ALMA is now fully operational, and has been observing in early science mode since 2011. The millimetric (mm) and sub-mm domain is ideal to tackle galaxies at high redshift, since the emission peak of ...the dust at 100
μ
m is shifted in the ALMA bands (0.3–1 mm) for
z
=
2–9, and the CO lines, stronger at the high-
J
levels of the ladder, are found all over the 0.3–3 mm range. Pointed surveys and blind deep fields have been observed, and the wealth of data collected reveal a drop at high redshifts (
z
>
6
) of dusty massive objects, although surprisingly active and gas-rich objects have been unveiled through gravitational lensing. The window of the reionization epoch is now wide open, and ALMA has detected galaxies at
z
=
8
–9 mainly in continuum, CII and OIII lines. Galaxies have a gas fraction increasing steeply with redshift, as
(
1
+
z
)
2
, while their star formation efficiency increases also but more slightly, as
(
1
+
z
)
0.6
to
(
1
+
z
)
1
. Individual object studies have revealed luminous quasars, with black hole masses much higher than expected, clumpy galaxies with resolved star formation rate compatible with the Kennicutt–Schmidt relation, extended cold and dense gas in a circumgalactic medium, corresponding to Lyman-
α
blobs, and proto-clusters, traced by their brightest central galaxies.
We present a high-resolution numerical study of the phase-space diversity in an isolated Milky Way-type galaxy. Using a single N-body simulation (N ≈ 0.14 × 109) we explore the formation, evolution, ...and spatial variation of the phase-space spirals similar to those recently discovered by Antoja et al. in the Milky Way disk with Gaia Data Release 2 (DR2). For the first time in the literature we use a self-consistent N-body simulation of an isolated Milky Way-type galaxy to show that the phase-space spirals develop naturally from vertical oscillations driven by the buckling of the stellar bar. Thus, we claim that the physical mechanism standing behind the observed incomplete phase-space mixing process can be internal and not necessarily due to the perturbation induced by a massive satellite. In our model, the bending oscillations propagate outward and produce axisymmetric variations of the mean vertical coordinate and vertical velocity component of about 100 − 200 pc and 1 − 2 km s−1, respectively. As a consequence, the phase-space wrapping results in the formation of patterns with various morphologies across the disk, depending on the bar orientation, distance to the galactic center, and time elapsed since the bar buckling. Once bending waves appear, they are supported for a long time via disk self-gravity. Such vertical oscillations trigger the formation of various time-dependent phase-space spirals in the entire disk. The underlying physical mechanism implies the link between in-plane and vertical motion that leads directly to phase-space structures whose amplitude and shape are in remarkable agreement with those of the phase-space spirals observed in the Milky Way disk. In our isolated galaxy simulation, phase-space spirals are still distinguishable at the solar neighborhood 3 Gyr after the buckling phase. The long-lived character of the phase-space spirals generated by the bar buckling instability cast doubts on the timing argument used so far to get back to the time of the onset of the perturbation: phase-space spirals may have been caused by perturbations originated several gigayearrs ago, and not as recent as suggested so far.
Recent molecular line observations with ALMA in several nearby Seyferts have revealed the existence of molecular tori, and the nature of gas flows at 10-20 pc scale. At 100 pc scale, or kpc-scale, ...previous NOEMA work on gravitational torques had shown that only about one third of Seyfert galaxies experienced molecular inflow and central fueling, while in most cases the gas was stalled in rings. At higher resolution, i.e. 10-20 pc scale, it is possible now to see in some cases AGN fueling due to nuclear trailing spirals, influenced by the black hole potential. This brings smoking gun evidence for nuclear fueling. In our sample galaxies, the angular resolution of up to 60 mas allows us to reach the black hole (BH) sphere of influence and the BH mass can be derived more directly than with the M-sigma relation.
We present the first high-resolution map of the cold molecular gas distribution as traced by CO(2−1) emission with ALMA in a long ram pressure stripped tail. The Norma cluster galaxy ESO 137-001 is ...undergoing a strong interaction with the surrounding intracluster medium and is one of the nearest jellyfish galaxies with a long multiphase and multicomponent tail. We have mapped the full extent of the tail at 1″ (350 pc) angular resolution and found a rich distribution of mostly compact CO regions extending to nearly 60 kpc in length and 25 kpc in width. In total, about 109 M of molecular gas was detected with ALMA. From comparison with previous APEX observations, we also infer the presence of a substantial extended molecular component in the tail. The ALMA CO features are found predominantly at the heads of numerous small-scale (∼1.5 kpc) fireballs (i.e., star-forming clouds with linear streams of young stars extending toward the galaxy) but also large-scale (∼8 kpc) superfireballs and double-sided fireballs that have additional diffuse ionized gas tails extending in the direction opposite the stellar tails. The new data help to shed light on the origin of the molecular tail; CO filaments oriented in the direction of the tail are likely young molecular features formed in situ, whereas large CO features tilted with respect to the tail may have originated from dense gas complexes that were gradually pushed away from the disk.
