A blazar in the epoch of reionization (2407.07236v2)

Abstract: Relativistic jets are thought to play a crucial role in the formation and evolution of massive galaxies and supermassive black holes. Blazars, which are quasars with jets aligned along our line of sight, provide insights into the jetted population and have been observed up to redshifts of z=6.1. Here, we report the discovery and multi-wavelength characterization of the blazar VLASS J041009.05-013919.88 at z=7 (Universe's age ~750 Myr), powered by a ~7x10^8 Msun black hole. The presence of this high-redshift blazar implies a large population of similar but unaligned jetted sources in the early Universe. Our findings suggest two possible scenarios: in one, the jet in J0410-0139 is intrinsically low-power but appears highly luminous due to relativistic beaming, suggesting that most UV-bright quasars at this redshift host jets. Alternatively, if J0410-0139 represents an intrinsically powerful radio source, there should be hundreds to thousands of radio-quiet quasars at z~7 with properties similar to J0410-0139, a prediction in tension with observed quasar densities based on their UV luminosity function. These results support the hypothesis that rapid black hole growth in the early Universe may be driven by jet-enhanced or obscured super-Eddington accretion, potentially playing a key role in forming massive black holes during the epoch of reionization.

• The paper presents the discovery and multi-wavelength characterization of blazar J0410–0139 at z=7, confirming its relativistic jet properties using radio, optical, and X-ray observations.
• It estimates a supermassive black hole mass of approximately 6.9×10^8 solar masses and suggests that jet-driven, potentially super-Eddington accretion accelerated early SMBH growth.
• The study implies that many similar jetted sources exist in the early universe, prompting a re-evaluation of SMBH evolution and the prevalence of radio-quiet quasars.

Overview of "A blazar in the epoch of reionization"

The paper "A blazar in the epoch of reionization" presents the discovery and analysis of a high-redshift blazar, VLASS J041009.05$-$013919.88 (referred to as J0410–0139), situated at a redshift of $z = 7$. This blazar is observed during the epoch of reionization, a pivotal era in cosmic history when the universe's intergalactic medium transitioned from being mostly neutral to ionized. The authors emphasize the significance of studying blazars, which are quasars with relativistic jets aligned closely with our line of sight, as they provide critical insights into the population of jetted sources and the formation of supermassive black holes (SMBHs) in the early universe.

Key Results and Insights

1. Detection and Characterization: The blazar J0410–0139 was identified through the cross-matching of optical surveys with radio observations from the NRAO VLA Sky Survey and the Very Large Array Sky Survey. The team confirmed its nature using multi-wavelength observations, including optical, near-infrared, radio, and X-ray data, supplemented by Very Large Telescope (VLT) spectroscopy. The observations confirmed the source's blazar characteristics, such as its highly variable radio emission, flat radio spectrum, and compact radio morphology.
2. Astrophysical Significance: The existence of J0410–0139 at such a high redshift (i.e., $z = 7$) suggests a significant population of similarly massive and jetted sources in the early universe. It is powered by a black hole with a mass estimated at $6.9^{+0.5}_{-0.4} \times 10^8 M_\odot$, potentially hinting at super-Eddington accretion processes catalyzed by jet activity. The paper suggests that such mechanisms might have facilitated rapid SMBH growth during the epoch of reionization.
3. Implications for Jet & Black Hole Evolution Models: The presence of this blazar infers that many other similar jetted sources must exist with their jets misaligned relative to our line of sight. The authors discuss scenarios such as low-power jets appearing luminous due to relativistic beaming or the possibility of numerous radio-quiet, powerful jets yet undiscovered.
4. Constraints and Predictions: If J0410–0139 is an intrinsically powerful radio source, the predictions indicate that numerous radio-quiet quasars at $z \approx 7$ exist, a possibility that challenges current observational data based on their UV luminosity function. Conversely, if the apparent luminosity is due to relativistic beaming of a weak jet, this would suggest that such jets are more common among UV-bright quasars.

Discussion and Future Directions

The findings emphasize the potential role of jet dynamics in early SMBH growth, possibly offering solutions to puzzles regarding how such massive entities formed so quickly after the Big Bang. The paper argues that further detections of high-redshift blazars, using more sensitive radio and X-ray surveys, would clarify the role of jets in this evolutionary context. The paper compels a reconsideration of the theoretical models concerning SMBH formation and accretion processes under extreme environmental conditions.

Concluding Remarks

"A blazar in the epoch of reionization" contributes significant knowledge to the understanding of early universe quasar physics, particularly the interplay between relativistic jets and massive black hole growth. The research elucidates key observational criteria for identifying high-redshift blazars and sets a framework for anticipating the existence of numerous, yet-to-be-detected jetted quasars. As observational techniques and theoretical models continue to advance, studies of sources like J0410–0139 will be instrumental in piecing together the cosmological evolution of massive black holes and their host galaxies.