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The nature of the relation between active galactic nuclei (AGN), and their host galaxies have been observed in detail throughout the Universe. Such work has found an intrinsic link between central supermassive black hole (SMBH) masses, and host galaxy properties such as the velocity dispersion of stars, and bulge mass. However, the difference in scale between SMBH and their host galaxies has led to debate on how this relation might form, and develop over time. In order to aid in understanding the relation between AGN and their host galaxies, the work throughout this thesis has therefore focused on the development and implementation of a new SED fitting code, using an up-to-date AGN SED to accurately infer both AGN and host galaxy properties. To this end, we explore the intricacies involved in producing useful property inferences using a Bayesian MCMC fitting method, whilst working to avoid common issues such as bimodality and lack of convergence. We then perform SED fitting using our methods to 711 luminous X-ray AGN at 0.7 < z < 4.5 using 10-bands of optical and infra-red photometric data for objects within XMMSERVS. Using these fits, we study the relation between AGN X-ray luminosity and host galaxy stellar mass, along with our ability to predict emission line strength and morphology from photometry alone. In order to further understand the intricacies of SED fitting, we also provide a case study into the effect of AGN SED choice on host galaxy and AGN property inferences, by comparing our AGN SED to another commonly used template. In this work, we show that it is important to consider host galaxy contamination when trying to produce a pure AGN template, and the effect that this contamination can have on AGN and host galaxy property inferences. We also find that the use of lower resolution SEDs can lead to repercussions on property inferences such as host galaxy stellar mass, which may provide incorrect assumptions on the relation between AGN and their host galaxies.

With its capacity to observe $\sim 10^{5-6}$ faint active galactic nuclei (AGN) out to redshift $z\approx 6$, Roman is poised to reveal a population of $10^{4-6}\, {\rm M_\odot}$ black holes during an epoch of vigorous galaxy assembly. By measuring the light curves of a subset of these AGN and looking for periodicity, Roman can identify several hundred massive black hole binaries (MBHBs) with 5-12 day orbital periods, which emit copious gravitational radiation and will inevitably merge on timescales of $10^{3-5}$ years. During the last few months of their merger, such binaries are observable with the Laser Interferometer Space Antenna (LISA), a joint ESA/NASA gravitational wave mission set to launch in the mid-2030s. Roman can thus find LISA precursors, provide uniquely robust constraints on the LISA source population, help identify the host galaxies of LISA mergers, and unlock the potential of multi-messenger astrophysics with massive black hole binaries., White Paper for the Nancy Grace Roman Space Telescope's Core Community Surveys (https://roman.gsfc.nasa.gov/science/ccs_white_papers.html)

Radio-loud active galactic nuclei (RLAGN) produce jets on large scales heating their local environments and preventing the hot phase of baryonic matter from cooling hence slowing or halting galaxy formation and evolution; a model popularly known as AGN feedback. To understand this model, new views of low-luminosity compact RLAGN inhabiting massive galaxies have been obtained using the new LOw Frequency ARray (LOFAR) northern-sky radio survey LoTSS (LOFAR Two Metre Sky Survey) to study RLAGN in the local Universe at low frequencies (150 MHz). In this thesis, I investigate lowluminosity compact RLAGN selected from LoTSS first Data Release (DR1) in an attempt to reveal their radio morphologies and the physical scales at which they affect the inter-galactic medium (IGM) of the host galaxy on sub-kpc scales. We have conservatively selected 55 low-luminosity compact RLAGN based on LoTSS DR1 within redshift range 0:03 < z < 0:1. I show using high-frequency Jansky Very Large Array (VLA) observations that only 9 out of 55 objects show extended radio emission (1-3 kpc), 43 are compact at the limiting angular resolution of 0.35 arcsec (corresponding to projected maximum physical sizes of < 1 kpc), while 3 are undetected. The extended objects display a wide range of radio morphologies on smaller angular scales: doubles (3), two-sided jets (3), one-sided jets (2), and complex (1). I discuss their radio spectra which range from steep to flat and/or inverted radio spectra (-1:31 < α < 0:36) and span the range seen in various compact RLAGN such as compact symmetric objects (CSOs), compact steep spectrum (CSS) sources, and gigahertz peaked-spectrum (GPS) sources. Assuming synchrotron self-absorption (SSA) models for flat and/or inverted radio spectrum sources, I predict the physical sizes of 35 RLAGN to be between 2-53 pc. On their position on the power-linear size (P - D) diagram, we see that these objects populate the bottom left lower-end of the diagram; this position corresponds to the low-radio power CSOs. Finally, I compare their radio properties with those of the Fanaroff-Riley class 0 (‘FR0’) sources. Interestingly, some of the compact RLAGN presented in this thesis show extended radio emission in the second Data Release (DR2) images; these appear to be in fact the radio cores of low-luminosity yet extended Fanaroff-Riley (FRI/FRII) sources that could populate the right-lower end of the P - D diagram, limited by LOFAR’s surface brightness. Could we be underestimating the sizes of some of these compact objects? Continued VLBI observations of LOFAR sources could help us answer this question, which in turn will help us further understand AGN feedback. i

Radio astronomy is a pioneering branch of astronomy research - new radio surveys have gathered a lot of attention in the last few years, due to the huge expansion in capabilities of new radio facilities, with new observatories such as MeerKAT and LOFAR surveying wide areas to large depths at great speed. But radio sources alone are not especially informative, e.g. no redshift information can be obtained from radio continuum data, and therefore no clear route to obtaining information about the physics in the sources. This work investigates the properties of the no-ID radio sources taken from the MIGHTEE catalogue produced by Prescott et al. (submitted), specifically in the COSMOS field. The catalogue we use for the NIR data is described by McCracken et al. (2012) the UltraVISTA survey with deep and ultra-deep coverage of the COSMOS field. Combining the data from these two catalogues we are able to determine that the 114 no-ID sources have 141.8±31.4 excess galaxies when the separation is up to 6”. We find that these sources have a flux density distribution of 0.007 - 1.840 mJy, KS magnitude distribution of mainly 20 < mK < 24 and a redshift distribution of 0 < z < 2. The magnitude distribution includes only the sources we can detect, thus the rest must be fainter. We therefore suspect a bimodal magnitude distribution for the no-ID counterparts. Some fraction of the sources also have unknown redshifts because we have not been able to detect any counterparts even in the UltraVISTA data reaching mK < 26. Our results suggest that data such as from VIDEO are as good for cross-identifying MIGHTEE sources as UltraVISTA data, considering there is no significant difference between the source population when mK < 24 and mK < 26, which may benefit MIGHTEE investigations in the XMM-LSS, ELAIS-S1 and ECDFS fields. To further our investigation, we look at how many of the 114 sources would have at least one possible multi-wavelength counterpart using part of the Likelihood Ratio technique. We find that 60.3±16.1 per cent or around 68 of the no-ID sources have at least one counterpart detected in the UltraVISTA data. We also find that at search radius of 10”, there are still three sources with no possible counterparts. We agree with other works in the literature that combining different methods of cross-identification may be the most efficient and rewarding approach for radio-continuum surveys.

The mid-infrared spectra of star-forming galaxies (SFGs) are characterized by characteristic broad PAH emission features at 3$-$20 $\mu$m. As these features are redshifted, they are predicted to dominate the flux at specific mid-infrared wavelengths, leading to substantial redshift-dependent color variations in broad-band photometry. The advent of JWST for the first time allows the study of this effect for normal SFGs. Based on spectral energy distribution templates, we here present tracks in mid-infrared (4.4, 7.7, 10, 15, and 18 $\mu$m) color-color diagrams describing the redshift dependence of SFG colors. In addition, we present simulated color-color diagrams by populating these tracks using the cosmic star-formation history and the star-formation rate function. Depending on redshift, we find that SFGs stand out in the color-color diagrams by several magnitudes. We provide the first observational demonstration of this effect for galaxies detected in the JWST Early Release Observations of the field towards the lensing cluster SMACS J0723.3$-$7327. While the distribution of detected galaxies is consistent with the simulations, the numbers are substantially boosted by lensing effects. The PAH emitter with the highest spectroscopic redshift, detected in all bands, is a multiply-imaged galaxy at $z=1.45$. There is also a substantial number of cluster members, which do not exhibit PAH emission, except for one Seyfert galaxy at $z=0.38$. Future wider-field observations will further populate mid-infrared color-color diagrams and provide insight into the evolution of typical SFGs., Comment: 8 pages, 5 figures, Submitted to ApJL, Comments are Welcome!

These are the slides of Elena Pian's presentation at the Conference

Galaxy evolution is an interplay of physical processes across a wide range of cosmological size scales, from star formation and black hole growth on sub-pc scales, to interactions with their environments on Mpc scales. The region surrounding individual galaxies within their host halos is known as the Circumgalactic Medium (CGM), and connects galaxies to the wider Intergalactic Medium (IGM). The CGM acts as both a reservoir of inflowing gas and a repository for outflowing gas as it is transported outwards via galactic feedback. Quasar absorption line surveys have revealed the CGM to be a complex, multiphase environment in which ions tracing cool and hot gas are present within the same absorber systems. Cosmological simulations are a powerful tool for building a theoretical understanding of these interconnected processes and resulting observations. They provide a 3D view of galaxies and their host halos, in which we intrinsically know the physical conditions of the constituent dark matter and baryons. As such, simulations are useful both for testing galaxy evolution models against the real universe, and for interpreting complex observations in a physical context. In this thesis I present detailed comparisons of simulations to observations of star formation and quenching in galaxies, and of absorbers in galactic halos in an effort to constrain physical models. I use Simba, a suite of state of the art cosmological simulations with realistic sub-grid physical models based on high resolution zoom simulations, including novel treatments of dust evolution and of black hole growth and feedback. I investigate the nature of gas in galaxies and their halos, and show comparisons with observations. In addition, I isolate the impacts of galactic feedback and ionising radiation on the results by varying elements of the input physical models. In Chapter 3, I present radial profiles of star forming and green valley galaxies in Simba at z=0 and compare with observations of MaNGA spatially resolved spectroscopy. My analysis shows strong central depressions in star formation rate (SFR), specific SFR (sSFR), and gas fraction in Simba's green valley galaxies and massive star-forming systems, qualitatively as] observed, owing to Active Galactic Nuclei (AGN) X-ray feedback, which pushes central gas radially outwards. These effects are less pronounced at higher redshift, owing to less powerful AGN feedback. I also present a comparison of galaxy half light radii to observations at various redshifts, finding that predictions for star-forming galaxy sizes are accurate but that quenched galaxies are impacted by numerical heating. In Chapter 4, I characterise the low redshift CGM in Simba and examine the impact of differing feedback prescriptions. Low mass galaxies live in multiphase, diverse halos, whereas high mass galaxies live in halos dominated by hot gas. Halo baryon fractions are generally < 50% of the cosmic fraction due to stellar feedback at low masses, and 'jet-mode' AGN feedback at high masses. I present a comparison of absorption statistics to the COS-Halos and COS-Dwarfs surveys: Simba reproduces HI absorption well around star forming galaxies and broadly reproduces absorption of selected metal lines, including the observed dichotomy in OVI absorption between star forming and quenched galaxies. These predictions of metal line absorption are sensitive to the choice of photo-ionising background. Varying the galactic feedback prescription shows that stellar feedback enriches the CGM, while AGN feedback sets the gas temperature phase. In Chapter 5 I extend this analysis with a theoretical perspective of the CGM in Simba using a sample of CGM absorbers from a representative sample of Simba galaxies, selected across a range of stellar masses and sSFR. Absorbers are more abundant around low mass, star forming galaxies; the CGM of green valley galaxies is more similar to that of quenched galaxies. The absorber overdensity depends on the sSFR of the galaxy, while the absorber temperature is set by galaxy stellar mass. Absorption from low ions arises from cold, dense CGM gas, whilst absorption from higher ions traces hotter, more diffuse gas. I also examine the proportion of absorption arising from collisionally ionised gas, and from gas that is associated with satellite galaxies. Finally, in Chapter 6 I develop a tree-based machine learning mapping between the observable properties and the underlying physical conditions of the absorbers in the CGM absorber sample from Chapter 5. Such a mapping has the potential to be used to interpret CGM observations within a full cosmological context, assuming the Simba galaxy evolution model.

