Shedding light on globular cluster formation: age and chemical composition in the multiple stellar population scenario

A lo largo de las últimas decadas, importantes evidencias observacionales han revelado que los Cúmulos Globulares (CG) en la Vía Láctea albergan distintas poblaciones estelares. Representando clásicamente los mejores ejemplos en la naturaleza de Poblaciones Estelares Simples, estos nuevos hallazgos han puesto a los CG en el centro de atención. En particular, desvelar el origen del fenómeno llamado de las Poblaciónes Estelares Múltiples (PEM), es hoy en día un campo de investigación en Astrofísica muy activo. De hecho, los CG desempeñan un papel clave en el estudio del comienzo de la formación estelar en el Universo y la evolución temprana de los sistemas estelares ya que son fundamentales para rastrear edades y la composición química en las galaxias a las que pertenecen. Esto es especialmente cierto para la Vía Láctea: los CG Galácticos son los objetos más antiguos para los cuales se pueden determinar edades absolutas con precisión; además, conocer la composición química detallada permite deducir las propiedades del medio ambiente en la época de formación. Se están llevando a cabo grandes programas de observación con el objetivo de caracterizar mejor el fenómeno de las PEM y proporcionar restricciones para los modelos teóricos. En este contexto, la presente investigación hizo uso de los datos recopilados dentro del programa Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. Estos datos exquisitos, junto con la adopción de técnicas de an álisis y reducción de datos de vanguardia, permitieron un estudio preciso del fenómeno de las PEM. En resumen, la presente investigación ha contribuido a la caracterización de este fenómeno extremadamente interesante a través de la detección de gradientes radiales entre el número de estrellas que pertenecen a diferentes poblaciones estelares en el CG Galáctico NGC 2808 (Simioni et al. 2016). Además, se ha llevado a cabo la reducción de toda la muestra de observaciones en parallel mode de la Advanced Camera for Surveys: los catálogos resultantes están destinados a ser utilizados como referencia para muchos estudios en varios ambitos (Simioni et al. 2018). También se presentan los resultados de otras investigaciones en curso. Específicamente, el advenimiento de los diagramas llamados chromosome maps ha llevado a la clasificación de los CG Gal ́acticos en tipo I y tipo II. Las relaciones entre esta nueva clasificación y las diversas propiedades de estos sistemas han sido investigadas por medio de un análisis de componentes principales y se encontraron aspectos interesantes que merecen estudios adicionales. Por último, se han caracterizado las PEM en NGC 6341, un CG Galáctico viejo y pobre en metal. Este cúmulo resulta compatible con ser de tipo I y se ha investigado la presencia de un gradiente radial en la distribución espacial de las poblaciones estelares

The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. X. The radial distribution of stellar populations in NGC 2808

Due to their extreme helium abundance, the multiple stellar populations of the globular cluster NGC 2808 have been widely investigated from a photometric, spectroscopic, and kinematic perspective. The most striking feature of the color-magnitude diagram of NGC 2808 is the triple main sequence (MS), with the red MS corresponding to a stellar population with primordial helium, and the middle and the blue MS being enhanced in helium up to Y$\sim$0.32 and $\sim$0.38, respectively. A recent study has revealed that this massive cluster hosts at least five distinct stellar populations (A, B, C, D, and E). Among them populations A, B, and C correspond to the red MS, while populations C and D are connected to the middle and the blue MS. In this paper we exploit Hubble-Space-Telescope photometry to investigate the radial distribution of the red, the middle and the blue MS from the cluster center out to about 8.5 arcmin. Our analysis shows that the radial distribution of each of the three MSs is different. In particular, as predicted from multiple-population formation models, both the blue MS and the middle MS appears to be more concentrated than the red MS with a significance level for this result wich is above 3{\sigma}.Comment: Accepted for publication in MNRA

