The formation and evolution of galaxies is intimately related to the growth of large-scale structure. Indeed, galaxies, and dark matter halos they reside in, form and grow within the cosmic web – the classification of large-scale structure as distinct environments, namely voids, sheets, filaments, and nodes. The development in the field of cosmological simulations and large galaxy redshift surveys over the past two decades allows us today to study the co-evolution of galaxies and halos with the cosmic web jointly in observations and simulations and compare the measurements with theoretical predictions. These lectures will give an overview of the curent understanding of galaxy and structure formation and evolution, emphasising the existing challenges both on the side of theory and observations and presenting future perspectives from ongoing and upcoming surveys.

Chapter 1: Formation and evolution of dark matter halos and galaxies

Chapter 2: Structure formation and the cosmic web

Chapter 3: The impact of the cosmic web on galaxies and halos

Chapter 4: The cosmic web as a tool to constrain cosmology and galaxy formation models

Prerequisites

The course will mostly be self-contained.

The formation and evolution of galaxies is intimately related to the growth of large-scale structure. Indeed, galaxies, and dark matter halos they reside in, form and grow within the cosmic web – the classification of large-scale structure as distinct environments, namely voids, sheets, filaments, and nodes. The development in the field of cosmological simulations and large galaxy redshift surveys over the past two decades allows us today to study the co-evolution of galaxies and halos with the cosmic web jointly in observations and simulations and compare the measurements with theoretical predictions. These lectures will give an overview of the curent understanding of galaxy and structure formation and evolution, emphasising the existing challenges both on the side of theory and observations and presenting future perspectives from ongoing and upcoming surveys.

Chapter 1: Formation and evolution of dark matter halos and galaxies

Chapter 2: Structure formation and the cosmic web

Chapter 3: The impact of the cosmic web on galaxies and halos

Chapter 4: The cosmic web as a tool to constrain cosmology and galaxy formation models

Prerequisites

The course will mostly be self-contained.

In the standard hierarchical cosmological model of structure formation, the first objects to form are predicted to have masses corresponding to virial temperatures Tvir < 10⁴ K. After gas virializes in the potential wells of pre-existing dark matter halos, further cooling is necessary for the gas to collapse and form stars. For a primordially composed gas at these low temperatures, molecular hydrogen is the primary coolant. The typical primordial H₂ fraction is usually too low for the formation of such objects. However, during the collapse phase, the H₂ abundance can increase to sufficient levels, depending on the object's mass. Once the gas has collapsed and cooled, star formation commences. The study of star formation in these primordial objects remains in its early stages. Although significant progress has been made through both analytical and numerical approaches, a robust physical understanding requires substantial further investigation. The emergence of the first sources profoundly influences subsequent galaxy formation. Their mass deposition, energy injection, and emitted radiation affect the evolution of the intergalactic medium (IGM) through various "feedback" effects. These first stars are also crucial for initiating cosmic reionization, the last major phase transition in cosmic history. These two Lectures will provide a pedagogical overview of these topics, including a discussion of open questions in the field. They will thereby establish the necessary background for the subsequent part of the course.rovide a pedagogical overview of cosmic reionization and intergalactic medium and of some of the open questions in these fields.

• I : Star Formation in Primordial Gas
• a. – Cooling diagram
• b. – H_{2} in the early universe
• c. – Collapse and accretion
• II : Initial Mass Function
• a. – Fragmentation
• b.– Role of rotation and molecules
• c. – Critical metallicity
• III. : First Stars
• a. – Characteristic masses
• b.– Emission spectrum
• c. – Evolutionary tracks
• d. – Final fate and heavy element yields

Prerequisites

The course will mostly be self-contained.

In the standard hierarchical cosmological model of structure formation, the first objects to form are predicted to have masses corresponding to virial temperatures Tvir < 10⁴ K. After gas virializes in the potential wells of pre-existing dark matter halos, further cooling is necessary for the gas to collapse and form stars. For a primordially composed gas at these low temperatures, molecular hydrogen is the primary coolant. The typical primordial H₂ fraction is usually too low for the formation of such objects. However, during the collapse phase, the H₂ abundance can increase to sufficient levels, depending on the object's mass. Once the gas has collapsed and cooled, star formation commences. The study of star formation in these primordial objects remains in its early stages. Although significant progress has been made through both analytical and numerical approaches, a robust physical understanding requires substantial further investigation. The emergence of the first sources profoundly influences subsequent galaxy formation. Their mass deposition, energy injection, and emitted radiation affect the evolution of the intergalactic medium (IGM) through various "feedback" effects. These first stars are also crucial for initiating cosmic reionization, the last major phase transition in cosmic history. These two Lectures will provide a pedagogical overview of these topics, including a discussion of open questions in the field. They will thereby establish the necessary background for the subsequent part of the course.rovide a pedagogical overview of cosmic reionization and intergalactic medium and of some of the open questions in these fields.

• I : Star Formation in Primordial Gas
• a. – Cooling diagram
• b. – H_{2} in the early universe
• c. – Collapse and accretion
• II : Initial Mass Function
• a. – Fragmentation
• b.– Role of rotation and molecules
• c. – Critical metallicity
• III. : First Stars
• a. – Characteristic masses
• b.– Emission spectrum
• c. – Evolutionary tracks
• d. – Final fate and heavy element yields

Prerequisites

The course will mostly be self-contained.

