Deep multi-telescope photometry of NGC 5466. II. The radial behaviour of the mass function slope

Abstract

We use a combination of data acquired with the Advanced Camera for Survey (ACS) on board the Hubble Space Telescope and the Large Binocular Camera (LBC-blue) mounted on the Large Binocular Telescope, to sample the main sequence stars of the globular cluster NGC~5466 in the mass range $0.3<M/M_{\odot }<0.8$. We derive the cluster's Luminosity Function in several radial regions, from the center of the cluster out to the tidal radius. After corrections for incompleteness and field-contamination, this has been compared to theoretical Luminosity Functions, obtained by multiplying a simple power law Mass Function in the form dN/dm$\propto m^{\alpha }$ by the derivative of the mass-luminosity relationship of the best-fit isochrone. We find that $\alpha$ varies from -0.6 in the core region to -1.9 in the outer region. This fact allows us to observationally prove that the stars in NGC 5466 have experienced the effects of mass segregation. We compare the radial variation of $\alpha$ from the center out to 5 core radii (r${}_c$) in NGC 5466 and the globular cluster M10, finding that the gradient of $\alpha$ in the first 5r${}_c$ is more than a factor of 2 shallower in NGC 5466 than in M10, in line with the differences in the clusters' relaxation timescales. NGC 5466 is dynamically younger than M10, with two-body relaxation processes only recently starting to shape the distribution of main sequence stars. This result fully agrees with the conclusion obtained in our previous works on the radial distribution of Blue Straggler Stars, further confirming that this can be used as an efficient clock to measure the dynamical age of stellar systems.

Accepted for publications on ApJ

References in corpus (9)

• Dynamical age differences among coeval star clusters as revealed by blue stragglers
• The fraction of binary systems in the core of thirteen low-density Galactic globular clusters
• Why haven't loose globular clusters collapsed yet?
• Faint X-ray Sources in the Globular Cluster Terzan 5
• Another Non-segregated Blue Straggler Population in a Globular Cluster: the Case of NGC 2419
• Deep multi-telescope photometry of NGC 5466. I. Blue Stragglers and binary systems
• Mass segregation in the outer halo globular cluster Palomar 14
• UV observations of the globular cluster M10 from HST and GALEX. The BSS population
• Photometry of the Globular Cluster NGC 5466: Red Giants and Blue Stragglers

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• Modelling the Observed Stellar Mass Function and its Radial Variation in Galactic Globular Clusters
• Testing lowered isothermal models with direct N-body simulations of globular clusters - II: Multimass models
• Testing multi-mass dynamical models of star clusters with real data: mass segregation in three Galactic globular clusters
• Inferring the Helium abundance of extragalactic Globular Clusters using Integrated Spectra
• Globular clusters as cosmic clocks: new cosmological hints from their integrated light