Origin and fate of surface drift in the oceanic convergence zones of the eastern Pacific

This study investigates the structure and intensity of the surface pathways connecting to and from the central areas of the large-scale convergence regions of the eastern Pacific Ocean. Surface waters are traced with numerical Lagrangian particles transported in the velocity field of three different ocean models with horizontal resolutions that range from ¼° to 1/32°. The connections resulting from the large-scale convergent Ekman dynamics agree qualitatively but are strongly modulated by eddy variability that introduces meridional asymmetry in the amplitude of transport. Lagrangian forward-in-time integrations are used to analyze the fate of particles originating from the central regions of the convergence zones and highlight specific outflows not yet reported for the southeastern Pacific when using the currents at the highest resolutions (1/12° and 1/32°). The meridional scales of these outflows are comparable to the characteristic width of the fine-scale striation of mean currents.

Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter

Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuz'min energy threshold, 6 x 10(19) eV. The anisotropy was measured by the fraction of arrival directions that are less than 3.1 degrees from the position of an active galactic nucleus within 75 Mpc (using the Veron-Cetty and Veron 12th catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating fraction is (38(-6)(+7))%, compared with 21% expected for isotropic cosmic rays. This is down from the early estimate of (69-(+11)(13))%. The enlarged set of arrival directions is examined also in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in hard X-rays by the Swift Burst Alert Telescope. A celestial region around the position of the radiogalaxy Cen A has the largest excess of arrival directions relative to isotropic expectations. The 2-point autocorrelation function is shown for the enlarged set of arrival directions and compared to the isotropic expectation. (C) 2010 Elsevier B.V. All rights reserved.

Modeling chemistry in massive star forming regions with internal PDRs

Over the past decades star formation has been a very attractive field because knowledge of star formation leads to a better understanding of the formation of planets and thus of our solar system but also of the evolution of galaxies. Conditions leading to the formation of high-mass stars are still under investigation but an evolutionary scenario has been proposed: As a cold pre-stellar core collapses under gravitational force, the medium warms up until it reaches a temperature of 100 K and enters the hot molecular core (HMC) phase. The forming central proto-star accretes materials, increasing its mass and luminosity and eventually it becomes sufficiently evolved to emit UV photons which irradiate the surrounding environment forming a hyper compact (HC) and then a ultracompact (UC) HII region. At this stage, a very dense and very thin internal photon-dominated region (PDR) forms between the HII region and the molecular core. Information on the chemistry allows to trace the physical processes occurring in these different phases of star formation. Formation and destruction routes of molecules are influenced by the environment as reaction rates depend on the temperature and radiation field. Therefore, chemistry also allows the determination of the evolutionary stage of astrophysical objects through the use of chemical models including the time evolution of the temperature and radiation field. Because HMCs host a very rich chemistry with high abundances of complex organic molecules (COMs), several astrochemical models have been developed to study the gas phase chemistry as well as grain chemistry in these regions. In addition to HMCs models, models of PDRs have also been developed to study in particular photo-chemistry. So far, few studies have investigated internal PDRs and only in the presence of outflows cavities. Thus, these unique regions around HC/UCHII regions remain to be examined thoroughly. My PhD thesis focuses on the spatio-temporal chemical evolution in HC/UC HII regions with internal PDRs as well as in HMCs. The purpose of this study is first to understand the impact and effects of the radiation field, usually very strong in these regions, on the chemistry. Secondly, the goal is to study the emission of various tracers of HC/UCHII regions and compare it with HMCs models, where the UV radiation field does not impact the region as it is immediately attenuated by the medium. Ultimately we want to determine the age of a given region using chemistry in combination with radiative transfer.