The LSST (Large Survey of Space and Time) survey [1] is currently being commissioned at the Vera Rubin observatory in Chile, and is due to begin operations before the end of 2025. The system consists of a main telescope 8.40 meters in diameter, equipped with a 3.2 Gigapixel CDD camera, and multiple calibration systems, including a 1.2-meter auxiliary telescope equipped with a slitless photo-spectrograph for measuring the transmission of the atmosphere in real time. This package makes LSST the most powerful wide-field instrument that will be in operation for the next decade. I will describe the system and its expected performance, and list the many possible scientific applications, from the study of the solar system to cosmology [2].

This talk is based on [1]. We explore the tomographic angular cross-correlation between gravitational-wave and galaxy catalogs as a probe of late-time cosmology. Focusing on next-generation interferometers combined with the Euclid photometric survey, we forecast constraints on the Hubble constant, Matter density parameter and other cosmological parameters.

Our analysis accounts for realistic GW populations, observational uncertainties, and nuisance parameters. This method can constrain the Hubble constant to percent-level accuracy, even when marginalizing over biases and other cosmological parameters. Combining galaxy auto-correlation with GW–galaxy cross-correlation boosts sensitivity by up to a factor of $\sim10$ compared to either probe alone.

We also discuss the use of a spectroscopic redshift catalog, as well as the detectability of the clustering bias of gravitational–wave sources.

This talk is based on [1]. We explore the tomographic angular cross-correlation between gravitational-wave and galaxy catalogs as a probe of late-time cosmology. Focusing on next-generation interferometers combined with the Euclid photometric survey, we forecast constraints on the Hubble constant, Matter density parameter and other cosmological parameters.

Our analysis accounts for realistic GW populations, observational uncertainties, and nuisance parameters. This method can constrain the Hubble constant to percent-level accuracy, even when marginalizing over biases and other cosmological parameters. Combining galaxy auto-correlation with GW–galaxy cross-correlation boosts sensitivity by up to a factor of $\sim10$ compared to either probe alone.

We also discuss the use of a spectroscopic redshift catalog, as well as the detectability of the clustering bias of gravitational–wave sources.

Using the AMICO and WaZP cluster finders [1, 2], we identified $523$ likely cluster candidates in the redshift range $0.1-3$ in the XMM-LSS and CDFS VIDEO fields.

For the candidates already identified, our photometric redshift measurements agree well with the literature. From ancillary spectroscopic data, we assign $z_\mathrm{spec}$ measurements to $93$ detections based on their members and to $172$ detections based on their likely Brightest Central Galaxy.

Using stacked rest-frame colour-magnitude diagrams, we study the evolution of the cluster red-sequence in the redshift range $0.8-2.0$, finding slopes consistent with a no evolution scenario.

Finally, our cluster sample is used to test MOONRISE [3] strategies to detect and characterise high redshift galaxy clusters. We show that cluster spectroscopic confirmation and characterisation can be done efficiently up to $z\sim1.7$ even with the shallowest strategy, opening unprecedented insight into the physical properties of high redshift galaxy clusters.

Most local spiral galaxies have been observed to contain a bar [1], and yet the formation of these bars is still not well understood. Galaxy mergers have been proposed as a possible driver [2], however investigating the impact of mergers over cosmic time observationally is challenging. Using a cosmological zoom-in simulation of a galaxy group with a high temporal resolution, I identify and trace a set of barred galaxies at high redshifts. I will show the ability of mergers to both create and destroy galactic bars even at redshifts beyond $z=2$, and find strong and persistent correlations between bar length, pattern speed and angular momentum. Finally, I will discuss a curious finding of the bar pattern speed increasing.

We present preliminary outcomes of our search for high-$z$ ($z \approx 8-12$) Lyman Break Galaxies (LBGs), motivated by reports of an excess of bright galaxies at unexpectedly high redshifts ($z \geq \sim 8$) [1], further supported by analyses of JWST data [2]. Utilising deep imaging from UltraVISTA and the Hyper Suprime-Cam, we identify ultra-luminous, rare LBG candidates, currently under-represented in the literature. We will address challenges such as colour-space contamination, for example by brown dwarfs [3]. By combining our population with existing photometric samples of fainter galaxies, we aim to refine constraints on the bright-end of the UV luminosity function and trace its evolution across cosmic time [1,2].

