Little Red Dots

Little Red Dots in the CEERS Field of View

Little red dots (LRDs), the mysterious compact objects with v-shaped energy distributions in the early Universe, gained and rose in popularity during my dissertation work. I commented on their contamination in EELG samples, particularly driven by a lack of medium-band photometric filter coverage in the rest-optical, in my EELG paper on spectroscopic coverage, “Extreme Emission Line Galaxies in CEERS are Powered by Star Formation, not AGN.” Most of my LRD work comes from my work with the OCEANS collaboration and supervisory work with my junior mentees.

I am a key contributor to the OCEANS program (program ID 8410, PI: R. Simons) which aimed to census the outflow kinematics of galaxies in CEERS using high-resolution (R~2700) spectroscopy. This coverage revealed line shapes with absorption features in four of the ten targeted LRDs. I showed these were consistent with significant amounts of excited (n=2) hydrogen with typically slow (~ 100s km/ s) outflow velocities. One source puzzlingly had kinematic differences between H$\alpha$ and H$\beta$ absorption. I built a qualitative model where the kinematic offsets could be attributed to absorbing gas co-located with emission regions. I further demonstrated that the continuum colors, which may trace either Balmer break strengths or black body temperature, relate to outflow speeds. This points to differences in LRDs which reflect different system phases, where amount of available gas changes outflow speeds, or differences in viewing angle, where some lines of sight have different amounts of available gas and this drives differences in outflow speeds and non-uniform geometry. The two cases are degenerate and resolution is a critical step in building a full picture of LRDs.