Figure majeure de l’astrophysique française, Jean-Claude Pecker s’est éteint le 20 février 2020, dans sa 97e année. Astronome de l’Observatoire de Paris, académicien des sciences et professeur au ...Collège de France, ce grand humaniste avait notamment œuvré au développement de l’Union astronomique internationale (UAI). Jean-Claude Pecker a joué un rôle de premier plan dans l’astrophysique française, pendant plus d’un demi-siècle, depuis les années 1950. Jean-Claude Pecker passe toute son enfan...
Galaxies et cosmologie Combes, Françoise
Annuaire du Collège de France,
02/2023
120
Journal Article
Odprti dostop
Enseignement Cours – L’époque de la réionisation de l’Univers Introduction L’Univers commence dans une gigantesque explosion, le Big Bang. La densité d’énergie et la température sont énormes, et dans ...l’expansion rapide qui suit, l’énergie se dilue et la température décroît. L’Univers est d’abord un plasma de particules chargées, essentiellement électrons et protons. 380 000 ans plus tard, la température est de 3 000 Kelvin, et le gaz se recombine en atome d’hydrogène. Les photons ne sont alor...
Using the latest sample of 48 spiral galaxies having a directly measured supermassive black hole mass, MBH, we determine how the maximum disk rotational velocity, vmax (and the implied dark matter ...halo mass, MDM), correlates with the (i) black hole mass, (ii) central velocity dispersion, 0, and (iii) spiral-arm pitch angle, φ. We find that M BH ∝ v max 10.62 1.37 ∝ M DM 4.35 0.66 , significantly steeper than previously reported, and with a total root mean square scatter (0.58 dex) similar to that about the MBH- 0 relation for spiral galaxies-in stark disagreement with claims that MBH does not correlate with disks. Moreover, this MBH-vmax relation is consistent with the unification of the Tully-Fisher relation (involving the total stellar mass, M*,tot) and the steep M BH ∝ M * , tot 3.05 0.53 relation observed in spiral galaxies. We also find that 0 ∝ v max 1.55 0.25 ∝ M DM 0.63 0.11 , consistent with past studies connecting stellar bulges (with 0 100 km s−1), dark matter halos, and a nonconstant vmax/ 0 ratio. Finally, we report that tan φ ∝ ( − 1.18 0.19 ) log v max ∝ ( − 0.48 0.09 ) log M DM , providing a novel formulation between the geometry (i.e., the logarithmic spiral-arm pitch angle) and kinematics of spiral galaxy disks. While the vmax-φ relation may facilitate distance estimations to face-on spiral galaxies through the Tully-Fisher relation and using φ as a proxy for vmax, the MDM-φ relation provides a path for determining dark matter halo masses from imaging data alone. Furthermore, based on a spiral galaxy sample size that is double the size used previously, the self-consistent relations presented here provide dramatically revised constraints for theory and simulations.
Galaxies et cosmologie Combes, Françoise
Annuaire du Collège de France,
03/2022
119
Journal Article
Odprti dostop
Enseignement Cours et séminaires – Amas de galaxies et grandes structures de l’Univers Introduction Ces dernières années ont été très riches dans la découverte de notre Univers, la cartographie des ...galaxies et des grandes structures, par la détermination des décalages vers le rouge (redshifts) de millions d’objets. Notre groupe local fait partie d’un super-amas de galaxies, Laniakea, qui contient l’amas de galaxies de Virgo avec d’autres amas. Les amas de galaxies sont un des outils qui perme...
We present a detailed study of the properties of the molecular gas in the fast outflow driven by the active galactic nucleus (AGN) in the nearby radio-loud Seyfert galaxy IC 5063. By using ALMA ...observations of a number of tracers of the molecular gas (12CO(1–0), 12CO(2–1), 12CO(3–2), 13CO(2–1) and HCO+(4–3)), we map the differences in excitation, density and temperature of the gas as function of position and kinematics. The results show that in the immediate vicinity of the radio jet, a fast outflow, with velocities up to 800 km s-1, is occurring of which the gas has high excitation with excitation temperatures in the range 30–55 K, demonstrating the direct impact of the jet on the ISM. The relative brightness of the 12CO lines, as well as that of 13CO(2–1) vs. 12CO(2–1), show that the outflow is optically thin. We estimate the mass of the molecular outflow to be at least 1.2 × 106 M⊙ and likely to be a factor between two and three larger than this value. This is similar to that of the outflow of atomic gas, but much larger than that of the ionised outflow, showing that the outflow in IC 5063 is dominated by cold gas. The total mass outflow rate we estimated to be ~12 M⊙ yr-1. The mass of the outflow is much smaller than the total gas mass of the ISM of IC 5063. Therefore, although the influence of the AGN and its radio jet is very significant in the inner regions of IC 5063, globally speaking the impact will be very modest. We used RADEX non-LTE modelling to explore the physical conditions of the molecular gas in the outflow. Models with the outflowing gas being quite clumpy give the most consistent results and our preferred solutions have kinetic temperatures in the range 20–100 K and densities between 105 and 106 cm-3. The resulting pressures are 106–107.5 K cm-3, about two orders of magnitude higher than in the outer quiescent disk. The highest densities and temperatures are found in the regions with the fastest outflow. The results strongly suggest that the outflow in IC 5063 is driven by the radio plasma jet expanding into a clumpy gaseous medium and creating a cocoon of (shocked) gas which is pushed away from the jet axis resulting in a lateral outflow, very similar to what is predicted by numerical simulations.
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