The Epoch of Reionization (EoR), the last major phase-transition of all of the hydrogen in the Universe, starts with the emergence of the first galaxies. Their stars, and possibly, black holes, produced the first photons capable of ionizing hydrogen and helium in the large-scale intergalactic medium (IGM). Over the past decade, a concordance picture has emerged in which, driven by these first galaxies, reionization ended within the first billion years of the Universe. This is supplemented by observatories such as the James Webb Space telescope (JWST) and the Atacama Large Millimetre Array (ALMA) yielding transformative insights on both the global properties and the interstellar media (ISM) of such galaxies well within the first billion years. Despite this enormous progress on the end stages of reionization, its key sources, patchy progress and interplay with early galaxy formation remain compelling frontiers in the field of astrophysics. This is because the process of reionization requires understanding the interplay between the small-scale physics of galaxy formation and its large-scale progress on cosmological scales. I will try to shed light on the multi-scale reionization process through the following lectures:

• Lecture 1 : The small-scale physics of reionization: theory & observations
• Chapter 1 – the emergence of the first sources and their physical properties
• Chapter 2 – the stellar populations and black holes in the first sources
• Chapter 3 – the escape of ionizing photons from galactic environments
• Lecture 2 : The large-scale physics of reionization and its feedback on galaxy formation: theory & observations
• Chapter 4 – propagation of ionization fronts in the (clumpy and metal-enriched) intergalactic medium
• Chapter 5 – the inhomogeneous reionization background & its impact on early galaxy formation
• Chapter 6 – using ionization fronts to shed light on dark galaxies (and dark matter) in the era of 21cm cosmology

Prerequisites

The course will mostly be self-contained.

The Epoch of Reionization (EoR), the last major phase-transition of all of the hydrogen in the Universe, starts with the emergence of the first galaxies. Their stars, and possibly, black holes, produced the first photons capable of ionizing hydrogen and helium in the large-scale intergalactic medium (IGM). Over the past decade, a concordance picture has emerged in which, driven by these first galaxies, reionization ended within the first billion years of the Universe. This is supplemented by observatories such as the James Webb Space telescope (JWST) and the Atacama Large Millimetre Array (ALMA) yielding transformative insights on both the global properties and the interstellar media (ISM) of such galaxies well within the first billion years. Despite this enormous progress on the end stages of reionization, its key sources, patchy progress and interplay with early galaxy formation remain compelling frontiers in the field of astrophysics. This is because the process of reionization requires understanding the interplay between the small-scale physics of galaxy formation and its large-scale progress on cosmological scales. I will try to shed light on the multi-scale reionization process through the following lectures:

• Lecture 1 : The small-scale physics of reionization: theory & observations
• Chapter 1 – the emergence of the first sources and their physical properties
• Chapter 2 – the stellar populations and black holes in the first sources
• Chapter 3 – the escape of ionizing photons from galactic environments
• Lecture 2 : The large-scale physics of reionization and its feedback on galaxy formation: theory & observations
• Chapter 4 – propagation of ionization fronts in the (clumpy and metal-enriched) intergalactic medium
• Chapter 5 – the inhomogeneous reionization background & its impact on early galaxy formation
• Chapter 6 – using ionization fronts to shed light on dark galaxies (and dark matter) in the era of 21cm cosmology

Prerequisites

The course will mostly be self-contained.

The nature of the sources emitting sufficient Lyman continuum (LyC) photons to conclude cosmic reionization by z~6 remains elusive. Competing models of the reionization process include those driven by abundant faint galaxies or rare but more luminous ones, and both can account for the evolving neutrality of the intergalactic medium assuming different values of LyC escape fraction. I will give an overview of the physical properties of early cosmic ionizers including in particular their photon production efficiency and the escape fraction of the produced ionizing photons, and how these two key quantities depend on the nature of the stellar populations.

• Lecture 1
• Chapter 1 – Modeling the physical properties of early galaxies
• Chapter 2 – The photon production efficiency of galaxies in the EoR
• Lecture 2
• Chapter 3 – Inferring Lyc escape fractions at high redshift
• Chapter 4 – The evolution of the total ionizing output from galaxies and AGN

JWST, ALMA, NOEMA and other facilities world-wide and beyond provide us with a unique set of multi-wavelength data from the most energetic range to radio. Combining these data and comparing them to models is crucial to better understand galaxie, their formation and their evolution. Photometric data are certainly very useful. However, JWST opened up a new world by securing very-high-quality spectra well within the epoch of reionization, and to z > 10. After an introduction on the input parameters that define the set of models, we will move to experimental tests on a pre-defined sample, focusing on a high redshift sample.. You could also bring you own sample of data that could include any photometric data plus (as of Feb. 2025) NIRSpec prism data.

Prerequisites

In order to use CIGALE, we recommend to read the paper Boquien et al. (2019) that describes the traditional photometric + spectral indices and lines fitting. By October 2025, we hope to have a new paper describing the spectrophotometric fiiting (Burgarella et al. 2025).

I will present the analysis of 34 outflow hosting candidates at redshift 2.5 $<$ z $<$ 9.0 identified through the blue-side broadening of the [O{\small III}]5007 emission line using medium resolution JWST NIRSpec spectroscopy from the JWST Advanced Deep Extragalactic Survey (JADES) [1]. I will argue that the majority of these outflows do not leave their hosts, instead returning as galactic fountains and potentially contributing to short-term quenching [2,3]. As well as discussing the properties of these galaxies and the relationship they have with their outflows, I will comment on the merits and limitations of our selection methodology and the outlook for future studies of this kind.

