A short overview is presented of several topics concerning the evolution of the Milky Way (MW) in a cosmological context. In particular, the metallicity distribution of the MW halo is derived analytically and the halo metallicity and abundance patterns are compared to those of Local Group galaxies. The inside-out formation of the MW disk is supported by the observed evolution of the abundance gradients, while their magnitude suggests that the role of the Galactic bar has been negligible. Finally, the empirical foundations (age-metallicity relation and metallicity distribution) of the evolution of the solar neighbourhood, which is the best studied galactic sub-system, have been seriously questioned recently.

Recent observations show that the number of stars with very lowmetallicities in the dwarf spheroidal satellites of the Milky Way islow, despite the low average metallicities of stars in these systems. Weundertake numerical simulations of star formation and metal enrichmentof dwarf galaxies in order to verify whether this result can bereproduced with ”standard” assumptions. The answer is likely to benegative, unless some selection bias against very low metallicity starsis present in the observations.

We present some preliminary results obtained with a new galacticchemodynamical tool under development. In the framework ofnon-instantaneous recycling approach, we follow the interactions dueto star formation and feedback processes.One of the main original features of our code is that we record theabundance evolution of several chemical elements. This allows us tobuild cooling functions dependent on the real abundances of individualelements. We illustrate the need for such metal-dependent coolingfunctions using a toy model made of a star cluster embedded in atwo-phase gas cloud. Our results suggest that computing cooling ratesaccording to individual abundances of chemical elements can influencethe star formation rate.

We present 3D hydrodynamic simulations aimed at studying the dynamical and chemical evolution of the interstellar medium in dwarf spheroidal galaxies. This evolution is driven by the explosions of type II and type Ia supernovae, whose different contribution is explicitly taken into account in our models. We compare our results with avaiable properties of the Draco galaxy. Despite the huge amount of energy released by SNe explosions, in our model the galaxy is able to retain most of the gas allowing a long period (>3 Gyr) of star formation, consistent with the star formation history derived by observations. The stellar [Fe/H] distribution found in our model matches very well the observed one. The chemical properties of the stars derive from the different temporal evolution between type Ia and type II supernova rate, and from the different mixing of the metals produced by the two types of supernovae. We reproduce successfully the observed [O/Fe]-[Fe/H] diagram.

The Fornax dSph is a nearby dwarf spheroidal galaxy with five globularclusters and a complex star formation history. It is one of the mostmassive dwarf spheroidal galaxies in the Local Group. Using theFLAMES/GIRAFFE spectrograph on the VLT, we have obtained highresolution (R ~ 20 000) spectra for 80 Red Giant Branch stars in thecentral 25' of the Fornax dSph. We present abundance ratios for someof the elements we have in our analysis, including alpha (Mg and Ca), iron-peak (Fe and Ni) and heavy (Y,Ba, Eu) elements. We compare our results with the Milky Way(MW) and our recent VLT/UVES abundancedeterminations of nine individual stars in Fornax globularclusters.

Chemodynamical disc galaxy simulations coupled with stellar populations synthesis models allow to build multi-wavelength images from numerical simulations, and then to follow their morphological evolution in colour and not only on the mass distribution. Using such technique, we present the evolution of several photometric observables, of the Tully-Fisher relation, as well as the evolution of disc structural parameters.

In most of numerical simulations of spiral galaxy formation,mass/spatial resolution is ~ 105-6 M๏ and kpc or sub-kpc,therefore inhomogeneous structure of the ISM in galaxies is notresolved. This is the most serious defect in simulating starformation and its feedback during galaxy formation/evolution. Here weshow an intrinsic structures of the ISM using 3-D high resolutionhydrodynamic simulations of galactic disks. We show that the PDFs inglobally stable, inhomogeneous ISM in galactic disks are well fittedby a single log-normal function over a wide density range. Thedispersion of the log-normal PDF (LN-PDF) is larger for more gas-richsystems. Using the LN-PDF, we give a generalized version ofSchmidt-Kennicutt law, i.e. SFR as a function of average gas density,a critical local density for star formation, and star formationefficiency. We also introduce our new project, “Project Milky Way”, in which weaim to resolve properly the cold, dense ISM, as found in abovesimulations, by ultra-high resolution during galaxy formation. We areplanning to construct a special cluster for simulating formation of“Milky Way” using the next generation GRAPE.

