A Novel Survey for Young Substellar Objects with the W-band Filter. I. Filter Design and New Discoveries in Ophiuchus and Perseus

TL;DR

This paper introduces a new near-infrared W-band filter designed to identify and classify young substellar objects like brown dwarfs with high accuracy, reducing contamination from background stars in star-forming regions.

Contribution

The paper presents the design, implementation, and successful application of a novel W-band filter for detecting and spectral typing low-mass stars and brown dwarfs in star-forming regions.

Findings

Successfully identified 48 ultracool dwarfs with 89% confirmation rate.

W-band filter enables spectral typing to within 1.4 subtypes for late-M and L dwarfs.

Effective in reducing background star contamination in young stellar object surveys.

Abstract

We present the design and implementation of a medium-band near-IR filter tailored for detecting low-mass stars and brown dwarfs from the summit of Maunakea. The W-band filter is centered at 1.45 micron with a bandpass width of 6%, designed to measure the depth of the H2O water absorption prominent in objects with spectral types of M6 and later. When combined with standard J- and H-band photometry, the W-band filter is designed to determine spectral types to $\approx$1.4 subtypes for late-M and L dwarfs, largely independent of surface gravity and reddening. This filter's primary application is completing the census of young substellar objects in star-forming regions, using W-band selection to greatly reduce contamination by reddened background stars that impede broad-band imaging surveys. We deployed the filter on the UH 88-inch telescope to survey $\approx$3 sq. deg. of the NGC 1333, IC 348, and rho Ophiuchus star-forming regions. Our spectroscopic followup of W-band selected candidates resulted in the confirmation of 48 ultracool dwarfs with a success rate of 89%, demonstrating the efficacy of this new filter and selection method.