Lonely Little Red Dots: Challenges to the AGN-nature of little red dots through their clustering and spectral energy distributions

TL;DR

This study investigates the nature of little red dots (LRDs) observed by JWST, analyzing their spectral energy distributions and clustering to determine if they host active galactic nuclei or are primarily forming compact galaxies or star clusters.

Contribution

The paper provides the first detailed analysis of LRDs' spectral energy distributions and clustering, challenging the assumption that they are predominantly AGN-hosting objects.

Findings

Models without AGN better fit LRD SEDs when MIRI data is included.

LRDs tend to be in less dense environments compared to galaxies.

LRDs are likely hosting compact galaxies or star clusters in formation.

Abstract

Observations with the James Webb Space Telescope (JWST) 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 $z$ $\sim$ 3 - 10 selected from NIRCam coverage of the CEERS, NEP-TDF, JADES and JEMS surveys. For JADES, the NEP-TDF and CEERS, we compare SED models with and without AGN components and analyse the impact of an AGN component on the goodness of fit using the Bayesian information criterion (BIC). We find that whilst the $\chi^{2}$ of the majority of models containing AGN components is improved compared to models without AGN components, we show that the BIC suggests models without AGN are a more appropriate fit to LRD SEDs, especially when MIRI data is 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. Whilst 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.