Fractal analysis on Enceladus: a global ocean underneath the icy crust

Plumes of water have been observed erupting from Enceladus' south polar terrain providing direct evidence of a reservoir of liquid below the surface, that could be considered global or just a small body of water concentrated at its south pole. Gravity data collected during the spacecraft's several close flyby over the south polar region determined that the icy shell above the liquid ocean must be 30-40 km thick extending from the south pole up to 50°S (Iess et al. 2014). The hypothesis of a global ocean beneath the icy crust has been raised even in a recent paper of Thomas et al. (2015) thanks to the measurements of the very slight wobble that Enceladus displays as it orbits Saturn. In this work we support the hypothesis of the presence of an ocean layer using the fractal percolation theory. This method allowed us to estimate the icy shell thickness values in different regions of Enceladus from the south polar terrain up to the north pole. The spatial distribution of fractures on Enceladus has been analyzed in terms of their self-similar clustering and a two-point correlation method was used to measure the fractal dimension of the fractures population (Mazzarini, 2004, 2010). A self-similar clustering of fractures is characterized by a correlation coefficient with a size range defined by a lower and upper cut-off, that represent a mechanical discontinuity and the thickness of the fractured icy crust, thus connected to the liquid reservoir. We mapped the fractures on Enceladus surface based on April 2010 global mosaic from Cassini mission and applied the fractal method firstly to the south polar terrain finding indeed a fractal correlation of fractures and providing an ice shell thickness of ~40 km. Then, we analyzed fractures of four different regions around the equator and around the north pole inferring an overall ice shell thickness ranging from 35 to 45 km. Our results are in agreement with the gravity observations (Iess et al., 2014) and the mechanical models (Yin and Pappalardo, 2015) of the south polar region and, in addition, they are consistent with the hypothesis of a global ocean beneath the icy shell

MICADO Italian Contribution

Citato dalla notizia media inaf https://www.media.inaf.it/2020/01/21/micado-elt/The Webpages of the Istituto Nazionale di Astrofisica (INAF) contribution to the MICADO project for the European Southern Observatory (ESO) Extremely Large Telescope (ELT). The Webpages serve as white pages for easy access to information relative to the MICADO and in particular to the Point Spread Function (PSF) reconstruction working group

BRUTE, PSF Reconstruction for the SOUL pyramid-based Single Conjugate Adaptive Optics facility of the LBT

The astronomical applications greatly benefit from the knowledge of the instrument PSF. We describe the PSF Reconstruction algorithm developed for the LBT LUCI instrument assisted by the SOUL SCAO module. The reconstruction procedure considers only synchronous wavefront sensor telemetry data and a few asynchronous calibrations. We do not compute the Optical Transfer Function and corresponding filters. We compute instead a temporal series of wavefront maps and for each of these the corresponding instantaneous PSF. We tested the algorithm both in laboratory arrangement and in the nighttime for different SOUL configurations, adapting it to the guide star magnitudes and seeing conditions. We nick-named it "BRUTE", Blind Reconstruction Using TElemetry, also recalling the one-to-one approach, one slope-to one instantaneous PSF the algorithm applies.Comment: 11 pages, 7 figures, Proceeding of the SPIE Conference 12185, Adaptive Optics Systems VIII, 1218540 (29 August 2022

Allergic diseases in the elderly: Biological characteristics and main immunological and non-immunological mechanisms

