Corona-Australis DANCe

Brandner

et al. 2020

A&A

Self Cite

100

Context. The β Pictoris moving group is one of the most well-known young associations in the solar neighbourhood and several members are known to host circumstellar discs, planets, and comets. Measuring its age precisely is essential to the study of several astrophysical processes, such as planet formation and disc evolution, which are strongly age-dependent. Aims. We aim to determine a precise and accurate dynamical traceback age for the β Pictoris moving group. Methods. Our sample combines the extremely precise Gaia DR2 astrometry with ground-based radial velocities measured in an homogeneous manner. We use an updated version of our algorithm to determine dynamical ages. The new approach takes into account a robust estimate of the spatial and kinematic covariance matrices of the association to improve the sample selection process and to perform the traceback analysis. Results. We estimate a dynamical age of 18.5−2.4+2.0 Myr for the β Pictoris moving group. We investigated the spatial substructure of the association at the time of birth and we propose the existence of a core of stars that is more concentrated. We also provide precise radial velocity measurements for 81 members of β Pic, including ten stars with the first determinations of their radial velocities. Conclusions. Our dynamical traceback age is three times more precise than previous traceback age estimates and, more importantly, for the first time it reconciles the traceback age with the most recent estimates of other dynamical, lithium depletion boundaries and isochronal ages. This has been possible thanks to the excellent astrometric and spectroscopic precisions, the homogeneity of our sample, and the detailed analysis of binaries and membership.

Section: Positionssupporting

confidence: 79%

Dynamical traceback age of theβPictoris moving group

Miret-Roig

Brandner

et al. 2020

A&A

Self Cite

100

“…The median age of the Lupus subgroups ranges from about 1 to 3 Myr and we therefore conclude that they are coeval. Both age indicators (fraction of disc-bearing stars and isochronal ages) reveal that the Lupus association is younger than the population of YSOs in the Corona-Australis star-forming region recently investigated by our team with the same methodology (Galli et al 2020). Our new sample of Lupus stars is complete down to 0.2 M and the IMF shows little variation compared to other star-forming regions.…”

Section: Discussionmentioning

confidence: 53%

Lupus DANCe

Bouy

Olivares

et al. 2020

A&A

Self Cite

Context. Lupus is recognised as one of the closest star-forming regions, but the lack of trigonometric parallaxes in the pre-Gaia era hampered many studies on the kinematic properties of this region and led to incomplete censuses of its stellar population. Aims. We use the second data release of the Gaia space mission combined with published ancillary radial velocity data to revise the census of stars and investigate the 6D structure of the Lupus complex. Methods. We performed a new membership analysis of the Lupus association based on astrometric and photometric data over a field of 160 deg 2 around the main molecular clouds of the complex and compared the properties of the various subgroups in this region. Results. We identified 137 high-probability members of the Lupus association of young stars, including 47 stars that had never been reported as members before. Many of the historically known stars associated with the Lupus region identified in previous studies are more likely to be field stars or members of the adjacent Scorpius-Centaurus association. Our new sample of members covers the magnitude and mass range from G 8 to G 18 mag and from 0.03 to 2.4 M , respectively. We compared the kinematic properties of the stars projected towards the molecular clouds Lupus 1-6 and showed that these subgroups are located at roughly the same distance (about 160 pc) and move with the same spatial velocity. Our age estimates inferred from stellar models show that the Lupus subgroups are coeval (with median ages ranging from about 1 to 3 Myr). The Lupus association appears to be younger than the population of young stars in the Corona-Australis star-forming region recently investigated by our team using a similar methodology. The initial mass function of the Lupus association inferred from the distribution of spectral types shows little variation compared to other starforming regions. Conclusions. In this paper, we provide an updated sample of cluster members based on Gaia data and construct the most complete picture of the 3D structure and 3D space motion of the Lupus complex.

“…We now compare the results obtained in this paper with the ones derived by our team for the Corona-Australis (Galli et al 2020a) and Lupus (Galli et al 2020b) star-forming regions using the same methodology applied in this paper. The two age indicators used in this study (isochronal ages and fraction of discbearing stars) suggest that the Chamaeleon stars are younger than the stellar population in the Corona-Australis star-forming region.…”

Section: Hertzsprung-russell Diagram and Relative Ages Of The Subgroupsmentioning

confidence: 86%

“…We computed robust distances based on the covariance matrix obtained from the minimum covariance determinant (MCD, Rousseeuw & Driessen 1999) estimator and removed potential outliers from these samples as described in Sect. 2.1 of Galli et al (2020a). This step reduces the lists of stars (with Gaia-DR2 data) in Cha I and Cha II to 161 and 36 stars, respectively.…”

Section: Field and Cluster Modelsmentioning

confidence: 99%

Chamaeleon DANCe

Bouy

Olivares

et al. 2021

A&A

Self Cite

Context. Chamaeleon is the southernmost low-mass star-forming complex within 200 pc from the Sun. Its stellar population has been extensively studied in the past, but the current census of the stellar content is not complete yet and deserves further investigation. Aims. We take advantage of the second data release of the Gaia space mission to expand the census of stars in Chamaeleon and to revisit the properties of the stellar populations associated to the Chamaeleon I (Cha I) and Chamaeleon II (Cha II) dark clouds. Methods. We perform a membership analysis of the sources in the Gaia catalogue over a field of 100 deg2 encompassing the Chamaeleon clouds, and use this new census of cluster members to investigate the 6D structure of the complex. Results. We identify 188 and 41 high-probability members of the stellar populations in Cha I and Cha II, respectively, including 19 and 7 new members. Our sample covers the magnitude range from G = 6 to G = 20 mag in Cha I, and from G = 12 to G = 18 mag in Cha II. We confirm that the northern and southern subgroups of Cha I are located at different distances (191.4−0.8+0.8 pc and 186.7−1.0+1.0 pc), but they exhibit the same space motion within the reported uncertainties. Cha II is located at a distance of 197.5−0.9+1.0 pc and exhibits a space motion that is consistent with Cha I within the admittedly large uncertainties on the spatial velocities of the stars that come from radial velocity data. The median age of the stars derived from the Hertzsprung-Russell diagram and stellar models is about 1−2 Myr, suggesting that they are somewhat younger than previously thought. We do not detect significant age differences between the Chamaeleon subgroups, but we show that Cha II exhibits a higher fraction of disc-bearing stars compared to Cha I. Conclusions. This study provides the most complete sample of cluster members associated to the Chamaeleon clouds that can be produced with Gaia data alone. We use this new census of stars to revisit the 6D structure of this region with unprecedented precision.