Supernova remnants observed by the Fermi Large Area Telescope: the case of HB 21

Since their discovery, Cosmic Rays (CRs) are one of the most studied phenomena in the Universe. The origin of the spectrum, which extends for more than 12 orders of magnitude, is still debated. Up to ~10^15 eV, cosmic rays are accelerated in the Galaxy, and Supernova remnants (SNRs) are the most likely candidates to accelerate them. If an expanding SNR interacts with molecular clouds, particles accelerated in the expanding shock can produce high-energy photons, the observation of which can provide valuable information about the accelerated particles population. Of particular interest are combined gamma-ray and radio observations: accelerated particles emit radio waves via synchrotron emission and gamma rays via bremsstrahlung, inverse Compton and nucleon-nucleon interaction. Thanks to its unprecedent angular resolution and sensitivity, the Fermi Gamma-ray Space Telescope is the gamma-ray detector ideal for the study of extended structures in the Galaxy. We present the analysis of Fermi Large Area Telescope gamma-ray observations of HB 21 (G89.0+4.7). We detected significant gamma-ray emission associated with the remnant: the flux above 100 MeV is 9.4± 0.8(stat)±1.6(syst)x10¹¹ erg cm² s-¹. HB 21 is well modeled by a uniform disk centered at l=88°.75±0°.04, b=+4°.65±0°.06 with a radius of 1°.19±0°.06. The gamma-ray spectrum shows clear evidence of curvature, suggesting a cutoff or break in the underlying particle population at an energy of a few GeV. We complement gamma-ray observations with the analysis of the WMAP 7 yr data from 23 to 93 GHz, achieving the first detection of HB 21 at these frequencies. In combination with archival radio data, the radio spectrum shows a spectral break, which helps to constrain the relativistic electron spectrum, hence parameters of simple non-thermal radiation models. In one-zone models multi-wavelength data favor the origin of gamma rays from nucleon-nucleon collisions. A single population of electrons cannot produce both gamma rays through bremsstrahlung and radio emission through synchrotron radiation. A predominantly inverse-Compton origin of the gamma-ray emission is disfavored because it requires lower interstellar densities than the ones inferred for HB 21. In the hadronic-dominated scenarios, accelerated nuclei contribute a total energy of ~3x10⁴⁹ erg, while, in a two-zone bremsstrahlung-dominated scenario, the total energy in accelerated particles is ~1x10⁴⁹ erg

