies appear as these galaxies achieve their maximum star formation rate, before their quenching phase.