The locations of recent supernovae near the Sun from modelling 60Fe transport

The signature of 60Fe in deep-sea crusts indicates that one or more supernovae exploded in the solar neighbourhood about 2.2 million years ago1–4. Recent isotopic analysis is consistent with a core-collapse or electron-capture supernova that occurred 60 to 130 parsecs from the Sun5. Moreover, peculiarities in the cosmic ray spectrum point to a nearby supernova about two million years ago6. The Local Bubble of hot, diffuse plasma, in which the Solar System is embedded, originated from 14 to 20 supernovae within a moving group, whose surviving members are now in the Scorpius– Centaurus stellar association7,8. Here we report calculations of the most probable trajectories and masses of the supernova progenitors, and hence their explosion times and sites. The 60Fe signal arises from two supernovae at distances between 90 and 100 parsecs. The closest occurred 2.3 million years ago at present-day galactic coordinates l = 327°, b = 11°, and the second-closest exploded about 1.5 million years ago at l = 343°, b = 25°, with masses of 9.2 and 8.8 times the solar mass, respectively. The remaining supernovae, which formed the Local Bubble, contribute to a smaller extent because they happened at larger distances and longer ago (60Fe has a half- life of 2.6 million years9,10). There are uncertainties relating to the nucleosynthesis yields and the loss of 60Fe during transport, but they do not influence the relative distribution of 60Fe in the crust layers, and therefore our model reproduces the measured relative abundances very well.

PRISM (Polarized Radiation Imaging and Spectroscopy Mission): an extended white paper

PRISM (Polarized Radiation Imaging and Spectroscopy Mission) was proposed to ESA in May 2013 as a large-class mission for investigating within the framework of the ESA Cosmic Vision program a set of important scientific questions that require high res- olution, high sensitivity, full-sky observations of the sky emission at wavelengths ranging from millimeter-wave to the far-infrared. PRISM’s main objective is to explore the distant universe, probing cosmic history from very early times until now as well as the structures, distribution of matter, and velocity flows throughout our Hubble volume. PRISM will survey the full sky in a large number of frequency bands in both intensity and polarization and will measure the absolute spectrum of sky emission more than three orders of magnitude bet- ter than COBE FIRAS. The data obtained will allow us to precisely measure the absolute sky brightness and polarization of all the components of the sky emission in the observed frequency range, separating the primordial and extragalactic components cleanly from the galactic and zodiacal light emissions. The aim of this Extended White Paper is to provide a more detailed overview of the highlights of the new science that will be made possible by PRISM, which include: (1) the ultimate galaxy cluster survey using the Sunyaev-Zeldovich (SZ) e↵ect, detecting approximately 106 clusters extending to large redshift, including a char- acterization of the gas temperature of the brightest ones (through the relativistic corrections to the classic SZ template) as well as a peculiar velocity survey using the kinetic SZ e↵ect that comprises our entire Hubble volume; (2) a detailed characterization of the properties and evolution of dusty galaxies, where the most of the star formation in the universe took place, the faintest population of which constitute the di↵use CIB (Cosmic Infrared Background); (3) a characterization of the B modes from primordial gravity waves generated during inflation and from gravitational lensing, as well as the ultimate search for primordial non-Gaussianity using CMB polarization, which is less contaminated by foregrounds on small scales than thetemperature anisotropies; (4) a search for distortions from a perfect blackbody spectrum, which include some nearly certain signals and others that are more speculative but more informative; and (5) a study of the role of the magnetic field in star formation and its inter- action with other components of the interstellar medium of our Galaxy. These are but a few of the highlights presented here along with a description of the proposed instrument.

Analysis of the high-resolution ro-vibrational spectrum of DC3N in the far and mid infrared regions

Cyanoacetylene HC3N is a molecule of great astronomical importance and it has been observed in many interstellar environments. Its deuterated form DC3N has been detected in number of sources from external galaxies to Galactic interstellar clouds, star-forming regions and planetary atmospheres. All these detections relied on previous laboratory investigations, which however still lack some essential information concerning its infrared spectrum. In this project, high-resolution ro-vibrational spectra of DC3N have been recorded in two energy regions: 150 – 450 cm-1 and 1800 – 2800 cm-1. In the first window the ν7← GS, 2ν7 ← ν7, ν5 ← ν7, ν5+ν7 ← 2ν7, ν6+ν7 → 2v7, 4ν7 ← 2ν7 bands have been assigned, while in the second region the three stretching fundamental bands ν1, ν2, ν3 have been observed and analysed. The 150 – 450 cm-1 region spectra have been recorded at the AILES beamline at the SOLEIL synchrotron (France), the 1800 – 2800 cm-1 spectra at the Department of Industrial Chemistry “Toso Montanari” in Bologna. In total, 2299 transitions have been assigned. Such experimental transition, together with data previously recorded for DC3N, were included in a least-squares fitting procedure from which several spectroscopic parameters have been determined with high precision and accuracy. They include rotational, vibrational and resonance constants. The spectroscopic data of DC3N have been included in a line catalog for this molecule in order to assist future astronomical observations and data interpretation. A paper which includes this research work has been published (M. Melosso, L. Bizzocchi, A. Adamczyk, E. Cane, P. Caselli, L. Colzid, L. Dorea, B. M. Giulianob, J.-C. Guillemine, M-A. Martin-Drumel, O. Piralif, A. Pietropolli Charmet , D. Prudenzano, V. M. Rivillad, F. Tamassia, Extensive ro-vibrational analysis of deuterated-cyanoacetylene (DC3N) from millimeter wavelengths to the infrared domain, Jour. of Quant. Spectr. and Rad. Tran. 254, 107221, 2020).

