Search

We present the first observational infrared luminosity function (IRLF) measurement in the Epoch of Reionization (EoR) based on a ultraviolet (UV)-selected galaxy sample with the Atacama Large Millimeter Array (ALMA) spectroscopic observations. Our analysis is based on the ALMA large program Reionization Era Bright Emission Line Survey (REBELS), which targets 42 galaxies at z = 6.4–7.7 with [C ii] 158 $\rm{\mu m}$ line scans. 16 sources exhibit dust detection, 15 of which are also spectroscopically confirmed through the [C ii] line. The infrared (IR) luminosities of the sample range from log LIR/L⊙ = 11.4 to 12.2. Using the UV luminosity function as a proxy to derive the effective volume for each of our target sources, we derive IRLF estimates, both for detections and for the full sample including IR luminosity upper limits. The resulting IRLFs are well reproduced by a Schechter function with the characteristic luminosity of $\log L_{*}/\mathrm{ L}_\odot =11.6^{+0.2}_{-0.1}$ . Our observational results are in broad agreement with the average of predicted IRLFs from simulations at z ∼ 7. Conversely, our IRLFs lie significantly below lower redshift estimates, suggesting a rapid evolution from z ∼ 4 to z ∼ 7, into the reionization epoch. The IR obscured contribution to the cosmic star formation rate density at z ∼ 7 amounts to $\mathrm{log(SFRD/{\rm M}_{\odot }\,yr^{-1}\,Mpc^{-3}) = -2.66^{+0.17}_{-0.14} }$ that is at least ∼10 per cent of UV-based estimates. We conclude that the presence of dust is already abundant in the EoR and discuss the possibility of unveiling larger samples of dusty galaxies with future ALMA and JWST observations.

The earliest JWST observations have revealed an unexpected abundance of super-early (z > 10), massive ($M_*\, \approx 10^9 {\rm M}_{\odot }$ ) galaxies at the bright-end (MUV ≈ −21) of the ultraviolet luminosity function (UV LF). We present a minimal physical model that explains the observed galaxy abundance at z = 10–14. The model primarily combines (i) the halo mass function, with (ii) an obscured star formation fraction prescription that is consistent with findings of the ALMA REBELS dusty galaxy survey. It has been successfully tested on well-known UV LFs up to z = 7. We argue that the weak evolution from z = 7 to z ≈ 14 of the LF bright-end can arise from a conspiracy between a decreasing dust attenuation, making galaxies brighter, that almost exactly compensates for the increasing shortage of their host halos. Our minimal model naturally reproduces the z = 10–14 LF if galaxies at $z\lower.5ex\rm{\,\, \buildrel\gt \over \sim \,\,}11$ contain a negligible amounts of dust. We speculate that dust could have been efficiently ejected during the very first phases of galaxy build-up.

Inhomogeneous reionization enhances the 1D Ly α forest power spectrum on large scales at redshifts z ≥ 4. This is due to coherent fluctuations in the ionized hydrogen fraction that arise from large-scale variations in the post-reionization gas temperature, which fade as the gas cools. It is therefore possible to use these relic fluctuations to constrain inhomogeneous reionization with the power spectrum at wavenumbers $\log _{10}(k/{\rm km^{-1}\, s})\lesssim -1.5$. We use the Sherwood-Relics suite of hybrid radiation hydrodynamical simulations to perform a first analysis of new Ly α forest power spectrum measurements at 4.0 ≤ z ≤ 4.6. These data extend to wavenumbers $\log _{10}(k/{\rm km^{-1}\, s})\simeq -3$, with a relative uncertainty of 10–20 per cent in each wavenumber bin. Our analysis returns a 2.7σ preference for an enhancement in the Ly α forest power spectrum at large scales, in excess of that expected for a spatially uniform ultraviolet background. This large-scale enhancement could be a signature of inhomogeneous reionization, although the statistical precision of these data is not yet sufficient for obtaining a robust detection of the relic post-reionization fluctuations. We show that future power spectrum measurements with relative uncertainties of ≲ 2.5 per cent should provide unambiguous evidence for an enhancement in the power spectrum on large scales.

Intervening CIV absorbers are key tracers of metal-enriched gas in galaxy halos over cosmic time. Previous studies suggest that the CIV cosmic mass density ($\Omega_{\rm CIV}$) decreases slowly over 1.5 $\lesssim z\lesssim$ 5 before declining rapidly at $z\gtrsim$ 5, but the cause of this downturn is poorly understood. We characterize the $\Omega_{\rm CIV}$ evolution over 4.3 $\lesssim z\lesssim$ 6.3 using 260 absorbers found in 42 XSHOOTER spectra of $z\sim$ 6 quasars, of which 30 come from the ESO Large Program XQR-30. The large sample enables us to robustly constrain the rate and timing of the downturn. We find that $\Omega_{\rm CIV}$ decreases by a factor of 4.8 $\pm$ 2.0 over the ~300 Myr interval between $z\sim$ 4.7 and $z\sim$ 5.8. The slope of the column density (log N) distribution function does not change, suggesting that CIV absorption is suppressed approximately uniformly across 13.2 $\leq$ log N/cm$^{-2}$ < 15.0. Assuming that the carbon content of galaxy halos evolves as the integral of the cosmic star formation rate density (with some delay due to stellar lifetimes and outflow travel times), we show that chemical evolution alone could plausibly explain the fast decline in $\Omega_{\rm CIV}$ over 4.3 $\lesssim z\lesssim$ 6.3. However, the CIV/CII ratio decreases at the highest redshifts, so the accelerated decline in $\Omega_{\rm CIV}$ at $z\gtrsim$ 5 may be more naturally explained by rapid changes in the gas ionization state driven by evolution of the UV background towards the end of hydrogen reionization., Comment: 20 pages, 8 figures, 4 tables. Published in MNRAS

Recent attempts to detect [OIII] 88$μ$m emission from super-early ($z>10$) galaxy candidates observed by JWST have been unsuccessful. By using zoom-in simulations, we show that these galaxies are faint, and mostly fall below the local metal-poor $\rm [OIII]-SFR$ relation as a result of their low ionization parameter, $U_{\rm ion}\lesssim 10^{-3}$. Such low $U_{\rm ion}$ values are found in galaxies that are in an early assembly stage, and whose stars are still embedded in high-density natal clouds. However, the most luminous galaxy in our sample ($\rm{log}[L_{\rm{[OIII]}}/L_\odot] = 8.4$, $U_{\rm ion} \approx 0.1$) could be detected by ALMA in only $2.8$ hrs., 6 pages, 3 figures, Submitted to MNRAS (comments are welcome)

We present the Sherwood-Relics simulations, a new suite of large cosmological hydrodynamical simulations aimed at modelling the intergalactic medium (IGM) during and after the cosmic reionization of hydrogen. The suite consists of over 200 simulations that cover a wide range of astrophysical and cosmological parameters. It also includes simulations that use a new lightweight hybrid scheme for treating radiative transfer effects. This scheme follows the spatial variations in the ionizing radiation field, as well as the associated fluctuations in IGM temperature and pressure smoothing. It is computationally much cheaper than full radiation hydrodynamics simulations and circumvents the difficult task of calibrating a galaxy formation model to observational constraints on cosmic reionization. Using this hybrid technique, we study the spatial fluctuations in IGM properties that are seeded by patchy cosmic reionization. We investigate the relevant physical processes and assess their impact on the z > 4 Lyman-alpha forest. Our main findings are: (i) Consistent with previous studies patchy reionization causes large scale temperature fluctuations that persist well after the end of reionization, (ii) these increase the Lyman-alpha forest flux power spectrum on large scales, and (iii) result in a spatially varying pressure smoothing that correlates well with the local reionization redshift. (iv) Structures evaporated or puffed up by photoheating cause notable features in the Lyman-alpha forest, such as flat-bottom or double-dip absorption profiles., Version accepted for publication in MNRAS, some discussions added, data added to Fig. 8. 24 pages, 15 figures. Images and movies may be viewed at https://www.nottingham.ac.uk/astronomy/sherwood-relics/

With this contribution we show the readout electronics for kinetic inductance detectors (KIDs) that we are developing based on commercial IQ transceivers from National Instruments and using a Virtex 5 class FPGA. It will be the readout electronics of the COSmic Monopole Observer (COSMO) experiment, a ground based cryogenic Martin–Puplett Interferometer searching for the cosmic microwave background spectral distortions. The readout electronics require a sampling rate in the range of tens of kHz, which is both due to a fast rotating mirror modulating the signal and the time constant of the COSMO KIDs. In this contribution we show the capabilities of our readout electronics using Niobium KIDs developed by Paris Observatory for our 5 K cryogenic system. In particular, we demonstrate the capability to detect 23 resonators from frequency sweeps and to readout the state of each resonator with a sampling rate of about 8 kHz. The readout is based on a finite-state machine where the first two states look for the resonances and generate the comb of tones, while the third one performs the acquisition of phase and amplitude of each detector in free running. Our electronics are based on commercial modules, which brings two key advantages: they can be acquired easily and it is relative simple to write and modify the firmware within the LabView environment in order to meet the needs of the experiment.