Studies of early galaxy formation are crucial for understanding the processes that have shaped the current Universe. Galaxies with intense star formation at $z > 6$ are key to events such as reionization, but their faintness limits detailed studies. At lower redshifts ($z \sim 1$), analogous galaxies allow for better characterization. Extreme Emission Line Galaxies (EELGs) stand out due to their high equivalent widths ($\sim 1000 Å$), high specific star formation rates, low metallicities, and low masses. We aim to characterize the physical properties of a sample of 123 EELGs at $0.7 < z < 3$, photometrically selected from the Extended Groth Strip catalog, obtaining results consistent with previous studies [1]. These results will serve as preparatory science for future MOSAIC instrument observations.

Extreme emission-line galaxies (EELGs) provide a unique window into the connection between star formation and mass assembly across cosmic time. Due to their compact structure, intense star formation, low metallicity, and potential for ionizing photon leakage, they are promising analogues of the galaxies that reionize the early Universe [1]. We present a sample of 917 EELGs selected with the 56 narrow bands of J-PAS over 30 deg$^{2}$ [2] and spanning redshifts $z \le 0.8$ for which we derive key physical properties. Most sources surpass the efficiency threshold required for reionization ($\log \xi_\mathrm{ion} = 25.3$), reinforcing their value as local analogues of early-Universe populations.

C'est dans la grotte de Lascaux que l'on trouve les indices les plus anciens de l'observation du ciel par l'Homme. Ces hommes préhistoriques pouvaient-ils imaginer que, 17 000 ans plus tard, leurs descendants développeraient des fusées de plus en plus puissantes, emmenant dans l'espace des satellites à la pointe de la technologie, avec pour seul objectif : repousser de plus en plus loin les limites de l'Univers observable ? Au cours de cette conférence, je vous propose de partir à la découverte de cet Univers, de la Terre jusqu'à la galaxie la plus lointaine, en passant par les millions de planètes et de galaxies qui le peuplent. Nous aborderons les grandes questions de l'astronomie moderne (sommes-nous seuls dans l'Univers, qu'est-ce que la matière noire, pouvons-nous remonter le temps, ...) et nous observerons les plus belles images que les télescopes (sur Terre ou dans l'espace) et les sondes spatiales ont capturées au cours de la dernière décennie. Nous aborderons également le futur de l'astronomie, notamment avec la mise en service en 2028 de l'Extremely Large Telescope.

The nature of the sources emitting sufficient Lyman continuum (LyC) photons to conclude cosmic reionization by z~6 remains elusive. Competing models of the reionization process include those driven by abundant faint galaxies or rare but more luminous ones, and both can account for the evolving neutrality of the intergalactic medium assuming different values of LyC escape fraction. I will give an overview of the physical properties of early cosmic ionizers including in particular their photon production efficiency and the escape fraction of the produced ionizing photons, and how these two key quantities depend on the nature of the stellar populations.

• Lecture 1
• Chapter 1 – Modeling the physical properties of early galaxies
• Chapter 2 – The photon production efficiency of galaxies in the EoR
• Lecture 2
• Chapter 3 – Inferring Lyc escape fractions at high redshift
• Chapter 4 – The evolution of the total ionizing output from galaxies and AGN

To probe the reionization era requires samples of galaxies and AGN at very high redshifts. Using deep photometric surveys it has been possible to select galaxies probing up to the first few hundred million years after the Big Bang. In the first lecture I will describe the main techniques and key datasets for the selection and study of galaxies in the reionization era within deep photometric surveys. The second lecture will focus on the results of these surveys in terms of basic galaxy properties - the number density, colours and physical properties. I will end by presenting a comparison with simulations, to put these observables into context, and open questions in the field.

• Lecture 1: Searching for the first stars and galaxies - techniques
• Chapter 1 – Observational signatures of the first galaxies
• Chapter 2 – Photometric surveys, the power of JWST to Euclid
• Chapter 3 – Selection techniques: principles and challenges
• Lecture 2: Searching for the first stars and galaxies - results and outlook
• Chapter 4 – Overview of galaxy samples to-date
• Chapter 5 – Distribution functions (luminosity function, mass function etc)
• Chapter 6 – Comparison to simulations and open questions

Prerequisites

The course will mostly be self-contained.

The formation and evolution of galaxies is a highly non-linear, multi-physics, multi-scales process that can only be approached theoretically using cosmological simulations to gain an understanding. With a synergy of observations and simulations evolving over the last three decades, a cohesive albeit incomplete picture has emerged of feedback-regulated galaxy growth over cosmic time. With the advent of the James Webb Space telescope, however, the plot has thickened, with seemingly overweight monster galaxies observed in the infancy of the Universe, and existing models appear to be increasingly challenged. I will review efforts to understand the formation of the first structures and the evolution of galaxies using cosmological simulations, with a focus on the first billion years and the epoch of reionization, and the challenges recently posed by JWST observations (which no doubt will have evolved significantly between the writing of this text and when the lectures will be given).

• Lecture 1 : An overview of simulations of galaxy evolution
• Chapter 1 – Different approaches to simulating the Universe
• Chapter 2 – The physical processes, and how to model them
• Chapter 3 – A history of cosmological simulations
• Chapter 4 – A transition to a resolved inter-stellar medium
• Lecture 2 : New challenges for simulations at high redshift
• Chapter 5 – PopIII stars
• Chapter 6 – Reionization with computers
• Chapter 7 – New challenges with JWST
• Chapter 8 – 'Observing' simulated galaxies
• Chapter 9 – The future: more physics, bigger computers, better methods

Prerequisites

The lectures are self-contained and no prior expertise in computational astrophysics is assumed.

