A Magellan IMACS Spectroscopic Search for Lyα‐emitting Galaxies at Redshift 5.7
Bibliographic record
Abstract
We present results from a blind, spectroscopic survey for z ∼ 5.7 Lyα-emitting galaxies (LAEs) using the Inamori Magellan Areal Camera and Spectrograph. A total of ~200 arcmin 2 were observed in the COSMOS and LCIRS fields using a narrowband filter, which transmits between atmospheric emission lines at 8190 Å, and a mask with 100 long slits. This observing technique provides higher emission-line sensitivity than narrowband imaging and probes larger volumes than strong lensing. We find 170 emission-line galaxies and identify their redshifts spectroscopically. We confirm three LAEs, the first discovered using multislit narrowband spectroscopy. Their line profiles are narrow, but fitted models suggest intrinsic, unattenuated widths ~400 km s −1 FWHM. The red wing of the line profiles presents features consistent with galactic winds. The star formation rates of these galaxies are at least 5-7 M ☉ yr −1 and likely a factor of 2 higher. We estimate that the number density of L ⩾ 5 × 10 42 erg s −1 LAEs is 9.0 −4 +12 × 10 −5 h 70 3 Mpc −3 at redshift 5.7 and constrain the Schechter function parameters describing this population. Galaxies fainter than our detection limit may well be the primary source of ionizing photons at z ∼ 6. We argue, however, that the break luminosity L *,Ly α is not yet well constrained. If this break luminosity is near our detection limit, and somewhat lower than previous estimates, then the detected LAE population could be responsible for ionizing the intergalactic gas at redshift z ∼ 6. We discuss the potential of multislit narrowband spectroscopy for deeper emission-line surveys.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".