Presentation of the results obtained by optical and infrared interferometry on Active Galactic Nuclei (AGN), especially from the Very Large Telescope Interferometer (VLTI). The presentation covers both continuum measurements of sizes, of radial brightness distributions and elongations, of detailed imaging studies, of variability, and of dust parallaxes, as well as spectro-interferometry of emission lines in the broad line region.

Relativistic jets launched by Active Galactic Nuclei are among the most powerful particle accelerators in the Universe. The emission over the entire electromagnetic spectrum of these relativistic jets can be extremely variable with scales of variability from less than few minutes up to several years. These variability patterns, which can be very complex, contain information about the acceleration processes of the particles and the area(s) of emission. Thanks to its sensitivity, five-to twenty-times better than the current generation of Imaging Atmospheric Cherenkov Telescopes depending on energy, the Cherenkov Telescope Array will be able to follow the emission from these objects with a very accurate time sampling and over a wide spectral coverage from 20 GeV to > 20 TeV and thus reveal the nature of the acceleration processes at work in these objects. We will show the first results of our lightcurve simulations and long-term behavior of AGN as will be observed by CTA, based on state-of-art particle acceleration models., Proceedings for Gamma 2022, 8 pages, 6 figures

Relativistic jets launched by Active Galactic Nuclei are among the most powerful particle accelerators in the Universe. The emission over the entire electromagnetic spectrum of these relativistic jets can be extremely variable with scales of variability from less than few minutes up to several years. These variability patterns, which can be very complex, contain information about the acceleration processes of the particles and the area(s) of emission. Thanks to its sensitivity, five-to twenty-times better than the current generation of Imaging Atmospheric Cherenkov Telescopes depending on energy, the Cherenkov Telescope Array will be able to follow the emission from these objects with a very accurate time sampling and over a wide spectral coverage from 20 GeV to > 20 TeV and thus reveal the nature of the acceleration processes at work in these objects. We will show the first results of our lightcurve simulations and long-term behavior of AGN as will be observed by CTA, based on state-of-art particle acceleration models.

Recent anisotropy studies of UHECR data at energies $\gtrsim$ 40 EeV, have disclosed a correlation of their angular distribution with the extragalactic local structure, specifically with either local starburst galaxies or AGN. Using Monte Carlo simulations taking into account photo-disintegration processes, we further explore a framework in which these UHECRs were accelerated by Centaurus A in a recent powerful outburst before being scattered by magnetic fields associated with local, Council of Giant, extragalactic structure. We find that the observed intermediate scale anisotropies can be accounted for by the Council of Giant structure imposing a response function on the initial outburst of UHECRs from a single source located at Centaurus A's position. The presence of these local structures create `echoes' of UHECRs after the initial impulse, and focusing effects. The strongest echo wave has a lag of $\sim$ 20 Myr, comparable to the age of synchrotron-emitting electrons in the giant Centaurus A lobes. Through consideration of the composition of both the direct and echo wave components, we find that the distribution of the light (1$

The accretion disks of active galactic nuclei (AGN) are promising locations for the merger of compact objects detected by gravitational wave (GW) observatories. Embedded within a baryon-rich, high density environment, mergers within AGN are the only GW channel where an electromagnetic (EM) counterpart must occur (whether detectable or not). Considering AGN with unusual flaring activity observed by the Zwicky Transient Facility (ZTF), we describe a search for candidate EM counterparts to binary black hole (BBH) mergers detected by LIGO/Virgo in O3. After removing probable false positives, we find nine candidate counterparts to BBH mergers mergers during O3 (seven in O3a, two in O3b) with a $p$-value of 0.019. Based on ZTF sky coverage, AGN geometry, and merger geometry, we expect $\approx 3(N_{\rm BBH}/83)(f_{\rm AGN}/0.5)$ potentially detectable EM counterparts from O3, where $N_{\rm BBH}$ is the total number of observed BBH mergers and $f_{\rm AGN}$ is the fraction originating in AGN. Further modeling of breakout and flaring phenomena in AGN disks is required to reduce our false positive rate. Two of the events are also associated with mergers with total masses $> 100M_\odot$, which is the expected rate for O3 if hierarchical (large mass) mergers occur in the AGN channel. Candidate EM counterparts in future GW observing runs can be better constrained by coverage of the Southern sky as well as spectral monitoring of unusual AGN flaring events in LIGO/Virgo alert volumes. A future set of reliable AGN EM counterparts to BBH mergers will yield an independent means of measuring cosmic expansion ($H_0$) as a function of redshift., 24 pages, 6 figures, submitted to ApJ

Recent anisotropy studies of UHECR data at energies $\gtrsim$ 40 EeV, have disclosed a correlation of their angular distribution with the extragalactic local structure, specifically with either local starburst galaxies or AGN. Using Monte Carlo simulations taking into account photo-disintegration processes, we further explore a framework in which these UHECRs were accelerated by Centaurus A in a recent powerful outburst before being scattered by magnetic fields associated with local, Council of Giant, extragalactic structure. We find that the observed intermediate scale anisotropies can be accounted for by the Council of Giant structure imposing a response function on the initial outburst of UHECRs from a single source located at Centaurus A's position. The presence of these local structures creates `echoes' of UHECRs after the initial impulse, and focusing effects. The strongest echo wave has a lag of $\sim$ 20 Myr, comparable to the age of synchrotron-emitting electrons in the giant Centaurus A lobes. Through consideration of the composition of both the direct and echo wave components, we find that the distribution of the light (1$, 12 pages, 11 figures

Astronomy and astrophysics 675, A138 (2023). doi:10.1051/0004-6361/202346056, The origin of the gamma-ray emission from M87 is currently a matter of debate. This work aims to localize the VHE (100 GeV-100 TeV) gamma-ray emission from M87 and probe a potential extended hadronic emission component in the inner Virgo Cluster. The search for a steady and extended gamma-ray signal around M87 can constrain the cosmic-ray energy density and the pressure exerted by the cosmic rays onto the intra-cluster medium, and allow us to investigate the role of the cosmic rays in the active galactic nucleus feedback as a heating mechanism in the Virgo Cluster. H.E.S.S. telescopes are sensitive to VHE gamma rays and have been utilized to observe M87 since 2004. We utilized a Bayesian block analysis to identify M87 emission states with H.E.S.S. observations from 2004 until 2021, dividing them into low, intermediate, and high states. Because of the causality argument, an extended ($\gtrsim$kpc) signal is allowed only in steady emission states. Hence, we fitted the morphology of the 120h low state data and found no significant gamma-ray extension. Therefore, we derived for the low state an upper limit of 58'(corresponding to $\approx$4.6kpc) in the extension of a single-component morphological model described by a rotationally symmetric 2D Gaussian model at 99.7% confidence level. Our results exclude the radio lobes ($\approx$30 kpc) as the principal component of the VHE gamma-ray emission from the low state of M87. The gamma-ray emission is compatible with a single emission region at the radio core of M87. These results, with the help of two multiple-component models, constrain the maximum cosmic-ray to thermal pressure ratio $X_{{CR,max.}}$$\lesssim$$0.32$ and the total energy in cosmic-ray protons (CRp) to $U_{CR}$$\lesssim$5$\times10^{58}$ erg in the inner 20kpc of the Virgo Cluster for an assumed CRp power-law distribution in momentum with spectral index $\alpha_{p}$=2.1., Published by EDP Sciences, Les Ulis

The origin and evolution of galaxies are closely linked to many different physical phenomena. Among them, the most important one is the environment they reside in. Isolated and cluster member galaxies indeed are affected by different forces which affect their evolution. The main concern of this thesis is to understand such forces and how they are related to galaxy evolution. Therefore, this thesis covers various topics including black hole mass calculations, the black hole mass-stellar velocity dispersion relation, the nature of AGN emission in galaxy clusters and field galaxies, a detailed investigation of X-ray and optical galaxy overdensity phenomenon, and the dynamical processes in pre-merging galaxy clusters.

The landmark black hole images recently taken by the Event Horizon Telescope (EHT) have allowed the detailed study of the immediate surroundings of supermassive black holes (SMBHs) via direct imaging. These tantalizing early results motivate an expansion of the array, its instrumental capabilities, and dedicated long-term observations to resolve and track faint dynamical features in the black hole jet and accretion flow. The next-generation Event Horizon Telescope (ngEHT) is a project that plans to double the number of telescopes in the VLBI array and extend observations to dual-frequency 230 + 345 GHz, improving total and snapshot coverage, as well as observational agility. The Large Millimeter Telescope (LMT) is the largest sub-mm single dish telescope in the world at 50 m in diameter, and both its sensitivity and central location within the EHT array make it a key anchor station for the other telescopes. In this work, we detail current and planned future upgrades to the LMT that will directly impact its Very Large Baseline Interferometry (VLBI) performance for the EHT and ngEHT. These include the commissioning of a simultaneous 230 + 345 GHz dual-frequency, dual-polarization heterodyne receiver, improved real-time surface measurement and setting, and improvements to thermal stability, which should enable expanded daytime operation. We test and characterize the performance of an improved LMT joining future ngEHT observations through simulated observations of Sgr A* and M 87.