Life expectancy and the number of elderly people are progressively increasing around the world. Together with other pathologies, allergic diseases also show an increasing incidence in geriatric age. This is partly due to the growing emphasis on a more accurate and careful diagnosis of the molecular mechanisms that do not allow to ignore the real pathogenesis of many symptoms until now unknown, and partly to the fact that the allergic people from 20 years ago represent the elderly population now. Moreover, environmental pollution predisposes to the onset of allergic asthma and dermatitis which are the result of internal pathologies more than the expression of allergic manifestations. At the same time the food contamination permits the onset of allergic diseases related to food allergy. In this review we provide the state of the art on the physiological changes in the elderly responsible for allergic diseases, their biological characteristics and the major immunological and extra immunological mechanisms. Much emphasis is given to the management of several diseases in the elderly, including anaphylactic reactions. Moreover, some new features are discussed, such as management of asthma with the support of physical activity and the use of the AIT as prevention of respiratory diseases and for the purpose of a real and long lasting benefit. The mechanisms of adverse reactions to drugs are also discussed, due to their frequency in this age, especially in polytherapy regimens. Study of the modifications of the immune system is also of great importance, as regards to the distribution of the lymphocytes and also the presence of a chronic inflammatory disease related to the production of cytokines, especially in prevision of all the possible therapies to be adopted to allow an active and healthy aging

Allergic diseases in the elderly: Biological characteristics and main immunological and non-immunological mechanisms

Life expectancy and the number of elderly people are progressively increasing around the world. Together with other pathologies, allergic diseases also show an increasing incidence in geriatric age. This is partly due to the growing emphasis on a more accurate and careful diagnosis of the molecular mechanisms that do not allow to ignore the real pathogenesis of many symptoms until now unknown, and partly to the fact that the allergic people from 20 years ago represent the elderly population now. Moreover, environmental pollution predisposes to the onset of allergic asthma and dermatitis which are the result of internal pathologies more than the expression of allergic manifestations. At the same time the food contamination permits the onset of allergic diseases related to food allergy. In this review we provide the state of the art on the physiological changes in the elderly responsible for allergic diseases, their biological characteristics and the major immunological and extra immunological mechanisms. Much emphasis is given to the management of several diseases in the elderly, including anaphylactic reactions. Moreover, some new features are discussed, such as management of asthma with the support of physical activity and the use of the AIT as prevention of respiratory diseases and for the purpose of a real and long lasting benefit. The mechanisms of adverse reactions to drugs are also discussed, due to their frequency in this age, especially in polytherapy regimens. Study of the modifications of the immune system is also of great importance, as regards to the distribution of the lymphocytes and also the presence of a chronic inflammatory disease related to the production of cytokines, especially in prevision of all the possible therapies to be adopted to allow an active and healthy aging

LBT SOUL data as a science test bench for MICADO PSF-R tool

Current state-of-the-art adaptive optics (AO) provides ground-based, diffraction-limited observations with high Strehl ratios (SR). However, a detailed knowledge of the point spread function (PSF) is required to fully exploit the scientific potential of these data. This is even more crucial for the next generation AO instruments that will equip 30-meter class telescopes, as the characterization of the PSF will be mandatory to fulfill the planned scientific requirements. For this reason, there is a growing interest in developing tools that accurately reconstruct the observed PSF of AO systems, the so-called PSF reconstruction. In this context, a PSF-R service is a planned deliverable for the MICADO@ELT instrument and our group is in charge of its development. In the case of MICADO, a blind PSF-R approach is being pursued to have the widest applicability to science cases. This means that the PSF is reconstructed without extracting information from the science data, relying only on telemetry and calibrations. While our PSF-R algorithm is currently being developed, its implementation is mature enough to test performances with actual observations. In this presentation we will discuss the reliability of our reconstructed PSFs and the uncertainties introduced in the measurements of scientific quantities for bright, on-axis observations taken with the SOUL+LUCI instrument of the LBT. This is the first application of our algorithm to real data. It demonstrates its readiness level and paves the way to further testing. Our PSF-R algorithm is able to reconstruct the SR and full-width at half maximum of the observed PSFs with errors smaller than 2% and 4.5%, respectively. We carried out the scientific evaluation of the obtained reconstructed PSFs thanks to a dedicated set of simulated observations of an ideal science case.Comment: 10 pages, 3 figures. Proceeding of the SPIE conference Adaptive Optics Systems VIII, SPIE Astronomical Telescopes + Instrumentation 2022 (paper 12185-12). arXiv admin note: substantial text overlap with arXiv:2209.0156