We are witnessing an epochal leap in the exploration of the primeval Universe and in understanding of the early formation of galaxies, stars and black holes. Many of these exciting recent developments have been possible especially thanks to the James Webb Space Telescope (JWST), which has opened a totally new discovery space. The lectures will provide an overview of the recent progress in this field, mostly from an observational perspective. I will review the current findings on the stellar populations and star formation histories in distant galaxies, as well as their properties of their interstellar and circumgalactic medium. I will discuss how these results provide important constraints on the formation, evolutionary and transformation processes of galaxies in the early Universe. I will also give an overview of the intriguing and puzzling findings on the connection between star formation and the formation and growth of black holes at their centres. I will conclude by summarising the open questions and the prospects of tackling them with future facilities.

• Chapter 1 - Properties of the early stellar populations
• Chapter 2 - Kinematical and dynamical properties of early galaxies
• Chapter 3 - Properties of the interstellar and circumgalactic medium in early galaxies
• Chapter 4 - Early chemical and dust enrichment
• Chapter 5 - The interplay between galaxies and early black holes
• Chapter 6 - Clustering of primeval galaxies
• Chapter 7 - Prospects from future facilities

The course will review the current status of exploring the first billion years of cosmological evolution using the redshifted 21 cm line, which requires very low-frequency radio observations. It will start with presenting the physics of the 21 cm line and its connection to the physical properties of the intergalactic medium. Then, we will define the three eras of the first billion years (The Dark Ages, Cosmic Dawn, and Epoch of Reionization) in terms of redshifted 21 cm observable. The topology and evolution of the redshifted 21 cm signal will be discussed. The relationship between such topologies and cosmological and structure formation models will be presented. The course will then focus on the observational status of the field and the various projects that are currently running or planned for the near future. The course will show the latest results from these experiments. The course will end with a discussion of the future prospects of the field.

• Lecture 1 : The Redshifted 21 cm Cosmological Probe: Theory and Modeling
• Chapter 1 – Physics of the 21 cm line
• Chapter 2 – The 21 cm brightness temperature and its relation to the IGM
• Chapter 3 – The three eras of the first billion years in terms of the redshifted 21 cm observable
• Chapter 4 – The evolution of the 21 cm and its relation to Cosmology and structure formation

...

• Lecture 2 : The Redshifted 21 cm Cosmological Probe: Observation and Interpretation
• Chapter 5 – The current observational effort and its various strategies
• Chapter 6 – The main Observational and data analysis challenges
• Chapter 7 – Recent results and their implications
• Chapter 8 – Future prospects of the field

Prerequisites

The course will mostly be self-contained.

During this workshop, you will learn how to use the galaxies SED fitting code CIGALE on various types of galaxies. As an exercise, you will have to perform a combined spectro-photometry SED fitting of this sample and then plot the results on a SFR-mass diagram and on a BPT diagram for instance. We will discuss the use of spectroscopy in galaxies fitting. You will work on a sample of nearby galaxies with observations spanning a good wavelength coverage: the Sings/KINGFISH sample.

In order to look at how the first dust grains formed in the early Universe, we studied 173 galaxies between redshifts 4 $<$ z $<$ 11.4 (1600 - 400 Myrs after Big Bang), when the universe was only 12 - 3% of its current age (Burgarella et al. 2025). We used the CIGALE code developed in Marseille to fit JWST NIRCam+NIRSpec data. The emission is modeled using stellar population syntheses integrating both spectroscopy and photometry from the UV to the InfraRed, including emission lines.

We identify 49 very small (about 300 pc) Galaxies with Extremely Low Dust Attenuation (GELDAs), with far-UV attenuations compatible with zero (estimated from the far-UV slope and optical line ratios) consistent with no dust contents, and with stellar masses M$_\star$ $<$ 10$^9$ M$_\odot$.

Beyond redshift z $>$ 9 (550 Myrs after Big Bang), we show that these galaxies dominate. Their dust/stellar mass ratios pinpoint a critical metallicity of Z $\sim$ 0.1 Z$_\odot$, marking the shift from supernova dust production to ISM dust grain growth (Fig. 1), in agreement with theoretical models (eg Asano et al. 2013 and many other following papers).

One of the main results from the JWST’s first years of observation is an unpredicted excess of UV-luminous galaxies at z $>$ 10 compared to HST-calibrated models (Finkelstein et al. 2024; Casey et al. 2024). This shift could explain the excess of bright UV galaxies observed by JWST at z > 9. but not predicted before JWST launch We will also present several other explanations to this excess.

An ongoing analysis suggests that spectroscopically-confirmed galaxies at z $>$ 10 are GELDAs, confirming the (not-unexpected) trend to lower and lower dust attenuation in the early Universe and to a possible evolution of the dust life cycle with cosmic time.

