Free-floating planets (FFPs) are the lightest products of star formation and they carry important information on the initial conditions of the environment in which they were formed. They were first ...discovered in the 2000s but still few of them have been identified and confirmed due to observational challenges. This is a review of the last advances in the detection of these objects and the understanding of their origin. Several studies indicate that the observed fraction of FFPs outnumbers the prediction of turbulent fragmentation and suggest that many were formed in planetary systems that were later abandoned. The JWST will certainly constitute a new step further in the detection and characterisation of FFPs. To interpret these new observations, precise ages for the nearby star-forming regions in which they were formed will be necessary.
Context: Debris discs orbiting young stars are key to understand dust evolution and the planetary formation process. We take advantage of a recent membership analysis of the 30 Myr nearby open ...cluster IC 4665 based on the Gaia and DANCe surveys to revisit the disc population of this cluster. Aims: We aim to study the disc population of IC 4665 using Spitzer (MIPS and IRAC) and WISE photometry. Methods: We use several colour-colour diagrams with empirical photospheric sequences to detect the sources with an infrared excess. Independently, we also fit the spectral energy distribution (SED) of our debris disc candidates with the Virtual Observatory SED analyser (VOSA) which is capable of automatically detecting infrared excesses and provides effective temperature estimates. Results: We find six candidates debris disc host-stars (five with MIPS and one with WISE) and two of them are new candidates. We estimate a disc fraction of 24\(\pm\)10\% for the B-A stars, where our sample is expected to be complete. This is similar to what has been reported in other clusters of similar ages (Upper Centaurus Lupus, Lower Centaurus Crux, the \(\beta\) Pictoris moving group, and the Pleiades). For solar type stars we find a disk fraction of 9\(\pm\)9%, lower than that observed in regions with comparable ages. Conclusions: Our candidates debris disc host-stars are excellent targets to be studied with ALMA or the future James Webb Space Telescope (JWST).
The Radcliffe Wave is Oscillating Konietzka, Ralf; Goodman, Alyssa A; Zucker, Catherine ...
arXiv.org,
02/2024
Paper, Journal Article
Odprti dostop
Our Sun lies within 300 pc of the 2.7-kpc-long sinusoidal chain of dense gas clouds known as the Radcliffe Wave. The structure's wave-like shape was discovered using 3D dust mapping, but initial ...kinematic searches for oscillatory motion were inconclusive. Here we present evidence that the Radcliffe Wave is oscillating through the Galactic plane while also drifting radially away from the Galactic Center. We use measurements of line-of-sight velocity for 12CO and 3D velocities of young stellar clusters to show that the most massive star-forming regions spatially associated with the Radcliffe Wave (including Orion, Cepheus, North America, and Cygnus X) move as if they are part of an oscillating wave driven by the gravitational acceleration of the Galactic potential. By treating the Radcliffe Wave as a coherently oscillating structure, we can derive its motion independently of the local Galactic mass distribution, and directly measure local properties of the Galactic potential as well as the Sun's vertical oscillation period. In addition, the measured drift of the Radcliffe Wave radially outward from the Galactic Center suggests that the cluster whose supernovae ultimately created today's expanding Local Bubble may have been born in the Radcliffe Wave.
Efforts to unveil the structure of the local interstellar medium and its recent star formation history have spanned the past seventy years. Recent studies utilizing precise data from space astrometry ...missions have revealed nearby, newly formed star clusters with connected origins. Nonetheless, mapping young clusters across the entire sky back to their natal regions has been hindered by a lack of clusters with precise radial velocity data. Here we show that 155 out of 272 (57 percent) high-quality young clusters within one kiloparsec of the Sun arise from three distinct spatial volumes. This conclusion is based upon the analysis of data from the third Gaia release and other large-scale spectroscopic surveys. Currently dispersed throughout the Solar Neighborhood, their past positions over 30 Myr ago reveal that these families of clusters each formed in one of three compact, massive star-forming complexes. One of these families includes all of the young clusters near the Sun -- the Taurus and Sco-Cen star-forming complexes. We estimate that over 200 supernovae were produced from these families and argue that these clustered supernovae produced both the Local Bubble and the largest nearby supershell GSH 238+00+09, both of which are clearly visible in modern three-dimensional dust maps.
The Tucana-Horologium association is one of the closest young stellar groups to the Sun and despite the close proximity its age is still debated in the literature. We take advantage of the ...state-of-the-art astrometry delivered by the third data release of the Gaia space mission combined with precise radial velocity measurements obtained from high-resolution spectroscopy to investigate the dynamical age of the association. We perform an extensive traceback analysis using a combination of different samples of cluster members, metrics to evaluate the minimum size of the association in the past and models for the galactic potential to integrate the stellar orbits back in time. The dynamical age of \(38.5^{+1.6}_{-8.0}\) Myr that we derive in this paper is consistent with the various age estimates obtained from isochrone fitting in the literature (30-50 Myr) and reconciles, for the first time, the dynamical age of the Tucana-Horologium association with the age obtained from lithium depletion (\(\sim40\) Myr). Our results are independent from stellar models and represent one more step towards constructing a self-consistent age scale for the young stellar groups of the Solar neighbourhood based on the 3D space motion of the stars.