The origin and evolution of galaxies are closely linked to many different physical phenomena. Among them, the most important one is the environment they reside in. Isolated and cluster member galaxies indeed are affected by different forces which affect their evolution. The main concern of this thesis is to understand such forces and how they are related to galaxy evolution. Therefore, this thesis covers various topics including black hole mass calculations, the black hole mass-stellar velocity dispersion relation, the nature of AGN emission in galaxy clusters and field galaxies, a detailed investigation of X-ray and optical galaxy overdensity phenomenon, and the dynamical processes in pre-merging galaxy clusters.

We report on recent technical developments in the front- and back-ends for the four 20 m radio telescopes of the Japanese Very-Long-Baseline Interferometry (VLBI) project, VLBI Exploration of Radio Astrometry (VERA). We present a brief overview of a dual-circular polarization receiving and ultrawideband (16 Giga bit s$^{-1}$) recording systems that were installed on each of the four telescopes operating at 22 and 43 GHz bands. The wider-band capability improves the sensitivity of VLBI observations for continuum emission, and the dual-polarization capability enables the study of magnetic fields in relativistic jets ejected from supermassive black holes in active galactic nuclei and in sites of star formation and around evolved stars. We present the linear polarization intensity maps of extragalactic sources at 22 and 43 GHz obtained from the most recent test observations to show the state of the art of the VERA polarimetric observations. At the end of this article, given the realization of VLBI polarimetry with VERA, we describe the future prospects for scientific aims and further technical developments., 14 pages, 7 figures, 3 tables, published in the Special issue " Challenges in Understanding Black Hole Powered Jets with VLBI", Galaxies Journal

A tidal disruption event (TDE) occurs when a star crosses the tidal radius of a nearby supermassive black hole (SMBH) and is subsequently torn apart. The fall-back of the stellar debris onto the black hole produces a luminous flare which we can use to understand the black hole and its environment. In particular TDEs allow us to probe SMBHs in otherwise quiescent galaxies and gain insight into the lower mass SMBH population distribution. The fact that TDEs evolve on human timescales make them excellent tools with which to probe accretion physics, allowing us to observe the formation of accretion disks and jets. Over the past decade, with the introduction of high cadence all-sky surveys an increasingly large number of TDEs with well sampled lightcurves and spectra have been discovered. These events have shown a remarkably diverse range of observational features and a strange preference to occur in E+A, or post-starburst galaxies. These two factors have given rise to two key questions: ’What processes produce the observed emission in TDEs?’ and ’Why is it that TDEs occur where and when that they do?’. In this thesis I present three separate studies which aim at answering these questions. The first project is a detailed spectroscopic analysis of the TDE AT2018hyz during outburst. The dataset used is a combination of spectra from a number of telescopes resulting in high-cadence spectroscopic follow-up. This allowed me to monitor closely the evolution of spectroscopic features. The Balmer and He II emission line profiles varied dramatically throughout the TDE’s evolution. Most notably from ∼ 30 − 100 days after optical lightcurve peak the Balmer lines develop a double-peaked shape. This, combined with an unusually low Hα/Hβ ratio lead me to determine that the observations show the formation of an accretion disk before it either dissipates or gets obscured from view. At the time this was the most clear sign of accretion disk formation in a TDE from optical spectra. The second project is my analysis of another TDE, AT2019qiz. Here I present and analyse very late time optical and X-ray spectra. The optical spectra show high ionisation coronal emission lines which have never before been seen in a TDE and a jump in the flux of narrow lower ionisation lines. The X-ray spectrum shows an order-of-magnitude jump in soft X-ray flux compared to a previous observation taken closer to the peak of the TDE outburst. The coronal line emission implies a source of highly ionising extreme UV photons which is predicted by accretion models but until now not shown in observations. From the emission line widths I show that the coronal lines originate from a region further out from the SMBH than the broad line region, but within the narrow line region distance. In addition, the distances imply that the structure reprocessing the material must have already been in place at the time of outburst, likely originating from previous nuclear activity. The finding raises questions as to why these lines appear in AT2019qiz and not other TDEs and I recommend systematically searching for them in late time spectra of other TDEs. In the final project I analyse spectra of a sample of 11 host galaxies of tidal disruption events. By measuring spectral indices of the galaxies such as D n 4000 and Lick Hδ A , I find that 6 of the objects fit the literature definition of a post- starburst galaxy. This is backed up by comparisons of my measurements to galaxy models from the Bagpipes synthetic population synthesis code. In the second half of the project I conduct detailed fitting to my host galaxy spectra using Bagpipes with the goal of uncovering the star formation histories. I find that the objects previously defined as post-starburst have had a burst of star-formation within the last few Gyrs, and that one object with ongoing star-formation may be undergoing a burst at the time of TDE outburst. In general my results are consistent with other’s findings that the TDE host-galaxy population is over- represented by E+A galaxies, and that this may be related to the presence of nuclear star clusters in TDE hosts.

The A3391/95 clusters harbor bright central radio sources, which makes them ideal objects to probe the ICM-AGN interaction. The future JAXA/NASA/ESA mission, the X-Ray Imaging and Spectroscopy Mission (XRISM) will enable us to resolve line emission and the motion of the ICM affected by AGN feedback. Through simulation using cluster properties obtained from eROSITA and XMM-Newton, a forecast of the best observing strategy for XRISM high-resolution spectroscopy will be made. Given the complexity of the system, we will probe their merger state, as well. We further extend the central AGN-ICM study to a larger sample, namely using the first eROSITA All-Sky Survey (eRASS1) cluster sample in the EMU pilot field using the Australian ASKAP radio telescopes. We present preliminary results of the X-ray morphological properties of this sample. Athena will complete the AGN-ICM study, for instance, to investigate in great detail the chemical distribution and central cluster gas motion due to the central AGN feedback.

A schematic of the AGN and the main source of linear polarization in the optical and UV range, the scattering, both from the continuum and from the broad lines, is shown. Some examples of potential uses of linear polarimetry are presented, such as the observation of broad lines in type 2 AGNs, the measurement and structure of the BLR, a new method to measure the mass of supermassive black holes, and binary supermassive black hole models. &nbsp

Supermassive black holes (SMBHs), residing in the nuclei of most galaxies, are capable of imparting extreme amounts of energy to their surroundings. Observations indicate the presence of collimated, relativistic jets as well as powerful, multiphase winds emanating from these active galactic nuclei (AGN). Whilst the clearest observational signatures of AGN jet feedback are found in galaxy clusters, there is growing evidence that these jets are, in fact, largely ubiquitous. Indeed, AGN jets have now been detected in a wide variety of galaxy contexts including dwarfs, Seyferts and ellipticals. Looking towards the future, observational facilities such as JWST, SKA and Athena will greatly expand our understanding of AGN physics by facilitating investigations of SMBH jet feedback at earlier times, lower luminosities and with higher spatial and spectral resolution. Additionally, the LISA mission will expand the field of multimessenger astronomy to the low-frequency range, detecting gravitational waves from the coalescence of SMBHs all the way back to cosmic dawn. Exploring the coupled evolution of AGN and their host galaxies is a highly non-linear, multiscale, problem and, thus, lends itself to exploration via numerical simulation techniques. For numerical simulations to provide firm theoretical predictions for, as well as accurately interpret the wealth of data from these next-generation facilities, however, it is vital that physically motivated models of AGN feedback are applied in realistic galaxy formation scenarios. In this thesis I present a novel numerical scheme to model SMBH spin-driven jet feedback in galaxy formation simulations. I then apply this model, first to simulations of isolated Seyfert galaxies and then to simulations of the major merger of gas-rich galaxies at cosmic noon, exploring how AGN jet feedback affects the properties and evolution of the host galaxies and the SMBHs themselves. In Chapter 1, I provide an overview of the relevant scientific concepts and historical events that set the scene for the work which is presented in the subsequent chapters. In Chapter 2, I introduce my model for black hole accretion through a (warped) α-disc and feedback in the form of a Blandford-Znajek jet and describe its numerical implementation. In the remainder of Chapter 2, I perform benchmarking of the model and explore the effects of AGN jet feedback on the central regions of a typical radio-loud Seyfert galaxy. Chapter 3 follows on directly from Chapter 2 and significantly expands the simulation suite presented therein. Using these simulations, I explore how varying the initial black hole spin magnitude and direction, the density of the medium into which the jet propagates and the rate at which gas is funnelled towards the black hole affect the evolution and properties of the jet-driven outflows. Then, in Chapter 4, I apply my spin-driven AGN jet model to black holes at the centres of gas-rich galaxies undergoing a major merger at z ≈ 2. With these simulations, I explore how the AGN jets affect the stellar component, the gaseous haloes of the galaxies and the dynamics of the merger. Additionally, I examine how the AGN jets self-regulate when subject to the extreme environments present in such mergers. Finally, in Chapter 5, I bring together the main conclusions from these three studies, before discussing some future prospects for work in this field., STFC studentship 2114057

Active Galactic Nuclei (AGN) are growing supermassive black holes found at the centers of massive galaxies. My research involves gathering data by simulating the light emitted by AGN, and then plotting the simulated light in the form of light curves.

