Y dwarf

Although our understanding of the star formation process has seen great advances in the past two decades, our knowledge of details at the lowest masses is still very limited. Two open questions are (1) what is the low-mass cutoff for star formation, if there is one, and (2) how frequently are these lowest mass objects formed? Through the identification and analysis of low-mass stars and brown dwarfs in the immediate Solar Neighborhood, we can provide the answers. Such a sample also allows us to identify the nearest examples at each spectral subclass to enable an eventual characterization of planetary systems as a function of host "star" mass. The Wide-field Infrared Survey Explorer (WISE) is uniquely suited to providing this census down to temperatures much colder than any previous all-sky survey.

The WISE spacecraft

WISE is an Earth-orbiting NASA mission that surveyed the entire sky at wavelengths of 3.4, 4.6, 12, and 22 μm. The 3.4- and 4.6-μm bands were specifically designed to probe the deep, 3.3-μm methane absorption band in brown dwarfs and the region relatively free of opacity near 4.6 μm. As such, WISE can readily identify the coldest brown dwarfs by their 3.4-to-4.6 μm color, although its sensitivity and full-sky coverage enable it to detect warmer brown dwarfs and low-mass stars within (and in some cases, well beyond) the immediate Solar Neighborhood. WISE has already begun to revolutionize our understanding of the stellar census near the Sun via the discovery of a new spectroscopic class, the Y dwarfs, and the identification of many new, heretofore overlooked nearby objects.

As well suited as the WISE data are to nearby star detection, observations at other wavelengths - usually in the near-infrared - are crucial to verifying or rejecting candidates. Past, on-going, and future investigations such as 2MASS, SDSS, UKIDSS, Pan-STARRS, VISTA, SkyMapper, and LSST can provide the needed verification. Likewise, WISE can provide the needed verification of candidates identified by those surveys themselves. The time difference between WISE and these other data sets also enables large-area proper motion searches at longer wavelengths than were previously possible.

T dwarf

The WISE Science Team has already published 100 new brown dwarfs near the Sun, including the discovery of the first six Y dwarfs and the subsequent discovery of seven more. Since the WISE Preliminary Data Release was made available to the general public in April 2011, many papers by researchers not on the WISE team have also been published. These include the proper motion discovery of nearby M and L dwarfs by comparing WISE data with those of 2MASS, the identification of other nearby L and T dwarf candidates using motion and color by comparing WISE data with 2MASS and SDSS, and the proper motion discovery of a nearby T8 dwarf by comparing WISE with 2MASS and Pan-STARRS data. These first papers already highlight the variety of investigations possible, and the early results provide strong hints that colder brown dwarfs greatly outnumber their warmer counterparts. In fact, the WISE data may not even be sensitive to the coldest (<200K) objects in the Sun's vicinity, meaning that an even vaster reservoir of the coldest brown dwarfs may remain out of reach.

A summary of results by the WISE brown dwarf team is already included as an invited talk at this conference, so the goal of this splinter session to hear from other groups. With the WISE Prelim Data Release and All-Sky Data Release already in the public domain, and the WISE 3-band cryo data scheduled for dissemination in late-June, 2012, we expect the low-mass star community to be teeming with new results and ideas.

Final schedule

The session will have six main talks of 15 minutes each with 5 minutes for a question and answer session following each. Just before the coffee break, there will be a pop-up session wherein selected authors have two minutes each to highlight the results of WISE-related posters.