Substellar Objects in Nearby Young Clusters (SONYC) IX : the planetary-mass domain of Chamaeleon-I and updated mass function in Lupus-3
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Substellar Objects in Nearby Young Clusters—SONYC—is a survey program to investigate the frequency and properties of substellar objects in nearby star-forming regions. We present new spectroscopic follow-up of candidate members in Chamaeleon-I (~2 Myr, 160 pc) and Lupus 3 (~1 Myr, 200 pc), identified in our earlier works. We obtained 34 new spectra (1.5–2.4 μm, R ~ 600) and identified two probable members in each of the two regions. These include a new probable brown dwarf in Lupus 3 (NIR spectral type M7.5 and (Teff =2800 K), and an L3 (Teff =2200 K) brown dwarf in Cha-I, with masses below the deuterium-burning limit. Spectroscopic follow-up of our photometric and proper motion candidates in Lupus 3 is almost complete (>90%), and we conclude that there are very few new substellar objects left to be found in this region, down to 0.01–0.02 MΘ and AV ≤ 5. The low-mass portion of the mass function in the two clusters can be expressed in the power-law form dN/dM α M-α, with α∼0.7, in agreement with surveys in other regions. In Lupus 3 we observe a possible flattening of the power-law IMF in the substellar regime: this region seems to produce fewer brown dwarfs relative to other clusters. The IMF in Cha-I shows a monotonic behavior across the deuterium-burning limit, consistent with the same power law extending down to 4–9 Jupiter masses. We estimate that objects below the deuterium-burning limit contribute of the order of 5%–15% to the total number of Cha-I members.
Mužić , K , Scholz , A , Geers , V C & Jayawardhana , R 2015 , ' Substellar Objects in Nearby Young Clusters (SONYC) IX : the planetary-mass domain of Chamaeleon-I and updated mass function in Lupus-3 ' Astrophysical Journal , vol 810 , no. 2 , 159 . DOI: 10.1088/0004-637X/810/2/159
© 2015. The American Astronomical Society. All rights reserved. This work is made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at http://dx.doi.org/10.1088/0004-637X/810/2/159
This work was co-funded by NSERC grants to R.J. Date of Acceptance: 14/07/2015