Lord of LRDs: Insights into a "Little Red Dot" with a low-ionization spectrum at z = 0.1

Recent observations by the James Webb Space Telescope (JWST) have revealed a puzzling population of optically red and compact galaxies with peculiar “V”-shaped spectra at high redshift, known as “Little Red Dots” (LRDs). Until now, most spectroscopically confirmed LRDs are found at $z>4$ and it has been speculated that LRDs are tracing the early stages of black hole evolution. We report an independent rediscovery of a broad-line active galactic nucleus (AGN), SDSS J102530.29+140207.3, at $z=0.1$, which shows spectral features matching those of LRDs seen in the early Universe, including the V-shaped spectrum, broad Balmer lines (with widths of 1000-2000 km/s), and deep Balmer absorption. We present a new GTC observation of this LRD, which reveals an optical continuum similar to those of G-to-K giant stars including an unambiguous G-band absorption originating from the CH molecule. In addition, this local LRD shows a series of absorption lines potentially related to low-ionization ions or atoms but are deeper than what is observed in empirical stellar templates. We further identify a series of [FeII] emission lines indicative of low-ionization gas, which we find also present in a JWST-selected LRD at $z=2.26$. We find small but statistically significant variability in the H$α$ of SDSS J102530.29+140207.3 consistent with previous findings. Finally, we report new observations with NuSTAR. We confirm the extreme X-ray weakness of this LRD, which might imply Compton-thick gas obscuration with $N_{\rm H}>10^{24}~{\rm cm^{-2}}$. All evidence suggests SDSS J102530.29+140207.3 has a complex gaseous environment and the strong ionic, atomic, and molecular absorptions are hard to explain with typical stellar and AGN models.

💡 Research Summary

This paper presents a groundbreaking study on the enigmatic class of objects known as “Little Red Dots” (LRDs), originally identified by the James Webb Space Telescope (JWST) at high redshifts (z > 4). The authors report the independent rediscovery and detailed analysis of a broad-line active galactic nucleus (AGN), SDSS J102530.29+140207.3, at a much lower redshift of z = 0.1, which exhibits spectral characteristics strikingly similar to those of the high-z LRDs.

The key finding is that this local AGN shares the defining features of JWST LRDs: a “V-shaped” optical continuum (steeply red), broad Balmer emission lines (with widths of 1000-2000 km/s), and deep Balmer absorption lines. New observations with the Gran Telescopio Canarias (GTC) revealed an optical continuum resembling that of G-to-K giant stars, including unambiguous G-band absorption from the CH molecule. Furthermore, a series of deep absorption lines from low-ionization species (e.g., Ca II, Na I, Mg I), stronger than typical stellar templates, were detected. The spectrum also shows prominent