The neutron star low-mass X-ray binary SWIFT J1749.4–2807 is the only known eclipsing accreting millisecond X-ray pulsar. In this manuscript, we perform a spectral characterization of the system throughout its 2021, 2-week-long outburst, analysing 11 NICER observations and quasi-simultaneous XMM-Newton and NuSTAR single observations at the outburst peak. The broad-band spectrum is well-modelled with a blackbody component with a temperature of ∼0.6 keV, most likely consistent with a hotspot on the neutron star surface, and a Comptonization spectrum with power-law index Γ ∼ 1.9, arising from a hot corona at ∼12 keV. No direct emission from the disc was found, possibly due to it being too cool. A high truncation radius for the disc, i.e. at ∼20–30 RG, was obtained from the analysis of the broadened profile of the Fe line in the reflection component. The significant detection of a blue-shifted Fe XXVI absorption line at ∼7 keV indicates weakly relativistic X-ray disc winds, which are typically absent in the hard state of X-ray binaries. By comparing the low flux observed during the outburst and the one expected in a conservative mass-transfer, we conclude that mass-transfer in the system is highly non-conservative, as also suggested by the wind detection. Finally, using the NICER spectra alone, we followed the system while it was fading to quiescence. During the outburst decay, as the spectral shape hardened, the hotspot on the neutron star surface cooled down and shrank, a trend which could be consistent with the pure power-law spectrum observed during quiescence., AM acknowledges a financial contribution from the agreement ASI-INAF n.2017-14-H.0 and the INAF mainstream grant (PI: T. Belloni, A. De Rosa). AM, TDS, AA, and RI acknowledge financial contribution from the HERMES project financed by the Italian Space Agency (ASI) Agreement n.2016/13 U.O. AM is supported by the H2020 ERC Consolidator Grant ‘MAGNESIA’ under grant agreement No. 817661 (PI: Rea) and National Spanish grant PGC2018-095512-BI00. This work was also partially supported by the program Unidad de Excelencia Maria de Maeztu CEX2020-001058-M and the PHAROS COST Action (No. CA16214). PB acknowledges support from the CRESST II cooperative agreement (80GSFC21M0002). SG acknowledges the support of the Centre National d’Etudes Spatiales (CNES). GCM was partially supported by Proyecto de Investigación Plurianual (PIP) 0102 (Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)) and PICT-2017-2865 (Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT)). DA acknowledges support from the Royal Society.

We present the results of a cluster search in the gamma-ray sky images of the Large Magellanic Cloud (LMC) region by means of the Minimum Spanning Tree (MST) and DBSCAN algorithms, at energies higher than 6 and 10 GeV, using 12 years of Fermi-LAT data. Several significant clusters were found, the majority of which associated with previously known gamma-ray sources. We confirm our previous detection of the Supernova Remnants N 49B and N 63A and found new significant clusters associated with the SNRs N 49, N 186D and N 44. These sources are among the brightest X-ray remnants in the LMC and corresponds to core-collapse supernovae interacting with dense HII regions, indicating that an hadronic origin of high energy photons is the most likely process., Comment: 14 pages, 4 figures. Accepted for publication in MNRAS

The mass of an exoplanet is a key parameter for the characterisation of the internal structure of a planet, as well as the study of the formation and the evolution of the planet, and its atmosphere. The radial velocity technique allows for measuring the planetary mass from the radial velocity variation of its parent star. However, limitations in the property determination of exoplanets, particularly in their masses, can arise from various sources especially from astrophysical noise due to stellar variability, caused by magnetic activity, which affects the detection and characterisation of exoplanets. This PhD thesis aims to understand the impact of our knowledge of the planetary mass in the planetary atmospheric characterisation and to reduce the sources of uncertainty by a deep study of the stellar activity and by developing new techniques for stellar variability filtering. To this end, I analysed the impact of the planetary mass uncertainties of atmospheric retrievals of multiple targets from the mission reference sample of Ariel, the forthcoming ESA M4 mission aimed at studying planetary atmospheres. I simulated different spectra as observed by Ariel, assuming a primordial or secondary atmosphere of hot Jupiters, and sub-Neptunes or super-Earths, respectively, under different cloudy configurations. I estimated both the accuracy and precision necessary for each analysed target, testing also the capability of retrieval in the case of incorrect mass estimation. I verified that one of the most crucial issues is the presence of high-altitude clouds, in particular in the secondary atmosphere cases. For this reason, I tested the capability to retrieve the cloudy configuration or the presence of a secondary atmosphere during the first tier of the Ariel mission, to take an informed decision if including the planet in the Tier-2 sample. In the second part of this thesis, I described SpotCCF, a photospheric stellar model that I developed to optimise the radial velocity extraction in fast-rotating stars. This model, based on the cross-correlation function technique, takes into account the contribution of stellar activity by considering the presence of multiple spots on the stellar surface that caused deformation of the profile of the cross-correlation function. I applied this model to the HARPS-N observations of V1298 Tau, a very active K1 star, which shows strongly deformed cross-correlation function (CCF) profiles. The SpotCCF model is also able to give information about the spot configuration (latitude, longitude and area covered by the spot). In the end, I also focused my study on understanding stellar activity in M dwarfs, which is crucial for improving our understanding of the physics of stellar atmospheres and for planet search programs. Specifically, I analysed HARPS and HARPS-N observation of AD Leonis, measuring the line profiles and intensities of sensitive activity indicators, and evaluating the correlations between them. Globally, the PhD thesis highlights the importance of planetary mass characterisation and the complexity of their determination due to the effects of stellar variability. In the context of the Ariel mission, it highlights the importance of a detailed and individual analysis of each target of the mission reference sample, to be able to accurately select the Tier-2 targets and characterise their planetary atmosphere, and represents a step forward towards the preparation of the ESA M4 Ariel mission. It also shows how this work cannot be disentangled from a detailed study of the stellar variability that is crucial in the determination of the planetary mass, both in its accuracy and precision.

In this PhD thesis I present the implementation of a method to study the evolution of the large scale structure in a weak-field approximation of General Relativity. Our starting point is the assumption that we can reproduce the classical evolution of the universe with an N-body code in which small scales---below 1 Mpc---interactions are particle-to-particle in the Newtonian limit, while in the large scales these interaction are mediated through the relativistic gravitational field in the weak-field approximation. We have implemented this idea by first redesigning Gevolution code from a monolithic application into a relativistic Particle-Mesh (PM) library libgevolution. Then we have modified Gadget4, a Newtonian TreePM code, adding libgevolution as a plug-in replacement to its original Newtonian PM. This project goes by the name of GrGadget. The advantage of a combined Tree+PM approach with respect to a pure PM method lies in the fact that we can simulate huge cubic boxes, with a length of the order of the 2 Gpc/h, representing a portion of the visible universe and still be able to resolve structures where dark matter halos hosting galaxies are formed on scales below 100 kpc/h using reasonable computational resources. Furthermore one can scale the size of the box without necessarily needing to increase the memory requirements or sacrifying the small scale resolution. Running GrGadget we have also realized that failing to resolve the non-linear structures, for example in the case of a pure PM code, would underestimate the amplitude of the highest Fourier modes of the relativistic fields by more that a 30% factor. In this PhD thesis I present the implementation of a method to study the evolution of the large scale structure in a weak-field approximation of General Relativity. Our starting point is the assumption that we can reproduce the classical evolution of the universe with an N-body code in which small scales---below 1 Mpc---interactions are particle-to-particle in the Newtonian limit, while in the large scales these interaction are mediated through the relativistic gravitational field in the weak-field approximation. We have implemented this idea by first redesigning Gevolution code from a monolithic application into a relativistic Particle-Mesh (PM) library libgevolution. Then we have modified Gadget4, a Newtonian TreePM code, adding libgevolution as a plug-in replacement to its original Newtonian PM. This project goes by the name of GrGadget. The advantage of a combined Tree+PM approach with respect to a pure PM method lies in the fact that we can simulate huge cubic boxes, with a length of the order of the 2 Gpc/h, representing a portion of the visible universe and still be able to resolve structures where dark matter halos hosting galaxies are formed on scales below 100 kpc/h using reasonable computational resources. Furthermore one can scale the size of the box without necessarily needing to increase the memory requirements or sacrifying the small scale resolution. Running GrGadget we have also realized that failing to resolve the non-linear structures, for example in the case of a pure PM code, would underestimate the amplitude of the highest Fourier modes of the relativistic fields by more that a 30% factor.

