<i>Euclid</i>: the potential of slitless infrared spectroscopy: a <i>z</i> = 5.4 quasar and new ultracool dwarfs
Bibliographic record
Abstract
ABSTRACT We demonstrate the potential of Euclid ’s slitless spectroscopy to discover high-redshift ($z>5$) quasars and their main photometric contaminant, ultracool dwarfs. Sensitive infrared spectroscopy from space is able to efficiently identify both populations, as demonstrated by Euclid Near-Infrared Spectrometer and Photometer Red Grism (NISP ${\rm RG}_{\scriptscriptstyle \rm E}$) spectra of the newly discovered $z=5.404$ quasar EUCL J181530.01$+$652054.0, as well as several ultracool dwarfs in the Euclid Deep Field North and the Euclid Early Release Observation field Abell 2764. The ultracool dwarfs were identified by cross-correlating their spectra with templates. The quasar was identified by its strong and broad ${\rm C \small {III]}}$ and ${\rm Mg {\small II}}$ emission lines in the NISP ${\rm RG}_{\scriptscriptstyle \rm E}$ 1206–1892 nm spectrum, and confirmed through optical spectroscopy from the Large Binocular Telescope. The NISP Blue Grism (NISP ${\rm BG}_{\scriptscriptstyle \rm E}$) 926–1366 nm spectrum confirms ${C {\small IV}}$ and $\rm{C \small {III]}}$ emission. NISP ${\rm RG}_{\scriptscriptstyle \rm E}$ can find bright quasars at $z\approx 5.5$ and $z\gtrsim 7$, redshift ranges that are challenging for photometric selection due to contamination from ultracool dwarfs. EUCL J181530.01$+$652054.0 is a high-excitation, broad absorption line quasar detected at 144 MHz by the LOw-Frequency Array ($L_{\rm 144}=4.0 \times 10^{25}\,$W Hz$^{-1}$). The quasar has a bolometric luminosity of $3\times 10^{12}\, {{\rm L}_{\odot }}{}$ and is powered by a $3.4\times 10^9\, {{\rm M}_{\odot }}$ black hole. The discovery of this bright quasar is noteworthy as fewer than one such object was expected in the $\approx$20 deg$^2$ surveyed. This finding highlights the potential and effectiveness of NISP spectroscopy in identifying rare, luminous high-redshift quasars, previewing the census of these sources that Euclid’s slitless spectroscopy will deliver over about $14\, 000\,$deg$^2$ of the sky.
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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 | 0.000 | 0.000 |
| 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".