The J1030 field: a new window on early large scale structures and faint radio-galaxy populations

The correlations between the evolution of the Super Massive Black Holes (SMBHs) and their host galaxies suggests that the SMBH accretion on sub-pc scales (active galactice nuclei, AGN) is linked to the building of the galaxy over kpc scales, through the so called AGN feedback. Most of the galaxy assembly occurs in overdense large scale structures (LSSs). AGN residing in powerful sources in LSSs, such as the proto-brightest cluster galaxies (BCGs), can affect the evolution of the surrounding intra-cluster medium (ICM) and nearby galaxies. Among distant AGN, high-redshift radio-galaxies (HzRGs) are found to be excellent BCG progenitor candidates. In this Thesis we analyze novel interferometric observations of the so-called "J1030" field centered around the z = 6.3 SDSS Quasar J1030+0524, carried out with the Atacama large (sub-)millimetre array (ALMA) and the Jansky very large array (JVLA). This field host a LSS assembling around a powerful HzRG at z = 1.7 that shows evidence of positive AGN feedback in heating the surrounding ICM and promoting star-formation in multiple galaxies at hundreds kpc distances. We report the detection of gas-rich members of the LSS, including the HzRG. We showed that the LSS is going to evolve into a local massive cluster and the HzRG is the proto-BCG. we unveiled signatures of the proto-BCG's interaction with the surrounding ICM, strengthening the positive AGN feedback scenario. From the JVLA observations of the "J1030" we extracted one of the deepest extra-galactic radio surveys to date (~12.5 uJy at 5 sigma). Exploiting the synergy with the X-ray deep survey (~500 ks) we investigated the relation of the X-ray/radio emission of a X-ray-selected sample, unveiling that the radio emission is powered by different processes (star-formation and AGN), and that AGN-driven sample is mostly composed by radio-quiet objects that display a significant X-ray/radio correlation.

Non-standard signatures from Cosmic Microwave Background polarisation

In this Thesis we focus on non-standard signatures from CMB polarisation, which might hint at the existence of new phenomena beyond the standard models for Cosmology and Particle physics. With the Planck ESA mission, CMB temperature anisotropies have been observed at the cosmic variance limit, but polarisation remains to be further investigated. CMB polarisation data are important not only because they contribute to provide tighter constraints of cosmological parameters but also because they allow the investigation of physical processes that would be precluded if just the CMB temperature maps were considered. We take polarisation data into account to assess the statistical significance of the anomalies currently observed only in the CMB temperature map and to constrain the Cosmic Birefringence (CB) effect, which is expected in parity-violating extensions of the standard electromagnetism. In particular, we propose a new one-dimensional estimator for the lack of power anomaly capable of taking both temperature and polarisation into account jointly. With the aim of studying the anisotropic CB we develop and perform two different and complementary methods able to evaluate the power spectrum of the CB. Finally, by employing these estimators and methodologies on Planck data we provide new constraints beyond what already known in literature. The measure of CMB polarisation represents a technological challenge and to make accurate estimates, one has to keep an exquisite control of the systematic effects. In order to investigate the impact of spurious signal in forthcoming CMB polarisation experiments, we study the interplay between half-wave plates (HWP) non-idealities and the beams. Our analysis suggests that certain HWP configurations, depending on the complexity of Galactic foregrounds and the beam models, significantly impacts the B-mode reconstruction fidelity and could limit the capabilities of next-generation CMB experiments. We provide also a first study of the impact of non-ideal HWPs on CB.