Funder: Istituto Nazionale di Astrofisica (INAF); Grant(s): “Progetti di Ricerca di Rilevante Interesse Nazionale” (PRIN), Bando 2019 “Piercing through the clouds: a multiwavelength study of obscured accretion in nearby supermassive black holes”, We present ALMA Band 9 continuum observation of the ultraluminous quasi-stellar object (QSO) SDSS J0100+2802 providing a ∼10σ detection at ∼670 GHz. SDSS J0100+2802 is the brightest QSO with the most massive supermassive black hole (SMBH) known at z > 6, and we study its dust spectral energy distribution in order to determine the dust properties and the star formation rate (SFR) of its host galaxy. We obtain the most accurate estimate so far of the temperature, mass, and emissivity index of the dust, which are T dust = 48.4 ± 2.3 K, M dust = (2.29 ± 0.83) × 107 M ⊙, and β = 2.63 ± 0.23, respectively. This allows us to measure the SFR with the smallest statistical error for this QSO, SFR = 265 ± 32 M ⊙yr−1. Our results enable us to evaluate the relative growth of the SMBH and host galaxy of J0100+2802. We find that the SMBH is dominating the process of black-hole galaxy growth in this QSO at z = 6.327, when the universe was 865 Myr old. Such unprecedented constraints on the host-galaxy SFR and dust temperature can only be obtained through high-frequency observations and highlight the importance of ALMA Band 9 to obtain a robust overview of the buildup of the first quasars’ host galaxies at z > 6.

The Cosmology and Astrophysics with Machine Learning Simulations (CAMELS) project was developed to combine cosmology with astrophysics through thousands of cosmological hydrodynamic simulations and machine learning. CAMELS contains 4233 cosmological simulations, 2049 N-body simulations, and 2184 state-of-the-art hydrodynamic simulations that sample a vast volume in parameter space. In this paper, we present the CAMELS public data release, describing the characteristics of the CAMELS simulations and a variety of data products generated from them, including halo, subhalo, galaxy, and void catalogs, power spectra, bispectra, Lyα spectra, probability distribution functions, halo radial profiles, and X-rays photon lists. We also release over 1000 catalogs that contain billions of galaxies from CAMELS-SAM: a large collection of N-body simulations that have been combined with the Santa Cruz semianalytic model. We release all the data, comprising more than 350 terabytes and containing 143,922 snapshots, millions of halos, galaxies, and summary statistics. We provide further technical details on how to access, download, read, and process the data at https://camels.readthedocs.io., The Astrophysical Journal. Supplement Series, 265 (2), ISSN:1538-4365, ISSN:0067-0049

A limiting systematic effect in 21-cm interferometric experiments is the chromaticity due to the coupling between the sky and the instrument. This coupling is sourced by the instrument primary beam; therefore it is important to know the beam to extremely high precision. Here we demonstrate how known beam uncertainties can be characterized using databases of beam models. In this introductory work, we focus on beam errors arising from physically offset and/or broken antennas within a station. We use the public code OSKAR to generate an "ideal" SKA beam formed from 256 antennas regularly-spaced in a 35-m circle, as well as a large database of "perturbed" beams sampling distributions of broken/offset antennas. We decompose the beam errors ("ideal" minus "perturbed") using Principal Component Analysis (PCA) and Kernel PCA (KPCA). Using 20 components, we find that PCA/KPCA can reduce the residual of the beam in our datasets by 60-90% compared with the assumption of an ideal beam. Using a simulated observation of the cosmic signal plus foregrounds, we find that assuming the ideal beam can result in 1% error in the EoR window and 10% in the wedge of the 2D power spectrum. When PCA/KPCA is used to characterize the beam uncertainties, the error in the power spectrum shrinks to below 0.01% in the EoR window and, 12 pages, 9 main figures

Colliding collisionless shocks appear in a great variety of astrophysical phenomena and are thought to be possible sources of particle acceleration in the Universe. We have previously investigated particle acceleration induced by single super-critical shocks (whose magnetosonic Mach number is higher than the critical value of 2.7) (Yao et al., Nat. Phys., vol. 17, issue 10, 2021, pp. 1177–1182; Yao et al., Matter Radiat. Extrem., vol. 7, issue 1, 2022, 014402), as well as the collision of two sub-critical shocks (Fazzini et al., Astron. Astrophys., vol. 665, 2022, A87). Here, we propose to make measurements of accelerated particles from interpenetrating super-critical shocks to observe the ‘phase-locking effect’ (Fazzini et al., Astron. Astrophys., vol. 665, 2022, A87) from such an event. This effect is predicted to significantly boost the energy spectrum of the energized ions compared with a single super-critical collisionless shock. We thus anticipate that the results obtained in the proposed experiment could have a significant impact on our understanding of one type of primary source (acceleration of thermal ions as opposed to secondary acceleration mechanisms of already energetic ions) of ion energization of particles in the Universe.

È stato dimostrato che il modello cosmologico "flat-LCDM" fornisce una buona descrizione delle proprietà osservate dell'Universo. Tuttavia, diverse domande senza risposta e tensioni sui parametri cosmologici indicano che la nostra conoscenza dell'Universo deve ancora essere approfondita. Gli ammassi di galassie, in quanto tracciatori della struttura su larga scala, sono notoriamente potenti sonde cosmologiche, sensibili alle proprietà del campo di densità iniziale dell'Universo, alla natura della materia oscura e dell'energia oscura e alle leggi della gravità su larga scala. In particolare, l'abbondanza di massa ("number counts") e la distribuzione spaziale ("clustering") di questi oggetti sono sensibili ai cambiamenti di diversi parametri cosmologici, principalmente l'ampiezza delle fluttuazioni di densità ($\sigma_8$) e il contenuto di materia dell'Universo ($\Omega_m$). Gli attuali vincoli cosmologici derivanti dalle indagini sugli ammassi sono limitati dal redshift (z

Galaxy clusters are the most massive systems in the Universe. They are usually located at the nodes of the cosmic web from which they continuously accrete matter. In this work, by combining cosmological simulations and local Universe observations, we examined several properties of the different collisionless tracers of the internal dynamics of galaxy clusters - namely Dark Matter (DM), stars, and galaxies -- to gain insights into the main processes operating in structure formation and evolution. We base our analysis on the DIANOGA zoom-in simulation set which is composed of 29 Lagrangian regions at different levels of resolution and under varying physical conditions (full hydrodynamical and/or N-body simulations). Recent measurements (Biviano et al. 2013,2016; Capasso et al. 2019) of the pseudo-entropy (σ^2⁄ρ^(2/3) , where σ velocity dispersion and ρ density of the collisionless tracer) allowed us to study its role in the evolution of clusters as dynamical attractor (e.g., Taylor et al. 2001, Dehnen et al. 2005). Its fingerprint is the universal radial profile described by a simple power-law. We find good agreement in both normalisation and slope between observations and simulations. A significant tension is present with the galaxy member population, we discuss in detail the probable reasons behind this finding. A large body of spectroscopic measurements (Loubser et al. 2018; Sohn et al. 2020, 2021) were able to provide a large statistical sample to study the dynamics of the Brightest Cluster Galaxy (BCG). We compare scaling relations between the BCG and cluster velocity dispersions and corresponding masses: we find in general a good agreement with observational results for the former and significant tension in the latter. We analyse the key features of the velocity dispersion profiles, as traced by stars, DM, and galaxies (Sartoris et al. 2020) and they are in excellent agreement with simulations. We also quantify the assumed impact of the IntraCluster Light (ICL) in these measurements. Furthermore, given the existing dynamical distinction between BCG and ICL, we developed a Machine Learning (ML) method based on a supervised Random Forest to classify stars in simulated galaxy clusters in these two classes. We employ matched stellar catalogues (built from a modified version of Subfind, Dolag et al. 2010) to train and test the classifier. The input features are cluster mass, normalised particle clustercentric distance, and rest-frame velocity. The model is found to correctly identify most of the stars, while the larger errors are exhibited at the BCG outskirts, where the differences between the physical properties of the two components are less obvious. We find that our classifier provides consistent results in simulations for clusters at z

