Examinando por Autor "Olivares Romero, Javier"
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Publicación Bayesian Inference on the Pleiades Open Cluster(Universidad de Educación a Distancia (UNED), 2023-09) Palmero Moya, Francisco José; Olivares Romero, Javier; Sarro Baro, Luis ManuelContext: Age is one of the fundamental parameters of any astrophysical object, being it a galaxy, a star, or a planet. The main three stellar dating techniques in astrophysics are dynamical ages, isochrone ages, and the chemical abundance of the Lithium isotopes. However, these methods produce ages that differ by up to 50 % for stars younger than the Sun. The main culprit for these differences is the lack of a consistent and robust age calibration due to the fact that the only sufficiently precise age available is that of the Sun. Aims: Our aim is to define and implement a Bayesian hierarchical model able to determine the ages of star clusters and associations through two age dating techniques: isochrones and Lithium abundance. Methods: The resulting model combines existent photometric, parallax, and chemical abundance of Lithium data sets of stars belonging to stellar open clusters to infer its age distribution through modern and robust artificial intelligence methods. A Neural Network is trained given a grid of pre-calculated BT-Settl models to interpolate the spectral energy distributions of stars, working as a black-box interpolator in the model. The Bayesian hierarchical model not only facilitates simultaneous inference of star-level parameters but also offers an elegant framework for effectively pooling open cluster information and propagating uncertainty. Markov Chain Monte Carlo techniques allow us to sample the posterior distribution using the Hamiltonian Monte Carlo algorithm. Results: Our model’s robust performance on a synthetic dataset with known parameters, coupled with its successful age estimation of the Pleiades Open Cluster (116.8 ± 1.9 Myr), represents a significant advancement in the field by overcoming key challenges that have hindered previous attempts mixing artifical intelligence paradigms. The resulting model signifies a new methodology for age estimation that can be applied to a wide range of open clusters, with the Pleiades serving as the initial test benchmark.Publicación The cosmic DANCe of Perseus - I. Membership, phase-space structure, mass, and energy distributions(EDP Sciences, 2023-02-27) Olivares Romero, Javier; Bouy, Hervé; Miret Roig, Nuria; Galli, P. A. B.; Sarro Baro, Luis Manuel; Moraux, Estelle; Berihuete, Ángel; https://orcid.org/0000-0002-7084-487X; https://orcid.org/0000-0001-5292-0421; https://orcid.org/0000-0003-2271-9297; https://orcid.org/0000-0003-4127-7295; https://orcid.org/0000-0002-8589-4423Context. Star-forming regions are excellent benchmarks for testing and validating theories of star formation and stellar evolution. The Perseus star-forming region, being one of the youngest (< 10 Myr), closest (280−320 pc), and most studied in the literature, is a fundamental benchmark. Aims. We aim to study the membership, phase-space structure, mass, and energy (kinetic plus potential) distribution of the Perseus star-forming region using public catalogues (Gaia, APOGEE, 2MASS, and Pan-STARRS). Methods. We used Bayesian methodologies that account for extinction to identify the Perseus physical groups in the phase-space, retrieve their candidate members, derive their properties (age, mass, 3D positions, 3D velocities, and energy), and attempt to reconstruct their origin. Results. We identify 1052 candidate members in seven physical groups (one of them new) with ages between 3 and 10 Myr, dynamical super-virial states, and large fractions of energetically unbounded stars. Their mass distributions are broadly compatible with that of Chabrier for masses ≳0.1 M⊙ and do not show hints of over-abundance of low-mass stars in NGC 1333 with respect to IC 348. These groups’ ages, spatial structure, and kinematics are compatible with at least three generations of stars. Future work is still needed to clarify if the formation of the youngest was triggered by the oldest. Conclusions. The exquisite Gaia data complemented with public archives and mined with comprehensive Bayesian methodologies allow us to identify 31% more members than previous studies, discover a new physical group (Gorgophone: 7 Myr, 191 members, and 145 M⊙), and confirm that the spatial, kinematic, and energy distributions of these groups support the hierarchical star formation scenario.Publicación Kalkayotl: A cluster distance inference code(EDP Sciences, 2020-11-24) Olivares Romero, Javier; Sarro Baro, Luis Manuel; Bouy, Hervé; Miret Roig, Nuria; Casamiquela, Laia; Galli, P. A. B.; Berihuete, Ángel; Tarricq, Y.; https://orcid.org/0000-0002-7084-487X; https://orcid.org/0000-0001-5292-0421; https://orcid.org/0000-0001-5238-8674; https://orcid.org/0000-0002-8589-4423Context. The high-precision parallax data of the Gaia mission allows for significant improvements in the distance determination to stellar clusters and their stars. In order to obtain accurate and precise distance determinations, systematics such as parallax spatial correlations need to be accounted for, especially with regard to stars in small sky regions. Aims. Our aim is to provide the astrophysical community with a free and open code designed to simultaneously infer