We conclude with an overview of PRIMA's IR capabilities and its status as a NASA probe finalist. (PRIMA is a NASA-led missions with a LAM-led PRIMAger instrument (CNES/SRON/DLR/ASI) 4.5-K proposed successor to Herschel for 2032 as currently no far-IR observations are feasible).

Early observations with the James Webb Space Telescope have revealed an unexpected excess of UV-bright galaxies at the redshift frontier ($z > 10$), with a derived UV luminosity function (UVLF) that exhibits a softer evolution than expected in the first 500 Myr after the Big Bang [1]. These findings could be attributed to various proposed mechanisms such as high star-formation efficiency, active galactic nuclei, top-heavy IMF, or bursty star formation history (SFH).

To investigate this, we aim at characterizing the burstiness level and its evolution in the SFHs of high-redshift galaxies. We implement a stochastic SFH module in CIGALE [2] using power spectrum densities [3], to estimate the burstiness level of star formation in galaxies at $6 < z < 12$. In this talk, I will present the framework and implementation of this stochastic modeling, and show that highly stochastic SFHs better reproduce the observed SEDs of $z > 6$ galaxies, whereas continuous SFHs tend to introduce biases when applied to bursty systems. I will discuss how burstiness affects the tightness of the SFR–M${}_\star$ relation and its redshift evolution. Successively assuming different levels of burstiness, I will present how we determined the best-suited SFH for each $6 < z < 12$ galaxies of the JADES sample and the evolution of the bursty galaxy fraction over cosmic time. In addition, I will discuss other tracers of burstiness as ratio of the recent start formation rate (SFR) to time-averaged SFR over the past 100 Myr. Finally, I will discuss the evolution of $\sigma_{\rm UV}$ and its implications for shaping the UVLF at $z > 10$.

A majority of JWST/NIRSpec-IFU studies at high redshifts to date have focused on UV-bright or massive targets, while early low-mass galaxies remain poorly understood. In this talk, I will revisit two low-mass ($M_*<10^9 M_\odot$, [1]) galaxies at $z\sim7.66$ observed with NIRSpec/MSA in the JWST ERO programme ([2], SMACS J0723.3-7327 NIRSpec-ID6355 and -ID10612). I will present results from new, higher-resolution NIRSpec-IFU follow-up observations of these low-metallicity ($[12+\log(\text{O/H})]<8$) galaxies, which were found to have evidence of hosting AGN [3, 4]. For instance, by using the spatially-resolved data to create maps of rest-frame optical emission lines, I have identified flat metallicity profiles in both galaxies, indicative of ISM redistribution by outflows or past merging. I have also identified high-velocity kinematical components decoupled from galactic rotation in both galaxies, and I will argue that these components likely trace outflows, possibly AGN-driven. I will therefore present the full picture of integrated and spatially-resolved galaxy properties for these two galaxies, and discuss my results in the context of earlier findings from the ERO data.

Recent studies with JWST have also revealed that AGN-driven outflows appear mysteriously absent in high-redshift, low-mass galaxies (e.g. [5]), especially as observed mini-quenching points towards stellar rather than AGN-driven feedback (e.g. [6]). However, recent simulations have suggested that AGN feedback may still play a significant role in early low-mass galaxies [7], necessitating observational verification of this claim. I will therefore present a comparison of the observationally-measured outflow properties of ID6355 and ID10612 to those calculated from the new large-volume \textsc{Aesopica} simulations [8], which fully incorporate different models of black hole growth and AGN feedback. I will discuss the implication these results may have on our understanding of the contribution of AGN-driven feedback to quenching in a wider population of early low-mass galaxies. Finally, I will summarise some of the main issues facing the comparison of simulated and observed AGN-driven outflow properties, and how observers and theorists can work together to address such problems.

Theoretically, models for the formation of massive black holes in the cosmological context have been developed in the early 2000s, following the seminal ideas of Martin Rees in 1978. The existence of black holes in the first billion years of the Universe has been proven by the discovery of bright quasars first (in the early 2000s) and recently by fainter AGN detected thanks to JWST (since 2023). These discoveries have also raised many questions as to how massive black holes form and how some of them grow very fast to explain the properties of the observed sources. I will provide an overview of the astrophysical aspects of massive black holes in the first billion year or so of the Universe, as well as how they can be detected when they accrete matter — through light — and when they merge — through gravitational waves.

Chapter 1 – Formation of massive black hole “seeds”

Chapter 2 – Massive black hole growth: accretion and mergers

Chapter 3 – Detectability of massive black holes: AGN and gravitational waves

Prerequisites

Familiarity with astrophysical concepts, and ideally some basics in galaxy evolution.

Theoretically, models for the formation of massive black holes in the cosmological context have been developed in the early 2000s, following the seminal ideas of Martin Rees in 1978. The existence of black holes in the first billion years of the Universe has been proven by the discovery of bright quasars first (in the early 2000s) and recently by fainter AGN detected thanks to JWST (since 2023). These discoveries have also raised many questions as to how massive black holes form and how some of them grow very fast to explain the properties of the observed sources. I will provide an overview of the astrophysical aspects of massive black holes in the first billion year or so of the Universe, as well as how they can be detected when they accrete matter — through light — and when they merge — through gravitational waves.

