Title: An extensive grid of synthetic spectral energy distributions for Seyfert 2 galaxies
Author: A. R. Chougule
Abstract: Extragalactic astrophysics researchers widely use spectral population synthesis codes to estimate the physical properties of galaxies. We created an extensive grid of realistic synthetic spectral energy distributions (SED) for Seyfert 2 narrow-line emission models specially tailored for benchmark tests, which will help quantify the accuracy in recovering the physical properties of Seyfert 2s from these codes.
Firstly, we produced single power-law templates as a fiducial mock sample to represent the primary source emission. This approach is standard in the literature. These models have various ranges in the parameters with single power-law indexes going from -2 to +1, Hydrogen number densities from 10 to 10^6 cm^−3, and six solar metallicities. To reproduce the observed properties of local Seyfert 2 galaxies, only a limited set of these parameters are valid. However, we kept the full range of the AGN template dataset parameters to account for reproducing the observed characteristics of intermediate to high redshift Seyfert 2s. We generated a total number of single power-law models of the order of 30000 models, with approximately 15% of these models being compatible with observed Seyfert 2 properties in the local universe.
Our main objective is to create a reference grid of Seyfert 2 narrow-line emission models using more realistic incident radiation field models. Therefore, for that purpose, we used the SKIRTOR models (Stalevski et al., 2012; Stalevski et al., 2016) as the primary source of emission from the AGN and produced AGN SEDs with emission lines calculated self-consistently. These models correspond to AGNs having a two-phase medium dust distribution in the torus – with a large number of high-density clumps embedded in a smooth, dusty component of low density. In addition, we account for the anisotropy of the accretion disk due to its projected area and limb darkening effect. We also include the impact of polar dust extinction and re-emission in our models. This strategy allowed us to develop a standalone AGN module primarily built from scratch in Python3 to compute the incident radiation field of AGNs. Furthermore, this module, combined with a photoionisation code, allows us to evaluate the corresponding nebular emission, i.e. continuum and lines in galaxies.
Finally, we used these mock datasets to generate realistic observations of AGNs across distinct redshift slices from 0.5 to 2.5. We passed the synthetic spectra through an in-house pipeline to simulate several millions of VLT/MOONS observations, which will be beneficial to benchmark different spectral synthesis codes. In addition, our results will provide a comprehensive framework to identify active galaxies in observations, i.e. detectability of AGNs at intermediate to higher redshifts. Our work has not only furnished a huge, distinct, diverse set of Seyfert 2 model reference grids but also helps in planning the VLT/MOONS future observations.
Title: Large Scale Structure Tessellation Statistics as a probe of Cosmology
Author: A. G. M. Guerreiro
Abstract: The spatial and angular distribution of galaxies and galaxy clusters are sensitive probes of Cosmology and large scale structure formation mechanisms. These probes involve, for example, the application of estimators of spatial/angular N-point correlations (and their fourier space/spherical harmonics counterparts) of sources to constrain theory parameters. Here we investigate the tessellation patterns of galaxies and galaxy clusters in simulations of future galaxy surveys (e.g. the Euclid mission survey) and observations (e.g. SDSS surveys), and characterize the dependence of their tessellation statistics with redshift and Cosmology.
Title: In a land (not so) far away…Gender Stereotypes in Children’s Books and Impacts on Career Choices
Author: A. Nunes
Abstract: By the age of 6, “girls already consider boys more likely to show brilliance and more suited to “really, really smart” activities than their own gender” (Bian, et al., 2017).
If you ask young children what they want to be when they grow up scientific jobs such as astronaut will appear high on the list, but if you ask them to draw a scientist, they are much more likely to draw a man than a woman (Miller et al., 2018). Why?
Gender biases and gender stereotypes can be the result of many agents and many sources. But one of the most important ones, are children’s books. Present even before birth, in the womb, books are a privileged vehicle to learn about the world and ourselves. Books can be important allies, as they are they are both a mirror and a window about who we are and who we can become. This author would share some of the results of her investigations about gender stereotypes in awarded children’s books in the Portuguese reality (Nunes, 2019) which seem to be in agreement with other international studies (Weitzman et. al, 1972, Naharara, 1998; Brugeilles, Cromer & Cromer, 2002; Hamilton et. al, 2006; Paynter, 2011), revealing a female underrepresentation and other gender inequalities in dimensions such as interests, skills, professions, hobbies, leisure time and household tasks.
The author would also like to share her experience as a book Author and present her children’s book “Valente Valentina/Mighty Valentina (Caminho, 2019) inspired by the first women astronaut, Valentina Tereshkova.