The possible detection of echoes in late gravitational-wave signals is the most promising way to test horizonless alternatives to general relativistic black holes, and probe the physics of these hypothetical ultra-compact objects. While there is currently no evidence for the presence of such signatures, better accuracy is expected with the growing wealth of data from gravitational waves observatories. So far, several searches for these specific signals have been performed considering equidistant intervals between consecutive echoes, i.e. quasi-periodic wave-forms, and ignoring possible backreaction effects of the incoming waves. Here we study scalar perturbations in exotic compact object scenarios that account for possible backreaction phenomena. In particular, we find that if one considers the increase of the central object mass due to the partial absorption of the energy carried by the perturbation, the echo signal can be quite different and non-periodic. Apart from this simple scenario, we also consider the case in which, in order to preserve its compactness above the black hole limit, the compact object absorption shuts down in a finite amount of time or leads to an expansion. In both these cases we find interesting new features that should be taken into account in future searches., Comment: 12 pages, 5 figures

The first billion years of the Universe, from the recombination era to the epoch of reionization still largely remain an enigma. How did the structures form and evolve in the Universe? When did the first stars begin to appear? What were their properties? What was the nature of the objects which heated and reionized the surrounding intergalactic medium? With advances in observational astronomy, it has been established that the tiny initial perturbations of the order∼ 10−5 in the cosmic microwave background (CMB) radiation grew under gravitational instability and evolved to the structures that we see today. However, the period from the Dark Ages till the epoch of reionization (EoR) remains unobserved by direct observations. Ongoing powerful telescopes such as James Webb Space Telescope, Atacama Large Millimeter/submillimeter Array, etc. aim to observe the galaxies at high redshifts. However, besides being unable to capture the faintest galaxies, they might not probe the first sources of heating and reionization. In this Thesis, we exploit the potential of the redshifted 21-cm neutral hydrogen line as an indirect yet significant complementary probe of early sources of heating of the intergalactic medium (IGM). The signal is sensitive to the thermal state of the IGM. Studies suggest that X-rays from High Mass X-ray Binaries (HMXBs) drive temperature fluctuations in the IGM, during the so-called epoch of heating (EoH). The corresponding cosmic 21-cm signal should be detectable at high signal-to-noise by the upcoming radio-interferometers such as the Hydrogen Epoch of Reionization (HERA) and Square Kilometer Array (SKA). Its timing and amplitude of fluctuations during the EoH can give reveal valuable information on the nature of early sources of heating. We predict the 21-cm signal by performing cosmological simulations using a semi-numerical simulation code, 21cmFAST. Since the early galaxies were rare and biased, with their abundances modulated by long-wavelength modes of the underlying density field, the limited size of the cosmological simulations can underestimate the amount of structure in the signal. This effect is significant, especially during the early EoH.We quantify the minimum box size needed for simulating the power spectrum of the 21-cm signal from the Cosmic Dawn up to the EoR. Current theoretical models of the EoH are based on empirical scaling relations between the population-averaged X-ray luminosity (LX) to star-formation rates (SFRs) of local galaxies. However, both theoretical models of HMXB evolution and recent observations suggest that this LX/SFR relation should have a strong dependence on metallicity. We model the impact of an evolving metallicity dependence of HMXBs on the 21-cm signal from the EoH. Motivated by the current uncertainties, we present forecasts for various mass-metallicity relations as well as LX/SFR relations. The Thesis is organized as follows. 1- Chapter 1 covers the cosmological and astrophysical framework which underlies the thesis. The topics range from the standard cosmological model to various aspects of galaxy formation and evolution. 2- Chapter 2 provides an overview of the properties of the IGM such as ionization and thermal evolution. It provides a detailed discussion on the heating of the IGM by X-rays by various X-ray sources, especially HMXBs, and their global scaling relations. The Chapter ends with a brief section on several observational probes of the IGM. 3- Chapter 3 provides details on the physics of the 21-cm signal, its role in probing the IGM, the relevant theoretical framework, observation of the signal, and the challenges it entails. 4- In Chapter 4, we work out what is the minimum size of the simulation box to simulate the 21-cm signal, without losing the structure due to missing wave modes. We quantify the bias and cosmic scatter by running simulations of different sizes and comparing the corresponding 21-cm power spectra with respect to a large simulation box, in terms of telescope noise. 5- In Chapter 5, we explore the metallicity dependence of HMXBs and its effect on the corresponding 21-cm signal. We develop a methodology to relate LX/SFR with gas-phase metallicity. We work out how well the metallicity-independent LX/SFR models can produce similar effects on the 21-cm signal as the metallicity-dependent ones. 6- In Chapter 6, we constrain the properties of the early HMXBs during the EoH. Following up the previous work of Chapter 5, we quantify how our metallicitydependent LX/SFR and mass-metallicity relations can be recovered from upcoming 21-cm observations 7- The Thesis ends with a discussion of conclusions and future aspects in the last chapter.

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer, studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory, a versatile observatory designed to address the Hot and Energetic Universe science theme, selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), it aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over an hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR, browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters. Finally we briefly discuss on the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, and touch on communication and outreach activities, the consortium organisation, and finally on the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. (abridged)., Comment: 48 pages, 29 figures, Accepted for publication in Experimental Astronomy with minor editing

Multi-messenger observations of the transient sky to detect cosmic explosions and counterparts of gravitational wave mergers critically rely on orbiting wide-FoV telescopes to cover the wide range of wavelengths where atmospheric absorption and emission limit the use of ground facilities. Thanks to continuing technological improvements, miniaturised space instruments operating as distributed-aperture constellations are offering new capabilities for the study of high energy transients to complement ageing existing satellites. In this paper we characterise the performance of the upcoming joint SpIRIT + HERMES-TP/SP nano-satellite constellation for the localisation of high-energy transients through triangulation of signal arrival times. SpIRIT is an Australian technology and science demonstrator satellite designed to operate in a low-Earth Sun-synchronous Polar orbit that will augment the science operations for the equatorial HERMES-TP/SP. In this work we simulate the improvement to the localisation capabilities of the HERMES-TP/SP when SpIRIT is included in an orbital plane nearly perpendicular (inclination = 97.6$^\circ$) to the HERMES orbits. For the fraction of GRBs detected by three of the HERMES satellites plus SpIRIT, the combined constellation is capable of localising 60% of long GRBs to within ~ 30 deg$^2$ on the sky, and 60% of short GRBs within ~ 1850 deg$^2$. Based purely on statistical GRB localisation capabilities (i.e., excluding systematic uncertainties and sky coverage), these figures for long GRBs are comparable to those reported by the Fermi GBM. Further improvements by a factor of 2 (or 4) can be achieved by launching an additional 4 (or 6) SpIRIT-like satellites into a Polar orbit, which would both increase the fraction of sky covered by multiple satellite elements, and enable $\geq$ 60% of long GRBs to be localised within a radius of ~ 1.5$^\circ$ on the sky., 17 pages, 10 figures, 1 table. Accepted for publication in PASA

The final phase of the reionization process can be probed by rest-frame UV absorption spectra of quasars at z>6, shedding light on the properties of the diffuse intergalactic medium within the first Gyr of the Universe. The ESO Large Programme "XQR-30: the ultimate XSHOOTER legacy survey of quasars at z~5.8-6.6" dedicated ~250 hours of observations at the VLT to create a homogeneous and high-quality sample of spectra of 30 luminous quasars at z~6, covering the rest wavelength range from the Lyman limit to beyond the MgII emission. Twelve quasar spectra of similar quality from the XSHOOTER archive were added to form the enlarged XQR-30 sample, corresponding to a total of ~350 hours of on-source exposure time. The median effective resolving power of the 42 spectra is R~11400 and 9800 in the VIS and NIR arm, respectively. The signal-to-noise ratio per 10 km/s pixel ranges from ~11 to 114 at $\lambda \simeq 1285$ \AA rest frame, with a median value of ~29. We describe the observations, data reduction and analysis of the spectra, together with some first results based on the E-XQR-30 sample. New photometry in the H and K bands are provided for the XQR-30 quasars, together with composite spectra whose characteristics reflect the large absolute magnitudes of the sample. The composite and the reduced spectra are released to the community through a public repository, and will enable a range of studies addressing outstanding questions regarding the first Gyr of the Universe., Comment: 21 pages, 10 figures. Final version accepted by MNRAS

