Surface brightness profiles and structural parameters for 53 rich stellar clusters in the Large Magellanic Cloud

By A. Mackey, G. G. IoA, Cambridge, UK.. 2002

237 citations recorded by the source corpus.

We have compiled a pseudo-snapshot data set of two-colour observations from the Hubble Space Telescope archive for a sample of 53 rich LMC clusters with ages of 106–1010 yr. We present surface brightness profiles for the entire sample, and derive structural parameters for each cluster, including core radii, and luminosity and mass estimates. Because we expect the results presented here to form the basis for several further projects, we describe in detail the data reduction and surface brightness profile construction processes, and compare our results with those of previous ground-based studies. The surface brightness profiles show a large amount of detail, including irregularities in the profiles of young clusters (such as bumps, dips and sharp shoulders), and evidence for both double clusters and post-core-collapse (PCC) clusters. In particular, we find power-law profiles in the inner regions of several candidate PCC clusters, with slopes of approximately −0.7, but showing considerable variation. We estimate that 20 ± 7 per cent of the old cluster population of the Large Magellanic Cloud (LMC) has entered PCC evolution, a similar fraction to that for the Galactic globular cluster system. In addition, we examine the profile of R136 in detail and show that it is probably not a PCC cluster. We also observe a trend in core radius with age that has been discovered and discussed in several previous publications by different authors. Our diagram has better resolution, however, and appears to show a bifurcation at several hundred Myr. We argue that this observed relationship reflects true physical evolution in LMC clusters, with some experiencing small-scale core expansion owing to mass loss, and others large-scale expansion owing to some unidentified characteristic or physical process.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/0dc8aadd91911ddac83863d1eeac2d67bd59eaf3

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Citations in the corpus

A double main-sequence turn-off in the rich star cluster NGC 1846 in the Large Magellanic Cloud (2007, methodology): “We determined the cluster centre using a surfacebrightness testing algorithm very similar to that described by Mackey & Gilmore (2003), with the result that the cluster centre lies within ≈ 20 pixels (1′′) of the pixel coordinates (xc, yc) = (2120, 3150).”
Young Massive Star Clusters (2010, methodology): “In §2 we discussed the remarkable increase in the observed core radii of clusters with ages 1–50Myr (Mackey & Gilmore 2003, Bastian et al. 2008).”
A general catalogue of extended objects in the Magellanic System (2008, background): “…proximity, chemical compositions, age distributions, star cluster structural properties and related dynamical evolution, and as two close-by interacting galaxies (e.g. Westerlund 1990, Da Costa 1991, Piatti et al. 2002, Mackey & Gilmore 2003, Dieball, Müller & Grebel 2002, Bekki & Chiba 2007).”
Comparing the properties of local globular cluster systems: implications for the formation of the Galactic halo (2004, methodology): “Any hypothetical merged external cluster system (such as that discussed in the previous Section) should therefore possess a characteristic distribution of core radii, matching those presented by Mackey & Gilmore (2003c) for the individual external galaxies.”
Resolved Massive Star Clusters in the Milky Way and Its Satellites: Brightness Profiles and a Catalog of Fundamental Parameters (2005, methodology): “12, however, we see that the SB profile from Mackey & Gilmore (2003a) extends only toR≃ 70′′ = 17 pc in this case—just barely outside the constant-density core region of NGC 2121—while our additional groundbased data reach toR≃ 100′′ ≃ 24 pc and are critical to accurately constraining any model fit.”
A complete N-body model of the old open cluster M67 (2005, methodology): “Then the magnitude and position information is passed through the pipeline described by Mackey & Gilmore (2003) in their analysis of Large Magellanic Cloud (LMC) clusters to give a projected surface density profile.”
A Universal Stellar Initial Mass Function? A critical look at variations in extreme environments (2010, methodology): “Many young clusters are currently expanding (Mackey & Gilmore 2003; Bastian et al. 2008), and possibly formed through the merger of several smaller sub-clusters.”
The structure and environment of young stellar clusters in spiral galaxies (2003, methodology): “Since FWHM is roughly equivalent to 2×rc, it is interesting to note that Mackey & Gilmore (2003) found a strong correlation between core radius and age for clusters in the LMC (confirming earlier results by Elson et al. 1989).”
The R136 star cluster dissected with Hubble Space Telescope/STIS. I. Far-ultraviolet spectroscopic census and the origin of He II λ1640 in young star clusters (2016, background): “Indeed, the two components contribute equally to the surface brightness at a radius of ∼5 pc from R136a1 according to Mackey & Gilmore (2003).”
The Initial Mass Function of the Massive Star-forming Region NGC 3603 from Near-Infrared Adaptive Optics Observations (2007, unknown): “Mackey & Gilmore (2003) derive 3×104 M⊙ pc−3 within r ≤ 0.32 pc.”
Gas expulsion and the destruction of massive young clusters (2006, unknown): “14; Mackey & Gilmore 2003).”
Evidence for the Strong Effect of Gas Removal on the Internal Dynamics of Young Stellar Clusters (2006, background): “Similar surface brightness profiles with an excess of light at large radii are seen in young LMC clusters: see EFF and Elson (1991) in which many clusters clearly show these unusual profiles, and also Mackey & Gilmore (2003) – in particular for R136.”