In this work we investigate the properties of the sources that reionized the intergalactic medium (IGM) in the high-redshift Universe. Using a semi-analytical model aimed at reproducing galaxies and black holes in the first 1.5 Gyr of the Universe, we revisit the relative role of star formation and black hole accretion in producing ionizing photons that can escape into the IGM. Both star formation and black hole accretion are regulated by supernova feedback, resulting in black hole accretion being stunted in low-mass halos. We explore a wide range of combinations for the escape fraction of ionizing photons (redshift-dependent, constant and scaling with stellar mass) from both star formation ($\langle f_{\rm esc}^{\rm sf} \rangle$) and AGN ($f_{\rm esc}^{\rm bh}$) to find: (i) the ionizing budget is dominated by stellar radiation from low stellar mass ($M_*6$ with the AGN contribution (driven by $M_{bh}>10^6 {\rm M_\odot}$ black holes in $M_* > 10^9 {\rm M_\odot}$ galaxies) dominating at lower redshifts; (ii) AGN only contribute $10-25\%$ to the cumulative ionizing emissivity by $z=4$ for the models that match the observed reionization constraints; (iii) if the stellar mass dependence of $\langle f_{\rm esc}^{\rm sf} \rangle$ is shallower than $f_{\rm esc}^{\rm bh}$, at $z, Accepted to MNRAS

We explore how the assumption of ionization equilibrium modulates the modeled intergalactic medium at the end of the hydrogen epoch of reionization using the cosmological radiation hydrodynamic Technicolor Dawn simulation. In neutral and partially ionized regions where the metagalactic ultraviolet background is weak, the ionization timescale t ion ≡ Γ−1 exceeds the Hubble time. Assuming photoionization equilibrium in such regions artificially boosts the ionization rate, accelerating reionization. By contrast, the recombination time t rec < t ion in photoionized regions, with the result that assuming photoionization equilibrium artificially increases the neutral hydrogen fraction. Using snapshots in the range 8 ≥ z ≥ 5, we compare the predicted Lyα forest (LAF) flux power spectrum with and without the assumption of ionization equilibrium. Small scales (k > 0.1 rad s km−1) exhibit reduced power from 7 ≤ z ≤ 5.5 in the ionization equilibrium case, while larger scales are unaffected. This occurs for the same reasons: ionization equilibrium artificially suppresses the neutral fraction in self-shielded gas and boosts ionizations in voids, suppressing small-scale fluctuations in the ionization field. When the volume-averaged neutral fraction drops below 10−4, the signature of nonequilibrium ionizations on the LAF disappears. Comparing with recent observations indicates that these nonequilibrium effects are not yet observable in the LAF flux power spectrum.

International audience; The Cherenkov Telescope Array (CTA) observatory is the next generation of ground-based imaging atmospheric Cherenkov telescopes (IACTs). Building on the strengths of current IACTs, CTA is designed to achieve an order of magnitude improvement in sensitivity, with unprecedented angular and energy resolution. CTA will also increase the energy reach of IACTs, observing photons in the energy range from 20 GeV to beyond 100 TeV. These advances in performance will see CTA heralding in a new era for high-energy astrophysics, with the emphasis shifting from source discovery, to population studies and precision measurements. In this talk we discuss CTA’s ability to conduct source population studies of $\gamma$-ray bright active galactic nuclei and how this ability will enhance our understanding on the redshift evolution of this dominant $\gamma$-ray source class.

Rotating black holes (BHs) are likely the largest energy reservoirs in the Universe as predicted by BH thermodynamics, while cosmic rays (CRs) are the most energetic among particles detected on Earth. Magnetic fields surrounding BHs combined with strong gravity effects, thanks to the spacetime symmetries, turn the BHs into powerful accelerators of charged particles. At the same time, in the age of multi-wavelength and multi-messenger astronomy, BHs and their environments have not yet been probed with CR messengers, despite being observed across most of the electromagnetic spectrum, and neutrino and gravitational waves. In this paper, we probe the acceleration capabilities of BHs in 8 galactic X-ray binaries and 25 local active galactic nuclei (AGNs) within 100 Mpc, based on the ultra-efficient regime of the magnetic Penrose process of a BH energy extraction combined with observational data. We find that the maximum energy of the galactic BHs can reach only up to the knee of the CR spectrum, including supermassive BH Sgr A* at the Galactic Center. On the other hand, for supermassive BHs in AGNs, we find that the mean energy of primary CRs is of the order of 1019 eV. It is therefore likely that local supermassive BHs give sufficient contribution to the ankle—a sharp change in the slope of the cosmic ray spectrum around 1018.6 eV energy. We also discuss the energy losses of primary CRs close to the acceleration zones. In the galactic BH cases, it is likely dominated by synchrotron radiation losses.

Active galactic nuclei play a key role in the evolution of galaxies, but their immediate environments are poorly understood due to a lack of angular resolution. Infrared interferometry makes it possible to resolve the circumnuclear dust in the nearest Seyfert 2, the Circinus Galaxy. Previous observations have revealed complex structures and polar dust emission but interpretation was limited to Gaussian modeling. MATISSE makes it possible to image these structures for the first time. We aim to precisely map the morphology and temperature of the dust surrounding this active nucleus through interferometric imaging. We observed the Circinus Galaxy with VLTI/MATISSE, producing 150 correlated flux spectra and 100 closure phase spectra. The novel inclusion of closure phases makes interferometric imaging possible for the first time. We use IRBis to reconstruct images in the N-band at ∼10mas resolution. We fit blackbody functions with dust extinction to several aperture-extracted fluxes from the images to produce a temperature distribution of central dusty structures. We find significant substructure in the circumnuclear dust: around 0.5 Jy of central unresolved flux, a thin disk with diameter 1.9 pc oriented along ∼ 45 deg, and ∼ 4pc × 1.5 pc polar emission extending orthogonal to the disk. The polar emission exhibits patchiness, which we attribute to clumps of dust. Flux enhancements to the East and West of the disk are seen for the first time. We distinguish the temperature profiles of the disk and the polar emission: the disk shows a steep temperature gradient indicative of denser material; the polar profile is flatter, indicating clumpiness and/or lower dust density. The unresolved flux shows a high temperature, ≈ 370 K. The polar dust remains warm (∼ 200 K) out to 1.5 pc from the disk. We attribute approximately 60% of the 12 μm flux to the polar dust, 10% to the disk, and 6% is unresolved; the remaining flux is resolved out. The recovered morphology and temperature distribution resembles modeling of accretion disks with radiation-driven winds at large scales, but we place new constraints on the sub-parsec dust. The subparsec features imaged here place new, spatially resolved constraints on physical modeling of circumnuclear dust in active galaxies; we show strong evidence that the polar emission consists of dust clumps. The dynamics of the structures and their role in the Unified Model remain to be explored.

The Mid-infrared E-ELT Thermal Infrared imager and Spectrograph (METIS) is one of the three first-light instruments selected for the European Extremely Large Telescope (ELT) and will cover the thermal infrared wavelength range, from ca. 3 - 13 microns. It will be a versatile instrument featuring diffraction-limited imaging and long-slit spectroscopy in the L/M and N bands as well as high spectral resolution (R ~ 100,000) integral field spectroscopy in the L and M bands. Its spatial resolution of 25 (70) mas in the L (N) band corresponds to a linear scale of 1 (3) parsec in nearby (10 Mpc) galaxies. For nearby AGNs, METIS forms the missing link between JWST and ground-based interferometry in both resolution and sensitivity. METIS will primarily observe continuum emission from dust at 100-800 K, but it will also be sensitive to the emission lines in this wavelength range, e.g. Brackett alpha, coronal lines like [SiIX] and [ArVI] and [AlVI], molecular lines of CO and H2O, and broad silicate emission and absorption lines. As such it is well matched to tackle several of the outstanding questions in current AGN research including "What triggers AGN activity?" and "How do AGN outflows connect to the host galaxy?". In this talk, I review METIS' instrumental capabilities with a particular focus on the prospects for AGN research.

A number of theoretical mechanisms have been invoked to explain the transformation of star forming galaxies into quenched galaxies, such as the removal of gas by active galactic nuclei- (AGN) and star formation-driven galactic outflows, and the heating of the galaxy halo and subsequent halting of gas accretion caused by virial shocks and preventative AGN feedback. Nonetheless, we still lack a clear understanding of which mechanism is the most important for quenching galaxies. The goal of this thesis is to study galaxy quenching from an observational perspective and to address the following question: why do galaxies stop forming stars? In the first part of this thesis I examine the relationship between molecular gas (observed with ALMA and NOEMA) and star formation on spatially resolved scales in seven green valley MaNGA galaxies. I find that both the star formation efficiency (SFE) and gas fraction of green valley galaxies is suppressed relative to typical star forming galaxies. These two effects are equally important for suppressing star formation in the outer disc, but it is not possible to rank their effect towards the strongly quenched galaxy centre, where SFE is only constrained to an upper limit. I also show that the significant reduction in gas fraction in the central regions is driven by an increase in stellar mass surface density rather than a decrease in molecular gas surface density, which disfavours quenching mechanisms that eject gas from galaxies. In the second part of this thesis I develop a 2D inclined rotating disc model to estimate the kinematic properties of 1862 MaNGA galaxies, and I use a random forest analysis to explore the relationship between galaxy kinematics and quenching. I find that the average velocity dispersion is overwhelmingly the most important kinematic parameter for predicting galaxy quenching. Furthermore, a full and partial correlation analysis shows that many commonly discussed correlations between galaxy properties (such as stellar mass) and quenching are spurious, and indeed at fixed velocity dispersion these correlations are almost entirely removed. I interpret this finding in the context of the BH-�� relation and argue for a scenario in which quenching occurs due to preventative feedback from AGN. In the third part of this thesis I attempt to directly probe preventative feedback from AGN by analysing a deep ALMA band 4 observation of HE0515-4414 to search for the Sunyaev-Zel'dovich (SZ) signal tracing the quasar's hot halo gas. I find marginal evidence (~3.3��) of large scale (~300 kpc) heating in the visibility plane, as well as ~3.2�� evidence of localised heating to the south west of the central quasar in the image plane. Furthermore, I use SZ maps from the FABLE simulation to demonstrate that ALMA and the ACA are effective at detecting the SZ signal in band 3, and I discuss the optimal strategy for future observations., ERC Advanced Grant 695671 ���QUENCH���

Recent studies indicate that the region of emission of coronal lines observed in some active galactic nuclei is located in the internal face of the obscurant toroid; however, there are numerous examples of Seyfert 2 galaxies with significant coronal emission. To clarify this anomaly, here we give some insights about the location of the coronal line region (CLR) and determine the physical conditions of the coronal gas in this type of galaxies. We executed a SQL query in the Sloan Digital Sky Survey (SDSS-DR14) database to select various Seyfert 2 galaxies under the following criteria: 3