Supernova remnants observed by the Fermi Large Area Telescope: the case of HB 21

Since their discovery, Cosmic Rays (CRs) are one of the most studied phenomena in the Universe. The origin of the spectrum, which extends for more than 12 orders of magnitude, is still debated. Up to ~10^15 eV, cosmic rays are accelerated in the Galaxy, and Supernova remnants (SNRs) are the most likely candidates to accelerate them. If an expanding SNR interacts with molecular clouds, particles accelerated in the expanding shock can produce high-energy photons, the observation of which can provide valuable information about the accelerated particles population. Of particular interest are combined gamma-ray and radio observations: accelerated particles emit radio waves via synchrotron emission and gamma rays via bremsstrahlung, inverse Compton and nucleon-nucleon interaction. Thanks to its unprecedent angular resolution and sensitivity, the Fermi Gamma-ray Space Telescope is the gamma-ray detector ideal for the study of extended structures in the Galaxy. We present the analysis of Fermi Large Area Telescope gamma-ray observations of HB 21 (G89.0+4.7). We detected significant gamma-ray emission associated with the remnant: the flux above 100 MeV is 9.4± 0.8(stat)±1.6(syst)x10¹¹ erg cm² s-¹. HB 21 is well modeled by a uniform disk centered at l=88°.75±0°.04, b=+4°.65±0°.06 with a radius of 1°.19±0°.06. The gamma-ray spectrum shows clear evidence of curvature, suggesting a cutoff or break in the underlying particle population at an energy of a few GeV. We complement gamma-ray observations with the analysis of the WMAP 7 yr data from 23 to 93 GHz, achieving the first detection of HB 21 at these frequencies. In combination with archival radio data, the radio spectrum shows a spectral break, which helps to constrain the relativistic electron spectrum, hence parameters of simple non-thermal radiation models. In one-zone models multi-wavelength data favor the origin of gamma rays from nucleon-nucleon collisions. A single population of electrons cannot produce both gamma rays through bremsstrahlung and radio emission through synchrotron radiation. A predominantly inverse-Compton origin of the gamma-ray emission is disfavored because it requires lower interstellar densities than the ones inferred for HB 21. In the hadronic-dominated scenarios, accelerated nuclei contribute a total energy of ~3x10⁴⁹ erg, while, in a two-zone bremsstrahlung-dominated scenario, the total energy in accelerated particles is ~1x10⁴⁹ erg.Fin dalla loro scoperta, i raggi cosmici sono uno dei fenomeni più studiati nell'Universo. L'origine del loro spettro, che si estende per più di 12 ordini di grandezza, è ancora incerta e dibattuta. Fino ad energie dell'ordine di ~10^15 eV, si ipotizza che i raggi cosmici siano accelerati all'interno della Galassia, e che i resti di supernova siano i principali acceleratori. Espandendosi, un resto di supernova può interagire con le nubi molecolari presenti nel mezzo circostante, in questo caso le particelle accelerate possono produrre fotoni di alta energia la cui osservazione può fornire informazioni sulla popolazione dei raggi cosmici. Di particolare interesse sono le osservazioni combinate nella bade gamma e radio: le particelle accelerate emettono nel radio tramite radiazione di sincrotrone, e nel gamma tramite Bremsstrahlung, effetto Compton inverso e interazione inelastica nucleone-nucleone. Grazie alla sua ottima risoluzione angolare e precisione spaziale, il Telescopio Spaziale Fermi è il rivelatore di raggi gamma ideale per lo studio di sorgenti estese. La tesi presenta l'analisi effettuata con dati Fermi della sorgente estesa HB 21 (G89.0+4.7). Riveliamo significativa emissione gamma associata al resto di supernova: il flusso sopra 100 MeV è di 9.4± 0.8(stat)±1.6(syst)x10¹¹ erg cm² s-¹. Dal punto di vista morfologico, l'emissione è ben modellata da un disco uniforme, centrato alle coordinate Galattiche l=88°.75±0°.04, b=+4°.65±0°.06 di raggio 1°.19±0°.06. Lo spettro gamma mostra un'evidente curvatura che suggerisce un taglio o un'interruzione dello spettro nella popolazione di particelle che generano lo spettro gamma, ad energie di qualche GeV. Insieme ai dati gamma , sono stati inclusi anche dati provenienti dal radio usando 7 anni di dati raccolti dall'esperimento WMAP da 23 a 93 GHz, che hanno portato alla prima osservazione di HB 21 a queste frequenze. Unendo tali dati ai quelli di archivio, si è potuto osservare come lo spettro radio presenti un'interruzione. Tale caratteristica aiuta a determinare lo spettro degli elettroni relativistici e, quindi, anche i parametri dei modelli di radiazione non termica. Nei modelli di singola zona, i dati su più lunghezze d'onda favoriscono un'origine dei raggi gamma da collisioni nucleone-nucleone. Una singola popolazione di elettroni non può spiegare contemporaneamente sia l'emissione di Bremsstrahlung nel gamma che quella di sincrotrone nel radio. L'effetto Compton inverso, invece, non può riprodurre bene lo spettro gamma perché richiederebbe basse densità del mezzo interstellare, molto più basse di quelle calcolate intorno a HB 21. Quindi, nello scenario adronico, i nuclei accelerati forniscono un'energia di ~3x10⁴⁹ erg, mentre in uno scenario in cui le zone di emissione di radio e gamma siano diverse e l'emissione gamma è dominata dal Bremsstrahlung, l'energia totale in particelle accelerate è di ~1x10⁴⁹ erg

Long time series analysis of air quality data in the Veneto region (Northern Italy) to support environmental policies

The world population is demonstrating an increasing awareness about the ecological impacts of air quality, including impacts on human health. The Veneto region and, more generally, the Po Valley (NE Italy), are characterised by frequent exceedance of limit values for air quality, in particular particulate matter (PM10), which causes these areas to be listed as hotspots; thus, this region has some of the worst air pollution in Europe. The aim of the current research was to analyse a 10 year-long time series of air quality data (2011–2021) in the Veneto region to investigate the influence of selected factors on air quality, such as natural processes (meteorological conditions), environmental policies, and health emergency measures due to the COVID-19 pandemic. Generally, the considered pollutants, PM10, NO, and NO2, presented a decreasing trend during the last ten years. The reduction in nitrogen oxides was clearly improved after the implementation of a specific environmental protocol (the “New Agreement of Po Valley Basin”). Conversely, the PM10 concentration seemed to be affected by other important emission sources, such as domestic heating systems, agricultural activities, and animal farms, which are not as strongly regulated as emission sources such as traffic. The 2020 lockdown mainly influenced nitrogen oxide concentrations

FOOD2GATHER: What is migrants’ food all about in Europe? A media discourse analysis through the lens of controversies

