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HST Survey of the Orion Nebula Cluster in the H₂O 1.4 μm Absorption Band. I. A Census of Substellar and Planetary-mass Objects

Robberto, Massimo and Gennaro, Mario and Ubeira Gabellini, Maria Giulia and Hillenbrand, Lynne A. and Pacifici, Camilla and Ubeda, Leonardo and Andersen, Morten and Barman, Travis and Bellini, Andrea and Da Rio, Nicola and de Mink, Selma E. and Lodato, Giuseppe and Manara, Carlo Felice and Platais, Imants and Pueyo, Laurent and Strampelli, Giovanni Maria and Tan, Jonathan C. and Testi, L. (2020) HST Survey of the Orion Nebula Cluster in the H₂O 1.4 μm Absorption Band. I. A Census of Substellar and Planetary-mass Objects. Astrophysical Journal, 896 (1). Art. No. 79. ISSN 1538-4357. doi:10.3847/1538-4357/ab911e.

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In order to obtain a complete census of the stellar and substellar population, down to a few M_(Jup) in the ~1 Myr old Orion Nebula Cluster, we used the infrared channel of the Wide Field Camera 3 of the Hubble Space Telescope with the F139M and F130N filters. These bandpasses correspond to the 1.4 μm H₂O absorption feature and an adjacent line-free continuum region. Out of 4504 detected sources, 3352 (about 75%) appear fainter than m₁₃₀ = 14 (Vega mag) in the F130N filter, a brightness corresponding to the hydrogen-burning limit mass M ≃ 0.072 M_⊙) at ~1 Myr. Of these, however, only 742 sources have a negative F130M–F139N color index, indicative of the presence of H₂O vapor in absorption, and can therefore be classified as bona fide M and L dwarfs, with effective temperatures T ≾ 2850 K at an assumed 1 Myr cluster age. On our color–magnitude diagram (CMD), this population of sources with H₂O absorption appears clearly distinct from the larger background population of highly reddened stars and galaxies with positive F130M–F139N color index and can be traced down to the sensitivity limit of our survey, m₁₃₀ ≃ 21.5, corresponding to a 1 Myr old ≃ 3 M_(Jup) planetary-mass object under about 2 mag of visual extinction. Theoretical models of the BT-Settl family predicting substellar isochrones of 1, 2, and 3 Myr down to ~1 M_(Jup) fail to reproduce the observed H₂O color index at M ≾ 20 M_(Jup). We perform a Bayesian analysis to determine extinction, mass, and effective temperature of each substellar member of our sample, together with its membership probability.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Robberto, Massimo0000-0002-9573-3199
Gennaro, Mario0000-0002-5581-2896
Ubeira Gabellini, Maria Giulia0000-0002-5980-4287
Pacifici, Camilla0000-0003-4196-0617
Andersen, Morten0000-0002-5306-4089
Barman, Travis0000-0002-7129-3002
Bellini, Andrea0000-0003-3858-637X
de Mink, Selma E.0000-0001-9336-2825
Lodato, Giuseppe0000-0002-2357-7692
Manara, Carlo Felice0000-0003-3562-262X
Platais, Imants0000-0003-2599-2459
Pueyo, Laurent0000-0003-3818-408X
Strampelli, Giovanni Maria0000-0002-1652-420X
Tan, Jonathan C.0000-0002-3389-9142
Testi, L.0000-0003-1859-3070
Additional Information:© 2020. The American Astronomical Society. Received 2019 July 4; revised 2020 March 29; accepted 2020 March 30; published 2020 June 16. Support for program No. GO-13826 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NASS-26555. C.F.M. acknowledges an ESO fellowship. The authors are indebted to an anonymous referee for useful comments and wish to thank Mike Meyer for reviewing an earlier version of the manuscript. This research has made use of the VizieR catalog access tool, CDS, Strasbourg, France. The original description of the VizieR service was published in Ochsenbein et al. (2000). Facility: HST (WFC3). -
Group:Astronomy Department
Funding AgencyGrant Number
European Southern Observatory (ESO)UNSPECIFIED
Subject Keywords:Pre-main sequence stars ; Brown dwarfs ; Young star clusters
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Pre-main sequence stars (1290); Brown dwarfs (185); Young star clusters (1833)
Record Number:CaltechAUTHORS:20200622-104136068
Persistent URL:
Official Citation:Massimo Robberto et al 2020 ApJ 896 79
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103950
Deposited By: George Porter
Deposited On:23 Jun 2020 15:23
Last Modified:16 Nov 2021 18:26

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