The ATLAS3D project – XX. Mass–size and mass–σ distributions of early-type galaxies: bulge fraction drives kinematics, mass-to-light ratio, molecular gas fraction and stellar initial mass function
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Notice bibliographique
Résumé
In the companion Paper XV of this series, we derive accurate total mass-to-light ratios (M/L)JAM≈(M/L)(r=Re) within a sphere of radius r=Re centred on the galaxy, as well as stellar (M/L)stars (with the dark matter removed) for the volume-limited and nearly mass selected (stellar mass M⋆≳6×109M⊙) ATLAS3D sample of 260 early-type galaxies (ETGs, ellipticals Es and lenticulars S0s). Here, we use those parameters to study the two orthogonal projections (MJAM,σe) and (MJAM,Rmaje) of the thin Mass Plane (MP) (MJAM,σe,Rmaje) which describes the distribution of the galaxy population, where MJAM≡L×(M/L)JAM≈M⋆. The distribution of galaxy properties on both projections of the MP is characterized by: (i) the same zone of exclusion (ZOE), which can be transformed from one projection to the other using the scalar virial equation. The ZOE is roughly described by two power laws, joined by a break at a characteristic mass MJAM≈3×1010M⊙, which corresponds to the minimum Re and maximum stellar density. This results in a break in the mean MJAM--σe relation with trends MJAM∝σ2.3e and MJAM∝σ4.7e at small and large σe, respectively; (ii) a characteristic mass MJAM≈2×1011M⊙ which separates a population dominated by flat fast rotator with discs and spiral galaxies at lower masses, from one dominated by quite round slow rotators at larger masses; (iii) below that mass the distribution of ETGs’ properties on the two projections of the MP tends to be constant along lines of roughly constant σe, or equivalently along lines with Rmaje∝MJAM, respectively (or even better parallel to the ZOE: Rmaje∝M0.75JAM); (iv) it forms a continuous and parallel sequence with the distribution of spiral galaxies; (v) at even lower masses, the distribution of fast-rotator ETGs and late spirals naturally extends to that of dwarf ETGs (Sph) and dwarf irregulars (Im), respectively. We use dynamical models to analyse our kinematic maps. We show that & 0963;e traces the bulge fraction, which appears to be the main driver for the observed trends in the dynamical (M/L)JAM and in indicators of the (M/L)pop of the stellar population like Hβ and colour, as well as in the molecular gas fraction. A similar variation along contours of σe is also observed for the mass normalization of the stellar initial mass function (IMF), which was recently shown to vary systematically within the ETGs’ population. Our preferred relation has the form log10[(M/L)stars/(M/L)Salp]=a+b& 0215;log10(σe/130kms−1) with a = −0.12 ± 0.01 and b = 0.35 ± 0.06. Unless there are major flaws in all stellar population models, this trend implies a transition of the mean IMF from Kroupa to Salpeter in the interval log10(& 0963;e/kms−1)≈1.9--2.5 (or σe≈90--290 km s−1), with a smooth variation in between, consistently with what was shown in Cappellari et al. The observed distribution of galaxy properties on the MP provides a clean and novel view for a number of previously reported trends, which constitute special two-dimensional projections of the more general four-dimensional parameters trends on the MP. We interpret it as due to a combination of two main effects: (i) an increase of the bulge fraction, which increases σe, decreases Re, and greatly enhance the likelihood for a galaxy to have its star formation quenched, and (ii) dry merging, increasing galaxy mass and Re by moving galaxies along lines of roughly constant σe (or steeper), while leaving the population nearly unchanged.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découle