Title: Near infrared H2 outflows through IFU observations: peering into the massive star forming region IRAS 18264-1152
Author: A. R. C. Silva
Abstract: Since massive protostars are deeply embedded in their parental clouds, it is highly challenging to directly observe their immediate environment in the near-infrared (NIR). However, it is known that accretion and ejection processes are intrinsically related, thus observing the outflows in the NIR can provide crucial information about the processes governing massive star formation very close to the central engine. We analyse the morphology and chemical composition of the NIR jets of the IRAS 18264-1152 (G19.88-0.53) massive star forming region via K-band (1.9um-2.5um) observations obtained with the integral field units VLT/SINFONI and VLT/KMOS. We compute K-band magnitudes for seven point sources identified. One point source shows a rising continuum in the K-band, which may indicate its youth and potential jet driving source. The spectro-imaging analysis focuses on the H2 jets, for which we derived visual extinction, temperature, column density, area and mass. Other atomic species, such as [FeII] and BrG, are also detected, although weaker than H2. The intensity, velocity, and excitation maps based on H2 emission strongly support the existence of a protostellar cluster in this region, with at least two different large scale outflows. Furthermore, the NIR H2 morphology agrees extremely well with that found in the radio CO 2-1 outflows observed with SMA at a comparable sub-arcsecond resolution.
Title: Blinking Lights in Taurus: Longer Term Variability of Young Stars
Author: A. d. Vale
Abstract: Young stellar and substellar objects are known to change their apparent brightness in an irregular way. By studying this variability from the optical to mid infrared it is possible to uncover information on the underlying physics. The Taurus cloud complex is one of the closest star forming regions to the solar system, containing newly formed, sparsely distributed, stellar and substellar sources. The aim of this work is to research the long term variability of these sources by creating a catalog of variable stars and studying their properties. To create the catalog of variables we have used archival multi-epoch data from the Zwicky Transient Facility (optical) and AllWISE (mid-infrared) surveys, thus covering photospheric variability and variability associated with the disk and gas around the star, and employ well known variability indices. Using a catalog of confirmed young sources in Taurus we find that about 37% are variable in the optical and about 36% are variable in the MIR. We then investigated the changes in color and brightness of single sources in a color-magnitude diagram (CMD) and found that 42% of optical variables and 36% of MIR variables show a common trend in the CMD. These changes influence parameters derived using colors and/or brightness, such as the mass or the envelope/circumstellar disk type. Using the 4 WISE bands to determine the disk type over all the epochs available, we found that some sources presented variable disk types. These results can be used for comparison with older regions in order to study the time evolution of YSO variability.
Title: Modelling sky polarization patterns
Author: B. M. d. S. Pereira
Abstract: The Moon is the main source of light at night, and for this reason, it is natural to study the influence of the moonlight in astronomical observations. Besides its evident influence in terms of light intensity, the Moon can influence observations in polarimetric studies due to the photon scattering in the Earth’s atmosphere. Therefore, we adjust different scattering models to multi-band BVRI linear polarimetric data taken during Full Moon with FORS2/VLT, to study the sky patterns caused by the moonlit sky. We explain the adopted single Rayleigh scattering model, a simple multiple scattering model, and compare it with the data. We present preliminary results and discuss future outlooks considering aspects such as atmospheric conditions.
Title: Surfing a (dark) gravitational wave
Author: C. Gomes
Abstract: Gravitational waves are solutions of General Relativity and have been directly detected in recent years. Notwithstanding, alternative theories of gravity also present such solutions with some new interesting features. In general, in alternative metric theories of gravity they may present up to six polarisation states. However, when matter is included, some additional features arise. Hence, in the context of non-minimal matter-curvature coupling theories these issues need to be addressed. We shall present the results of such analysis, both from the usual linearisation process and from the Newman-Penrose formalism. Some comments on different gravity models will be presented, thus giving some insights on how to surf dark gravitational waves!
Title: Searching for very distant radio sources in the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Survey
Author: D. D. Barbosa
Abstract: The MeerKAT International Gigahertz Tiered Extragalactic Exploration (MIGHTEE), one of MeerKAT’s flagship Large Survey Projects, is a very deep radio survey providing radio continuum, spectral line and polarisation information in order to investigate the formation and evolution of galaxies over cosmic time. It is using over 1000h of observations with MeerKAT’s L-band (870 – 1670 MHz) receivers, imaging 20 square degrees over four extragalactic deep fields, namely COSMOS, the Extended Chandra Deep Field Source (E- CDFS), ELAIS-S1, and the XMM-Newton Large Scale Structure field, reaching the classical confusion limit of MeerKAT at a depth of approximately 2 uJy/beam.
