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Register a new userInvestigating early-type galaxy evolution with a multi-wavelength approach. III. Insights from SPH simulations with chemo-photometric implementation
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We are exploring galaxy evolution in low density environments exploiting smooth particle hydrodynamic simulations including chemo-photometric implementation. From a large grid of simulations of galaxy encounters and mergers starting from triaxial halos of gas e dark matter, we single out the simulations matching the global properties of our targets. These simulations are used to give insights into their evolution. We focus on 11 early-type galaxies selected because of their nearly passive stage of evolution in the nuclear region. However, a variety of UV features are detected in more than half of these galaxies. We find no significant differences in the formation mechanisms between galaxies with or without UV features. Major and minor mergers are able to reproduce their peculiar UV morphologies, galaxy encounters are more suitable for normal early-type galaxies. Their star formation rate self-quenches several Gyr later the merger/encounter occurred, via gas exhaustion and stellar feedback, moving the galaxy from blue to red colors, driving the galaxy transformation. The length of the quenching is mass dependent and lasts from 1 to 5 Gyr or more in the less massive systems. All our targets are gas rich at redshift 1. Three of them assembled at most 40% of their current stellar mass at z>1, and seven assembled more than 50% between redshift 0.5 and 1. Their stellar mass grows with 4% by crossing the Green Valley before reaching their current position on the NUV-r vs. Mr diagram.
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We are investigating the co-evolution of galaxies within groups combining multi-wavelength photometric and 2D kinematical observations. Here we focus on S0s showing star formation in ring/arm-like structures. We use smooth particle hydrodynamical simulations (SPH) with chemo-photometric implementation which provide dynamical and morphological information together with the spectral energy distribution (SED) at each evolutionary stage. As test cases, we simulate the evolution of two such S0s: NGC 1533 and NGC 3626. The merging of two halos with mass ratio 2:1, initially just composed of dark matter (DM) and gas, well match their observed SEDs, their surface brightness profiles and their overall kinematics. The residual star formation today rejuvenating the ring/arm like structures in these S0s is then a mere consequence of a major merger, i.e. this is a phase during the merger episode. The peculiar kinematical features, e.g. gas-stars counter rotation in NGC 3626, depends on the halos initial impact parameters. Furthermore, our simulations allow to follow, in a fully consistent way, the transition of these S0s through the green valley in the NUV-r vs. Mr colour magnitude diagram, which they cross in about 3-5 Gyr, before reaching their current position in the red sequence. We conclude that a viable mechanism driving the evolution of S0s in groups is of gravitational origin.
The Galaxy Evolution Explorer (GALEX) detected ultraviolet emission in about 50% of multi-spin early-type galaxies (ETGs), suggesting the occurrence of a recent rejuvenation episode connected to the formation of these kinematical features. With the aim at investigating the complex evolutionary scenario leading to the formation of counter rotating ETGs (CR-ETGs) we use our Smooth Particle Hydrodynamic (SPH) code with chemo-photometric implementation. We discuss here the UV evolutionary path of two CR-ETGs, NGC 3593 and NGC 5173, concurrently best fitting their global observed properties, i.e., morphology, dynamics, as well as their total B-band absolute magnitude and spectral energy distribution (SED) extended over three orders of magnitude in wavelength. These simulations correspond to our predictions about the target evolution which we follow in the color-magnitude diagram (CMD), near-UV (NUV) versus r-band absolute magnitude, as a powerful diagnostic tool to emphasize rejuvenation episodes.
GALEX detected a significant fraction of early-type galaxies showing Far-UV bright structures. These features suggest the occurrence of recent star formation episodes. We aim at understanding their evolutionary path[s] and the mechanisms at the origin of their UV-bright structures. We investigate with a multi-lambda approach 11 early-types selected because of their nearly passive stage of evolution in the nuclear region. The paper, second of a series, focuses on the comparison between UV features detected by Swift-UVOT, tracing recent star formation, and the galaxy optical structure mapping older stellar populations. We performed their UV surface photometry and used BVRI photometry from other sources. Our integrated magnitudes have been analyzed and compared with corresponding values in the literature. We characterize the overall galaxy structure best fitting the UV and optical luminosity profiles using a single Sersic law. NGC 1366, NGC 1426, NGC 3818, NGC 3962 and NGC 7192 show featureless luminosity profiles. Excluding NGC 1366 which has a clear edge-on disk , n~1-2, and NGC 3818, the remaining three have Sersics indices n~3-4 in optical and a lower index in the UV. Bright ring/arm-like structures are revealed by UV images and luminosity profiles of NGC 1415, NGC 1533, NGC 1543, NGC 2685, NGC 2974 and IC 2006. The ring/arm-like structures are different from galaxy to galaxy. Sersic indices of UV profiles for those galaxies are in the range n=1.5-3 both in S0s and in Es. In our sample optical Sersic indices are usually larger than the UV ones. (M2-V) color profiles are bluer in ring/arm-like structures with respect to the galaxy body. The lower values of Sersics indices in the UV bands with respect to optical ones, suggesting the presence of a disk, point out that the role of the dissipation cannot be neglected in recent evolutionary phases of these early-type galaxies.
One of the major challenges in modern astrophysics is to understand the origin and the evolution of galaxies, the bright, massive early type galaxies (ETGs) in particular. Therefore, these galaxies are likely to be good probes of galaxy evolution, star formation and, metal enrichment in the early Universe. In this context it is very important to set up a diagnostic tool able to combine results from chemo-dynamical N-Body-TSPH (NB-TSPH) simulations of ETGs with those of spectro-photometric population synthesis and evolution so that all key properties of galaxies can be investigated. The main goal of this paper is to provide a preliminary validation of the software package before applying it to the analysis of observational data. The galaxy models in use where calculated by the Padova group in two different cosmological scenarios: the SCDM, and the Lambda CDM. For these models, we recover their spectro-photometric evolution through the entire history of the Universe. We computed magnitudes and colors and their evolution with the redshift along with the evolutionary and cosmological corrections for the model galaxies at our disposal, and compared them with data for ETGs taken from the COSMOS and the GOODS databases. Starting from the dynamical simulations and photometric models at our disposal, we created synthetic images from which we derived the structural and morphological parameters. The theoretical results are compared with observational data of ETGs selected form the SDSS database. The simulated colors for the different cosmological scenarios follow the general trend shown by galaxies of the COSMOS and GOODS. Within the redshift range considered, all the simulated colors reproduce the observational data quite well.
In this review I give a summary of the state-of-the-art for what concerns the chemo-dynamical numerical modelling of galaxies in general and of dwarf galaxies in particular. In particular, I focus my attention on (i) initial conditions; (ii) the equations to solve; (iii) the star formation process in galaxies; (iv) the initial mass function; (v) the chemical feedback; (vi) the mechanical feedback; (vii) the environmental effects. Moreover, some key results concerning the development of galactic winds in galaxies and the fate of heavy elements, freshly synthesised after an episode of star formation, have been reported. At the end of this review, I summarise the topics and physical processes, relevant for the evolution of galaxies, that in my opinion are not properly treated in modern computer simulations of galaxies and that deserve more attention in the future.
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