Proto-planetary discs, the birth environment of planets, are an example of a structure commonly found in astrophysics, accretion discs. Identifying the mechanism responsible for accretion is a long-standing problem, dating back several decades. The common picture is that accretion is a consequence of turbulence, with several instabilities proposed for its origin. While traditionally this field used to be a purely theoretical endeavour, the landscape is now changing thanks mainly to new observational facilities such as the ALMA radio interferometer. Thanks to large improvements in spatial and spectral resolution and sensitivity (which have enabled the study of disc substructure, kinematics and surveys of large disc populations), multiple techniques have been devised to observationally measure the amount of turbulence in discs. This review summarises these techniques, ranging from attempts at direct detection of turbulence from line broadening, to more indirect approaches that rely on properties of the dust or consider the evolution of global disc properties (such as masses, radii and accretion rates) for large samples, and what their findings are. Multiple lines of evidence suggest that discs are in fact not as turbulent as thought one decade ago. On the other hand, direct detection of turbulence in some discs and the finite radial extent of dust substructures and in some cases the finite vertical extent strongly indicate that turbulence must be present at some level in proto-planetary discs. It is still an open question whether this amount of turbulence is enough to power accretion or if this is instead driven by other mechanisms, such as MHD winds., Comment: 24 pages, 7 figures. Accepted for publication on New Astronomy Reviews; small changes following community feedback in v2

Supernova remnants (SNRs), the products of stellar explosions, are powerful astrophysical laboratories, which allow us to study the physics of collisionless shocks, thanks to their bright electromagnetic emission. Blast wave shocks generated by supernovae (SNe) provide us with an observational window to study extreme conditions, characterized by high Mach (and Alfvenic Mach) numbers, together with powerful nonthermal processes. In collisionless shocks, temperature equilibration between different species may not be reached at the shock front. In this framework, different particle species might be heated at different temperatures (depending on their mass) in the post-shock medium of SNRs. SNRs are also characterized by a broadband nonthermal emission stemming at the shock front as a result of nonthermal populations of leptons and hadrons. These particles, known as cosmic rays, are accelerated up to ultrarelativistic energies via diffusive shock acceleration. If SNRs lose a significant fraction of their ram energy to accelerate cosmic rays, the shock dynamics should be altered with respect to the adiabatic case. This shock modification should result in an increase of the total shock compression ratio with respect to the Rankine-Hugoniot value of 4. Here I show that the combination of X-ray high resolution spectroscopy (to measure ion temperatures) and moderate resolution spectroscopy (for a detailed diagnostic of the post-shock density) can be exploited to study both the heating mechanism and the particle acceleration in collisionless shocks. I report on new results in the temperatures measured for different ion species in the remnant of SN 1987A. I also discuss evidence of shock modification recently obtained in the remnant of SN 1006 a. D., where the shock compression ratio increases significantly as the angle between the shock velocity and the ambient magnetic field is reduced., Comment: Author's preprint. Accepted for publication in Plasma Physics and Controlled Fusion after minor revisions

ALMA observations have revealed that many high redshift galaxies are surrounded by extended (10-15 kpc) [CII]-emitting halos which are not predicted by even the most advanced zoom-in simulations. Using a semi-analytical model, in a previous work we suggested that such halos are produced by starburst-driven, catastrophically cooling outflows. Here, we further improve the model and compare its predictions with data from 7 star-forming ($10\lesssim \rm SFR/ M_\odot \rm yr^{-1}, Comment: Accepted for publication in MNRAS. 11 pages, 6 figures

The local Cosmic Ray (CR) energy spectrum exhibits a spectral softening at energies around 3~PeV. Sources which are capable of accelerating hadrons to such energies are called hadronic PeVatrons. However, hadronic PeVatrons have not yet been firmly identified within the Galaxy. Several source classes, including Galactic Supernova Remnants (SNRs), have been proposed as PeVatron candidates. The potential to search for hadronic PeVatrons with the Cherenkov Telescope Array (CTA) is assessed. The focus is on the usage of very high energy $\gamma$-ray spectral signatures for the identification of PeVatrons. Assuming that SNRs can accelerate CRs up to knee energies, the number of Galactic SNRs which can be identified as PeVatrons with CTA is estimated within a model for the evolution of SNRs. Additionally, the potential of a follow-up observation strategy under moonlight conditions for PeVatron searches is investigated. Statistical methods for the identification of PeVatrons are introduced, and realistic Monte--Carlo simulations of the response of the CTA observatory to the emission spectra from hadronic PeVatrons are performed. Based on simulations of a simplified model for the evolution for SNRs, the detection of a $\gamma$-ray signal from in average 9 Galactic PeVatron SNRs is expected to result from the scan of the Galactic plane with CTA after 10 hours of exposure. CTA is also shown to have excellent potential to confirm these sources as PeVatrons in deep observations with $\mathcal{O}(100)$ hours of exposure per source., Comment: 34 pages, 16 figures, Accepted for publication in Astroparticle Physics

Non-equilibrium chemistry is a key process in the study of the InterStellar Medium (ISM), in particular the formation of molecular clouds and thus stars. However, computationally it is among the most difficult tasks to include in astrophysical simulations, because of the typically high (>40) number of reactions, the short evolutionary timescales (about $10^4$ times less than the ISM dynamical time) and the characteristic non-linearity and stiffness of the associated Ordinary Differential Equations system (ODEs). In this proof of concept work, we show that Physics Informed Neural Networks (PINN) are a viable alternative to traditional ODE time integrators for stiff thermo-chemical systems, i.e. up to molecular hydrogen formation (9 species and 46 reactions). Testing different chemical networks in a wide range of densities ($-2< \log n/{\rm cm}^{-3}< 3$) and temperatures ($1 < \log T/{\rm K}< 5$), we find that a basic architecture can give a comfortable convergence only for simplified chemical systems: to properly capture the sudden chemical and thermal variations a Deep Galerkin Method is needed. Once trained ($\sim 10^3$ GPUhr), the PINN well reproduces the strong non-linear nature of the solutions (errors $\lesssim 10\%$) and can give speed-ups up to a factor of $\sim 200$ with respect to traditional ODE solvers. Further, the latter have completion times that vary by about $\sim 30\%$ for different initial $n$ and $T$, while the PINN method gives negligible variations. Both the speed-up and the potential improvement in load balancing imply that PINN-powered simulations are a very palatable way to solve complex chemical calculation in astrophysical and cosmological problems., 16 pages, 12 figures, accepted for publication on MNRAS

The large total infrared (TIR) luminosities ($L_{\rm TIR} \gtrsim 10^{12}~L_\odot$) observed in $z \sim 6$ quasars are generally converted into high star formation rates ($SFR \gtrsim 10^2~M_\odot$ yr$^{-1}$) of their host galaxies. However, these estimates rely on the assumption that dust heating is dominated by stellar radiation, neglecting the contribution from the central Active Galactic Nuclei (AGN). We test the validity of this assumption by combining cosmological hydrodynamic simulations with radiative transfer calculations. We find that, when AGN radiation is included in the simulations, the mass (luminosity)-weighted dust temperature in the host galaxies increases from $T\approx 50$ K ($T \approx 70$ K) to $T\approx 80$ K ($T\approx 200$ K), suggesting that AGN effectively heat the bulk of dust in the host galaxy. We compute the AGN-host galaxy $SFR$ from the synthetic spectral energy distribution by using standard $SFR - L_{\rm TIR}$ relations, and compare the results with the "true" values in the simulations. We find that the $SFR$ is overestimated by a factor of $\approx 3$ ($\gtrsim 10$) for AGN bolometric luminosities of $L_{\rm bol} \approx 10^{12}~L_\odot$ ($\gtrsim 10^{13}~ L_\odot$), implying that the star formation rates of $z\sim 6$ quasars can be overestimated by over an order of magnitude., Comment: 9 pages, 6 figures. Accepted for publication by MNRAS