Chapter 1 – Formation of massive black hole “seeds”

Chapter 2 – Massive black hole growth: accretion and mergers

Chapter 3 – Detectability of massive black holes: AGN and gravitational waves

Prerequisites

Familiarity with astrophysical concepts, and ideally some basics in galaxy evolution.

The course will review the current status of exploring the first billion years of cosmological evolution using the redshifted 21 cm line, which requires very low-frequency radio observations. It will start with presenting the physics of the 21 cm line and its connection to the physical properties of the intergalactic medium. Then, we will define the three eras of the first billion years (The Dark Ages, Cosmic Dawn, and Epoch of Reionization) in terms of redshifted 21 cm observable. The topology and evolution of the redshifted 21 cm signal will be discussed. The relationship between such topologies and cosmological and structure formation models will be presented. The course will then focus on the observational status of the field and the various projects that are currently running or planned for the near future. The course will show the latest results from these experiments. The course will end with a discussion of the future prospects of the field.

• Lecture 1 : The Redshifted 21 cm Cosmological Probe: Theory and Modeling
• Chapter 1 – Physics of the 21 cm line
• Chapter 2 – The 21 cm brightness temperature and its relation to the IGM
• Chapter 3 – The three eras of the first billion years in terms of the redshifted 21 cm observable
• Chapter 4 – The evolution of the 21 cm and its relation to Cosmology and structure formation

...

• Lecture 2 : The Redshifted 21 cm Cosmological Probe: Observation and Interpretation
• Chapter 5 – The current observational effort and its various strategies
• Chapter 6 – The main Observational and data analysis challenges
• Chapter 7 – Recent results and their implications
• Chapter 8 – Future prospects of the field

Prerequisites

The course will mostly be self-contained.

Among the emerging excess of massive, bright galaxies at cosmic dawn $z > 9$ seen by the James Webb Space Telescope, several exhibit spectral features associated with active galactic nuclei (AGN) [1,2,3,4]. These AGN candidates suggest that supermassive black holes (SMBHs) grow rapidly in the early Universe. In this talk I highlight results from a series of numerical experiments, in these experiments we investigate how SMBHs grow within and influence the most massive galaxies at cosmic dawn using cosmological hydrodynamic zoom-in simulations run with the adaptive mesh refinement code \textsc{ramses} [5]. These simulations are built upon the precursory zoom-in simulations of [6], designed to simulate the massive cosmic dawn galaxy (MDG) environment with intrinsically efficient star formation using a novel turbulence based subgrid model framework. Our suite of simulations explore how super-Eddington accretion, seed mass, and AGN feedback efficiency influence SMBH-galaxy co-evolution in the early universe. We find that self-regulation via AGN feedback at cosmic dawn is not guaranteed in our simulations. It is dependent upon whether the SMBH can become massive enough to enter the self-regulated regime, either by accretion or seeding, before stellar feedback generates significant turbulence in the interstellar medium. Additionally, we find no evidence of galaxy-scale, AGN-driven quenching in the star formation rate (SFR) across all simulations in our suite.

Faint galaxies are thought to be the main drivers behind the Epoch of Reionisation (EoR), while their amount of escaping Lyman continuum (LyC) photons remains unknown. Direct observations of LyC at $z > 5$ are impossible, due to the increased neutrality of the intergalactic medium (IGM). One indirect tracer of LyC escape is linked to the Ly$\alpha$ emission line morphology. Ly$\alpha$ photons scatter on H{\small I} which also blocks LyC, giving rise to a double-peaked profile [1]. Detections of the blue peak are sparse at $z < 5$, due to the resonant scattering of $\lambda < 1215$ \AA~photons on the H{\small I} IGM [2]. The only way to observe the blue peak with no attenuation is if the galaxy lies in the proximity zone of a bright quasar. We present an observation of a double-peaked “proximate galaxy” at the highest detected redshift yet ($z\sim6.6$) near the quasar J0910-0414 [3]. We find a significant escape of LyC into the IGM ($\sim15%$), pointing towards a powerful source behind the EoR. If this LAE can be taken as a representative of early galaxies, comparably faint objects would be sufficient to reionise the bulk of H{\small I} in the Early Universe.

JWST has uncovered a population of compact “Little Red Dots” (LRDs) at $z \gtrsim 3$, characterized by red rest-frame optical colors ($0.4 - 1 \mu m$) and blue rest-frame UV slopes ($0.15 - 0.4 \mu m$). The physical nature of these objects is still debated, but they are thought to host obscured AGN, making this population a unique window to study black hole growth and evolution in the first billion years.

To address this, we develop a detailed framework to model the photometric properties of massive AGN-hosting and purely star-forming galaxies extracted from \code{GADGET-3} cosmological simulations [1]. Using \code{SKIRTv8} radiative transfer calculations, we generate synthetic SEDs for sources at $z = 6 - 9$, exploring variations in dust properties and AGN intrinsic SEDs. By applying commonly used LRD selection criteria [2] to these simulated sources, we identify both AGN and star-forming galaxies as LRD candidates. By analyzing their decomposed spectra and attenuation properties, we investigate the factors that drive LRD selection and assess how dust-reddening influences their classification. In particular, we identify distinguishing features that can help isolate the fraction of JWST-detected LRDs that correspond to MBHs rather than purely star-forming galaxies.

