HST Survey of the Orion Nebula Cluster in the H2O 1.4 μm Absorption Band. I. A Census of Substellar and Planetary-mass Objects
Journal article, 2020
In order to obtain a complete census of the stellar and substellar population, down to a few MJup 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 m 130 = 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, m 130 ≃ 21.5, corresponding to a 1 Myr old ≃3 MJup 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 MJup fail to reproduce the observed H2O color index at M ≲ 20 MJup. We perform a Bayesian analysis to determine extinction, mass, and effective temperature of each substellar member of our sample, together with its membership probability.
Author
Massimo Robberto
Johns Hopkins University
Space Telescope Science Institute (STScI)
Mario Gennaro
Space Telescope Science Institute (STScI)
Maria Giulia Ubeira Gabellini
University of Milan
European Southern Observatory (ESO)
Lynne A. Hillenbrand
California Institute of Technology (Caltech)
Camilla Pacifici
Space Telescope Science Institute (STScI)
Leonardo Ubeda
Space Telescope Science Institute (STScI)
Morten Andersen
Gemini Observatory South
Travis Barman
University of Arizona
Andrea Bellini
Space Telescope Science Institute (STScI)
Nicola Da Rio
University of Virginia
Selma E. De Mink
Harvard-Smithsonian Center for Astrophysics
University of Amsterdam
Giuseppe Lodato
University of Milan
Carlo F. Manara
European Southern Observatory (ESO)
Imants Platais
Johns Hopkins University
Laurent Pueyo
Space Telescope Science Institute (STScI)
Giovanni Maria Strampelli
Johns Hopkins University
Space Telescope Science Institute (STScI)
University of La Laguna
Jonathan Tan
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
University of Virginia
L. Testi
European Southern Observatory (ESO)
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 896 1 79Subject Categories
Subatomic Physics
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
DOI
10.3847/1538-4357/ab911e