We reconstruct the star formation history of the Sco-Cen OB association using a novel high-resolution age map of the region. We develop an approach to produce robust ages for Sco-Cen's recently ...identified 37 stellar clusters using the SigMA algorithm. The Sco-Cen star formation timeline reveals four periods of enhanced star formation activity, or bursts, remarkably separated by about 5 Myr. Of these, the second burst, which occurred about 15 million years ago, is by far the dominant, and most of Sco-Cen's stars and clusters were in place by the end of this burst. The formation of stars and clusters in Sco-Cen is correlated but not linearly, implying that more stars were formed per cluster during the peak of the star formation rate. Most of the clusters that are large enough to have supernova precursors were formed during the 15 Myr period. Star and cluster formation activity has been continuously declining since then. We have clear evidence that Sco-Cen formed from the inside out and contains 100-pc long chains of contiguous clusters exhibiting well-defined age gradients, from massive older clusters to smaller young clusters. These observables suggest an important role for feedback in forming about half of Sco-Cen stars, although follow-up work is needed to quantify this statement. Finally, we confirm that the Upper-Sco age controversy discussed in the literature during the last decades is solved: the nine clusters previously lumped together as Upper-Sco, a benchmark region for planet formation studies, exhibit a wide range of ages from 3 to 19 Myr.
A&A 618, C7 (2018) The Young Local Associations constitute an excellent sample for the study of
a variety of astrophysical topics, especially the star formation process in
low-density environments. ...Data from the Gaia mission allows us to undertake
studies of the YLAs with unprecedented accuracy. We determine the dynamical age
and place of birth of a set of associations in a uniform and dynamically
consistent manner. There are nine YLAs in our sample $\epsilon$ Chamaeleontis,
TW Hydrae, $\beta$ Pictoris, Octans, Tucana-Horologium, Columba, Carina, Argus
and AB Doradus. We designed a method for deriving the dynamical age of the YLAs
based on the orbital integration. It involves a strategy to account for the
effect of observational errors and we tested it using mock YLAs. Finally, we
applied it to our set of nine YLAs with astrometry from the first Gaia data
release and complementary on-ground radial velocities from the literature. Our
orbital analysis yields a first estimate of the dynamical age of 3$^{+9}_{-0}$
Myr, 13$^{+7}_{-0}$ Myr and 5$^{+23}_{-0}$ Myr for $\epsilon$ Cha, $\beta$ Pict
and Tuc-Hor, respectively. For four other associations (Oct, Col, Car and Arg),
we provide a lower limit for the dynamical age. Our rigorous error treatment
indicates that TW Hya and AB Dor deserve further study. Our dynamical ages are
compatible spectroscopic and isochrone fitting ages obtained elsewhere. From
the orbital analysis, we suggest a scenario with two episodes of star
formation: one ~40 Myr ago in the first quadrant that gave birth to $\epsilon$
Cha, TW Hya and $\beta$ Pic, and another 5-15 Myr ago close to the Sun that
formed Tuc-Hor, Col, and Car. Future Gaia data will provide the necessary
accuracy to improve the present results, especially for the controversial age
determinations, and additional evidence for the proposed scenario, once a
complete census of YLAs and better membership can be obtained.
The nature and origin of free-floating planets (FFPs) are still largely unconstrained because of a lack of large homogeneous samples to enable a statistical analysis of their properties. So far, most ...FFPs have been discovered using indirect methods; microlensing surveys have proved particularly successful to detect these objects down to a few Earth masses. However, the ephemeral nature of microlensing events prevents any follow-up observations and individual characterization. Several studies have identified FFPs in young stellar clusters and the Galactic field 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 and Ophiuchus, the closest young OB association to the Sun. We found an excess of FFPs by a factor of up to seven compared with core-collapse model predictions, 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.
VISIONS is an ESO public survey of five nearby (d < 500 pc) star-forming molecular cloud complexes that are canonically associated with the constellations of Chamaeleon, Corona Australis, Lupus, ...Ophiuchus, and Orion. The survey was carried out with VISTA, using VIRCAM, and collected data in the near-infrared passbands J, H, and Ks. With a total on-sky exposure time of 49.4 h VISIONS covers an area of 650 deg\(^2\), and it was designed to build an infrared legacy archive similar to that of 2MASS. Taking place between April 2017 and March 2022, the observations yielded approximately 1.15 million images, which comprise 19 TB of raw data. The observations are grouped into three different subsurveys: The wide subsurvey comprises shallow, large-scale observations and has visited the star-forming complexes six times over the course of its execution. The deep subsurvey of dedicated high-sensitivity observations has collected data on the areas with the largest amounts of dust extinction. The control subsurvey includes observations of areas of low-to-negligible dust extinction. Using this strategy, the VISIONS survey offers multi-epoch position measurements, is able to access deeply embedded objects, and provides a baseline for statistical comparisons and sample completeness. In particular, VISIONS is designed to measure the proper motions of point sources with a precision of 1 mas/yr or better, when complemented with data from VHS. Hence, VISIONS can provide proper motions for sources inaccessible to Gaia. VISIONS will enable addressing a range of topics, including the 3D distribution and motion of embedded stars and the nearby interstellar medium, the identification and characterization of young stellar objects, the formation and evolution of embedded stellar clusters and their initial mass function, as well as the characteristics of interstellar dust and the reddening law.