We present Atacama Large Millimeter/Submillimeter Array (ALMA) [CII] and $\sim158$ $\rm\mu m$ continuum observations of REBELS-25, a massive, morphologically complex ultra-luminous infrared galaxy (ULIRG; $L_{\rm IR}=1.5^{+0.8}_{-0.5}\times10^{12}$ L$_\odot$) at $z=7.31$, spectroscopically confirmed by the Reionization Era Bright Emission Line Survey (REBELS) ALMA Large Programme. REBELS-25 has a significant stellar mass of $M_{*}=8^{+4}_{-2}\times10^{9}$ M$_\odot$. From dust-continuum and ultraviolet observations, we determine a total obscured + unobscured star formation rate of SFR $=199^{+101}_{-63}$ M$_\odot$ yr$^{-1}$. This is about four times the SFR estimated from an extrapolated main-sequence. We also infer a [CII]-based molecular gas mass of $M_{\rm H_2}=5.1^{+5.1}_{-2.6}\times10^{10}$ $M_\odot$, implying a molecular gas depletion time of $ t_{\rm depl, H_2}=0.3^{+0.3}_{-0.2}$ Gyr. We observe a [CII] velocity gradient consistent with disc rotation, but given the current resolution we cannot rule out a more complex velocity structure such as a merger. The spectrum exhibits excess [CII] emission at large positive velocities ($\sim500$ km s$^{-1}$), which we interpret as either a merging companion or an outflow. In the outflow scenario, we derive a lower limit of the mass outflow rate of 200 M$_\odot$ yr$^{-1}$, which is consistent with expectations for a star formation-driven outflow. Given its large stellar mass, SFR and molecular gas reservoir $\sim700$ Myr after the Big Bang, we explore the future evolution of REBELS-25. Considering a simple, conservative model assuming an exponentially declining star formation history, constant star formation efficiency, and no additional gas inflow, we find that REBELS-25 has the potential to evolve into a galaxy consistent with the properties of high-mass quiescent galaxies recently observed at $z\sim4$., Comment: Accepted for publication in MNRAS. 21 pages, 8 figures

Transition disks are protoplanetary disks with inner cavities possibly cleared by massive companions, which makes them prime targets to observe at high resolution to map their velocity structure. We present ALMA Band 6 dust and gas observations of the transition disk around RXJ1604.3-2130 A, known to feature nearly symmetric shadows in scattered light. We studied the $^{12}$CO line channel maps and moment maps of the line of sight velocity and peak intensity. We fitted a Keplerian model of the channel-by-channel emission to study line profile differences and produced deprojected radial profiles for all velocity components. The $^{12}$CO emission shows a cavity inwards of $\sim$56 au and within the dust continuum ring at 81 au. The azimuthal brightness variations in the $^{12}$CO line and dust continuum are broadly aligned with the shadows detected in scattered-light observations. We find a strong localized non-Keplerian feature toward the west within the continuum ring (at $R=41\pm 10$ au and $PA=280\pm 2 ^\circ$). A tightly wound spiral is also detected which extends over 300$^\circ$ in azimuth, possibly connected to the localized non-Keplerian feature. Finally, a bending of the iso-velocity contours within the gas cavity indicates a highly perturbed inner region, possibly related to the presence of a misaligned inner disk. While broadly aligned with the scattered-light shadows, the localized non-Keplerian feature cannot be solely due to changes in temperature. Instead, we interpret the kinematical feature as tracing a massive companion located at the edge of the dust continuum ring. We speculate that the spiral is caused by buoyancy resonances driven by planet-disk interactions. However, this potential planet at $\sim$41 au cannot explain the gas-depleted cavity, the low accretion rate, and the misaligned inner disk, which suggests the presence of another companion closer in., 13 pages, 14 figures. To be published in Astronomy & Astrophysics Letters

Characterising the properties of exoplanet atmospheres relies on several interconnected parameters, which makes it difficult to determine them independently. Planetary mass plays a role in determining the scale height of atmospheres, similarly to the contribution from the average molecular weight of the gas. We investigate the relevance of planetary mass knowledge in spectral retrievals, identifying cases where mass measurements are needed for clear or cloudy and primary or secondary atmospheres, along with the relevant precision, in the context of the ESA M4 Ariel Mission. We used TauREx to simulate the Ariel transmission spectra of representative targets of the Ariel mission reference sample, assuming different scenarios: a primordial cloudy atmosphere of a hot Jupiter and a hot Neptune, as well as the secondary atmosphere of a super-Earth that also exhibits a cloud presence. We extracted information on the various properties of the atmospheres for the cases of unknown mass or mass with different uncertainties. We also tested how the signal-to-noise ratio impacts atmospheric retrieval for different wavelength ranges. We accurately retrieved the primordial atmospheric composition independently from mass uncertainties for clear atmospheres, while we found that the uncertainties increased for high altitude clouds. We highlight the importance of the signal-to-noise ratio in the Rayleigh scattering region of the spectrum. For the secondary atmosphere cases, a mass uncertainty no larger than 50% is sufficient to retrieve the atmospheric parameters, even in the presence of clouds. Our analysis suggests that even in the worst-case scenario, a 50% mass precision level is enough for producing reliable retrievals, while an atmospheric retrieval without any knowledge of a planetary mass could lead to biases in cloudy primary atmospheres as well as in secondary atmospheres., Comment: 29 pages, 21 figures. Accepted for publication in Section 10. Planets and planetary systems of Astronomy and Astrophysics. The official date of acceptance is 15/11/2022. Abstract shortened for the arXiv listing

We investigate neutron star solutions in scalar-tensor theories of gravity with first-order derivative self-interactions in the action and in the matter coupling. We assess the robustness of the kinetic screening mechanism present in these theories against general conformal couplings to matter. The latter include ones leading to the classical Damour-Esposito-Far\`ese scalarization, as well as ones depending on the kinetic term of the scalar field. We find that kinetic screening always prevails over scalarization, and that kinetic couplings with matter enhance the suppression of scalar gradients inside the star even more, without relying on the non-linear regime. Fine tuning the kinetic coupling with the derivative self-interactions in the action allows one to partially cancel the latter, resulting in a weakening of kinetic screening inside the star. This effect represents a novel way to break screening mechanisms inside matter sources, and provides new signatures that might be testable with astrophysical observations., Comment: 8 pages, 5 figures. Journal Version. Minor changes, added summary table

The accurate reconstruction of the plasma and magnetic field parameters in the ambient interplanetary medium is fundamental to reproduce the interplanetary propagation of solar disturbances such as solar energetic particles (SEPs), stream and corotating interaction regions (SIRs and CIRs), and coronal mass ejections (CMEs), both for understanding the physics of these phenomena and for applications in space weather forecasting. The small-scale features of the ambient solar wind, in fact, affect the evolution, arrival times, and geo-effectiveness of solar transients. The Reverse In situ and MHD Approach (RIMAP) is a hybrid analytical-numerical method to reconstruct the heliosphere on the ecliptic plane from in situ measurements acquired by spacecraft with heliocentric orbits. RIMAP uses the in situ measurements as boundary conditions for a MHD simulation based on the PLUTO code, combining ballistic and MHD approaches in order to preserve the small-scale variability of the solar wind flow lines and thus offering a structured, realistic background medium for modelling the propagation of solar eruptions. In this dissertation, after an introduction about the main topics and models of heliospheric physics and the magnetohydrodynamics equations, we present the detailed description of the novelties of the RIMAP model, and its application to the measurements acquired by spacecraft at 1 AU in correspondence of solar minima configurations. Then, one of these reconstructions is used as a background medium to propagate an interplanetary CME. The perturbation is modelled as a spheroidal, homogeneous plasma cloud without internal magnetic flux rope. We use an artificial, passive tracer to quantify the mixing at 1 AU between ambient solar wind material and the one with coronal eruption origins, in order to evaluate the fraction of plasma measured in situ that can be traced back to its sources on the Sun. The RIMAP reconstruction is also carried out using measurements acquired by NASA’s Parker Solar Probe (PSP) during its seventh solar encounter, in January 2021, between 20 and 40 solar radii. This was the time of the first quadrature between PSP and ESA-NASA’s Solar Orbiter (SolO), which at the time was orbiting the Sun around 0.5 AU and providing remote sensing observations of the solar corona via the Metis coronagraph. The RIMAP reconstruction connects density and wind speed estimates inferred from the coronal features observed by Metis/SolO between 3 and 6 solar radii to the measurements acquired by PSP at 21.5 solar radii along the corresponding plasma streamline. Thus, the magnetic connection between the inner corona and the super Alfvénic wind is reconstructed with a high degree of accuracy with a detailed data-driven MHD simulation. Finally, we describe the possible future developments of the RIMAP technique such as the extension to a two-fluids treatment, the testing of different models of magnetized coronal mass ejections, the simulation of solar wind switchbacks, and the extension to full three-dimensional boundaries, using coronagraphic observations to infer the input parameters.