We describe the Early Science dataset, covering COSMOS and XMM-LSS fields, down to a source detection level of 30 uJy, and our early efforts in identifying robust candidates for very high-redshift radio powerful AGN, capable to reveal the earliest steps of galaxy formation and evolution. Hosting an unrivalled combination of depth, area, and corresponding multiwavelength coverage, and reaching similar depths to the planned SKA all-sky survey, MIGHTEE thus provides an exciting pilot to the early galaxy evolution experiments that will be carried out by the SKA over a much larger survey volume.
Title: Coherent emission from QED cascades in pulsar polar caps
Author: F. Cruz
Abstract: Pulsar magnetospheres are thought to be filled with electron-positron plasma generated in pair cascades. The driving mechanism of these cascades is the emission of gamma-ray photons and their conversion into pairs via Quantum Electrodynamics (QED) processes. In this work, we present 2D particle-in-cell (PIC) simulations of pair cascades in pulsar polar caps with realistic magnetic field geometry that include the relevant QED processes from first principles. QED-PIC simulations capture the self-consistent coupling between particles and fields down to the plasma kinetic scales and include the interplay between these and QED effects. Our results show that, due to variation of magnetic field curvature across the polar cap, pair production bursts self-consistently develop an inclination with respect to the local magnetic field that favors the generation of coherent electromagnetic modes with properties consistent with pulsar radio emission. We show that this emission is peaked along the magnetic axis and close to the polar cap edge and may thus offer an explanation for the core and conal components of pulsar radio emission.
Title: Self-consistent population spectral synthesis with Fado: III. Nebular contributions and main sequence galaxies
Author: H. Miranda
Abstract: Context: Galaxy evolution has been studied through the interpretation of the galactic spectral energy distribution (SED) using spectral synthesis codes and these methods have been crucial in discovering different pillars of modern galaxy evolution theories. FADO is the first spectral synthesis code to consider the contribution of ionised gas to the observed emission. This assumption is expected to be particularly influential when considering star-forming (SF) galaxies, namely in the determination of the star formation rate (SFR). Up to now, most of the existent spectral synthesis codes are purely stellar, assuming a negligible nebular contribution to the total continuum. This is a strong assumption that needs to be thoroughly tested. Aim: The aim of this poster is to study the contribution of nebular emission in the determination of the Star Formation Rate (SFR) and its effect on the Main Sequence (MS). Methods: We considered the spectral database of SDSS and we applied FADO to this sample to derive the galactic properties. As a comparison, we used the data in the MPA-JHU catalogue, which derived the properties of SDSS without considering the nebular contribution. We selected a sample of SF galaxies with Hα flux measurements, and we corrected the line for the nebular extinction through the Balmer decrement. We then calculated the Hα luminosity to estimate the SFR. We considered the stellar mass from FADO and the presented in the MPA-JHU catalogue. Finally, the MS was plotted. Results: The SFR estimated with FADO is consistently higher than the SFR estimated with the data from the MPA-JHU. The median difference between the two data sets for galaxies with SFR<1 M☉/yr is 0.189 dex (55%), for galaxies with 1<SFR< 10 M☉/yr is 0.258 dex (81%) and for galaxies with SFR>10 M☉/yr is 0.298 dex (98%). With FADO the obtained MS is shifted to higher SFR values Conclusions: The obtained results show that as the SFR increases FADO recovers higher SFRs compared to MPA-JHU. Thus, the higher is the SFR the higher is the importance of the nebular component on the fit. The effect on the SFR consequently changes the MS towards higher SFRs, which implies that taking into account the nebular continuum will impact the the MS at higher redshifts.
Title: Y-NBS: Probing the epoch of reionisation with the brightest distant LAEs
Author: H. Wade
Abstract: The very early Universe remains elusive and the physics of the first galaxies and how they might have contributed towards cosmic reionisation remains one of the most exciting areas of Observational Astrophysics. The Epoch of Reionisation (EoR) marks the last major phase transition of hydrogen, and the Lyman-alpha (Lya) emission line is a powerful tool with which to probe it, as it is sensitive to the fraction of neutral hydrogen in the intergalactic medium.
Recently, the Lya luminosity function (LF) has become well constrained up to z=6.6, but now it is time to push this further to z=7.7, deeper in the EoR, where there has been a lack of ultra-wide narrowband surveys. There are various claims stating that the faint- and bright-ends of the Lya LF evolve differently, yet surveys focussing on the faint-end have failed to constrain the z=7.7 Lya LF.
Therefore, I will present the first results from Y-NBS, a large narrowband survey (1.06 um) conducted with HAWK-I on the VLT to find bright z~7.7 Lyman-alpha emitters in the COSMOS and GOODS-S fields. We combine an area of ~1 deg^2 (~600,000 Mpc^3) down to a Lya luminosity limit of 10^43.5 erg/s with a volume of ~9000 Mpc^3 down to 10^42.3 erg/s for the first time at z=7.7.
