THE<i>CHANDRA</i>DEEP PROTOCLUSTER SURVEY: EVIDENCE FOR AN ENHANCEMENT OF AGN ACTIVITY IN THE SSA22 PROTOCLUSTER AT<i>z</i>= 3.09
Bibliographic record
Abstract
We present results from a new ultra-deep ≈400 ks Chandra observation of the SSA22 protocluster at z = 3.09. We have studied the X-ray properties of 234 z ∼ 3 Lyman Break Galaxies (LBGs; protocluster and field) and 158 z = 3.09 Lyα Emitters (LAEs) in SSA22 to measure the influence of the high-density protocluster environment on the accretion activity of supermassive black holes (SMBHs) in these UV-selected star-forming populations. We detect individually X-ray emission from active galactic nuclei (AGNs) in six LBGs and five LAEs; due to small overlap between the LBG and LAE source population, ten of these sources are unique. At least six and potentially eight of these sources are members of the protocluster. These sources have rest-frame 8–32 keV luminosities in the range of L 8−32 keV = (3–50) × 10 43 ergs s −1 and an average observed-frame 2–8 keV to 0.5–2 keV band ratio (BR) of ≈0.8 (mean effective photon index of Γ eff ≈ 1.1), suggesting significant absorption columns of N H ≳ 10 22 –10 24 cm −2 . We find that the fraction of LBGs and LAEs in the z = 3.09 protocluster harboring an AGN with L 8−32 keV ≳ 3 × 10 43 ergs s −1 is 9.5 +12.7 −6.1 % and 5.1 +6.8 −3.3 %, respectively. These AGN fractions are somewhat larger (by a mean factor of 6.1 +10.3 −3.6 ; significant at the ≈95% confidence level) than z ∼ 3 sources found in lower-density "field" environments. Theoretical models imply that these results may be due to the presence of more actively growing and/or massive SMBHs in LBGs and LAEs within the protocluster compared to the field. Such a result is expected in a scenario where enhanced merger activity in the protocluster drives accelerated galaxy and SMBH growth at z ≳ 2–3. Using Spitzer IRAC imaging we found that the fraction of IRAC-detected LBGs is significantly larger in the protocluster than in the field (by a factor of 3.0 +2.0 −1.3 ). From these data, we constrained the median rest-frame H -band luminosity in the protocluster to be ≳ 1.2–1.8 times larger than that for the field. When combined with our X-ray data, this suggests that both galaxies and SMBHs grew more rapidly in protocluster environments.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".