Kavli Affiliate: Luis C. Ho
| First 5 Authors: Zijian Zhang, Linhua Jiang, Weiyang Liu, Luis C. Ho,
| Summary:
James Webb Space Telescope (JWST) has revealed a population of red and
compact sources at $z gtrsim 5$ known as “Little Red Dots” (LRDs) that are
likely active galactic nuclei (AGNs). Here we present a comprehensive study of
the variability of 314 LRDs with multi-epoch JWST observations in five deep
fields: UDS, GOODS-S, GOODS-N, Abell 2744, and COSMOS. Our analyses use all
publicly available JWST NIRCam imaging data in these fields, together with
multi-epoch JWST MIRI images available. We measure the significance
(signal-to-noise ratio or ${rm SNR}_{rm var}$) of the variabilities for all
LRDs and statistically evaluate their variabilities using the ${rm SNR}_{rm
var}$ distributions. We pay particular attention to the systematic offsets of
photometric zero points among different epochs that seem to commonly exist. The
derived ${rm SNR}_{rm var}$ distributions of the LRDs, including those with
broad H$alpha$/H$beta$ emission lines, follow the standard Gaussian
distribution, and are generally consistent with those of the comparison samples
of objects detected in the same images. This finding suggests that the LRD
population on average does not show strong variability, which can be explained
by super-Eddington accretion of the black holes in AGNs. Alternatively, many of
them may be dominated by galaxies. We also find eight strongly variable LRD
candidates with variability amplitudes of 0.24 — 0.82 mag. The rest-frame
optical SEDs of these variable LRDs should have significant AGN contribution.
Future JWST observations will provide more variability information of LRDs.
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