Our results provide new theoretical constraints on the nature of this population, offering a framework to interpret ongoing and future JWST observations. By bridging simulations with photometric selection techniques, this work contributes to refining searches for faint AGN at high redshifts and informs theoretical models of early MBH formation, growth, and feedback.

The first billion years of cosmic history mark an important phase in galaxy evolution, when metal enrichment, feedback, and the assembly of the circumgalactic medium (CGM) were rapidly taking shape. With JWST now providing spatially resolved near-infrared spectroscopy at unprecedented redshifts, we are able to directly probe the distribution of metals in early galaxies and assess the physical processes that drive the baryon cycle. In this work, I present the largest analysis to date of gas-phase metallicity gradients at $z \sim7–9$, using NIRSpec IFU observations of seven low-metallicity galaxies. Specifically, this project builds upon the methodologies developed in Curti et al. (2023, 2025) and Venturi et al. (2025) [1,2,3], applying similar emission-line diagnostics to a new sample of low-metallicity galaxies at $z \sim 7-9$.

Initial metallicity maps, which are limited by low signal-to-noise ratio (S/N), suggest predominantly flat but complex gradients, consistent with expectations from theory where gas mixing processes and stellar feedback dominate [4]. These early results already hint at a metal distribution shaped more by turbulence and outflows than by inside-out growth. To better quantify these gradients, I will implement two complementary approaches: deriving radial metallicity profiles using concentric annuli and applying Voronoi binning to improve the S/N. This will allow a more detailed investigation of the interplay between star formation, gas flows, and metal enrichment during the epoch of reionisation. These observations offer new constraints on early galaxy evolution and represent a step forward in connecting internal galactic processes to the larger-scale CGM environment in the early universe.

Observations indicate that void galaxies differ from the general galaxy population in various properties, requiring a better look at how halos in voids collapse and merge as compared to the general population. Using the cosmological hydrodynamical simulation suite Magneticum Pathfinder, I introduce the void halo mass function (HMF) and compare it to the general HMF from $z \approx 7$ to $z=0$. I demonstrate that the earliest collapsing halos are bad tracers of their surrounding environment, with the HMF of voids and the general population diverging only from $z=4$ and below. These differences in HMF increase toward the centers of the voids, and I will show how general void properties impact the galaxy distribution.

The growth of supermassive black holes (SMBHs) in the early Universe remains an open question, particularly regarding the role of accretion episodes above the Eddington limit [1]. In this work, we investigate whether galaxy mergers can act as triggers for super-Eddington accretion onto SMBHs. To address this problem, we performed cosmological hydrodynamical zoom-in simulations with a modified version of the GIZMO code [2]. Our analysis focuses on a representative major merger, which we progressively re-simulate at increasing resolution in order to maintain a cosmological environment while achieving high resolution within the galaxies.

The luminosity function (LF) of active galactic nuclei (AGN) is a key demographic to understand the evolution of their population across cosmic time. Before the advent of JWST it was extremely challenging to build large ($N>10$) samples of spectroscopically-confirmed AGN at high redshift ($z>5$) [1]. The new JWST treasury program COSMOS-3D (C3D) addresses this limitation by providing wide-field slitless spectroscopy (WFSS) in the wavelength range ${\sim}3.9\mbox{–}5.0\,\mu\mathrm{m}$ over a $0.33\,\mathrm{deg}^2$ area, enabling the confident identification of the largest sample of line emitters at high redshift to date. \par NIRCam WFSS and images [2] are utilised to identify broad, i.e. FWHM ${>}1000\,\mathrm{km}\mathrm{s}^{-1}$, H$\alpha$ lines within $4.9 < z < 6.6$ among photometrically pre-selected candidates within the complete C3D dataset. Based on the identifications we are building a BL AGN catalogue with measured line properties (flux, FWHM of narrow and broad components) and derived quantities (e.g., line luminosities, black hole masses) which serves as the foundation for constructing the AGN LF. \par Several BL H$\alpha$-emitter candidates show asymmetric emission lines with double-peak features. NIRSpec Integral Field Unit follow-up observations will reveal whether these signatures originate from interacting galaxies or represent dual AGN within a single host [3].

Science as a factor in human life is a latecomer. Art existed before the last ice age and is at least fifty thousand years old. Modern science, on the contrary, was born only four hundred years ago: Galileo was the father and gravity the midwife; historiography and tradition have assigned the role of founding mythical event to the story of Galileo’s Experiment at the Leaning Tower of Pisa. Two other tales, Newton Sitting Under the Apple Tree and Einstein’s Happiest Thought of His Life, articulate the history of our ideas about gravity.

We'll talk about inexorable Gravity

We'll talk about Galileo

Newton and Einstein

And Pythagoras

Shamans and the fall from the earthly paradise

The three-body problem

and Robert and Johannes' love for Clara

The friendship of Chopin and Bellini

And above all

The moon in all this

and its lunar music

Two moonlights and Casta Diva

And perhaps an intermezzo by Brahms and another by Schumann