Design For The First Narrowband Filter For The Dark Energy Camera: Optimizing The LAGER Survey For Z ~ 7 Galaxies

Area of Science:

• Cosmology
• Astrophysics
• Observational Astronomy

Background:

• The epoch of reionization is a critical period in cosmic history.
• Detecting Lyman alpha emitting galaxies (LAEs) is key to studying this era.
• Existing instruments require specialized filters for efficient LAE detection.

Purpose of the Study:

• To design and test the NB964 narrowband filter for the Dark Energy Camera (DECam).
• To optimize the filter for detecting LAEs at redshift ~7.
• To assess the filter's performance considering night sky background and instrument efficiency.

Main Methods:

• Designed the NB964 filter with a central wavelength of 964.2 nm and FWHM of 9.2 nm.
• Manufactured the filter using advanced optical coating techniques.
• Conducted laboratory tests, on-site tests, and observational campaigns with the NB964 filter.

Main Results:

• The NB964 filter was successfully manufactured and integrated with DECam.
• Lab and on-site tests confirmed the filter's excellent performance characteristics.
• The filter enables high-efficiency detection of LAEs at redshift ~7.

Conclusions:

• The NB964 filter is a crucial instrument for the Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) survey.
• The filter's performance validates its design for studying early galaxy formation.
• The LAGER survey, utilizing the NB964 filter, will significantly advance our understanding of the epoch of reionization.