Exploring the white dwarf cooling sequence in Globular Clusters

White dwarfs (WDs) are electron-degenerate structures that are commonly assumed to evolve via a pure cooling process, with no stable thermonuclear activity at work. Their cooling rate is adopted as a cosmic chronometer to constrain the age of several Galactic populations, including the disk, Globular Clusters (GCs) and open clusters. This thesis work is aimed at the study of the WD populations in globular clusters and is articulated in two branches. The first was focused on the study of the bright portion of the WD cooling sequence. By analyzing high resolution UV data acquired with the Hubble Space Telescope (HST), we compared the WD luminosity functions (LFs) in four Galactic GCs (namely M13, M3, NGC6752, and M5) finding an unexpected over-abundance of WDs in M13 and NGC6752 with respect to M3 and M5. Theoretical models suggest that, consistently with the blue-tail horizontal branch (HB) morphology of M13 and NGC6752, this overabundance is due to a population of slowly cooling WDs, i.e., WDs fading more slowly than in a pure cooling process thanks to an extra-energy source provided by stable thermonuclear burning in their residual hydrogen-rich envelope. This is the first empirical evidence of WDs fading at a slower rate than usually assumed, and has a crucial impact on the use of the cooling sequence as a cosmic chronometer. The second branch was focused on the search for the companion star to binary millisecond Pulsars (MSP) in the globular clusters M13 and NGC 6652: the identified companions turned out to be helium-core WDs, and provided a invaluable constraints on the mass of the neutron star and the epoch of the MSP formation.

New indicators of star cluster dynamical evolution

This thesis presents a study of globular clusters (GCs), based on analysis of Monte Carlo simulations of globular clusters (GCs) with the aim to define new empirical parameters measurable from observations and able to trace the different phases of their dynamical evolution history. During their long term dynamical evolution, due to mass segregation and and dynamical friction, massive stars transfer kinetic energy to lower-mass objects, causing them to sink toward the cluster center. This continuous transfer of kinetic energy from the core to the outskirts triggers the runaway contraction of the core, known as "core collapse" (CC), followed by episodes of expansion and contraction called gravothermal oscillations. Clearly, such an internal dynamical evolution corresponds to significant variations also of the structure of the system. Determining the dynamical age of a cluster can be challenging as it depends on various internal and external properties. The traditional classification of GCs as CC or post-CC systems relies on detecting a steep power-law cusp in the central density profile, which may not always be reliable due to post-CC oscillations or other processes. In this thesis, based on the normalized cumulative radial distribution (nCRD) within a fraction of the half-mass radius is analyzed, and three diagnostics (A5, P5, and S2.5) are defined. These diagnostics show sensitivity to dynamical evolution and can distinguish pre-CC clusters from post-CC clusters.The analysis performed using multiple simulations with different initial conditions, including varying binary fractions and the presence of dark remnants showed the time variations of the diagnostics follow distinct patterns depending on the binary fraction and the retention or ejection of black holes. This analysis is extended to a larger set of simulations matching the observed properties of Galactic GCs, and the parameters show a potential to distinguish the dynamical stages of the observed clusters as well.

A comprehensive study of the AGN feedback cycle in galaxy clusters from high resolution X-ray and radio observations

At the center of galaxy clusters, a dramatic interplay known as feedback cycle occurs between the hot intracluster medium (ICM) and the active galactic nucleus (AGN) of the central galaxy. The footprints of this interplay are evident from X-ray observations of the ICM, where X-ray cavities and shock fronts are associated with radio lobe emission tracing energetic AGN outbursts. While such jet activity reduces the efficiency of the hot gas to cool to lower temperatures, residual cooling can generate warm and cold gas clouds around the central galaxy. The condensed gas parcels can ultimately reach the core of the galaxy and be accreted by the AGN. This picture is the result of tremendous advances over the last three decades. Yet, a deeper understanding of the details of how the heating–cooling regulation is achieved and maintained is still missing. In this Thesis, we delve into key aspects of the feedback cycle. To this end, we leverage high-resolution (sub-arcsecond), multifrequency observations (mainly X-ray and radio) of several top-level facilities (e.g., Chandra, JVLA, VLBA, LOFAR). First, we investigate which conditions trigger a feedback response to gas cooling, by studying the properties of clusters where feedback is just about to start. Then, we focus on the details of how the AGN–ICM interaction progresses by examining cavity and shock heating in the cluster RBS797, an exemplary case of the jet feedback paradigm. Furthermore, we explore the importance of shock heating and the coupling of distinct jet power regimes (i.e., FRII, FRI and FR0 radio galaxies) to the environment. Ultimately, as heating models rely on the connection between the direct evidence (the jets) and the smoking gun (the X-ray cavities) of feedback, we examine the cases in which these two are dramatically misaligned.

