A near infrared search for brown dwarfs in the Pleiades

Abstract

Deep mosaic imaging of the Pleiades was conducted at wavelengths of 0.9 µm (I-band) and 2.2 µm (K-band) in an effort to find free-floating low mass cluster members. Fields outside of the cluster were also imaged as part of a control data set to check the overall significance of the results, leading to a total of 575 arcmin^2 of data. Photometry of all detected point sources led to the detection of 29±13 objects that lie near the lower Pleiades main sequence, when compared to the control data set. These objects have theoretical masses of ~0.1 to 0.04 solar masses and are described well by a power-law distribution with a slope of -2.8. The vast majority of the sources detected were background field stars. The derived number-magnitude counts for these field stars agree well with established Galaxy models, with a measured lower limit on the local space density of stars of 0.06 pc^-3 .