cluster parameters (i.e., distance and size) and distances to the cluster stars using Gaia parallax measurements. The code includes cluster-oriented prior families and it is specifically designed to deal with the Gaia parallax spatial correlations. Methods. A Bayesian hierarchical model is created to allow for the inference of both the cluster parameters and distances to its stars. Results. Using synthetic data that mimics Gaia parallax uncertainties and spatial correlations, we observe that our cluster-oriented prior families result in distance estimates with smaller errors than those obtained with an exponentially decreasing space density prior. In addition, the treatment of the parallax spatial correlations minimizes errors in the estimated cluster size and stellar distances, and avoids the underestimation of uncertainties. Although neglecting the parallax spatial correlations has no impact on the accuracy of cluster distance determinations, it underestimates the uncertainties and may result in measurements that are incompatible with the true value (i.e., falling beyond the 2σ uncertainties). Conclusions. The combination of prior knowledge with the treatment of Gaia parallax spatial correlations produces accurate (error < 10%) and trustworthy estimates (i.e., true values contained within the 2σ uncertainties) of cluster distances for clusters up to ∼5 kpc, along with cluster sizes for clusters up to ∼1 kpc.Publicación Miec: A Bayesian hierarchical model for the analysis of nearby young open clusters(EDP Sciences, 2021-06-01) Olivares Romero, Javier; Bouy, Hervé; Sarro Baro, Luis Manuel; Berihuete, Ángel; P. A. B. Galli; Miret Roig, Nuria; https://orcid.org/0000-0002-7084-487X; https://orcid.org/0000-0003-4127-7295; https://orcid.org/0000-0002-8589-4423; https://orcid.org/0000-0001-5292-0421Context. The analysis of luminosity and mass distributions of young stellar clusters is essential to understanding the star-formation process. However, the gas and dust left over by this process extinct the light of the newborn stars and can severely bias both the census of cluster members and itsss luminosity distribution. Aims. We aim to develop a Bayesian methodology to infer, with minimal biases due to photometric extinction, the candidate members and magnitude distributions of embedded young stellar clusters. Methods. We improve a previously published methodology and extend its application to embedded stellar clusters. We validate the method using synthetically extincted data sets of the Pleiades cluster with varying degrees of extinction. Results. Our methodology can recover members from data sets extincted up to Av ∼ 6 mag with accuracies, true positive, and contamination rates that are better than 99%, 80%, and 9%, respectively. Missing values hamper our methodology by introducing contaminants and artifacts into the magnitude distributions. Nonetheless, these artifacts vanish through the use of informative priors in the distribution of the proper motions. Conclusions. The methodology presented here recovers, with minimal biases, the members and distributions of embedded stellar clusters from data sets with a high percentage of sources with missing values (> 96%).Publicación A rich population of free-floating planets in the Upper Scorpius young stellar association(Springer Nature, 2021-12-22) Miret Roig, Nuria; Bouy, Hervé; Raymond, Sean N.; Tamura, Motohide; Bertin, Emmanuel; Barrado, David; Olivares Romero, Javier; Galli, P. A. B.; Cuillandre, Jean-Charles; Sarro Baro, Luis Manuel; Berihuete, Ángel; Huelamo, Nuria; https://orcid.org/0000-0001-5292-0421; https://orcid.org/0000-0002-7084-487X; https://orcid.org/0000-0001-8974-0758; https://orcid.org/0000-0002-6510-0681; https://orcid.org/0000-0002-3602-3664; https://orcid.org/0000-0002-5971-9242; https://orcid.org/0000-0003-2271-9297; https://orcid.org/0000-0002-3263-8645; https://orcid.org/0000-0002-8589-4423; https://orcid.org/0000-0002-2711-8143Free-floating planets (FFPs) are planetary-mass objects that are not bound to host stars. First discovered in the 1990s, their nature and origin are still largely unconstrained because of a lack of large homogeneous samples enabling a statistical analysis of their properties. To date, most FFPs have been discovered using indirect methods; micro-lensing surveys have proven particularly successful to detect these objects down to a few Earth masses1, 2. However, the ephemeral nature of micro-lensing events prevents any follow-up observations and individual characterisation. Several studies have identified FFPs in young stellar clusters3, 4 and the Galactic field5 but their samples are small or heterogeneous in age and origin. Here we report the discovery of between 70 and 170 FFPs (depending on the assumed age) in the region encompassing Upper Scorpius (USC) and Ophiuchus (Oph), the closest young OB association to the Sun. It is the largest homogeneous sample of nearly coeval FFPs discovered to date. We found an excess of FFPs by a factor of up to seven compared to core-collapse models predictions6–8, demonstrating that other formation mechanisms may be at work. We estimate that ejection from planetary systems might have a contribution comparable to that of core-collapse in the formation of FFPs. Therefore, ejections due to dynamical instabilities in giant exoplanet systems must be frequent within the first 10 Myr of a system’s life.