Free-floating Planet Mass Function from MOA-II 9 yr Survey toward the Galactic Bulge

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dc.citation.issue3
dc.citation.volume166
dc.contributor.authorSumi T
dc.contributor.authorKoshimoto N
dc.contributor.authorBennett DP
dc.contributor.authorRattenbury NJ
dc.contributor.authorAbe F
dc.contributor.authorBarry R
dc.contributor.authorBhattacharya A
dc.contributor.authorBond IA
dc.contributor.authorFujii H
dc.contributor.authorFukui A
dc.contributor.authorHamada R
dc.contributor.authorHirao Y
dc.contributor.authorIshitani Silva S
dc.contributor.authorItow Y
dc.contributor.authorKirikawa R
dc.contributor.authorKondo I
dc.contributor.authorMatsubara Y
dc.contributor.authorMiyazaki S
dc.contributor.authorMuraki Y
dc.contributor.authorOlmschenk G
dc.contributor.authorRanc C
dc.contributor.authorSatoh Y
dc.contributor.authorSuzuki D
dc.contributor.authorTomoyoshi M
dc.contributor.authorTristram PJ
dc.contributor.authorVandorou A
dc.contributor.authorYama H
dc.contributor.authorYamashita K
dc.date.accessioned2024-05-09T02:37:23Z
dc.date.available2024-05-09T02:37:23Z
dc.date.issued2023-08-16
dc.description.abstractWe present the first measurement of the mass function of free-floating planets (FFPs), or very wide orbit planets down to an Earth mass, from the MOA-II microlensing survey in 2006-2014. Six events are likely to be due to planets with Einstein radius crossing times t E < 0.5 days, and the shortest has t E = 0.057 ± 0.016 days and an angular Einstein radius of θ E = 0.90 ± 0.14 μas. We measure the detection efficiency depending on both t E and θ E with image-level simulations for the first time. These short events are well modeled by a power-law mass function, dN 4/d log M = ( 2.18 − 1.40 + 0.52 ) × ( M / 8 M ⊕ ) − α 4 dex−1 star−1 with α 4 = 0.96 − 0.27 + 0.47 for M/M⊙ < 0.02. This implies a total of f = 21 − 13 + 23 FFPs or very wide orbit planets of mass 0.33 < M/M ⊕ < 6660 per star, with a total mass of 80 − 47 + 73 M ⊕ star−1. The number of FFPs is 19 − 13 + 23 times the number of planets in wide orbits (beyond the snow line), while the total masses are of the same order. This suggests that the FFPs have been ejected from bound planetary systems that may have had an initial mass function with a power-law index of α ∼ 0.9, which would imply a total mass of 171 − 52 + 80 M ⊕ star−1. This model predicts that Roman Space Telescope will detect 988 − 566 + 1848 FFPs with masses down to that of Mars (including 575 − 424 + 1733 with 0.1 ≤ M/M ⊕ ≤ 1). The Sumi et al. large Jupiter-mass FFP population is excluded.
dc.description.confidentialfalse
dc.edition.editionSeptember 2023
dc.identifier.citationSumi T, Koshimoto N, Bennett DP, Rattenbury NJ, Abe F, Barry R, Bhattacharya A, Bond IA, Fujii H, Fukui A, Hamada R, Hirao Y, Silva SI, Itow Y, Kirikawa R, Kondo I, Matsubara Y, Miyazaki S, Muraki Y, Olmschenk G, Ranc C, Satoh Y, Suzuki D, Tomoyoshi M, Tristram PJ, Vandorou A, Yama H, Yamashita K. (2023). Free-floating Planet Mass Function from MOA-II 9 yr Survey toward the Galactic Bulge. Astronomical Journal. 166. 3.
dc.identifier.doi10.3847/1538-3881/ace688
dc.identifier.eissn1538-3881
dc.identifier.elements-typejournal-article
dc.identifier.issn0004-6256
dc.identifier.number108
dc.identifier.urihttps://mro.massey.ac.nz/handle/10179/69537
dc.languageEnglish
dc.publisherIOP Publishing
dc.publisher.urihttps://iopscience.iop.org/article/10.3847/1538-3881/ace688/pdf
dc.relation.isPartOfAstronomical Journal
dc.rights(c) 2023 The Author/s
dc.rightsCC BY 4.0
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.subjectspace and planetary science
dc.subjectastronomy and astrophysics
dc.titleFree-floating Planet Mass Function from MOA-II 9 yr Survey toward the Galactic Bulge
dc.typeJournal article
pubs.elements-id480238
pubs.organisational-groupOther
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