Lonely Little Red Dots: Challenges to the Active Galactic Nucleus Nature of Little Red Dots through Their Clustering and Spectral Energy Distributions
María Carranza-Escudero, Christopher J. Conselice, Nathan Adams, Thomas Harvey, Duncan Austin, Peter Behroozi, Leonardo Ferreira, Katherine Ormerod, Qiao Duan, James Trussler, Qiong Li, Lewi Westcott, Rogier A. Windhorst, Dan Coe, Seth H. Cohen, Cheng Cheng, Simon P. Driver, Brenda Frye, Lukas J. Furtak, Norman A. Grogin, Nimish P. Hathi, Rolf A. Jansen, Anton M. Koekemoer, Madeline A. Marshall, Rosalia O’Brien, Nor Pirzkal, M. Polletta, A. S. G. Robotham, Michael J. Rutkowski, Jake Summers, Stephen M. Wilkins, Christopher N. A. Willmer, Haojing Yan, Adi Zitrin
Abstract
Abstract Observations with the James Webb Space Telescope reveal a previously unseen population of compact red objects, known as “little red dots” (LRDs). We study a new photometrically selected sample of 124 LRDs in the redshift range z ∼ 3–10 selected from Near Infrared Camera coverage of the Cosmic Evolution Early Release Science Survey (CEERS), North Ecliptic Pole Time Domain Field (NEP-TDF), James Webb Space Telescope Advanced Deep Extragalactic Survey (JADES), and JEMS. For JADES, the NEP-TDF, and CEERS, we compare spectral energy distribution (SED) models with and without active galactic nucleus (AGN) components and analyze the impact of an AGN component on the goodness of fit using the Bayesian information criterion (BIC). We find that while the χ 2 of the majority of models containing AGN components is improved compared to models without AGN components, we show that the BIC suggests that models without AGN are a more appropriate fit to LRD SEDs, especially when MIRI data are available. We also measure LRD clustering in the CEERS field, JADES field, and NEP-TDF, where we compare the spatial distribution of LRDs and galaxies with Kolmogorov–Smirnov tests of equality of distribution. We find that the neighbourhood of LRDs tends to be less dense compared to galaxies at all selections and masses and at similar redshifts. We further measure upper limit estimates for the halo masses of LRDs using abundance matching. While the population of LRDs could be a mixture of several different inherent populations, as a whole, it does appear that these systems are mostly hosting compact galaxies or star clusters in formation.