International audience; We develop a thermodynamical model of fermionic dark matter halos at finite temperature. Statistical equilibrium states may be justified by a process of violent collisionless relaxation in the sense of Lynden-Bell or from a collisional relaxation of nongravitational origin if the fermions are self-interacting. The most probable state (maximum entropy state) generically has a “core-halo” structure with a quantum core (fermion ball) surrounded by an isothermal atmosphere. The quantum core is equivalent to a polytrope of index n=3/2. The Pauli exclusion principle creates a quantum pressure that prevents gravitational collapse and solves the core-cusp problem of the cold dark matter model. The isothermal atmosphere (which is similar to the Navarro-Frenk-White profile of cold dark matter) accounts for the flat rotation curves of the galaxies at large distances. We numerically solve the equation of hydrostatic equilibrium with the Fermi-Dirac equation of state and determine the density profiles and rotation curves of fermionic dark matter halos. We impose that the surface density of the dark matter halos has the universal value Σ0=ρ0rh=141 M⊙/pc2 obtained from the observations. For a fermion mass m=165 eV/c2, the “minimum halo” has a mass (Mh)min=108 M⊙ and a radius (rh)min=597 pc similar to dwarf spheroidals like Fornax. This ultracompact halo corresponds to a completely degenerate fermion ball at T=0. This is the ground state of the self-gravitating Fermi gas. For ultracompact dark matter halos with a mass (Mh)min(Mh)CCP are dominated by the classical isothermal atmosphere. They may be purely gaseous (similar to the Burkert profile) or harbor a fermion ball. The gaseous solution is stable in all statistical ensembles. The core-halo solution is canonically unstable (having a negative specific heat) but, for small dark matter halos with a mass (Mh)CCP(Mh)MCP, the quantum core-halo solution is microcanonically unstable. Large dark matter halos may undergo a gravothermal catastrophe leading ultimately to the formation of a small out-of-equilibrium condensed core or, in the case of very large dark matter halos with Mh>MOV, to a supermassive black hole when the core mass overcomes the Oppenheimer-Volkoff (OV) limit. The isothermal halo is left undisturbed and is in agreement with the Burkert profile. Our model has no free parameter (the mass m=165 eV/c2 of the fermionic particle is determined by the minimum halo) so it is completely predictive. It predicts that the Milky Way should harbor a fermionic dark matter bulge of mass Mc=9.45×109 M⊙ and radius Rc=240 pc in possible agreement with the observations. We also consider another model involving a larger fermion mass m=54.6 keV/c2. In this model, a fermion ball of mass Mc=4.2×106 M⊙ and radius Rc=6×10-4 pc could mimic the effect of a supermassive black hole at the center of the Milky Way (Sagittarius A*). In bigger galaxies, the fermion ball should be replaced by a supermassive black hole of mass MBH=2.10×108 M⊙ which could account for active galactic nuclei. For an even larger fermion mass m=386 keV/c2, a supermassive black hole of mass MBH=4.2×106 M⊙ should be formed in the Milky Way instead of a fermion ball. However, models with a fermion mass m=54.6 keV/c2 predict that ultracompact dark matter halos of mass ∼108 M⊙ should contain a fermionic core of mass Mc∼104 M⊙ and radius Rc∼5 mpc similar to intermediate mass black holes, a prediction which may be challenged by observations.

Binaries of relatively massive black holes like GW190521 have been proposed to form in dense gas environments, such as the disks of Active Galactic Nuclei (AGNs), and they might be associated with transient electromagnetic counterparts. The interactions of this putative environment with the binary could leave a significant imprint at the low gravitational wave frequencies observable with the Laser Interferometer Space Antenna (LISA). We show that LISA will be able to detect up to ten GW190521-like black hole binaries, with sky position errors $\lesssim1$ deg$^2$. Moreover, it will measure directly various effects due to the orbital motion around the supermassive black hole at the center of the AGN, especially the Doppler modulation and the Shapiro time delay. Thanks to a careful treatment of their frequency domain signal, we were able to perform the full parameter estimation of Doppler and Shapiro-modulated binaries as seen by LISA. We find that the Doppler and Shapiro effects will allow for measuring the AGN parameters (radius and inclination of the orbit around the AGN, central black hole mass) with up to percent-level precision. Properly modeling these low-frequency environmental effects is crucial to determine the binary formation history, as well as to avoid biases in the reconstruction of the source parameters and in tests of general relativity with gravitational waves., 13+4 pages, 7+1 figures v3: corrected typo in Fig 5

This thesis sums up a bachelor project in which gamma-ray emission from an extra-galactic source (S50716+71) is studied using data collected by the Fermi Large Area Telescope (LAT). The emission consists of 12,5 years of data (April 2008 to February 2020) in the energy range 100 MeV - 300 GeV. The source has a high significance (>298) and is believed to be an active galactic nucleus in which there have to be mechanisms able to accelerate photons to these high energies. The mechanisms are believed to be of non-thermal origin and the general consensus is that they are the synchrotron radiation-process as well as the inverse Compton-process. These processes are discussed to some extent in the thesis as part of a fairly large theoretical background. The data was analyzed in several ways. The Enrico software contained in the package Fermitools provided by NASA was used to create curves of the flux as a function of time (lightcurves) as well as spectral distributions. The light curve showed that the source varies considerably with hardly any “quiet periods” at all during the twelve-year period. The light curve also showed a fast rise and fall of intensity between the high intensity and low intensity points. Spectral analyses were made for six chosen time-periods of interest through the fitting of three different functions, a powerlaw-function, a logparabola-function and a powerlaw function with exponential cutoff. The powerlaw function with exponential cutoff was favored in all periods except one where the log parabola-function was preferred. The data from one of the periods was then put into a multi-wavelength context of the source showing that the data is in agreement with previous collected data. This broad spectrum was then used to model the underlying energy distribution through a theoretical framework called the Synchrotron Self-Compton model (SSC). This was done using a modelling software called JetSet. The modelling resulted in a reasonable fit of the data and parameters that overall (at least in magnitude) seem to agree with results from other publications.

International audience; Gravitational wave observations of extreme mass-ratio inspirals (EMRIs) offer the opportunity to probe the environments of active galactic nuclei (AGN) through the torques that accretion disks induce on the binary. Within a Bayesian framework, we study how well such environmental effects can be measured using gravitational wave observations from the Laser Interferometer Space Antenna (LISA). We focus on the torque induced by planetary-type migration on quasi-circular inspirals, and use different prescriptions for geometrically-thin and radiatively-efficient disks. We find that LISA could detect migration for a wide range of disk viscosities and accretion rates, for both $\alpha$ and $\beta$ disk prescriptions. For a typical EMRI with masses $50M_\odot+10^6M_\odot$, we find that LISA could distinguish between migration in $\alpha$ and $\beta$ disks and measure the torque amplitude with $\sim 20\%$ relative precision. Provided an accurate torque model, we also show how to turn gravitational-wave measurements of the torque into constraints on the disk properties. Furthermore, if an electromagnetic counterpart is identified, the multimessenger observations of the AGN-EMRI system could yield direct measurements of the disk viscosity. Finally, we investigate the impact of neglecting environmental effects in the analysis of the gravitational-wave signal of our reference system, finding 3-sigma biases in the primary mass and spin. Our analysis can be easily generalized to any environmental effect, provided that the torque has a simple power law-like dependence on the orbital separation.

37. International Cosmic Ray Conference, ICRC 2021, Berlin, Germany, 15 Jul 2021 - 22 Jul 2021; Proceedings of Science 395, 949 (2022). doi:10.22323/1.395.0949 special issue: "37th International Cosmic Ray Conference : ICRC2021 : 12-23 July 2021 : Berlin, Germany - Online / Editorial Board: Alexander Kappes, Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany ; Bianca Keilhauer, Karlsruhe Institute of Technology, Institute for Astroparticle Physics (IAP)", Published by SISSA, Trieste

Powerful winds with wide opening angles, likely driven by accretion disks around black holes (BHs), are observed in the majority of active galactic nuclei (AGN) and can play a crucial role in AGN and galaxy evolution. If protons are accelerated in the wind near the BH via diffusive shock acceleration, $p\gamma$ processes with AGN photons generate neutrinos as well as pair cascade emission from the gamma-ray to radio bands. The TeV neutrinos detected by IceCube from the obscured Seyfert galaxy NGC 1068 can be interpreted consistently if the shock velocity is appreciably lower than the local escape velocity, which may correspond to a failed, line-driven wind that is physically well motivated. Although the $p\gamma$-induced cascade is $\gamma\gamma$-attenuated above a few MeV, it can still contribute significantly to the sub-GeV gamma rays observed from NGC 1068. At higher energies, gamma rays can arise via $pp$ processes from a shock where an outgoing wind impacts the obscuring torus, along with some observable radio emission. Tests and implications of this model are discussed. Neutrinos and gamma rays may offer unique probes of AGN wind launching sites, particularly for objects obscured in other forms of radiation., Comment: 14 pages including supplemental material, submitted to PRL