The use of chemodynamical simulations of disc galaxies calibrated in Band K bands allows us to compare the location of Ultra HarmonicResonance (UHR) and corotation (CR) with photometrically estimated barlengths. We apply several observational criteria to determine barlengths. We show that the minimum of ellipticity located just outsidethe bulk of the bar is correlated with CR whereas the location of UHRcan be approximated using the end of the position-angle plateau of barisophotes. We give evidence that the classification of slow/fastbars, based on the ratio ${\cal R} = RCR/Rbarcould increase from 1 (fast bar) to 1.4 (slow bar) just by a change ofmethod.

I review studies of the hot gaseous medium in and around nearbynormal disk galaxies, including the Milky Way. This medium represents a reservoir of materials required for lasting star formation, a depository of galacticfeedback (e.g., stellar mass loss and supernovae), and an interface between the interstellar and intergalactic media. Important progress has been made recently with the detection of X-ray absorption lines in the spectra of X-ray binaries and AGNs.The X-ray absorption line spectroscopy, together with existing X-rayemission and far-UV O iv absorption measurements now allowsfor the first time to characterize the global spatial, thermal, andchemical properties of hot gas in the Galaxy. The results aregenerally consistent with those inferred from X-ray imaging of nearby edge-on galaxies similar to the Milky Way.Observed diffuse X-ray emitting/absorbing gas doesnot extend significantly more than ~10 kpc away from galactic disks/bulges, except in nuclear starburst or very massive galaxies. The X-ray cooling rate of this gas is generally far less than the expected supernova mechanical energy input alone. So the bulk of the energy is “missing”. On the other hand, evidence for alarge-scale (≲ 102 kpc) hot gaseous halo around the Milky Way to explain varioushigh-velocity clouds is mounting. The theoretical argument for ongoing accretion of intergalactic gas onto disk galaxies is also compelling. Idiscuss possible solutions that reconcile these facts.In particular, large-scale hot gaseous halos appear to be low inmetallicity, hence X-ray emission. The metal enrichment in theintergalactic medium may be substantially non-uniform; fast-cooling clumps ofrelatively high metallicity may have largely dropped out and may partly account for high-velocity clouds. In addition, ongoing galactic mechanical energy feedbackis likely important in balancing the cooling of the halos and may bestrong enough to produce galactic winds in bulge-dominated galaxies.

Bright early-type galaxies are still forming stars at low-level residualstar formation (RSF) mode.The GALEX UV satellite has detected excessive UV flux in >30% of our volume-limited sample of ~ 103 galaxies. The RSF galaxy fractionis higher among the dynamically low-mass sample (RSF-σ relation).We postulate that this is a result of a “critical”MBH − σ relation that regulates residual star formation activities inearly type galaxies. Implications are discussed.

There is a strong connection between the formation of a disk galaxy and the properties of the interstellar medium (ISM). Theoretical work has typically either focused on the cosmological buildup of a galaxy with a relatively crude model for the gas physics, or examined local processes in the ISM and ignored the global evolution of the galaxy itself. Here, I briefly review what has been learned from both of these approaches, and what can be done to bridge the gap between them. I argue that cosmological simulations need to learn from observational and theoretical work on local ISM properties and adopt more sophisticated models for the processes that they cannot resolve. Since the ISM is still incompletely understood, there are a number of reasonable approaches for these “subgrid" models, and I will discuss the strengths and limitations of each.

This contribution discusses the challenges of implementing star formation andstellar feedback processes in galaxy simulations. Insufficient computational power and numerous poorly understoodphysical processes, force simulations to adopt sub-grid models of the interstellar medium. These maycrucially bias results. We advocate for smaller (~ kiloparsec) scale simulations of the interstellar medium to guide the development of sub-grid models in larger simulations. In this vein, I show results on ever increasing scales ranging from ~1 h-1 kpc3 ISM simulations, to a 1 h-1 Mpc3 simulation of a galaxy forming at high redshift, to a larger cosmological volume, 6.25 h-1 Mpc3, evolved down to redshift 3. We find that galactic winds can be poweredby SN implemented as point explosions in high redshift galaxiessimulated with sufficient spatial resolution. Galaxies at lower redshift require alternative sub-grid feedback models and we present one possible solution to generate winds from galaxies atredshift ~4.



