The Search for More Low Redshift Lyman Alpha Nebulae
Abstract
Extended emission line nebulae allow us to study the gas reservoir outside of galaxies, which is the fuel for star formation. At high redshifts, the focus has been on finding giant Lyman-alpha nebulae, as redshifted Lyman-alpha is one of the brightest emission lines accessible from the ground. Searching for these nebulae at lower redshifts gives us the opportunity to study their evolution, which could give us insight into how the gas outside galaxies is evolving over cosmic time. There are currently only 17 objects, selected due to their unusual "green" colors in Sloan Digital Sky Survey (SDSS) imaging, that have been identified as low redshift extended Lyman-alpha nebulae. These rare objects, colloquially named "Green Beans," are powered by Type 2 AGN. They have high [OIII] luminosities and excess flux in the far ultraviolet band, which contains Lyman-alpha at this redshift. Since this "Green Bean" sample was initially selected with optical color-cuts, there are likely additional low redshift Lyman-alpha nebulae that have been overlooked. Therefore, our main goal is to identify more objects that are similar to the "Green Beans" by searching through existing data from SDSS and the Galaxy Evolution Explorer (GALEX). Using follow-up APO/DIS spectroscopy and APO/ARCTIC imaging, we are studying the properties and kinematics of these candidate low redshift Lyman-alpha nebulae, and investigating the relationship between these systems and the existing "Green Bean" sample.
- Publication:
-
The 35th Annual New Mexico Symposium
- Pub Date:
- February 2020
- Bibcode:
- 2020anms.conf...19D