Dusty disks at the bottom of the initial mass function

Alexander Scholz, Ray Jayawardhana

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)


Isolated planetary-mass objects (IPMOs) have masses close to or below the deuterium-burning mass limit (similar to 15 M-Jup)-at the bottom of the stellar initial mass function. We present an exploratory survey for disks in this mass regime, based on a dedicated observing campaign with the Spitzer Space Telescope. Our targets include the full sample of spectroscopically confirmed IPMOs in the sigma Orionis cluster, a total of 18 sources. In the mass range, we identify four objects with > 13 sigma color excess at a wavelength of 8.0 mu m, interpreted as emission 8-20 M-Jup from dusty disks. We thus establish that a substantial fraction of IPMOs harbor disks with lifetimes of at least 2 4 Myr (the likely age of the cluster), indicating an origin from core collapse and fragmentation processes. The disk frequency in the IPMO sample is 29 +/-(16)(13)% at 8.0 mu m, very similar to what has been found for stars and brown dwarfs (similar to 30%). The object S Ori 70, a candidate 3 M-Jup object in this cluster, shows IRAC colors in excess of the typical values for field T dwarfs (on a 2 sigma level), possibly due to disk emission or low gravity. This is a new indication for youth and thus an extremely low mass for S Ori 70.

Original languageEnglish
Pages (from-to)L49-L52
Number of pages4
JournalAstrophysical Journal Letters
Issue number1
Publication statusPublished - 1 Jan 2008


  • Circumstellar matter
  • Planetary systems
  • Planetary systems : protoplanetary disks
  • Stars : formation
  • Stars : low-mass
  • Brown dwarfs
  • Young brown dwarfs
  • Sigma-orionis cluster
  • Objects
  • Photometry
  • spectroscopy
  • Population


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