This allows us to combine ultra-faint line emitters with bright line emitters to obtain the best constraints so far. I will present an analysis of the fully reduced HAWK-I data with stricter constraints on the z=7.7 Lya LF and also discuss potential plans for follow-up observations with ALMA and JWST and the need for further wide and deep narrowband surveys.
Title: CMB from standard and current-carrying cosmic strings
Author: I. Rybak
Abstract: Cosmic strings keep popping up as an outcome of extended high energy models of physics. Therefore we can impose constraints on these scenarios by an accurate probe of strings presence. For this purpose, we will use Cosmic Microwave Background (CMB). This poster will present an extended Unconnected Segment Model (USM) to include CMB anisotropies generated by cosmic string loops. Implementing this extension to the CMBACT code, we demonstrate an enhancement of the CMB anisotropies on small angular scales for vector modes produced by loops, which dominates over those produced by long strings. This extension provides a more accurate prediction of the CMB anisotropies generated by cosmic string networks. We also go beyond vanilla cosmic strings and discuss superconducting cosmic strings. We derive equations that describe the string network evolution in terms of four macroscopic parameters: the mean string separation, root mean square velocity current amplitude and chirality variable. We demonstrate how the current can modify the evolution of a cosmic string network and estimate such influence on our predictions for CMB anisotropies from these types of cosmic string networks.
Title: First Sample of Dust Extinction Slopes for DES Galaxies
Author: J. Duarte
Abstract: Type Ia supernovae (SN Ia) are a set extremely useful distance indicators in cosmology. However, before they can be used as such, their peak luminosity must be standardized by applying some empirical corrections. One of the factors motivating these correction is the dust extinction of the light emitted from the SNe Ia, which leads to a reddening of the spectral and photometric observations. The accurate modelling of dust extinction is thus of foremost importance to SNe cosmology. We propose a novel approach of determining dust extinction laws for a cosmological sample of SNe Ia from their respective host galaxy’s global and local (4 kpc) data. Simple Stellar Population (SSP) models are fitted to broad-band photometry from the Dark Energy Survey (DES) for each of the hosts, complemented when possible with GALEX UV and 2MASS NIR photometry. Bayesian inference methods are employed during the fitting procedure, which greatly improves the quality of the results. We find strong evidence for a relation between the fitted dust parameters, which appears to match simulated predictions for similar galaxies. We conclude that our fitting methodology results in an accurate determination of the dust extinction laws, which may then be used in further SNe Ia cosmology.
Title: Asteroid astrometry by stellar occultations: statistics on accuracy from orbital fitting
Author: J. F. Ferreira
Abstract: Stellar occultations by small bodies of the Solar System are a powerful way of investigating physical properties of objects that are in general too far and small to offer details at telescopes on Earth. Revived by the publication of the Gaia data releases, this technique permits not only the determination of asteroid size and shape, but also the retrieval of additional very accurate astrometry, with a possible relevant impact on the study of dynamical properties. In previous works, we presented the impact of the Gaia Data Release 1 on the precision of occultation astrometry, and the possible performances of a single telescope used to systematically collect asteroid astrometry. In recent times, a new error model for occultation astrometry was also implemented to better describe the uncertainties specific to this technique, and the data reduction was refined. We explore in more details the improvement in performance brought by Gaia DR2 and EDR3, exploited jointly to the new occultation error model and the new astrometry. Our goal is to verify that the extreme quality of DR2, in particular, brings a sensible progress in the exploitation of occultation astrometry. We proceed by accurate orbit computation of occultation data, alone or joined to the other available ground-based observations. We find that Gaia DR2 brings a noticeable improvement to the accuracy of occultation data. This is particularly visible when occultations alone are used, resulting in very good orbits for a large fraction of objects. The joint use of archival data and occultations remains more challenging as the higher uncertainties and systematic errors of existing data have the tendency to deteriorate the results obtained by occultations alone.
Title: SPACE RIDER CdTe MONITOR FOR ASTROPHYSICS AND AVIATION SAFETY
Author: J. Mingacho
Abstract: The i-Astro LIP group is setting up a Space Rider based experiment opportunity, by proposing further studies of the orbital radiation environment effects on the detection material and operational performance of a CdTe/CZT pixelized gamma-ray detector as well as its scientific potential as Terrestrial Gamma-ray Flashes’ (TGFs) monitor. This experiment provides new scientific and technological horizons, addressing the following topics: i) Orbital radiation effects on CdTe/CZT detectors for high-energy astrophysics telescopes’ detection plane. Scientific observations will also be performed to the Crab Nebula and GRBs emissions, in particular polarimetric measurements will be performed. TGFs emissions science will be also addressed, in particular the possibility to measure the linear polarization of this emissions may contribute to answer open questions concerning the physical processes that generate these emissions. Real time monitorization of TGFs will provide the potential of CdTe/CZT pixelized detector as a TGF monitor, with the ultimate goal of developing a commercial product for aviation safety. A CdTe/CZT TGF monitor solution on board aircrafts to alert the occurrence and to characterize the magnitude of the TGFs’ emissions would provide a valuable contribute for the health and safety of aircraft crews and passengers.