Large-scale outflows are believed to be an important mechanism in the evolution of galaxies. We can determine the impact of these outflows by studying either current galaxy outflows and their effect in the galaxy or by studying the effect of past outflows on the gas surrounding the galaxy. In this work, we examine the CO(7−6), [C i] ($^{3} \rm P_{1} \rightarrow {\rm ^3 P}_{0}$), H2O 211–202, and dust continuum emission of 15 extremely red quasars at z ∼ 2.3 using ALMA. By investigating the radial surface brightness profiles of both the individual sources and the stacked emission, we detect extended cold gas and dust emission on scales of ∼14 kpc in CO(7−6), [C i](2−1), and dust continuum. This is the first time that the presence of a large amount of molecular gas was detected on large, circumgalactic medium scales around quasar host galaxies using [C i] extended emission. We estimate the dust and molecular gas mass of these haloes to be 107.6 and 1010.6 M⊙, indicating significant dust and molecular gas reservoirs around these extreme quasars. By estimating the time-scale at which this gas can reach these distances by molecular gas outflows (7–32 Myr), we conclude that these haloes are a relic of past AGN or starburst activity, rather than an effect of the current episode of extreme quasar activity.

La tesi si concentra sulla quantificazione dell'impatto dell'attività stellare sulle osservazioni dei pianeti in transito e sull'identificazione di una metodologia per correggere questi effetti. In particolare, viene approfondito l'effetto delle macchie stellari, sia non occultate che occulte. La presenza di macchie sul disco stellare visibile può distorcere la curva della luce di transito primaria in modo dipendente dalla lunghezza d'onda, mimando la presenza di un'atmosfera. Per tener conto di questo effetto, la tesi presenta un metodo innovativo per stimare le proprietà delle macchie e la loro distribuzione dalle osservazioni fuori transito e, su questa base, correggere le curve di luce del transito planetario, evitando possibili degenerazioni tra la presenza di un' atmosfera planetaria e delle macchie. Il metodo è sviluppato per la spettroscopia di transito a bassa risoluzione ed è testato su simulazioni realistiche di future osservazioni di transiti planetari con Ariel, una missione spaziale dedicata all'osservazione di circa 1000 esopianeti in transito il cui lancio è previsto nel 2029. Successivamente, il metodo viene applicato a osservazioni reali di HST di un pianeta in transito. Il primo capitolo della tesi presenta il problema delle macchie stellari sulla spettroscopia a bassa risoluzione e gli sforzi finora compiuti per mitigare il loro effetto sulle osservazioni di pianeti transitanti. Il capitolo 2 presenta un metodo per correggere l'effetto delle macchie non attraversate dal pianeta in transito, partendo da un modello base dell'attività stellare, dove la stella macchiata è simulata come una combinazione lineare di spettri stellari a diverse temperature e la stella ha un emissione uniforme. Il metodo è testato su 3 bersagli simulati di sistemi in transito che saranno osservati dalla missione Ariel. Nel capitolo 3 è introdotto un altro componente nel modello stellare, rendendolo più realistico. Infatti, sono simuli nuovamente gli stessi target analizzati nel Capitolo 2 ma includendo l'effetto di oscuramento al bordo al modello stellare. In questo capitolo è illustrata l'importanza di tener conto di questo effetto se si vuole ottenere una buona stima dei parametri delle macchie e una buona correzione dell'atmosfera del pianeta. Nel Capitolo 4, l'approccio presentato nei capitoli precedenti, e testato su simulazioni, è applicato alle osservazioni dei transiti planetari del pianeta LHS 1140 b, acquisite con il Telescopio Spaziale Hubble. L'analisi porta a due possibili scenari: nel primo la stella è molto attiva e quasi il 65% della sua superficie è ricoperta da macchie (contro altri indicatori in letteratura che suggeriscono una stella tranquilla); nel secondo, la stella è quieta ma è circa 300 K più fredda rispetto al primo scenario. In entrambi i casi, la modulazione cromatica osservata derivata dalle curve di luce di transito planetario non è dovuta alla presenza di un'atmosfera planetaria. Nel Capitolo 5, analizzo le curve di luce TESS della stella attiva V1298 Tau, modellando la stella con un modello a 4 macchie, corotanti con la superficie stellare. Tale studio permette non solo di ricavare la distribuzione delle macchie su V1298 Tau ma anche di correggere le curve di luce di transito dei 4 pianeti orbitanti intorno alla stella per l'effetto delle macchie non occultate. I risultati mostrano che l'effetto delle macchie può produrre differenti profondità di transito per i 4 pianeti in banda TESS e K2, giustificando così la discrepanza tra i raggi planetari nelle due bande riportata nella letteratura scientifica. This thesis focuses on the quantification of the impact of stellar activity on observations of transiting planets and on the identification of a methodology to correct these effects. In particular, the role of starspots, both un-occulted and occulted is considered. The presence of spots on the visible stellar disk may distort the primary transit light curve in a wavelength-dependent way, mimicking the presence of an atmosphere. To take into account this bias, the thesis presents an innovative method to estimate the spots properties and their distribution from the out-of-transit observations and, on this basis, correct the planetary transit light curves, avoiding possible degeneracy between the presence of the planetary atmosphere and of the spots. The method is developed for low-resolution transit spectroscopy and is tested on realistic simulations of future observations of planetary transits with Ariel, a space mission dedicated to the observation of about 1000 transiting exoplanets whose launch is expected in 2029. Then, the method is applied to real observations of HST of a transiting planet. The first chapter of the thesis presents the state of the art of efforts done so far to mitigate the effect of the spots in planetary observations (chapter 1). Chapter 2 presents a method for correcting the effect of spots not-crossed by the transiting planet, starting from a basic model of the stellar activity, where the spotted star is simulated as a linear combination of stellar spectra at different temperatures and the star has a uniform emission. The method is tested on 3 simulated targets of transiting systems that will be observed by the Ariel mission. In Chapter 3, I introduced another component in the stellar model, making it more realistic. In fact, I simulate again the same targets analyzed in Chapter 2 but including the limb darkening effect to the stellar model. In this chapter, I show the importance of taking into account this effect if a good estimate of the spots’ parameters and a good correction of the planet's atmosphere have to be obtained. In Chapter 4 the approach presented in the previous chapters, and tested on simulations, is applied to observations of planetary transits of the planet LHS 1140 b, acquired with the Hubble Space Telescope. The analysis leads to two possible scenarios: in the first one the star is very active and almost the 65% of its surface is covered by spots (against other indicators in the literature suggesting a quiet star); in the second one, the star is quiet but is about 300 K cooler than in the first scenario. In both cases, the observed chromatic modulation derived from the planetary transit light curves is not due to the presence of a planetary atmosphere. In Chapter 5, I analyze the TESS light curves of the active star V1298 Tau, by modeling the star with a model dominated by 4 spots, co-rotating with the stellar surface. Such a study allows not only to derive the distribution of spots on V1298 Tau but also to correct the transit light curves of the 4 planets orbiting around the star for the effect of non-occulted spots. The results show that the spots’ effect may produce different transit depths for the 4 planets in the TESS and the K2 band, thus justifying the discrepancy between the planetary radii in the two bands reported in the scientific literature.