Observations give evidences of the presence of metals in the intergalactic medium (IGM). The stars responsible for transforming hydrogen and helium into more complex atoms do not form outside the galaxies in the standard scenario of galaxy formation. Supernovae–driven winds and theirassociated feedback was proposed as a possiblesolution to explain such enrichment of the IGM. It turned out that a proper modelling of supernovaeexplosions within a turbulent interstellar medium (ISM) is a difficulttask. Recent advances have been obtained using a multiphase approachto solve for the thermal state of the ISM, plus some additionalrecipes to account for the kinetic effect of supernovae on thegalactic gas. We briefly describe here our implementation of supernovaefeedback within the RAMSES code, and apply it to the formation andevolution of isolated galaxies of various masses and angularmomenta. We have explored under what conditions a galactic wind candevelop, if one considers only a quiescent mode of star formation. We have also characterized the distribution and evolution of metallicity in the gas outflow spreading in the IGM.

Due to their low gravitational energies, dwarf galaxies are greatly exposed to energetical influences from internal and external sources. By means of chemodynamical models we show that their star formation is inherently self-regulated, that peculiar abundance ratios can only be achieved assuming different star-formation episodes and that evaporation of interstellar clouds embedded in a hot phase can lead to a fast mixing of the interstellar gas. Metal-enriched hot outflows can accrete onto infalling clouds by means of condensation leading to a large range of timescales for the self-enrichment of the ISM from local scales within a few tens of Myr up to a few Gyr for the large-range circulation. Infall of clouds is also required to explain abundance ratios of metal-poor galaxies at evolved stages because it reduces the metallicity altering only marginally the abundance ratios.


We integrate three fundamental physical processes, i.e. star formation, structure formation,and radiative transfer inside galaxies, into our chemodynamical model. Our model simulates dynamical evolution in N-body SPH method, and simulates star formation as well as radiative gas cooling, feedback processes from stellar wind and supernovae. Furthermore, we implement radiative transfer in the galaxy so that we can simulate gas photoionization heating by ultraviolet (UV) photons emitted by OB stars inside the galaxy, and so that we can obtain the whole spectral energydistribution after dust absorption without assumption on dust, gas and stellar geometry, even if the simulated galaxy has very irregular morphology. We simulate seven galaxies. Our model galaxies with photoionization by UV photons show two differences from model galaxies without them. UV photons invoke gas outflow from the system, and result in smaller star formation rate at z < 1. Our simulated galaxies successfully reproduce star formation rate and density profile of nearby elliptical galaxies. Comparison with recent observations on high redshift galaxy populations suggests the following evolutionary paths. In our main model, simulated galaxy becomes LBG at z = 4.5 and 3.0 > z > 2.8, and satisfies the criteria of BzK at 3.0 > z > 2.0. Then the model galaxy enters into the short passively evolving ERO phase at z = 1.6 and finally evolves to a passively evolving elliptical galaxy. In all our simulations, evolutionary path from LBGs at z = 4, through the BzK phase at 3 > z > 1.8, to passively evolving elliptical galaxies at z < 0.8, are universal.


Here results of numerical radiation hydrodynamical simulations arepresented which explore the energetic impact of massive stars on the interstellar medium. We study the evolution of the ambient gas around isolated massive stars in the mass range between 15 and 85 M๏ in order to analyze the formation of structures and further the transfer and deposit of the stellar wind and radiation energy into the circumstellar medium until the stars explode as a supernovae. The derived energy transfer efficiencies are much smaller thananalytically estimated and should be inserted into chemo-dynamicalevolutionary models of galaxies as appropriate parameter values. As an additional issue the element release in the Wolf-Rayet phases and its detectability have been investigated for comparison with observations.


The enrichment of the Intra-Cluster Medium (ICM) with heavy elementsis reviewed. There is now good observational evidence for enrichment includingabundance ratios and metallicity distributions. Various processes involved in the enrichment process –ram-pressure stripping, galactic winds, galaxy-galaxy interactions,AGN outflows and intra-cluster supernovae – are described. Simulationsof the ICM evolution taking into account metal enrichment are presented.

We review recent developments in the field of chemodynamical simulations ofelliptical galaxies, highlighting (in an admittedly biased fashion) the work conducted with our cosmological N-body/SPH code GCD+. We have demonstrated previously therecovery of several primary integratedearly-type system scalingrelations (e.g. colour-magnitude relation, LX − TX − [Fe/H]X) when employing a phenomenological AGN heating scheme in conjunctionwith a self-consistent treatment of star formation, supernovae feedback, radiative cooling, chemical enrichment, and stellar/X-raypopulation synthesis. Here we emphasise characteristics derivedfrom the full spatial information contained within the simulated dataset, including stellar and coronal morphologies, metallicity distributionfunctions, and abundance gradients.