Full list of authors: Acharyya, A.; Adam, R.; Adams, C.; Agudo, I.; Aguirre-Santaella, A.; Alfaro, R.; Alfaro, J.; Alispach, C.; Aloisio, R.; Alves Batista, R.; Amati, L.; Ambrosi, G.; Angüner, E. O.; Antonelli, L. A.; Aramo, C.; Araudo, A.; Armstrong, T.; Arqueros, F.; Asano, K.; Ascasíbar, Y. Ashley, M.; Balazs, C.; Ballester, O.; Baquero Larriva, A.; Barbosa Martins, V.; Barkov, M.; Barres de Almeida, U.; Barrio, J. A.; Bastieri, D.; Becerra, J.; Beck, G.; Becker Tjus, J.; Benbow, W.; Benito, M.; Berge, D.; Bernardini, E.; Bernlöhr, K.; Berti, A.; Bertucci, B.; Beshley, V.; Biasuzzi, B.; Biland, A.; Bissaldi, E.; Biteau, J.; Blanch, O.; Blazek, J.; Bocchino, F.; Boisson, C.; Bonneau Arbeletche, L.; Bordas, P.; Bosnjak, Z.; Bottacini, E.; Bozhilov, V.; Bregeon, J.; Brill, A.; Bringmann, T.; Brown, A. M.; Brun, P.; Brun, F.; Bruno, P.; Bulgarelli, A.; Burton, M.; Burtovoi, A.; Buscemi, M.; Cameron, R.; Capasso, M.; Caproni, A.; Capuzzo-Dolcetta, R.; Caraveo, P.; Carosi, R.; Carosi, A.; Casanova, S.; Cascone, E.; Cassol, F.; Catalani, F.; Cauz, D.; Cerruti, M.; Chadwick, P.; Chaty, S.; Chen, A.; Chernyakova, M.; Chiaro, G.; Chiavassa, A.; Chikawa, M.; Chudoba, J.; Çolak, M.; Conforti, V.; Coniglione, R.; Conte, F.; Contreras, J. L.; Coronado-Blazquez, J.; Costa, A.; Costantini, H.; Cotter, G.; Cristofari, P.; D'Aimath, A.; D'Ammando, F.; Damone, L. A.; Daniel, M. K.; Dazzi, F.; De Angelis, A.; De Caprio, V.; de Cássia dos Anjos, R.; de Gouveia Dal Pino, E. M.; De Lotto, B.; De Martino, D.; de Oña Wilhelmi, E.; De Palma, F.; de Souza, V.; Delgado, C.; Delgado Giler, A. G.; della Volpe, D.; Depaoli, D.; Di Girolamo, T.; Di Pierro, F.; Di Venere, L.; Diebold, S.; Dmytriiev, A.; Domínguez, A.; Donini, A.; Doro, M.; Ebr, J.; Eckner, C.; Edwards, T. D. P.; Ekoume, T. R. N.; Elsässer, D.; Evoli, C.; Falceta-Goncalves, D.; Fedorova, E.; Fegan, S.; Feng, Q.; Ferrand, G.; Ferrara, G.; Fiandrini, E.; Fiasson, A.; Filipovic, M.; Fioretti, V.; Fiori, M.; Foffano, L.; Fontaine, G.; Fornieri, O.; Franco, F. J.; Fukami, S.; Fukui, Y.; Gaggero, D.; Galaz, G.; Gammaldi, V.; Garcia, E.; Garczarczyk, M.; Gascon, D.; Gent, A.; Ghalumyan, A.; Gianotti, F.; Giarrusso, M.; Giavitto, G.; Giglietto, N.; Giordano, F.; Giuliani, A.; Glicenstein, J.; Gnatyk, R.; Goldoni, P.; González, M. M.; Gourgouliatos, K.; Granot, J.; Grasso, D.; Green, J.; Grillo, A.; Gueta, O.; Gunji, S.; Halim, A.; Hassan, T.; Heller, M.; Hernández Cadena, S.; Hiroshima, N.; Hnatyk, B.; Hofmann, W.; Holder, J.; Horan, D.; Hörandel, J.; Horvath, P.; Hovatta, T.; Hrabovsky, M.; Hrupec, D.; Hughes, G.; Humensky, T. B.; Hütten, M.; Iarlori, M.; Inada, T.; Inoue, S.; Iocco, F.; Iori, M.; Jamrozy, M.; Janecek, P.; Jin, W.; Jouvin, L.; Jurysek, J.; Karukes, E.; Katarzyński, K.; Kazanas, D.; Kerszberg, D.; Kherlakian, M. C.; Kissmann, R.; Knödlseder, J.; Kobayashi, Y.; Kohri, K.; Komin, N.; Kubo, H.; Kushida, J.; Lamanna, G.; Lapington, J.; Laporte, P.; Leigui de Oliveira, M. A.; Lenain, J.; Leone, F.; Leto, G.; Lindfors, E.; Lohse, T.; Lombardi, S.; Longo, F.; Lopez, A.; López, M.; López-Coto, R.; Loporchio, S.; Luque-Escamilla, P. L.; Mach, E.; Maggio, C.; Maier, G.; Mallamaci, M.; Malta Nunes de Almeida, R.; Mandat, D.; Manganaro, M.; Mangano, S.; Manicò, G.; Marculewicz, M.; Mariotti, M.; Markoff, S.; Marquez, P.; Martí, J.; Martinez, O.; Martínez, M.; Martínez, G.; Martínez-Huerta, H.; Maurin, G.; Mazin, D.; Mbarubucyeye, J. D.; Medina Miranda, D.; Meyer, M.; Miceli, M.; Miener, T.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Mizuno, T.; Mode, B.; Moderski, R.; Mohrmann, L.; Molina, E.; Montaruli, T.; Moralejo, A.; Morcuende-Parrilla, D.; Morselli, A.; Mukherjee, R.; Mundell, C.; Nagai, A.; Nakamori, T.; Nemmen, R.; Niemiec, J.; Nieto, D.; Nikołajuk, M.; Ninci, D.; Noda, K.; Nosek, D.; Nozaki, S.; Ohira, Y.; Ohishi, M.; Ohtani, Y.; Oka, T.; Okumura, A.; Ong, R. A.; Orienti, M.; Orito, R.; Orlandini, M.; Orlando, S.; Orlando, E.; Ostrowski, M.; Oya, I.; Pagano, I.; Pagliaro, A.; Palatiello, M.; Pantaleo, F. R.; Paredes, J. M.; Pareschi, G.; Parmiggiani, N.; Patricelli, B.; Pavletić, L.; Pe'er, A.; Pecimotika, M.; Pérez-Romero, J.; Persic, M.; Petruk, O.; Pfrang, K.; Piano, G.; Piatteli, P.; Pietropaolo, E.; Pillera, R.; Pilszyk, B.; Pintore, F.; Pohl, M.; Poireau, V.; Prado, R. R.; Prandini, E.; Prast, J.; Principe, G.; Prokoph, H.; Prouza, M.; Przybilski, H.; Pühlhofer, G.; Pumo, M. L.; Queiroz, F.; Quirrenbach, A.; Rainò, S.; Rando, R.; Razzaque, S.; Recchia, S.; Reimer, O.; Reisenegger, A.; Renier, Y.; Rhode, W.; Ribeiro, D.; Ribó, M.; Richtler, T.; Rico, J.; Rieger, F.; Rinchiuso, L.; Rizi, V.; Rodriguez, J.; Rodriguez Fernandez, G.; Rodriguez Ramirez, J. C.; Rojas, G.; Romano, P.; Romeo, G.; Rosado, J.; Rowell, G.; Rudak, B.; Russo, F.; Sadeh, I.; Sæther Hatlen, E.; Safi-Harb, S.; Salesa Greus, F.; Salina, G.; Sanchez, D.; Sánchez-Conde, M.; Sangiorgi, P.; Sano, H.; Santander, M.; Santos, E. M.; Santos-Lima, R.; Sanuy, A.; Sarkar, S.; Saturni, F. G.; Sawangwit, U.; Schussler, F.; Schwanke, U.; Sciacca, E.; Scuderi, S.; Seglar-Arroyo, M.; Sergijenko, O.; Servillat, M.; Seweryn, K.; Shalchi, A.; Sharma, P.; Shellard, R. C.; Siejkowski, H.; Silk, J.; Siqueira, C.; Sliusar, V.; Słowikowska, A.; Sokolenko, A.; Sol, H.; Spencer, S.; Stamerra, A.; Stanič, S.; Starling, R.; Stolarczyk, T.; Straumann, U.; Strišković, J.; Suda, Y.; Suomijarvi, T.; Świerk, P.; Tavecchio, F.; Taylor, L.; Tejedor, L. A.; Teshima, M.; Testa, V.; Tibaldo, L.; Todero Peixoto, C. J.; Tokanai, F.; Tonev, D.; Tosti, G.; Tosti, L.; Tothill, N.; Truzzi, S.; Travnicek, P.; Vagelli, V.; Vallage, B.; Vallania, P.; van Eldik, C.; Vandenbroucke, J.; Varner, G. S.; Vassiliev, V.; Vázquez Acosta, M.; Vecchi, M.; Ventura, S.; Vercellone, S.; Vergani, S.; Verna, G.; Viana, A.; Vigorito, C. F.; Vink, J.; Vitale, V.; Vorobiov, S.; Vovk, I.; Vuillaume, T.; Wagner, S. J.; Walter, R.; Watson, J.; Weniger, C.; White, R.; White, M.; Wiemann, R.; Wierzcholska, A.; Will, M.; Williams, D. A.; Wischnewski, R.; Yanagita, S.; Yang, L.; Yoshikoshi, T.; Zacharias, M.; Zaharijas, G.; Zakaria, A. A.; Zampieri, L.; Zanin, R.; Zaric, D.; Zavrtanik, M.; Zavrtanik, D.; Zdziarski, A. A.; Zech, A.; Zechlin, H.; Zhdanov, V. I.; Živec, M.-- This is an open access article published by IOP Publishing Ltd on behalf of Sissa Medialab. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI., We provide an updated assessment of the power of the Cherenkov Telescope Array (CTA) to search for thermally produced dark matter at the TeV scale, via the associated gamma-ray signal from pair-annihilating dark matter particles in the region around the Galactic centre. We find that CTA will open a new window of discovery potential, significantly extending the range of robustly testable models given a standard cuspy profile of the dark matter density distribution. Importantly, even for a cored profile, the projected sensitivity of CTA will be sufficient to probe various well-motivated models of thermally produced dark matter at the TeV scale. This is due to CTA's unprecedented sensitivity, angular and energy resolutions, and the planned observational strategy. The survey of the inner Galaxy will cover a much larger region than corresponding previous observational campaigns with imaging atmospheric Cherenkov telescopes. CTA will map with unprecedented precision the large-scale diffuse emission in high-energy gamma rays, constituting a background for dark matter searches for which we adopt state-of-the-art models based on current data. Throughout our analysis, we use up-to-date event reconstruction Monte Carlo tools developed by the CTA consortium, and pay special attention to quantifying the level of instrumental systematic uncertainties, as well as background template systematic errors, required to probe thermally produced dark matter at these energies. © 2021 The Author(s)., We gratefully acknowledge financial support from the following agencies and organisations: State Committee of Science of Armenia, Armenia; The Australian Research Council, Astronomy Australia Ltd, The University of Adelaide, Australian National University, Monash University, The University of New South Wales, The University of Sydney, Western Sydney University, Australia; Federal Ministry of Education, Science and Research, and Innsbruck University, Austria; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Fundacao de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ), Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Ministry of Science, Technology, Innovations and Communications (MCTIC), and Instituto Serrapilheira, Brasil; Ministry of Education and Science, National RI Roadmap Project DO1-153/28.08.2018, Bulgaria; The Natural Sciences and Engineering Research Council of Canada and the Canadian Space Agency, Canada; CONICYT-Chile grants CATA AFB 170002, ANID PIA/APOYO AFB 180002, ACT 1406, FONDECYT-Chile grants, 1161463, 1170171, 1190886, 1171421, 1170345, 1201582, Gemini-ANID 32180007, Chile; Croatian Science Foundation, Rudjer Boskovic Institute, University of Osijek, University of Rijeka, University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Zagreb, Faculty of Electrical Engineering and Computing, Croatia; Ministry of Education, Youth and Sports, MEYS LM2015046, LM2018105, LTT17006, EU/MEYS CZ.02.1.01/0.0/0.0/16_013/0001403, CZ.02.1.01/0.0/0.0/18_046/0016007 and CZ.02.1.01/0.0/0.0/16_019/0000754, Czech Republic; Academy of Finland (grant nr.317636, 320045, 317383 and 320085), Finland; Ministry of Higher Education and Research, CNRS-INSU and CNRS-IN2P3, CEA-Irfu, ANR, Regional Council Ile de France, Labex ENIGMASS, OSUG2020, P2IO and OCEVU, France; Max Planck Society, BMBF, DESY, Helmholtz Association, Germany; Department of Atomic Energy, Department of Science and Technology, India; Istituto Nazionale di Astrofisica (INAF), Istituto Nazionale di Fisica Nucleare (INFN), MIUR, Istituto Nazionale di Astrofisica (INAF-OABRERA) Grant Fondazione Cariplo/Regione Lombardia ID 2014-1980/RST_ERC, Italy; ICRR, University of Tokyo, JSPS, MEXT, Japan; Netherlands Research School for Astronomy (NOVA), Netherlands Organization for Scientific Research (NWO), Netherlands; University of Oslo, Norway; Ministry of Science and Higher Education, DIR/WK/2017/12, the National Centre for Research and Development and the National Science Centre, UMO-2016/22/M/ST9/00583, Poland; Slovenian Research Agency, grants P1-0031, P1-0385, I0-0033, J1-9146, J1-1700, N1-0111, and the Young Researcher program, Slovenia; South African Department of Science and Technology and National Research Foundation through the South African Gamma-Ray Astronomy Programme, South Africa; The Spanish Ministry of Science and Innovation and the Spanish Research State Agency (AEI) through grants AYA2016-79724-C4-1-P, AYA2016-80889-P, AYA2016-76012-C3-1-P, BES-2016-076342, ESP2017-87055-C2-1-P, FPA2017-82729-C6-1-R, FPA2017-82729-C6-2-R, FPA2017-82729-C6-3-R, FPA2017-82729-C6-4-R, FPA2017-82729-C6-5-R, FPA2017-82729-C6-6-R, PGC2018-095161-B-I00, PGC2018-095512-B-I00; the \Centro de Excelencia Severo Ochoa"program through grants no. SEV-2015-0548, SEV-2016-0597, SEV-2016-0588, SEV-2017-0709; the "Unidad de Excelencia Maria de Maeztu" program through grant no. MDM-2015-0509; the "Ramon y Cajal" programme through grants RYC-2013-14511, RyC-2013-14660, RYC-2017-22665; and the MultiDark Consolider Network FPA2017-90566-REDC. Atraccion de Talento contract no. 2016-T1/TIC-1542 granted by the Comunidad de Madrid; the "Postdoctoral Junior Leader Fellowship" programme from La Caixa Banking Foundation, grants no. LCF/BQ/LI18/11630014 and LCF/BQ/PI18/11630012; the "Programa Operativo" FEDER2014-2020, Consejeria de Economia y Conocimiento de la Junta de Andalucia (ref. 1257737), PAIDI 2020 (ref. P18-FR-1580), and Universidad de Jaen; the Spanish AEI EQC2018-005094-P FEDER 2014-2020; the European Union's "Horizon 2020" research and innovation programme under Marie Sklodowska-Curie grant agreement no. 665919; and the ESCAPE project with grant no. GA:824064, Spain; Swedish Research Council, Royal Physiographic Society of Lund, Royal Swedish Academy of Sciences, The Swedish National Infrastructure for Computing (SNIC) at Lunarc (Lund), Sweden; State Secretariat for Education, Research and Innovation (SERI) and Swiss National Science Foundation (SNSF), Switzerland; Durham University, Leverhulme Trust, Liverpool University, University of Leicester, University of Oxford, Royal Society, Science and Technology Facilities Council, U.K.; U.S. National Science Foundation, U.S. Department of Energy, Argonne National Laboratory, Barnard College, University of California, University of Chicago, Columbia University, Georgia Institute of Technology, Institute for Nuclear and Particle Astrophysics (INPAC-MRPI program), Iowa State University, the Smithsonian Institution, Washington University McDonnell Center for the Space Sciences, The University of Wisconsin and the Wisconsin Alumni Research Foundation, U.S.A. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreements No 262053 and No 317446. This project is receiving funding from the European Union's Horizon 2020 research and innovation programs under agreement No 676134.