Pulse shape studies of neutral particles with a liquid scintillator

The hadrontherapy exploits beams of charged particles against deep cancers. These ions have a depth-dose profile in which there is a little release of energy at the beginning of their path, whereas there is a sharp maximum, the Bragg Peak, near its end path. However, if heavy ions are used, the fragmentation of the projectile can happen and the fragments can release some dose outside the treatment volume beyond the Bragg peak. The fragmentation process takes place also when the Galactic Cosmic Rays at high energy hit the spaceship during space missions. In both cases some neutrons can be produced and if they interact with the absorbing materials nuclei some secondary particles are generated which can release energy. For this reason, studies about the cross section measurements of the fragments generated during the collisions of heavy ions against the tissues nuclei are very important. In this context, the FragmentatiOn Of Target (FOOT) experiment was born, and aims at measuring the differential and double differential fragmentation cross sections for different kinetic energies relevant to hadrontherapy and space radioprotection with high accuracy. Since during fragmentation processes also neutrons are produced, tests of a neutron detection system are ongoing. In particular, recently a neutron detector made up of a liquid organic scintillator, BC-501A with neutrons/gammas discrimination capability was studied, and it represents the core of this thesis. More in details, an analysis of the data collected at the GSI laboratory, in Darmstadt, Germany, is effectuated which consists in discriminating neutral and charged particles and then to separate neutrons from gammas. From this analysis, a preliminary energy-differential reaction cross-section for the production of neutrons in the 16O + (C_2H_4)_(n) and 16O + C reactions was estimated.

Analytic models of self-gravitating rotating gaseous tori with central black hole

In this thesis project, I present stationary models of rotating fluids with toroidal distributions that can be used to represent the active galactic nuclei (AGN) central obscurers, i.e. molecular tori (Combes et al., 2019), as well as geometrically thick accretion discs, like ADAF discs (Narayan and Yi, 1995) or Polish doughnuts (Abramowicz, 2005). In particular, I study stationary rotating systems with a more general baroclinic distribution (with a vertical gradient of the angular velocity), which are often more realistic and less studied, due to their complexity, than the barotropic ones (with cylindrical rotation), which are easier to construct. In the thesis, I compute analytically the main intrinsic and projected properties of the power-law tori based on the potential-density pairs of Ciotti and Bertin (2005). I study the density distribution and the resulting gravitational potential for different values of α, in the range 2 < α < 5. For the same models, I compute the surface density of the systems when seen face-on and edge-on. I then apply the stationary Euler equations to obtain rotational velocity and temperature distributions of the self-gravitating models in the absence of an external gravitational potential. In the thesis I also consider the power-law tori with the presence of a central black hole in addition to the gas self-gravity, and solving analytically the stationary Euler equations, I compute how the properties of the system are modified by the black hole and how they vary as a function of the black hole mass. Finally, applying the Solberg-Høiland criterion, I show that these baroclinic stationary models are linearly stable in the absence of the black hole. In the presence of the black hole I derive the analytical condition for stability, which depends on α and on the black hole mass. I also study the stability of the tori in the hypothesis that they are weakly magnetized, finding that they are always unstable to this instability.

Exploration of X-ray, optical and radio emission of the radio-galaxy 3C 277.3

This thesis explores the X-ray nuclear and extended properties of the radio galaxy 3C 277.3, where a recent optical observation performed with the multi-unit spectroscopic explorer (MUSE) has revealed star-forming regions triggered by the propagation of non-thermal plasma in the intergalactic medium. This work aims to study the nuclear engine and its environment and, possibly, discover signatures of non-thermal plasma-gas interaction at high energies. 3C 277.3 was observed with the Chandra satellite five times from 2010 to 2014 for a total of about 200 ks. Data in the Chandra public archive were retrieved and analyzed. When necessary, the different pointings were combined to improve the signal-to-noise ratio. A detailed analysis of the Chandra image (obtained by combining all the observations) has revealed several emission regions. In addition to a bright nucleus, two jet knots and the northern hot spot were clearly detected by overlapping the X-ray data to a VLA map of the source at 1.4 GHz. An X-ray spectral analysis was performed for all these structures. Finally, the X-ray image was over-imposed on the MUSE data.