MusE GAs FLOw and Wind (MEGAFLOW) VIII. Discovery of a MgII emission halo probed by a quasar sightline
Bibliographic record
Abstract
Using deep ($11.2\, \rm{h}$) VLT/MUSE data from the MEGAFLOW survey, we report the first detection of extended $\rm{Mg\, \small {II}}$ emission from a galaxy's halo that is probed by a quasar sightline. The $\rm{Mg\, \small {II}}\, \lambda \lambda \, 2796, 2803$ emission around the z = 0.702 galaxy ($\log (M_∗/\rm{M_\odot })=10.05_{-0.11}^{+0.15}{}$) is detected out to $\approx 25\, \hbox{kpc}$ from the central galaxy and covers $1.0\times 10^3\, \hbox{kpc}^2$ above a surface brightness of $14\times 10^{-19}\, \rm{erg}\, \rm{s}^{-1}\, \rm{cm}^{-2}\, \rm{arcsec}^{-2}{}$ ($2\, \sigma$; integrated over $1200\, \rm{km\, s}^{-1}= 19\mathring{\rm A}$ and averaged over $1.5\, \rm{arcsec}^{2}$). The $\rm{Mg\, \small {II}}$ emission around this highly inclined galaxy (i ? 75 deg) is strongest along the galaxy's projected minor axis, consistent with the $\rm{Mg\, \small {II}}$ gas having been ejected from the galaxy into a bi-conical structure. The quasar sightline, which is aligned with the galaxy's minor axis, shows strong $\rm{Mg\, \small {II}}$ absorption ($\hbox{$EW_0^{\lambda 2796}$}{}=1.8{}\, \mathring{\rm A}$) at an impact parameter of $39{}\, \hbox{kpc}$ from the galaxy. Comparing the kinematics of both the emission and the absorption - probed with VLT/UVES - to the expectation from a simple toy model of a bi-conical outflow, we find good consistency when assuming a relatively slow outflow ($v_\rm{out}=130{}\, \rm{km\, s}^{-1}$). We investigate potential origins of the extended $\rm{Mg\, \small {II}}$ emission using simple toy models. With continuum scattering models we encounter serious difficulties in explaining the luminosity of the $\rm{Mg\, \small {II}}$ halo and in reconciling density estimates from emission and absorption. Instead, we find that shocks might be a more viable source to power the extended $\rm{Mg\, \small {II}}$ (and non-resonant $[\rm{O\, \small {II}}]$) emission.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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".