sci21016 — Announcement

DECam Narrow-Band Filters Available

February 18, 2021

Three new DECam narrow-band filters have been acquired in the past few months, through survey projects led by Dr. Kyoungsoo Lee (Purdue) and Dr. Alexie Leauthaud (UCSC), with two additional filters still to arrive in connection with these projects. The ODIN survey (PI: K. Lee) will search for Lyα emitters at redshifts of z ~ 2.4, 3.1, and 4.5, straddling the epoch in which the mass assembly of cluster galaxies is thought to peak, while the Merian Survey (PI: A. Leauthaud) will use two custom narrow-band filters to study the properties of star-forming dwarf galaxies at z = 0.04-0.1. These filters are available for use by the community for other programs subject to scientific and technical rules summarized below. In particular two of the filters for the ODIN survey, N501 and N673, were deliberately designed as “dual use” filters supporting the filter PI’s science at high redshift but also enabling community proposals to study emission nebulae in our own or nearby galaxies.

Firstly, all of the narrow-band filters have been purchased by teams to carry out specific science projects, and the use of these privately-owned filters is governed by MOUs with AURA. The MOUs make the filters available to the NOIRLab and Chilean communities for use in their own programs, but do not permit duplication of the science for which the filter was purchased. Any community scientist wishing to use a DECam narrow-band filter should therefore initiate a correspondence with the relevant filter PI well before writing a proposal. Any resulting proposal should include a summary of the correspondence with the filter PI. As an exception to this general requirement, the “dual use” N673 and N501 filters may be freely used for proposals to study emission line objects at low redshift without prior approval.

Secondly, the current inventory of filters (the new filters plus the existing u, g, r, i, z, Y, VR, N662, and N964 filters) now exceeds the total number of DECam filters that can be installed at any given time (eight). Because installing and removing filters from DECam is a non-trivial procedure that needs to be carried out with great care, we do not anticipate changing filters more than a few times each semester. While the g, r, i, and z filters will always be available, the other filters will not be available at all times. For this reason, although the Blanco scheduler will make every effort to schedule highly ranked DECam proposals, it may not be possible to schedule some projects with excellent TAC grades.

The narrow-band filters that will be available in semester 2021B are listed in the Table below. The filter passbands are approximately rectangular in shape, and so are characterized by a center wavelength and the width at half-peak transmission. Further details are available from Alistair Walker (awalker@ctio.noao.edu) and should soon appear on the DECam webpages.