The existence of high-energy astrophysical neutrinos has been unambiguously demonstrated, but their sources remain elusive. IceCube reported an association of a 290-TeV neutrino with a gamma-ray flare of TXS 0506+056, an active galactic nucleus with a compact radio jet pointing to us. Later, radio blazars were shown to be associated with IceCube neutrino events with high statistical significance. These associations remained unconfirmed with the data of independent experiments. Here we report on the detection of a rare neutrino event with the estimated energy of 224 +- 75 TeV from the direction of TXS 0506+056 by the new Baikal-GVD neutrino telescope in April 2021 followed by a radio flare observed by RATAN-600. This event is the highest-energy cascade detected so far by Baikal-GVD from a direction below horizon. The result supports previous suggestions that radio blazars in general, and TXS 0506+056 in particular, are the sources of high-energy neutrinos, and opens up the cascade channel for the neutrino astronomy., Comment: 12 pages, 6 figures, 2 tables

An analysis is made on the Flat Spectrum Radio Quasar PKS 0426-380 using two sets of data. The first set of data is the Fermi-LAT data collected over the time 54682.66 − 59317.66 in Modified Julian Date within the energy range of 100 MeV to 500 GeV. The second set of data is a multi-wavelength spectral energy distribution within the approximate frequencies of . First, the Fermi-LAT data were analysed and after modelling a lightcurve over the entire available time, a period of interest was located. The next step was to obtain a multi-wavelength spectral energy distribution of said period. Then, using JetSeT modelling, the data were analysed and a model of the Synchrotron Self-Compton, External-Compton and Synchrotron curves was fitted to the data. The final model which contained the best fit provided a set of physical parameters that described the source. These parameters were finally compared to two other Flat Spectrum Radio Quasars and conclusions regarding the properties of PKS 0426-380 were eventually drawn. A discussion comparing a related work on the same source to the results in this thesis followed. With the large differences in the constrained data between the Flat Spectrum Radio Quasars as background, three predictions concluded the thesis. These are, firstly, a cautioned approach to future searches for periodicity in AGN's. Secondly, in time, local periodicity for AGN's might be more common and interesting for future research. Finally, no certain values for the physical parameters of the AGN can be assessed and the results can only be wived as indications of the actual properties. Passed

37. International Cosmic Ray Conference, ICRC 2021, Berlin, Germany, 15 Jul 2021 - 22 Jul 2021; Proceedings of Science 395, 1115 (2022). doi:10.22323/1.395.1115 special issue: "37th International Cosmic Ray Conference : ICRC2021 : 12-23 July 2021 : Berlin, Germany - Online / Editorial Board: Alexander Kappes, Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany ; Bianca Keilhauer, Karlsruhe Institute of Technology, Institute for Astroparticle Physics (IAP)", Published by SISSA, Trieste

Physical review / D 106(2), 022005 (2022). doi:10.1103/PhysRevD.106.022005, The sources of the majority of the high-energy astrophysical neutrinos observed with the IceCube neutrino telescope at the South Pole are unknown. So far, only a flaring gamma-ray blazar was compellingly associated with the emission of high-energy neutrinos. However, several studies suggest that the neutrino emission from the gamma-ray blazar population only accounts for a small fraction of the total astrophysical neutrino flux. In this work we probe the production of high-energy neutrinos in the cores of active galactic nuclei (AGN), induced by accelerated cosmic rays in the accretion disk region. We present a likelihood analysis based on eight years of IceCube data, searching for a cumulative neutrino signal from three AGN samples created for this work. The neutrino emission is assumed to be proportional to the accretion disk luminosity estimated from the soft x-ray flux. Next to the observed soft x-ray flux, the objects for the three samples have been selected based on their radio emission and infrared color properties. For the largest sample in this search, an excess of high-energy neutrino events with respect to an isotropic background of atmospheric and astrophysical neutrinos is found, corresponding to a post-trial significance of 2.60σ. If interpreted as a genuine signal with the assumptions of a proportionality of x-ray and neutrino fluxes and a model for the subthreshold flux distribution, then this observation implies that at 100 TeV, 27%–100% of the observed neutrinos arise from particle acceleration in the core of AGN at 1σ confidence interval., Published by Inst., Melville, NY

Blazars are Active Galactic Nuclei (AGNs) whose jet is pointed towards the observer. They are usually divided in two sub-classes, depending on the aspect of their optical spectrum. Blazars which present an optical spectrum which lacks of emission lines are categorised as BL Lacertae objects (BL Lacs), while blazars whose optical spectrum shows strong emission lines are named Flat Spectrum Radio Quasars (FSRQs). The majority of blazars who have been found emitting VHE γ-rays are BL Lacs. MAGIC observed and discovered in the VHE γ-ray band many of them in the past years. Nevertheless some of them remained undetected, meaning the significance of the signal was lower than 5 σ. For my work of thesis, I gathered information and data from such undetected sources and created a catalog of 41 sources, 25 of which are BL Lacs. From them, I selected a sample of 5 sources which were observed in 2020-2022 as a starting point for a more complete upper limits study which is in preparation within the MAGIC collaboration. The sources I analysed in detail are: 4FGLJ0955.1+ 3551, 87GB-225250.5+235403, TXS1700+685, PKS2247-131 and PKS2345-16. From the selected sample of sources I obtained upper limits (ULs) to the light curves (LCs) and spectral energy distributions (SEDs), which can be used in the future to study such sources in a multiwavelength (MWL) context and define a baseline for future studies in case of detection. ULs can in fact, combined with other MWL data, help in understanding the possible emission scenarios of those sources and into defining strategies to detect them., Blazari su Aktivne Galaktičke Jezgre (AGN) čiji je mlaz uperen prema promatračcu. Uobičajeno su podijeljeni u dvije klase ovisno o svojstvima njihova optičkog spektra. Blazari koji imaju optički spektar u kojem nedostaju emisijske linije kategorizirani su kao BL Lacertae objekt (BL Lac), dok se blazari, čiji optički spektar ima jake emisijske linije, nazivaju Flat Spectrum Radio Quasars (FSRQ). Većina blazara koji emitiraju VHE (eng. very high energy) γ-zrake su BL Lac objekti. U proteklim godinama mnogo ih je promatrano i otkriveno sa MAGIC teleskopima. Ipak, neki izvori i dalje ostaju nedetektirani, na što upućuje podatak da je značcajnost manja od 5σ. U svojem radu prikupila sam informacije i podatke upravo od takvih nedetektiranih izvora i stvorila katalog koji sadrži 41 izvor, od kojih su 25 BL Lac objekti. Potom sam izdvojila uzorak od 5 izvora koji su bili promatrani u periodu od 2020. do 2022. godine i to mi je bila početna tocka za detaljniju analizu gornjih granica detekcije koja je u pripremi s kolaboracijom MAGIC. Izvori koje sam detaljnije analizirala su: 4FGL-J0955.1+3551, 87GB-225250.5+235403, TXS1700+685, PKS2247-131 i PKS2345-16. Iz odabranog uzorka uspjela sam odrediti gornje granice detekcije za svjetlosne krivulje i spektralnu distribuciju energije. Ti podatci se u budućnosti mogu upotrijebiti za promatranje sličnih izvora u kontekstu istraživanja u cijelom području elektromagnetskog spektra, i mogu poslužiti kao vodilja u slučaju detekcije. Gornje granice, u kombinaciji sa podatcima u ostalim područjima spektra, mogu pomoći pri razumijevanju moguće emisije za te izvore baš te za određivanje mogućih strategija za detekciju.

