arXiv subjects

Núria Miret Roig

Publications and source records attributed to Núria Miret Roig.

3 recordsLinked to original sources

arXiv2026

Expanding stellar associations as Galactic accelerometers

The gravitational potential of the Milky Way is fundamental for understanding the evolution of our Galaxy and the nature of dark matter. We introduce a new method to constrain the Galactic potential using expanding young stellar associations. We exploit the physical constraint that these stars share a common, compact origin to reconstruct their most likely orbits and infer the gravitational potential in which they have evolved. We define the size of an association using the trace and determinant of its position covariance matrix. By integrating synthetic associations backward in different trial potentials, we show how the true potential can be identified as the one that minimises these metrics. We demonstrate that, while current observational errors are still too large, upcoming observations will allow us to distinguish between different potentials. Our results suggest that with Gaia DR4 astrometry and radial velocity errors below 0.2 km/s, the halo mass can be constrained with a precision of 0.6 trillion solar masses and the concentration with a precision of < 0.8 using a single association, albeit with significant degeneracies. In addition, we show that the inferred dynamical traceback age is sensitive to the gravitational potential, suggesting that independent age information can help break existing degeneracies, but also that traceback-age estimates are not independent of the assumed potential. Expanding stellar associations carry information about the gravitational potential in which they have evolved. With the arrival of next-generation astrometry and high-precision radial velocities, they will provide a complementary tool for constraining the Galactic potential.

astro-ph.GA↗

arXiv2025

Disk fraction among free-floating planetary-mass objects in Upper Scorpius

Free-floating planetary-mass objects (FFPs) have been detected through direct imaging in several young, nearby star-forming regions. The properties of circumstellar disks around these objects may provide a valuable probe into their origin but are currently limited by the small sample sizes explored. We aim to perform a statistical study of the occurrence of circumstellar disks down to the planetary-mass regime. We performed a systematic survey of disks among the population identified in the 5-10 Myr-old Upper Scorpius association (USC), restricted to members outside the younger, embedded Ophiuchus region and with estimated masses below 105 M_Jup. We took advantage of unWISE photometry to search for mid-infrared excesses in the WISE (W1-W2) color. We implemented a Bayesian outlier detection method, which models the photospheric sequence and computes excess probabilities for each object, enabling a statistically sound estimation of disk fractions. We explored disk fractions across an unprecedentedly fine mass grid, reaching down to objects as low as ~6 M_Jup assuming 5 Myr or ~8 M_Jup assuming 10 Myr, thus extending the previous lower boundary of disk fraction studies. Depending on the age, our sample includes between 17 and 40 FFPs. We confirm that the disk fraction steadily rises with decreasing mass and exceeds 30% near the substellar-to-planetary mass boundary at ~13 M_Jup. We find hints of a possible flattening in this trend around 25-45 M_Jup, potentially signaling a transition in the dominant formation processes. This shift in trend should be considered with caution and needs to be confirmed with more sensitive observations. Our results are consistent with the gradual dispersal of disks over time, as disk fractions in Upper Scorpius appear systematically lower than those in younger regions.

astro-ph.SR↗

arXiv2023

Insights into star formation and dispersal from the synchronisation of stellar clocks

Age is one of the most fundamental parameters of stars, yet it is one of the hardest to determine as it requires modelling various aspects of stellar formation and evolution. When we compare the ages derived from isochronal and dynamical traceback methods for six young stellar associations, we find a systematic discrepancy. Specifically, dynamical traceback ages are consistently younger by an average of $\langleΔ_{\rm Age}\rangle = 5.5 \pm 1.1$ Myr. We rule out measurement errors as the cause of the age mismatch and propose that $Δ_{\rm Age}$ indicates the time a young star remains bound to its parental cloud before moving away from its siblings. In this framework, the dynamical traceback "clock" starts when a stellar cluster or association begins to expand after expelling most of the gas, while the isochronal "clock" starts earlier when most stars form. The difference between these two age-dating techniques is a powerful tool to constraint evolutionary models, as isochronal ages cannot be younger than dynamical traceback ages. Measuring the $Δ_{\rm Age}$ accurately and understanding its variations across different environments will provide further information on the impact of local conditions and stellar feedback on the formation and dispersal of stellar clusters.

astro-ph.SR↗