Stellar halos of massive galaxies: morphology, kinematics, and cosmological origin

This thesis studies the kinematics, the photometry, and the intrinsic shapes of massive early type galaxies (ETGs) out to large radii, using both observations and cosmological simulations. The goal is the characterisation of the structural properties of these galaxies, their variation with radius, and their dependence on the merger history. The bright central regions (~1 Re) of ETGs have long been known to display a bimodal distribution of physical properties, so that they are distinguished in fast (FRs) and slow rotators (SRs). On the other hand, much less is known about the dynamical structure of ETGs at larger radii. Stellar kinematic measurements in the ETG faint outskirts are observationally challenging as they rely on absorption line spectroscopy, which is limited to the central ~2 Re. In this study, this issue is overcome by using planetary nebulae (PNe) as tracers of the stellar halo kinematics. As part of the ePN.S survey, I performed a kinematic analysis of 33 nearby ETG halos out to typically 6 Re. This work revealed that ETGs have a larger diversity of kinematic behaviors in the halos than they do in their central regions: a considerable fraction of the ePN.S FRs shows reduced rotational support at large radii, and almost half of the FR sample shows indications for a variation of their intrinsic shape, from oblate in the center to triaxial in the halo. SRs instead are found to have increased but still modest rotation at large radii. These results were compared and interpreted using simulated galaxies from the IllustrisTNG cosmological magneto-hydrodynamical simulations. Kinematics and intrinsic shapes are found to be deeply connected: transitions to lower rotational support in the halos of FRs are accompanied by changes from flattened and oblate to more spheroidal shapes, with a higher degree of triaxiality. SRs have more homogeneous structural properties with radius, with overall high triaxiality and modest rotational support. The properties of simulated ETG stellar halos are largely determined by the balance between the in-situ component and the stars accreted through mergers, which strongly depends on stellar mass. In low mass systems, the in-situ stars determine peaked rotation profiles and near-oblate shapes with flattening decreasing with radius. In higher mass systems, mergers modify both rotation and shape profiles, generating local correlations between rotational support, shapes, and ex-situ fractions, and dynamically couple the stellar component to the dark matter halo. These results suggest that the large variety of kinematic and photometric properties of stellar halos is the direct consequence of the evolution of ETGs in a cosmological context: at large radii the FR/SR dichotomy of the cores partially breaks and is substituted by a smooth continuity of halo properties. In this picture, ETG halos would represent the connection between the bimodal core regions and the accretion dominated stochastic regime of large scale structure formation

Infectious aetiology of marginal zone lymphoma and role of anti-infective therapy

Marginal zone lymphomas have been associated with several infectious agents covering both viral and bacterial pathogens and in some cases a clear aetiological role has been established. Pathogenetic mechanisms are currently not completely understood. However, the role of chronic stimulation of the host immune response with persistent lymphocyte activation represents the most convincing explanation for lymphoproliferation. Gastric MALT lymphoma is strictly associated with Helicobacter pylori infection and various eradicating protocols, developed due to increasing antibiotic resistance, represent the first line therapy for gastric MALT. The response rate to eradication is good with 80% of response at 1 year; this finding is also noteworthy because it recapitulates cancer cured only by the antibacterial approach and it satisfies the Koch postulates of causation, establishing a causative relationship between Hp and gastric MALT lymphoma. Patients with chronic HCV infection have 5 times higher risk to develop MZL, in particular, an association with splenic and nodal MZL has been shown in several studies. Moreover, there is evidence of lymphoma regression after antiviral therapy with interferon+ribavirin, thus raising hope that newly available drugs, extremely efficient against HCV replication, could improve outcome also in HCV-driven lymphomas. Another case-study are represented by those rare cases of MZL localized to orbital fat and eye conjunctivas that have been associated with Chlamydophila psittaci infection carried by birds. Efficacy of antibacterial therapy against C. psittaci are conflicting and generally poorer than gastric MALT. Finally, some case reports will cover the relationship between primary cutaneous B-cell Lymphomas and Borrelia Burgdorferi

Development of experimental setups for the characterization of the mechanoelectrical coupling of cells in vitro

The field of mechanobiology emerged from the many evidences that mechanical forces acting on cells have a central role in their development and physiology. Cells, in fact, convert such forces into biochemical activities and gene expression in a process referred as mechanotransduction. In vitro models that mimic cell environment also from the mechanical point of view represent therefore a key tool for modelling cell behaviour and would find many applications, e.g. in drug development and tissue engineering. In this work I introduce novel tools for the study of mechanotransduction. In particular, I present a system for the evaluation of the complex response of electrically active cells, such as neurons and cardiomyocytes. This system integrates atomic force microscopy, extracellular electrophysiological recording, and optical microscopy in order to investigate cell activity in response to mechanical stimuli. I also present cell scaffolds for the in vitro study of cancer. Obtained results, although preliminary, show the potential of the proposed systems and methods to develop accurate in vitro models for mechanobiology studies