Full list of authors: Amaro-Seoane, Pau; Andrews, Jeff; Sedda, Manuel Arca; Askar, Abbas.; Baghi, Quentin; Balasov, Razvan; Bartos, Imre; Bavera, Simone S.; Bellovary, Jillian; Berry, Christopher P. L.; Berti, Emanuele; Bianchi, Stefano; Blecha, Laura; Blondin, Stephane; Bogdanovic, Tamara; Boissier, Samuel; Bonetti, Matteo; Bonoli, Silvia; Bortolas, Elisa; Breivik, Katelyn; Capelo, Pedro R.; Caramete, Laurentiu; Cattorini, Federico; Charisi, Maria; Chaty, Sylvain; Chen, Xian; Chruslinska, Martyna; Chua, Alvin J. K.; Church, Ross; Colpi, Monica; D'Orazio, Daniel; Danielski, Camilla; Davies, Melvyn B.; Dayal, Pratika; De Rosa, Alessandra; Derdzinski, Andrea; Destounis, Kyriakos; Dotti, Massimo; Dutan, Ioana; Dvorkin, Irina; Fabj, Gaia; Foglizzo, Thierry; Ford, Saavik; Fouvry, Jean-Baptiste; Franchini, Alessia; Fragos, Tassos; Fryer, Chris; Gaspari, Massimo; Gerosa, Davide; Graziani, Luca; Groot, Paul; Habouzit, Melanie; Haggard, Daryl; Haiman, Zoltan; Han, Wen-Biao; Istrate, Alina; Johansson, Peter H.; Khan, Fazeel Mahmood; Kimpson, Tomas; Kokkotas, Kostas; Kong, Albert; Korol, Valeriya; Kremer, Kyle; Kupfer, Thomas; Lamberts, Astrid; Larson, Shane; Lau, Mike; Liu, Dongliang; Lloyd-Ronning, Nicole; Lodato, Giuseppe; Lupi, Alessandro; Ma, Chung-Pei; Maccarone, Tomas; Mandel, Ilya; Mangiagli, Alberto; Mapelli, Michela; Mathis, Stephane; Mayer, Lucio; McGee, Sean; McKernan, Berry; Miller, M. Coleman; Mota, David F.; Mumpower, Matthew; Nasim, Syeda S.; Nelemans, Gijs; Noble, Scott; Pacucci, Fabio; Panessa, Francesca; Paschalidis, Vasileios; Pfister, Hugo; Porquet, Delphine; Quenby, John; Ricarte, Angelo; Roepke, Friedrich K.; Regan, John; Rosswog, Stephan; Ruiter, Ashley; Ruiz, Milton; Runnoe, Jessie; Schneider, Raffaella; Schnittman, Jeremy; Secunda, Amy; Sesana, Alberto; Seto, Naoki; Shao, Lijing; Shapiro, Stuart; Sopuerta, Carlos; Stone, Nicholas C.; Suvorov, Arthur; Tamanini, Nicola; Tamfal, Tomas; Tauris, Thomas; Temmink, Karel; Tomsick, John; Toonen, Silvia; Torres-Orjuela, Alejandro; Toscani, Martina; Tsokaros, Antonios; Unal, Caner; Vazquez-Aceves, Veronica; Valiante, Rosa; van Putten, Maurice; van Roestel, Jan; Vignali, Christian; Volonteri, Marta; Wu, Kinwah; Younsi, Ziri; Yu, Shenghua; Zane, Silvia; Zwick, Lorenz; Antonini, Fabio; Baibhav, Vishal; Barausse, Enrico; Bonilla Rivera, Alexander; Branchesi, Marica; Branduardi-Raymont, Graziella; Burdge, Kevin; Chakraborty, Srija; Cuadra, Jorge; Dage, Kristen; Davis, Benjamin; de Mink, Selma E.; Decarli, Roberto; Doneva, Daniela; Escoffier, Stephanie; Gandhi, Poshak; Haardt, Francesco; Lousto, Carlos O.; Nissanke, Samaya; Nordhaus, Jason; O'Shaughnessy, Richard; Portegies Zwart, Simon; Pound, Adam; Schussler, Fabian; Sergijenko, Olga; Spallicci, Alessandro; Vernieri, Daniele; Vigna-Gomez, Alejandro.-- This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/., The Laser Interferometer Space Antenna (LISA) will be a transformative experiment for gravitational wave astronomy, and, as such, it will offer unique opportunities to address many key astrophysical questions in a completely novel way. The synergy with ground-based and space-born instruments in the electromagnetic domain, by enabling multi-messenger observations, will add further to the discovery potential of LISA. The next decade is crucial to prepare the astrophysical community for LISA’s first observations. This review outlines the extensive landscape of astrophysical theory, numerical simulations, and astronomical observations that are instrumental for modeling and interpreting the upcoming LISA datastream. To this aim, the current knowledge in three main source classes for LISA is reviewed; ultra-compact stellar-mass binaries, massive black hole binaries, and extreme or interme-diate mass ratio inspirals. The relevant astrophysical processes and the established modeling techniques are summarized. Likewise, open issues and gaps in our understanding of these sources are highlighted, along with an indication of how LISA could help making progress in the different areas. New research avenues that LISA itself, or its joint exploitation with upcoming studies in the electromagnetic domain, will enable, are also illustrated. Improvements in modeling and analysis approaches, such as the combination of numerical simulations and modern data science techniques, are discussed. This review is intended to be a starting point for using LISA as a new discovery tool for understanding our Universe. © The Author(s) 2023, corrected publication 2023., P. Dayal acknowledges support from the European Research council (ERC-717001) and from the Netherlands Research Council NWO (016.VIDI.189.162). P.H. Johansson acknowledges the support from the European Research Council (ERC-818930). S. Toonen acknowledges support from the Netherlands Research Council NWO (VENI 639.041.645 Grants) C. Unal is supported by European Structural and Investment Funds and the Czech Ministry of Education, Youth and Sports (Project CoGraDS - CZ.02.1.01/0.0/0.0/15_003/0000437). S. Chaty acknowledges the LabEx UnivEarthS for the funding of Interface project I10 “From binary evolution towards merging of compact objects”. A. De Rosa acknowledges financial contribution from the agreement ASI-INAF n.2017-14-H.O E. Berti is supported by NSF Grants No. PHY-1912550 and AST-2006538, NASA ATP Grants No. 17-ATP17-0225 and 19-ATP19-0051, NSF-XSEDE Grant No. PHY-090003, and NSF Grant PHY-20043. D. Gerosa is supported by European Union’s H2020 ERC Starting Grant No. 945155–GWmining, Leverhulme Trust Grant No. RPG-2019-350 and Royal Society Grant No. RGS-R2-202004. T. Bogdanovic acknowledges support by the NASA award No. 80NSSC19K0319 and by the NSF award AST-1908042. D. Porquet acknowledges funding support from CNES. C. Danielski acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709) B.L. Davis acknowledges support from Tamkeen under the NYU Abu Dhabi Research Institute Grant CAP3. F. Pacucci acknowledges support from a Clay Fellowship by the SAO and from the Black Hole Initiative, which is funded by grants from the John Templeton Foundation and the Gordon and Betty Moore Foundation. A.J. Ruiter acknowledges support from the Australian Research Council Future Fellowship Grant FT170100243. V. Paschalidis is supported by NSF Grant PHY-1912619 and NASA Grant 80NSSC20K1542 to the University of Arizona, and NSF-XSEDE Grant TG-PHY190020. D. Haggard acknowledges support from the NSERC Discovery Grant and Canada Research Chairs programs, and the Bob Wares Science Innovation Prospectors Fund. M. Toscani acknowledges European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant Agreement No. 823823 (RISE DUSTBUSTERS project) and COST Action CA16104 - Gravitational waves, black holes and fundamental physics, supported by COST (European Cooperation in Science and Technology). M. Chruslinska, A. Istrate and G. Nelemans acknowledge support from Netherlands Research Council NWO. T. Fragos and S. Bavera acknowledge support from a Swiss National Science Foundation Professorship Grant (project numbers PP00P2_176868 and PP00P2_211006)., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

Many circumstellar discs appear to have misaligned central regions that give rise to shadows seen in scattered light observations. Small warps ($, 16 pages. Accepted to MNRAS

In recent years a correlation between mass accretion rates onto new-born stars and their proto-planetary disc masses was detected in nearby young star-forming regions. Although such a correlation can be interpreted as due to viscous-diffusion processes in the disc, highly-accreting sources with low disc masses in more evolved regions remain puzzling. In this paper, we hypothesise that the presence of a stellar companion truncating the disc can explain these outliers. Firstly, we searched the literature for information on stellar multiplicity in Lupus, Chamaeleon~I and Upper Sco, finding that roughly 20 per cent of the discs involved in the correlation are in binaries or higher-order multiple stellar systems. We prove with high statistical significance that at any disc mass these sources have systematically higher accretion rates than those in single-stars, with the bulk of the binary population being clustered around $M_\mathrm{disc}/\dot{M}_\mathrm{acc}\approx0.1\,\mathrm{Myr}$. We then run coupled gas and dust one-dimensional evolutionary models of tidally truncated discs to be compared with the data. We find that these models are able to reproduce well most of the population of observed discs in Lupus and Upper Sco, even though the unknown eccentricity of each binary prevents an object by object comparison. In the latter region, the agreement improves if the grain coagulation efficiency is reduced, as may be expected in discs around close binaries. Finally, we mention that thermal winds and sub-structures can be important in explaining few outlying sources., Comment: 13 pages, 6 figures; accepted for publication in MNRAS