Trou noir stellaire

Résumé

Un trou noir stellaire est l'un des quatre types de trous noirs, avec les trous noirs primordiaux, les trous noirs intermédiaires et les trous noirs supermassifs. Créé par l'effondrement d'une étoile massive sur elle-même, un tel trou noir a une masse comprise entre un minimum de trois à cinq masses solaires () et un maximum de . Observation En 2019 un trou noir stellaire de a été identifié dans la Voie lactée mais son existence a été remise en cause l'année suivante. En 2021, la masse du trou noir du système Cygnus X-1 est recalculée, faisant passer l'estimation initiale de 14,8 à 21,2 masses solaires. Ainsi, si ce chiffre est confirmé, il s'agira du trou noir stellaire le plus massif jamais détecté. Les principaux progéniteurs de trous noirs stellaires par effondrement sont les étoiles Wolf-Rayet. Formation On peut envisager un trou noir d'une masse quelconque, en se basant uniquement sur la loi de l'attraction universelle telle qu'énoncée par Newton. Tou

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https://fr.wikipedia.org/wiki/Trou_noir_stellaire

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Morphological Segregation in the Surroundings of Cosmic Voids

Elena Ricciardelli, Amélie Tamone

We explore the morphology of galaxies living in the proximity of cosmic voids, using a sample of voids identified in the Sloan Digital Sky Survey Data Release 7. At all stellar masses, void galaxies exhibit morphologies of a later type than galaxies in a control sample, which represent galaxies in an average density environment. We interpret this trend as a pure environmental effect, independent of the mass bias, due to a slower galaxy build-up in the rarefied regions of voids. We confirm previous findings about a clear segregation in galaxy morphology, with galaxies of a later type being found at smaller void-centric distances with respect to the early-type galaxies. We also show, for the first time, that the radius of the void has an impact on the evolutionary history of the galaxies that live within it or in its surroundings. In fact, an enhanced fraction of late-type galaxies is found in the proximity of voids larger than the median void radius. Likewise, an excess of early-type galaxies is observed within or around voids of a smaller size. A significant difference in galaxy properties in voids of different sizes is observed up to 2 R-void, which we define as the region of influence of voids. The significance of this difference is greater than 3 sigma for all the volume-complete samples considered here. The fraction of star-forming galaxies shows the same behavior as the late-type galaxies, but no significant difference in stellar mass is observed in the proximity of voids of different sizes.

Iop Publishing Ltd2017

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Is ram-pressure stripping an efficient mechanism to remove gas in galaxies?

Elena Ricciardelli

We study how the gas in a sample of galaxies (M-* > 10(9) M-circle dot) in clusters, obtained in a cosmological simulation, is affected by the interaction with the intracluster medium (ICM). The dynamical state of each elemental parcel of gas is studied using the total energy. At z similar to 2, the galaxies in the simulation are evenly distributed within clusters, later moving towards more central locations. In this process, gas from the ICM is accreted and mixed with the gas in the galactic halo. Simultaneously, the interaction with the environment removes part of the gas. A characteristic stellar mass around M-* > 10(10) M-circle dot appears as a threshold marking two differentiated behaviours. Below this mass, galaxies are located at the external part of clusters and have eccentric orbits. The effect of the interaction with the environment is marginal. Above, galaxies are mainly located at the inner part of clusters with mostly radial orbits with low velocities. In these massive systems, part of the gas, strongly correlated with the stellar mass of the galaxy, is removed. The amount of removed gas is subdominant compared with the quantity of retained gas, which is continuously influenced by the hot gas coming from the ICM. The analysis of individual galaxies reveals the existence of a complex pattern of flows, turbulence and a constant fuelling of gas to the hot corona from the ICM, which could mean that the global effect of the interaction of galaxies with their environment is substantially less dramatic than previously expected.

Oxford Univ Press2017

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We investigate how the galaxy reservoirs of molecular gas fuelling star formation are transformed while the host galaxies infall onto galaxy cluster cores. As part of the Spatially Extended ESO Distant Cluster Survey (SEEDisCS), we present CO(3-2) observations of 27 star-forming galaxies obtained with the Atacama Large Millimeter Array. These sources are located inside and around CL1411.1-1148 at z=0.5195, within five times the cluster virial radius. These targets were selected to have stellar masses (Mstar), colours, and magnitudes similar to those of a field comparison sample at similar redshift drawn from the Plateau de Bure high-z Blue Sequence Survey (PHIBSS2). We compare the cold gas fraction (mu H2=MH2/Mstar), specific star formation rates (SFR/Mstar) and depletion timescales (tdepl=MH2/SFR) of our main-sequence galaxies to the PHIBSS2 subsample. While the most of our galaxies (63%) are consistent with PHIBSS2, the remainder fall below the relation between mu H2 and Mstar of the PHIBSS2 galaxies at z similar to 0.5. These low-mu H2 galaxies are not compatible with the tail of a Gaussian distribution, hence they correspond to a new population of galaxies with normal SFRs but low gas content and low depletion times (less than or similar to 1 Gyr), absent from previous surveys. We suggest that the star formation activity of these galaxies has not yet been diminished by their low fraction of cold molecular gas.

EDP SCIENCES S A2021

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