Title: A reanalysis of ISO-SWS Jupiter observations: first results
Author: J. L. F. Ribeiro
Abstract: Determining the abundances of chemicals species and their isotopic ratios is fundamental to understand how and when the planets formed, in what conditions and what processes happen in their atmosphere. Jupiter still has some unanswered questions in this regard. The apparent low-temperature origin of the elements that formed the planet, the detailed meteorological processes that happen in its atmosphere remain largely unknown and the chemistry responsible for the colours of clouds of Jupiter is one of its oldest mysteries (Taylor et al.). With this work, we hope to contribute to the progress of unravelling some of these questions. We used the observations of Jupiter from the ESA mission Infrared Space Observatory (ISO) (Kessler et al. 1996) in the 793.65-3125 cm-1 (3.2-12.6 µm) region using the Short-Wave Spectrometer (SWS) (de Graauw et al., 1996). Our work is focused on the 793.65-1492.54 cm-1 (6.7-12.6 µm) region of the spectrum. Even though this data set is old, it was an important step in the study of Jupiter’s atmosphere and with the advancements in atmospheric models and line data, we argue that it warrants a revisit and reanalysis. Firstly, we used the NEMESIS radiative transfer suite (Irwin et al. 2008) to reproduce the results from Encrenaz et al. 1999 as a way to verify the validity of our method. This study is done using the CIRS NEMESIS template as a base adapted to the ISO-SWS data. We used correlated k-tables compiled for NH3, PH3, 12CH3D, 12CH4, 13CH4, C2H2, C2H6, CH3Br, CH3OH, HCOOH and SF6, with our results showing good agreement. Having verified our method, we present here our first results of the study of abundances of 12CH3D, 12CH4, 13CH4, C2H2 and C2H6 of Jupiter’s atmosphere as well as our initial study of the pressure-temperature profile of Jupiter. We use the NEMESIS suite to determine the abundances as a function of altitude and retrieve the pressure-temperature profile. We compare our results with the profiles and abundances from Neimann et al. and Fletcher et al. 2016 with the aim to constrain the number of possible best fit profiles. We also present our initial study the H/D and 12C/13C isotopic ratio of the Jovian atmosphere from the abundances of 12CH3D, 13CH4 and 12CH4 following the methodology from Fouchet et al. 2000. Despite the ISO-SWS data used being global, with this preliminary work we hope to further advance the knowledge about the chemical processes that happen in Jupiter, as well as the chemical and temperature vertical distribution. As future work, we expect to extend our frequency domain to the range of ISO/SWS observations and study the 15N/14N ratio.
References • de Graauw et al., Observing with the ISO short-wavelength spectrometer, A&A 315, L49-L54, 1996 • Encrenaz et al., The atmospheric composition and structure of Jupiter and Saturn form ISO observations: a preliminary review, Planetary and Space Science 47, 1225-1242, 1999 • Fletcher et al., Mid-infrared mapping of Jupiter’s temperatures, aerosol opacity and chemical distributions with IRTF/TEXES, Icarus 278, 128–161, 2016 • Fouchet et al., ISO-SWS Observations of Jupiter: Measurement of the Ammonia Tropospheric Profile and of the 15N/14N Isotopic Ratio, Icarus 143, 223–243, 2000 • Irwin et al., The NEMESIS planetary atmosphere radiative transfer and retrieval tool, Journal of Quantitative Spectroscopy & Radiative Transfer 109, 1136–1150, 2008 • Kessler et al., The Infrared Space Observatory (ISO) mission, A&A 315, L27, 1996 • Neimann et al., The composition of the Jovian atmosphere as determined by the Galileo probe mass spectrometer, Journal of Geophysical Research Atmospheres 103(E10):22831-45, 1998 • Taylor et al., Jupiter, The Planet, Satellites and Magnetosphere, Ch.4, Cambridge Planetary Science, Eds. Bagenal, Dowling, McKinnon, 2006
Acknowledgements We acknowledge support from the Portuguese Fundação Para a Ciência e a Tecnologia (ref. PTDC/FIS-AST/29942/2017) through national funds and by FEDER through COMPETE 2020 (ref. POCI-01-0145 FEDER-007672).
