Young brown dwarfs in IC 348, Serpens, Ophiuchus, Upper Scorpius, and Orion

hs-2013-04-b-full_jpg

Spitzer image credit: NASA, ESA, J. Muzerolle (STScI), E. Furlan (NOAO and Caltech), K. Flaherty (University of Arizona/Steward Observatory), Z. Balog (Max Planck Institute for Astronomy), and R. Gutermuth (University of Massachusetts, Amherst)

The young (3 Myr) star-forming region IC 348 has been in the news recently concerning pulsed accretion in the protostar LRLL 54361. The region has now been examined extremely thoroughly by C. Alves de Oliveria and co-workers at Grenoble, who have spectroscopically confirmed thirteen new brown dwarfs to add to the previously known thirty. The latest objects have spectral type L0 and masses at the deuterium-burning limit.

The log-normal initial mass function measured in this work is consistent with the expectation of one further T dwarf, which has indeed been observed by the Grenoble group using methane imaging, but not yet spectroscopically confirmed.

The Grenoble group is also searching in core of Serpens, where two objects have been found with masses of a few Jupiters. Together with S Ori 70, and contingent upon confirmation spectroscopy, these are among the lowest-mass brown dwarf candidates yet found in star forming regions.

The controversy surrounding S Ori 70 appears not yet resolved, with some arguments favouring membership of the star-forming region and others indicating this is a T dwarf in the foreground. H-band spectroscopy does not in this case indicate youth. However the small proper motion, along with other factors, does point towards cluster membership. Two papers from 2008, both making use of mid-infrared imaging from Spitzer, come to opposite conclusions on the matter.

Rho_Ophiuchi

Other low mass young cluster candidates have been found in the Trapezium and the rho Ophiuchi (pictured; WISE image from Wikipedia) star-forming regions. In addition to the disk brown dwarf ISO-Oph 102* and binary objects I have referred to in a previous post, the least massive candidate brown dwarf member of the latter cluster has two or three Jupiter masses, a temperature around 1400 K and, remarkably, is seen behind fifteen or sixteen magnitudes of visual extinction. However, there is doubt about the status of this object, as pointed out by Lodieu et al., who give a recent overview of the topic. Furthermore, methane imaging might not be an effective tool to find young T dwarfs. The reasons for this likely originate in cloud formation in these low-gravity atmospheres, which may be methane-poor.

*The designation comes from the original ISOCAM study of star formation in the region.

As a footnote: the astrophysics research institute at Grenoble used to be called the Laboratoire d’Astrophysique de Grenoble (LAOG), but has undergone a name change and is now IPAG, the Institut de PlanĂ©tologie et Astrophysique de Grenoble.

Update: Upper Scorpius is part of the Sco-Cen OB association and now has a revised age of around 11 Myr, with implications for the model-derived masses of brown dwarfs found there. A new, complete census of the substellar population in the region has been published very recently.

One Response to “Young brown dwarfs in IC 348, Serpens, Ophiuchus, Upper Scorpius, and Orion”

  1. […] cluster of similar age is IC 4665 in Ophiuchus (above). A complete mass function down to the substellar regime has now been published, in agreement with findings from older […]

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