学术文献库

The 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 {\it Swift}-{\tt 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 multi-wavelength spectral energy distributions extending it over about 3 orders of magnitude in wavelength. We exploit our smooth-particle hydro-dynamical simulations with chemo-photometric implementation anchored, a posteriori, to the global multi-wavelength 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 occurred several Gyrs ago, in the redshift range $0.5\leq z \leq 4.5$, 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 signatures on the properties of our targets. Several rejuvenation episodes, triggered by {\it in situ} accretion, are highlighted. Moreover, jelly-fish morphologies appear as these galaxies achieve their maximum star formation rate, before their quenching phase.