Title: Host galaxy FORS2 polarization
Author: J. Rino-Silvestre
Abstract: Dust grains are key ingredients in understanding the interstellar medium (ISM) and the largest effects of dust on astronomical observations, the extinction of light in the line of sight and the wavelength dependent reddening it causes, both affecting distance measurements for cosmology when using extragalactic sources such as supernovae. Size, shape and distribution of the dust grains may also polarize light as it traverses the ISM. A comprehensive galaxy polarization study is thus justified. In this poster I will describe the reduction steps undertaken and how simply switching the Stoke parameter calculation method yields more reliable and less biased polarimetry. Finally, preliminary multi-band polarization maps of an ensemble of galaxies observed with VLT’s FORS2 are shown.
Title: Follow-Up Lightcurves Multitool Assisting Radial velocities (FULMAR)
Author: J. Rodrigues
Abstract: TESS is now routinely discovering new exoplanets and candidates (2647 TOIs in April 2021). Detailed analysis of the TESS lightcurves is necessary to select the best candidates for Radial Velocities (RV) follow-up as we cannot observe all TOIs due to the instrument time required. We developed a modular tool called “Follow-Up Lightcurves Multitool Assisting Radial velocities (FULMAR)” to help with this process. Our code compiles available TESS lightcurves for any selected target. It can filter the activity using different methods, compute the rotation period of the star using Gaussian Processes, search for transits in the cleaned lightcurve using BLS or TLS and probe signals that were detected with RV. FULMAR aims at helping astronomers involved in RV Follow-up of TESS candidates select their targets and speed their analysis up, requiring fewer observations per target and allowing for more of them to be characterized.
Title: Cosmological constraints on f(Q)-gravity
Author: L. Atayde
Abstract: Despite the Lambda CDM overall success, there are still some theoretical and observational problems. Looking beyond Lambda CDM is thus a priority. Here I show an alternative scenario of the non-metricity f(Q)-gravity. The poster presents the phenomenology and observational constraints, using Cosmic Microwave Background (CMB) radiation, baryonic acoustic oscillations (BAO), redshift-space distortions (RSD), supernovae type Ia (SNIa), galaxy clustering (GC) and weak gravitational lensing (WL) measurements, on the non-metricity f(Q)-gravity which reproduces an exact Lambda CDM background expansion history while modifying the evolution of linear perturbations.
Title: The cosmological constant in voids
Author: M. A. Botas
Abstract: Astronomical observations reveal the existence of large regions of both concentration of matter, and nearly empty space populated by small amounts of cosmic structures. The latter are often designated as voids in the Universe, exactly because they are vast areas that contain very few or no galaxies, in comparison to commonly observed dense structures. They are regions characterized by having less than one tenth of the Universe’s average density, which indicates the significant absence of matter. Voids are comprised mostly of invisible matter detected through gravitational effects, possibly being influenced by dark energy. In sum, they are important astrophysical structures whose dynamics aren’t as well known as, for example, that of over-dense structures. And in addition they may provide information about the dark components of the universe without the local contamination by matter.
In this poster, we report on a study of the conditions for the existence of voids, and we claim that the presence of a cosmological constant plays a significant role in the process of avoiding the collapse of matter into the empty region. We adopt a Newtonian approach, first, and subsequently we build a “swiss cheese” model based on the theory of General Relativity to assess the role of a cosmological constant in providing appropriate conditions for the stability of voids. By the same token we argue that observations of the parameters characterizing voids may conversely give information about the cosmological constant.
Title: Building Next-Generation Tools for the Exploitation of Space-Based Seismic Data
Author: M. T. Clara
Abstract: As a star enters the subgiant phase of evolution, changes in its physical and chemical structure allow the emergence of mixed modes. The frequency of these mixed modes is characterized by a fast evolution with age, potentially allowing us to determine stellar properties with great precision. However, the stellar grids used in today’s forward modelling techniques lack the resolution necessary for such determinations, requiring interpolating algorithms to cover the parameter space in between the grid models when applying model-data comparison methods. In this context, we explore several possibilities to improve on interpolation, by searching for well-motivated parameters capable of better describing a stellar grid located around the subgiant region, and by testing pre-existing interpolation schemes that have been successfully applied in other scientific areas. In this poster, I will present the problem, and discuss some preliminary results.
Title: Challenges to the assembly and integration of the WSS with METIS
Author: M. Filho
Abstract: The METIS consortium in Portugal will build the support and access structure (WSS) for the mid-infrared, first generation ELT instrument - METIS. The specific characteristics of the METIS instrument and the ELT pose several challenges to building the WSS according to functional requirements. In addition, the assembly of the WSS and integrating the WSS with METIS poses its own particular challenges due to the singular loads and dimensions. Transversal to all phases of assembly and integration of the WSS and METIS is the concern for the safety of the instruments and personnel involved. We here present these requirements, challenges and mitigation measures in light of the assembly and integration of the WSS, and the WSS with METIS.
