Compact oddballs in COSMOS: The Faint End of the z>6 Quasar Luminosity Function and the Growth of Ionized Bubbles
Abstract
Finding galaxies with an active galactic nucleus (AGN), or quasars, in the early Universe is the forefront of today's astronomical research. While luminous quasars have been well characterized, the number density of low-luminosity (<1E45 erg/s) quasars at z>6 is still uncertain. Constraining their numbers will tremendously advance our understanding of the processes which lead to the reionization of our Universe as well as the formation of the first supermassive black holes. Through stringent selection criteria including color and size, we have identified a complete sample of 7 low-luminosity quasar candidates in the 1.64 deg2 COSMOS field.
Here we propose to use ACS/G800L slitless spectroscopy to confirm their redshifts via Ly-alpha and to study the spatial morphology of the emission. We will use the power of the grism to simultaneously measure Ly-alpha emission from color-selected star-forming galaxies within the ionized bubble of the quasar. This will allow us to (i) place the first constraints on the faint end of the quasar luminosity function at z>6, (ii) quantify the importance of low-luminosity quasars in the reionization process and place constraints on models of early supermassive black hole formation, (iii) study the relationship between Ly-alpha sizes and UV luminosities of low-luminosity quasars, a tracer of the size of the ionized bubbles and the clumping factor of the gas and (iv) measure star-formation in smaller halos in the local neighborhood of the quasars and statistically the Ly-alpha emitter density in the bubbles, compared to the field to further constrain the interplay between low-mass and high-mass halos in the growth of large scale structure.- Publication:
-
HST Proposal
- Pub Date:
- June 2022
- Bibcode:
- 2022hst..prop17091F