This report is part of the HERANET funded project FOOD2GATHER. The project aims at understanding the question of integration/exclusion of migrants through foodscapes. An important step in this direction is to analyse the contextual framework within which food-related practices, norms and values are embedded in European societies. Food controversies that have raised and have been reported in the media since the “2015 migrants’ crisis” across Europe can reveal important aspects related to such norms and values and indicate possible tensions and compromises. This report presents and discusses relevant food controversies that occurred in the six countries participating in the study (Belgium, France, Germany, Italy, Norway, and the Netherlands). This will generate a contextual overview of the integration/exclusion of migrants through foodscapes. Controversy has been used as a tool and a scanner. Each of the six FOOD2GATHER teams provided two relevant controversies that have reached media attention in the last ten years. One of the two had to be related to halal food. The analysis of the controversies has been conducted by identifying issues they tackled, agents they involved, (public) spaces and situations in which controversies took place and what they produced. A comparative analysis of relevant variables related to migrations, such as the geopolitical position of the countries, organization of reception and food provision, has been conducted as well. The six countries included in the study have different traditions related to migration and have been exposed to the “migrants’ crisis” in different ways. These differences are reflected in the proposed controversies. However, some common traits tend to emerge and reveal power relationships within societies that are different or shared by the countries involved in the project. We show that these power relationships particularly deal with the right to food, citizens’ commitment, identity, the place of religion, animal welfare and political issues. Our study indicates that analysing controversies adds an important dimension to the study of foodscapes. Food controversies that reach the media attention are seldom something migrants have brought up themselves. The migrants’ representation in the media based on food controversies indicated that migrants are given little opportunity to negotiating values and practices, as norms about “the right” quantity and quality of food tend to reproduce the food model of the country they migrate to, also when there is a “positive” focus on ethnic business. To better understand these dynamics, we propose the concept of “food encounters” and illustrate how the type of food encounters can play a role in how foodscapes could evolve or even emerge

Isotopically modified Ge detectors for GERDA: from production to operation

The GERDA experiment searches for the neutrinoless double beta (0v beta beta) decay of Ge-76 using high-purity germanium detectors made of material enriched in Ge-76. For Phase II of the experiment a sensitivity for the half life T-1/2(0v) similar to 2.10(26) yr is envisioned. Modified Broad Energy Germanium detectors (BEGe) with thick n(+) electrodes provide the capability to efficiently identify and reject background events, while keeping a large acceptance for the 0v beta beta-decay signal through novel pulse-shape discrimination (PSD) techniques. The viability of producing thick-window BEGe-type detectors for the GERDA experiment is demonstrated by testing all the production steps from the procurement of isotopically modified germanium up to working BEGe detectors. Comprehensive testing of the spectroscopic as well as PSD performance of the GERDA Phase II prototype BEGe detectors proved that the properties of these detectors are identical to those produced previously from natural germanium material following the standard production line of the manufacturer. Furthermore, the production of BEGe detectors from a limited amount of isotopically modified germanium served to optimize the production, in order to maximize the overall detector mass yield. The results of this test campaign provided direct input for the subsequent production of the enriched germanium detectors

SEARCH FOR COSMIC-RAY-INDUCED GAMMA-RAY EMISSION IN GALAXY CLUSTERS

Current theories predict relativistic hadronic particle populations in clusters of galaxies in addition to the already observed relativistic leptons. In these scenarios hadronic interactions give rise to neutral pions which decay into \u3b3 rays that are potentially observable with the Large Area Telescope (LAT) on board the Fermi space telescope. We present a joint likelihood analysis searching for spatially extended \u3b3-ray emission at the locations of 50 galaxy clusters in four years of Fermi-LAT data under the assumption of the universal cosmic-ray (CR) model proposed by Pinzke & Pfrommer. We find an excess at a significance of 2.7\u3c3, which upon closer inspection, however, is correlated to individual excess emission toward three galaxy clusters: A400, A1367, and A3112. We discuss these cases in detail and conservatively attribute the emission to unmodeled background systems (for example, radio galaxies within the clusters).Through the combined analysis of 50 clusters, we exclude hadronic injection efficiencies in simple hadronic models above 21% and establish limits on the CR to thermal pressure ratio within the virial radius, R 200, to be below 1.25%-1.4% depending on the morphological classification. In addition, we derive new limits on the \u3b3-ray flux from individual clusters in our sample

Dark matter constraints from observations of 25 Milky\ua0Way satellite galaxies with the Fermi Large Area Telescope

The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via \u3b3 rays. Here we report on \u3b3-ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in \u3b3 rays, and we present \u3b3-ray flux upper limits between 500 MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the annihilation of dark matter particles with masses between 2 GeV and 10 TeV into prototypical standard model channels. We find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse \u3b3-ray background modeling, and assumed dark matter density profile