Title: Detection of high-redshift Radio Galaxies using Machine Learning models.
Author: R. Carvajal
Abstract: Observations of quasars at very high redshifts show the presence of supermassive black holes (SMBH), which trigger the formation of active galactic nuclei (AGN) at early epochs –redshift greater than 6–. From models and simulations, it is projected that these early AGN can be detected in radio frequencies –which are also known as Radio Galaxies, RG–, although the characteristics and triggering processes of radio emission are still quite indeterminate. It is expected to observe a large number of high-redshift AGN, but up to this moment, no more than 250 AGN at redshift higher than 6 have been detected from initial optical observations. And from them, only a small fraction have been detected in radio frequencies as deep radio observations are often non-existent. In light of the projected number of high-redshift AGN, critical attention has been drawn to developing procedures to predict the detection and properties of high-redshift RGs given previously available information. Future large-scale radio observatories, surveys, and their ongoing precursors (EMU, MIGHTEE, LoTSS), with their very large output data volumes, will make applying regular AGN detection techniques an inefficient task. As a way to tackle this challenge, we have implemented a series of Machine Learning (ML) models which take photometric catalogues –in several wavelength bands– as input and produce a list of Radio Galaxy candidates, along with their predicted redshift values. We will present early results of the use of these ML models with data from photometric catalogues in the HETDEX Spring Field (~400 deg2) and the Stripe 82 Field (~100 deg2).
Title: AMEGO-X POLARIMETRIC PROSPECTS
Author: R. C. d. Silva
Abstract: The discovery of gravitational waves and neutrinos from gamma-ray sources have triggered a new era in multi-messenger astronomy and established the importance of gamma-ray observations for this emerging field. AMEGO-X (All-sky Medium Energy Gamma-Ray Observatory eXplorer) is a joint European and NASA proposal, a MeV gamma-ray instrument that will survey the sky in the energy range from ~100 keV to 1 GeV with unprecedented sensitivity, filling the sensitivity gap between hard X-ray and high-energy gamma ray bands. AMEGO-X scientific instrument is composed by double-sided silicon strip detector (DSSD) trackers and CsI calorimeter. The polarimetric potential of AMEGO-X is herein analysed, in particular its sensitivity to the strongest celestial gamma-ray sources as well as to GRBs, providing important contributions both to multi-messenger science and time-domain gamma-ray astronomy.
Title: General relativistic particle-in-cell simulations of compact neutron star magnetospheres
Author: R. Torres
Abstract: Magnetospheres of compact objects such as neutron stars and black holes are complex systems where quantum electrodynamic (QED) processes, kinetic-scale pair plasma physics and general relativity (GR) play all an important role. To study such intricate and exotic systems, advanced simulation techniques are required. In this work, we present a GR module recently developed for the particle-in-cell (PIC) code OSIRIS. PIC simulations treat the plasma as particles and capture the self-consistent coupling between particles and fields down to the plasma kinetic scales. All algorithms in this GR-PIC module of OSIRIS (field solver, particle pusher and current deposit) support Minkowski, Schwarzschild or the slow-rotation limit of the Kerr metric. We present two-dimensional simulations of isolated neutron star magnetospheres, where the QED processes are mimicked by injecting plasma at the stellar surface. We discuss the differences in the plasma current distribution in the vicinity of the star for different ratios between the Schwarzschild and the stellar radii, identifying possible locations of unscreened electric field and potential emission of coherent radiation. Finally, we compare analytical estimates of the polar cap geometry with simulations when the magnetospheric solution converges to the force-free regime and considering GR effects in both particles and electromagnetic fields.
This work was supported by the European Research Council (ERC-2015-AdG Grant 695088) and FCT (Portugal) (grant PD/BD/142971/2018). We acknowledge PRACE for granting access to MareNostrum4 (Barcelona, Spain) and AMD Irene ROME (France) where the simulations were performed.
Title: New numerical approaches to test the cosmological principle with the Euclid Mission
Author: S. Nóbrega
Abstract: The cosmological principle, which states that the Universe is homogeneous and isotropic, is the basis of modern cosmology. The upcoming ESA/Euclid satellite mission will test this paradigm over a wide range of scales allowing us to assess whether the non-homogeneous Lemaitre-Tolman-Bondi (LTB) models should be considered to accurately describe observations locally and at intermediate cosmological scales. The Euclid survey is expected to reveal/confirm more than 40 thousand new clusters in the optical and infrared bands, which represents a new era for cluster cosmology as well as for understanding the physical processes that govern the evolution of these structures. This project proposes to address the problem of modeling the galaxy cluster population in the context of LTB models, and the development of new numerical tools that may be used to provide ways of confronting model predictions with observations from galaxy surveys (e.g. Euclid) and the CMB (such as Planck). Our first objective is to modify the galaxy cluster component of Planck Sky Model (PSM) to a LTB framework. We will extend this software to predict catalogues with optical cluster observables, such as cluster richness, and integrated mass maps that may be used to study model signatures and galaxy surveys - CMB/SZ (eg Euclid - Planck) correlations. The study proposed in this project is timely and innovative. This is the first time the galaxy cluster population will be modelled in the LTB context with a set of new tools predicting CMB/SZ and galaxy survey observables in a consistent way at the beginning of a new era for cluster cosmology with the Euclid satellite.