Notes on some of the ethnonyms in the Veneranda dies

The article deals with some of the ethnonyms mentioned in the Veneranda dies, proposing some identifications for the names “Daci” and “Romani” that have not hitherto been considered

Notas sobre algúns nomes de pobos no Veneranda dies

O artigo trata sobre algúns nomes de pobos que aparecen no Veneranda dies, propoñendo algunhas identificacións dos nomes “Dacios” e “Romanos” que ata agora non se tomaran en consideración

J. Mansoor, Marshall plan Modernism: Italian postwar abstraction and the beginnings of autonomia

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The extended Planetary Nebula Spectrograph (ePN.S) early type galaxy survey: the kinematic diversity of stellar halos

In this contribution we report on a kinematic study for 33 early type galaxies (ETGs) into their outer halos (average 6 effective radii, Re). We use planetary nebulae (PNe) as tracers of the main stellar population at large radii, where absorption line spectroscopy is no longer feasible. The ePN.S survey is the largest survey to-date of ETG kinematics with PNe, based on data from the Planetary Nebula Spectrograph (PN.S), counter-dispersed imaging, and high-resolution PN spectroscopy. We find that ETGs typically show a kinematic transition between inner regions and halos. Slow rotators have increased rotational support at large radii. Most of the ePN.S fast rotators show a decrease in rotation, due to the fading of the stellar disk in the outer, more slowly rotating spheroid. 30% of these fast rotators are dominated by rotation also at large radii, 40% show kinematic twists or misalignments, indicating a transition from oblate to triaxial in the halo. Despite this variety of kinematic behaviors, the ePN.S ETG halos have similar angular momentum content, independently of fast/slow rotation of the central regions. Estimated kinematic transition radii in units of Re are ~1-3 Re and anti-correlate with stellar mass. These results are consistent with cosmological simulations and support a two-phase formation scenario for ETGs.Comment: 5 pages, 1 figure, proceeding of the 6th Focus Meeting (FM6) at the XXXth IAU GA 201

Planetary nebulae as tracers of stellar population properties: unlocking their potential with integral-field spectroscopy

Planetary nebulae (PNe) are essential tracers of the kinematics of the diffuse halo and intracluster light where stellar spectroscopy is unfeasible, due to their strong emission lines. However, that is not all they can reveal about the underlying stellar population. In recent years, it has also been found that PNe in the metal-poor halos of galaxies have different properties (specific frequency, luminosity function), than PNe in the more metal-rich galaxy centers. A more quantitative understanding of the role of age and metallicity in these relations would turn PNe into valuable stellar-population tracers. In order to do that, a full characterization of PNe in regions where the stellar light can also be analysed in detail is necessary. In this work, we make use of integral-field spectroscopic data covering the central regions of galaxies, which allow us to measure both stellar ages and metallicities as well as to detect PNe. This analysis is fundamental to calibrate PNe as stellar population tracers and to push our understanding of galaxy properties at unprecedented galactocentric distances.Comment: Submitted to the Proceedings of IAU Symposium 384: Planetary Nebulae: a Universal Toolbox in the Era of Precision Astrophysics. Eds: O. De Marco, A. Zijlstra, R. Szczerb

The stellar halos of ETGs in the IllustrisTNG simulations: the photometric and kinematic diversity of galaxies at large radii

We characterize the photometric and kinematic properties of simulated early-type galaxy (ETG) stellar halos, and compare them to observations. We select a sample of ~1200 ETGs in the TNG100 and TNG50 simulations, spanning a stellar mass range of $10^{10.3}-10^{12}M_{\odot}$ and within the range of (g-r) colour and lambda-ellipticity diagram populated by observed ETGs. We determine photometric parameters, intrinsic shapes, and kinematic observables in their extended stellar halos. We study the variation in kinematics from center to halo and connect it to a change in the intrinsic shape of the galaxies. We find that the simulated galaxy sample reproduces the diversity of kinematic properties observed in ETG halos. Simulated fast rotators (FRs) divide almost evenly in one third having flat lambda profiles and high halo rotational support, a third with gently decreasing profiles, and another third with low halo rotation. Slow rotators (SRs) tend to have increased rotation in the outskirts, with half of them exceeding lambda=0.2. For $M_{*}>10^{11.5}M_{\odot}$ halo rotation is unimportant. A similar variety of properties is found for the stellar halo intrinsic shapes. Rotational support and shape are deeply related: the kinematic transition to lower rotational support is accompanied by a change towards rounder intrinsic shape. Triaxiality in the halos of FRs increases outwards and with stellar mass. Simulated SRs have relatively constant triaxiality profiles. Simulated stellar halos show a large variety of structural properties, with quantitative but no clear qualitative differences between FRs and SRs. At the same stellar mass, stellar halo properties show a gradual transition and significant overlap between the two families, despite the clear bimodality in the central regions. This is in agreement with observations of extended photometry and kinematics. [abridged]Comment: accepted for publication in A&A, 25 pages, 22 figure