The physical nature of the mechanism responsible for the emission of neutrinos in active galactic nuclei (AGN) has been matter of debate in the literature, with relativistic jets of radio-loud AGNs as possible candidates to be the sources of high energy neutrinos. The most prominent candidate so far is the blazar TXS 0506+056, which is found to be associated with the neutrino event IceCube-170922A. Furthermore, the IceCube reported an excess of neutrinos towards TXS 0506+056 between September 2014 and March 2015, even though this association needs additional investigation, considering the presence of a nearby gamma-ray source, the quasar PKS 0502+049. Motivated by this, we studied the parsec-scale structures of TXS 0506+056 and PKS 0502+049 through radio interferometry at 8 and 15\,GHz. We identified twelve jet components in TXS 0506+056 and seven components in PKS 0502+049. The most reliable jet components show superluminal speeds ranging from 9.5c to 66c in the case of TXS 0506+056, and from 14.3c to 59c for PKS 0502+049, which were used to estimate a lower (upper) limit for the Lorentz factor (jet viewing angle) for both sources. A novel approach using simultaneously the brightness temperature of the core region and the apparent speeds of the jet components allowed us to infer basic jet parameters for TXS 0506+056 at distinct epochs. We also found that the emergence of new jet components coincides with the occurrence of gamma-ray flares. Interestingly, two of these coincidences in the case of PKS 0502+049 and one for TXS 0506+056 seems to be correlated with neutrino events detected by the IceCube Observatory., Comment: 18 pages, 7 figures. Accepted for publication in The Monthly Notices of the Royal Astronomical Society

Since its launch in 1999, the Chandra X-ray observatory has detected about 200 large-scale extragalactic jets. Surprisingly, for many of the powerful jets, the detected X-ray emission is spectrally too powerful and/or too hard to be part of the radio (and optical, when observations exist) spectral component. This strongly suggests a second, high-energy, spectral component. These X-rays, the working model argues, can be produced by low-energy electrons in the jet that inverse-Compton (IC) scatter photons of the cosmic microwave background (CMB) to X-ray energies. In the simplest scenario, this IC/CMB model predicts the X-ray jet to extend past its radio counterpart. However, observations reveal that X-rays decay \textit{before} the radio in many jets, thereby producing offsets that contradict the IC/CMB model. Alternatively, a second-electron population with energies up to a hundred TeV can produce the X-rays. However, such alternative models also do not offer any explanation for these offsets. Despite both models reproducing the observed X-rays, they imply contrasting jet energetics and, in turn, contrasting environmental impacts that have important implications for the evolution of structure in the universe. In this thesis, I will present a detailed observational and statistical analysis of X-ray/radio offsets and spectral properties of a large sample of X-ray jets, which collectively rule out one-zone IC/CMB interpretations. I will also present the possibility that knots and offsets in powerful jets are produced when slow-moving portions of the jet plasma act as obstacles to a faster outer flow and discuss the implications of this setup for the energy budget of jets.

Somboonpanyakul et al., We present the results of an analysis of Wide-field Infrared Survey Explorer (WISE) observations of the full 2500 deg2 South Pole Telescope (SPT)-Sunyaev–Zel'dovich cluster sample. We describe a process for identifying active galactic nuclei (AGN) in brightest cluster galaxies (BCGs) based on WISE mid-IR color and redshift. Applying this technique to the BCGs of the SPT-SZ sample, we calculate the AGN-hosting BCG fraction, which is defined as the fraction of BCGs hosting bright central AGNs over all possible BCGs. Assuming an evolving single-burst stellar population model, we find statistically significant evidence (>99.9%) for a mid-IR excess at high redshift compared to low redshift, suggesting that the fraction of AGN-hosting BCGs increases with redshift over the range of 0 < z < 1.3. The best-fit redshift trend of the AGN-hosting BCG fraction has the form (1 + z)4.1±1.0. These results are consistent with previous studies in galaxy clusters as well as as in field galaxies. One way to explain this result is that member galaxies at high redshift tend to have more cold gas. While BCGs in nearby galaxy clusters grow mostly by dry mergers with cluster members, leading to no increase in AGN activity, BCGs at high redshift could primarily merge with gas-rich satellites, providing fuel for feeding AGNs. If this observed increase in AGN activity is linked to gas-rich mergers rather than ICM cooling, we would expect to see an increase in scatter in the Pcav versus Lcool relation at z > 1. Last, this work confirms that the runaway cooling phase, as predicted by the classical cooling-flow model, in the Phoenix cluster is extremely rare and most BCGs have low (relative to Eddington) black hole accretion rates., T.S. and M.M. acknowledge support from the Kavli Research Investment Fund at MIT, and from NASA through Chandra grant GO5-16143. F.R. acknowledges financial support provided by NASA through SAO Award Number SV2-82023 issued by the Chandra X-Ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. The South Pole Telescope is supported by the National Science Foundation through grant PLR-1248097. Partial support is also provided by the NSF Physics Frontier Center grant PHY-1125897 to the Kavli Institute of Cosmological Physics at the University of Chicago, the Kavli Foundation, and the Gordon and Betty Moore Foundation grant GBMF 947. Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Cientìfico e Tecnológico and the Ministério da Ciência, Tecnologia e Inovação, the Deutsche Forschungsgemeinschaft and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Enérgeticas, Medioambientales y Tecnológicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgenössische Technische Hochschule (ETH) Zürich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ciències de l'Espai (IEEC/CSIC), the Institut de Fìsica d'Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians-Universität München and the associated Excellence Cluster Universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, The Ohio State University, the OzDES Membership Consortium, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, and Texas A&M University.

Editorial on the Research Topic Frontiers in astronomy and space sciences: Rising stars

The astrophysical journal 926(1), 59 (2022). doi:10.3847/1538-4357/ac3cb6, Ultraluminous infrared galaxies (ULIRGs) have infrared luminosities L $_{IR}$ ��� 10$^{12}$ L $_{���}$, making them the most luminous objects in the infrared sky. These dusty objects are generally powered by starbursts with star formation rates that exceed 100 M $_{���}$ yr$^{���1}$, possibly combined with a contribution from an active galactic nucleus. Such environments make ULIRGs plausible sources of astrophysical high-energy neutrinos, which can be observed by the IceCube Neutrino Observatory at the South Pole. We present a stacking search for high-energy neutrinos from a representative sample of 75 ULIRGs with redshift z ��� 0.13 using 7.5 yr of IceCube data. The results are consistent with a background-only observation, yielding upper limits on the neutrino flux from these 75 ULIRGs. For an unbroken E $^{���2.5}$ power-law spectrum, we report an upper limit on the stacked flux at 90% confidence level. In addition, we constrain the contribution of the ULIRG source population to the observed diffuse astrophysical neutrino flux as well as model predictions., Published by Univ., Chicago, Ill. [u.a.]

Este artículo se propone analizar la gestión de usuarios en el Departamento de Documentos Escritos del Archivo General de la Nación (AGN) Argentina, a partir de la revisión de las planillas de datos completadas por los nuevos usuarios durante el periodo 2015 – 2019. En primer lugar, el texto reconstruye el circuito administrativo de aquellos documentos, centrales para el funcionamiento de la oficina, y expone la problemática gestión de la información contenida en ellos. Así, se presenta un ejercicio cotidiano de trabajo atravesado por condicionamientos tecnológicos, legales y de antiguas prácticas que inciden en la óptima labor del Departamento. En este sentido, el AGN no está exento a los innumerables desafíos a los que se enfrentan actualmente los archivos en materia de avances tecnológicos, custodia documental, gestión de información y un paradigma de eficiencia administrativa. En una segunda parte, el trabajo atiende la cuestión de la cantidad de nuevos usuarios a lo largo de dicho periodo, su distribución geográfica y el tipo de investigación realizada, matizando la tradicional imagen del historiador como único usuario del Archivo. La fuerte imbricación entre los desafíos mencionados requiere contar con profesionales conscientes de la relevancia de las políticas de acceso y salvaguarda de derechos en instituciones públicas como los archivos. En suma, este trabajo ofrece un espíritu crítico de gestión, necesario para la implementación de mejoras constantes en el servicio ofrecido a la comunidad., This article aims to analyse the user registration at the Departamento de Documentos Escritos of the Archivo General de la Nación (AGN) Argentina, through the review of registration forms filled by new users arrived in the span between 2015 and 2019. First, this text explains the administrative process of those important records for the office, and shows the difficulties in managing the information included in them. In doing so, it presents a daily outlook blocked by technological hindrances, legal or old fashioned practices that affect the optimal task of the office. Thus, the institution is not freed from the many challenges faced by archives in terms of technological development, chain of custody, information management and a new paradigm of efficiency in public administrations. Secondly, the article cast a little light upon new archive users registered, their amount all along the period, their geographical provenance and their area of research, with the aim of questioning and nuancing the archetypal image of the historian as the only kind of user of the archive. The close intertwining between the challenges above-mentioned requires professionals aware of the relevance of safeguarding access to archives policies in public institutions. Briefly, this article offers a required critical spirit of management in order to develop continuous development practices in public services., Archivo Histórico de la Universidad Nacional de La Plata