New low-mass members of Chamaeleon I and ϵ Cha
Abstract
Aims: The goal of this paper is to increase the membership list of the Chamaeleon star-forming region and the ϵ Cha moving group, in particular for low-mass stars and substellar objects. We extended the search region significantly beyond the dark clouds.
Methods: Our sample has been selected based on proper motions and colours obtained from Gaia and 2MASS. We present and discuss the optical spectroscopic follow-up of 18 low-mass stellar objects in Cha I and ϵ Cha. We characterize the properties of objects by deriving their physical parameters from spectroscopy and photometry.
Results: We add three more low-mass members to the list of Cha I and increase the census of known ϵ Cha members by more than 40%, thereby spectroscopically confirming 13 new members and relying on X-ray emission as youth indicator for 2 more. In most cases the best-fitting spectral template is from objects in the TW Hya association, indicating that ϵ Cha has a similar age. The first estimate of the slope of the initial mass function in ϵ Cha down to the substellar regime is consistent with that of other young clusters. We estimate our initial mass function (IMF) to be complete down to ≈0.03 M⊙. The IMF can be represented by two power laws: for M < 0.5 M⊙ α = 0.42 ± 0.11 and for M > 0.5 M⊙ α = 1.44 ± 0.12.
Conclusions: We find similarities between ϵ Cha and the southernmost part of Lower Centaurus Crux (LCC A0), which lie at similar distances and share the same proper motions. This suggests that ϵ Cha and LCC A0 may have been born during the same star formation event
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 2021
- DOI:
- 10.1051/0004-6361/202039899
- arXiv:
- arXiv:2102.05589
- Bibcode:
- 2021A&A...650A..48K
- Keywords:
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- stars: low-mass;
- stars: pre-main sequence;
- open clusters and associations: individual: ϵ Cha young moving group;
- brown dwarfs;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 18 pages, 15 figure, accepted by A&