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Title: Lack of Rest-frame Ultraviolet Variability in Little Red Dots Based on HST and JWST Observations
Abstract Variability is a fundamental signature for active galactic nuclei (AGN) activity and serves as an unbiased indicator for rapid instability happening near the center of supermassive black holes (SMBHs). Previous studies showed that AGN variability does not have strong redshift evolution, and scales with their bolometric luminosity and BH mass, making it a powerful probe to identify low-mass, low-luminosity AGNs at high redshift. JWST has discovered a new population of high-redshift galaxies likely hosting moderate accreting BHs (>106M⊙)—the little red dots (LRDs;z ∼ 4–10). In this Letter, we study the variability of a sample of 22 LRDs with V-shaped spectral energy distributions in three JWST deep fields that also have reliable Hubble Space Telescope observations in closely paired filters at 1–2μm (rest-frame UV), with the time difference between 6 and 11 yr. This LRD sample covers a redshift range of 3 < z < 8 with −21.3 < MUV < −18.4. Based on both photometry and imaging difference analyses, we find a mean magnitude difference of ∼0.15 ± 0.26 mag, with none of the LRDs showing photometric variability at 3σsignificance. Extrapolation of Sloan Digital Sky Survey quasar variability predicts a magnitude change of order 0.3 mag for our LRD sample. This suggests an upper limit of about ∼30% AGN contribution to the total observed UV light in our sample of LRDs.  more » « less
Award ID(s):
2308258 2513040
PAR ID:
10609793
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
ApJ
Date Published:
Journal Name:
The Astrophysical Journal Letters
Volume:
983
Issue:
1
ISSN:
2041-8205
Page Range / eLocation ID:
L26
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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