Title: Galactic archaeology with TESS and APOGEE
Author: T. Boulet
Abstract: The formation history and evolution of the Milky Way through cosmological time is a complex field of research requiring the sampling of highly accurate and reliable stellar ages for all the components of the Galaxy. Such highly reliable ages are starting to become available due to the synergy between asteroseismology, spectroscopy, and stellar modeling in the era of all-sky astronomical surveys. Based on a sample of 227 red giants in the Galactic disk sampled from the TESS Southern Continuous Viewing Zone, with a mean relative uncertainty on the stellar age of 22% and precise chemical abundances from APOGEE DR16, we aim at finding the best possible Galactic chemical clocks. We proceed by comparing the evolution of the abundance ratios to those predicted by state-of-the-art Galactic evolution models. We identified new chemical clocks ratios that have not been previously considered in the literature and we investigate the non-universality of chemical clocks by taking into account the birth radius across the Galactic disk for stars in our sample
Title: Cosmology in scalar-tensor f(R,T) gravity
Author: T. Gonçalves
Abstract: We apply cosmological reconstruction methods to f(R,T) modified gravity, in its recently developed scalar-tensor representation. We do this analysis assuming a perfect fluid in a Friedmann-Lemaı̂tre-Robsertson-Walker (FLRW) universe. Solutions with general scale factor, curvature parameter and equation of state are found for the energy density, pressure, and one of the dynamical fields of the scalar-tensor representation. We then apply three particular forms of the scale factor: an exponential expansion (in analogy with the de Sitter solution); and two types of power-law expansion (radiation domination and matter domination). This allows us to find, in each particular case, a complete solution. We do so for each of the three values of the curvature parameter, and with three different values of the equation of state corresponding, in general relativity, to the equation of state of a cosmological constant, of matter and of radiation.
Title: A curious planetary system: A Dense Hot Super Mercury and a Cold Jupiter
Author: T. Silva
Abstract: Most of the currently known planets are small worlds with radii between that of the Earth and Neptune. The characterization of planets in this regime shows a large diversity in compositions and system architectures, with distributions hinting at a multitude of formation and evolution scenarios. However many planetary populations, such as high-density planets, are significantly under-sampled limiting our understanding on planet formation and evolution. NCORES is a large observing program conducted on the HARPS high-resolution spectrograph which aims to confirm the planetary status and to measure the masses of small transiting planetary candidates detected by transit photometry surveys in order to constrain their internal composition.
Using photometry from the K2 satellite and radial velocities measured with the HARPS and CORALIE spectrographs, we search for planets around a bright (V mag = 10) and slightly evolved Sun-like star. We precisely estimate the stellar parameters, together with the chemical composition of the slightly evolved star. We then detect two planets, a super-Mercury (an Earth-sized planet with the density of Mercury) composed mainly of iron, with the core representing over 70% of the planet’s mass together with an eccentric, long period giant planet for which we do not detect a transit.
The accurate characterization reported here enhances its role as a key target to better understand the formation and evolution of planetary systems. The detection of an eccentric long period giant companion also reinforces the link between the presence of small transiting inner planets and long period gas giants.
Title: Terrestrial planets: they are all made of star stuff
Author: V. Adibekyan
Abstract: Young stars and planets both grow by accreting material from the proto-stellar disks. Planetary structure and formation models assume a common origin of the building blocks, yet, thus far, there is no direct observational evidence correlating the composition of rocky planets to their host stars. Here we present evidence of a tight chemical link between rocky planets and their host stars. The iron-mass fraction of the most precisely characterized rocky planets is compared to that of their building blocks, as inferred from the atmospheric composition of their host stars. We find a clear and statistically significant correlation between the two. Our results explain the deviations from the Earth-like densities of planets which have been previously considered as anomalous. We also find that on average the iron-mass fraction of planets is higher than that of the primordial iron content in the planet building blocks, owing to the disk-chemistry and planet formation processes. Finally, our results provide some hints that the giant impact alone is not responsible for the high-densities of super-Mercuries. We conclude that rocky planet composition depends on the chemical composition of the proto-planetary disk and contains signatures about planet formation processes.