Mass segregation

About: Mass segregation is a research topic. Over the lifetime, 1024 publications have been published within this topic receiving 57729 citations.

Matching Globular Cluster Models to Observations

Abstract: As ancient, gravitationally bound stellar populations, globular clusters are abundant, vibrant laboratories characterized by high frequencies of dynamical interactions coupled to complex stellar evolution. Using surface brightness and velocity dispersion profiles from the literature, we fit $59$ Milky Way globular clusters to dynamical models from the \texttt{CMC Cluster Catalog}. Without doing any interpolation, and without any directed effort to fit any particular cluster, $26$ globular clusters are well-matched by at least one of our models. We discuss in particular the core-collapsed clusters NGC 6293, NGC 6397, NGC 6681, and NGC 6624, and the non-core-collapsed clusters NGC 288, NGC 4372, and NGC 5897. As NGC 6624 lacks well-fitting snapshots on the main \texttt{CMC Cluster Catalog}, we run six additional models in order to refine the fit. We calculate metrics for mass segregation, explore the production of compact object sources such as millisecond pulsars, cataclysmic variables, low-mass X-ray binaries, and stellar-mass black holes, finding reasonable agreement with observations. Additionally, closely mimicking observational cuts, we extract the binary fraction from our models, finding good agreement except in the dense core regions of core-collapsed clusters. Accompanying this paper are a number of \textsf{python} methods for examining the publicly accessible \texttt{CMC Cluster Catalog}, as well as any other models generated using \texttt{CMC}.

Mass segregation of embedded clusters in the Milky Way

Abstract: Embedded clusters are ideal laboratories for understanding the early phase of the dynamical evolution of clusters as well as massive star formation. An interesting observational phenomenon is that some of the embedded clusters show mass segregation, i.e., the most massive stars are preferentially found near the cluster center. We develop a new approach to describe mass segregation. Using this approach and the Two Micron All Sky Survey Point Source Catalog (2MASS PSC), we analyze 18 embedded clusters in the Galaxy. We find that 11 of them are mass-segregated and that the others are not mass-segregated. No inversely mass-segregated cluster is found.

The luminosity function of the cluster Palomar 1—testing a new technique

Abstract: The luminosity function of the globular cluster Palomar 1 is determined together with its confidence interval by applying an adaptive kernel estimator to data from the Isaac Newton Telescope. The luminosity function of Palomar 1 has two minima in the V band and one in the I band. The cluster core contains a relatively high fraction of bright stars, indicative of mass segregation.

Determination of the globular cluster and halo stellar mass functions and stellar and brown dwarf densities

Abstract: We use recent low-mass star models, which reproduce accurately the observed sequences of various globular clusters, to convert the observed luminosity functions into bolometric luminosity functions. These latter are shown to exhibit a similar behaviour with a rising slope up to Mbol ∼ 9, i.e. m ∼ 0.2 − 0.3M , and a decreasing behaviour beyond this limit. We then derive mass functions for globular star clusters down to the bottom of the main sequence. These mass functions are well described by a slowly rising power-law dN/dm ∝ m−α, with 0.5 ∼< α ∼< 1.5, down to ∼ 0.1M , independently of the metallicity, suggesting a rather universal behaviour of the cluster initial mass functions. The effects of tidal stripping and mass segregation are illustrated by the overabundance of very low-mass stars in the outer parts of NGC6397 and their depletion in the central parts. This analysis confirms that the mass function determined near the half-mass radius has been weakly affected by external and internal dynamical effects and reflects relatively closely the initialmass function. We predict luminosity functions in the NICMOS filters in the stellar and in the brown dwarf domains for different mass functions and metallicities. We apply these calculations to the determination of the mass function in theGalactic halo, including theDeVaucouleurs spheroid and the 1/r2 dark halo.We derive the slope and the normalization of the spheroidmass functionwhich iswell described by the afore-mentioned power-law function with α ∼ 1.7±0.2 down to 0.1 M , although a slowly decreasing mass function below ∼ 0.15M can not be excluded with the data presently available. Comparisonwith theHubbleDeep Field star counts is consistent with such a mass function and excludes a significant stellar population in the dark halo. This shows that essentially all the high-velocity subdwarfs observed in the solar neighborhood belong to the Galactic spheroid. Consistent analysis with recent microlensing experiments towards the LMC shows that the spheroid and the dark-halo stellar+brown dwarf populations represent at most ∼ 1% of ? The bolometric LF’s displayed in Fig. 1 are available at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html the Galactic dark matter density. This clearly excludes brown dwarfs and low-mass stars as significant darkmatter candidates.