Radial variation of the stellar mass functions in the globular clusters M15 and M30: clues of a non-standard IMF?

Abstract

We exploit a combination of high-resolution Hubble Space Telescope and wide-field ESO-VLT observations to study the slope of the global mass function (alphaG) and its radial variation (alpha(r)) in the two dense, massive and post core-collapse globular clusters M15 and M30. The available data-set samples the clusters' Main Sequence down to 0.2 Msun and the photometric completeness allows the study of the mass function between 0.40 Msun and 0.75 Msun from the central regions out to their tidal radii. We find that both clusters show a very similar variation in alpha(r) as a function of clustercentric distance. They both exhibit a very steep variation in alpha(r) in the central regions, which then attains almost constant values in the outskirts. Such a behavior can be interpreted as the result of long-term dynamical evolution of the systems driven by mass-segregation and mass-loss processes. We compare these results with a set of direct N-body simulations and find that they are only able to reproduce the observed values of alpha(r) and alphaG at dynamical ages (t/trh) significantly larger than those derived from the observed properties of both clusters. We investigate possible physical mechanisms responsible for such a discrepancy and argue that both clusters might be born with a non-standard (flatter/bottom-lighter) initial mass function.

Accepted for publication by MNRAS

References in corpus (18)

• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• What is a globular cluster? An observational perspective
• Dynamical age differences among coeval star clusters as revealed by blue stragglers
• Surface Brightness Profiles of Galactic Globular Clusters from Hubble Space Telescope Images
• Homogeneous photometry VII. Globular clusters in the Gaia era
• A New Catalog of Globular Clusters in the Milky Way
• Isochrones for Old (> 5 Gyr) Stars and Stellar Populations. I. Models for $-2.4\le$ [Fe/H] $\le +0.6$, $0.25\le Y\le 0.33$, and $-0.4\le$ [$\alpha$\Fe] $\le +0.4$
• The global mass functions of 35 Galactic globular clusters: I. Observational data and correlations with cluster parameters
• A family picture: tracing the dynamical path of the structural properties of multiple populations in globular clusters
• The surprising external upturn of the Blue Straggler radial distribution in M55
• Biases in the inferred mass-to-light ratio of globular clusters: no need for variations in the stellar mass function
• Direct $N$-body simulations of globular clusters - II. Palomar 4
• The Blue Straggler Star Population in NGC 1261: Evidence for a Post-Core-Collapse Bounce State
• An extremely low-mass He white dwarf orbiting the millisecond pulsar J1342+2822B in the globular cluster M3
• Discovery of a double Blue Straggler sequence in M15: new insight into the core-collapse process
• Radial Variation in the Stellar Mass Functions of Star Clusters
• Modelling the Observed Stellar Mass Function and its Radial Variation in Galactic Globular Clusters
• New Insight into the stellar mass function of Galactic globular clusters

Cited by in corpus (21)

• Evidence for a bottom-light initial mass function in massive star clusters
• Dynamical Evolution of Multiple-Population Globular Clusters
• Discovery of a double sequence of blue straggler stars in the core-collapsed globular cluster NGC 6256
• Expanding the time domain of multiple populations: evidences of nitrogen variations in the ~1.5 Gyr old star cluster NGC 1783
• Slowly cooling white dwarfs in M13 from stable hydrogen burning
• Empirical measurement of the dynamical ages of three globular clusters and some considerations on the use of the dynamical clock
• Structure and Internal Kinematics of Nine Inner Milky Way Globular Clusters
• Second generation star formation in globular clusters of different masses
• Internal kinematics and structure of the bulge globular cluster NGC 6569
• Slowly cooling white dwarfs in NGC 6752
• The structural properties of multiple populations in the dynamically young globular cluster NGC 2419
• Stellar collisions in globular clusters: Constraints on the initial mass function of the first generation of stars
• The $Hubble$ Missing Globular Cluster Survey. I. Survey overview and the first precise age estimate for ESO452-11 and 2MASS-GC01
• Millisecond Pulsars in Dense Star Clusters: Evolution, Scaling Relations, and the Galactic-Center Gamma-ray Excess
• An ongoing tidal capture in the Large Magellanic Cloud: the low-mass star cluster KMK88-10 captured by the massive globular cluster NGC 1835?
• The dynamical age of the LMC globular cluster NGC 1835 using the "dynamical clock"
• The dynamical state of the globular clusters Rup 106 and IC 4499
• Discovery of an extended Horizontal Branch in the Large Magellanic Cloud globular cluster NGC1835
• The "canonical" White Dwarf Cooling Sequence of M5
• Detection of a white dwarf orbiting a Carbon-Oxygen depleted blue straggler in 47 Tucanae
• Structural parameters, chronological age and dynamical age of the LMC globular cluster NGC 1754