Star Cluster Demographics. I. A General Framework and Application to the Antennae Galaxies

By B. Whitmore, R. Chandar, S. M. Fall. 2006

137 citations recorded by the source corpus.

We present a framework for understanding the demographics of star cluster systems and develop a toy model that incorporates a universal initial power-law mass function, selected formation histories, selected disruption laws, and a convolution with common artifacts and selection effects found in observational data. A wide variety of observations can be explained by this simple model, including the observed correlation between the brightest young cluster in a galaxy and the total number of young clusters. The model confirms that this can be understood as a statistical size-of-sample effect rather than a difference in the physical process responsible for the formation of the clusters, suggesting that active mergers have the brightest clusters simply because they have the most clusters. A comparison is made of different cluster disruption laws, and it is shown that the break in the dN/dτ diagram used to determine the parameters in the Boutloukos & Lamers model may be produced by incompleteness near the break point. A model of the Antennae galaxies is developed and compared with the observational data; this extends the mass-age range for cluster comparison over previous studies. An important component of our model is the use of a "two-stage" disruption process, with a very high "infant mortality" rate for the clusters with ages less than ∼108 yr (i.e., roughly 80%- 90% are lost each factor of 10 in time, τ, independent of mass), and two-body relaxation, which becomes the dominant disruption mechanism at older ages, preferentially removing the lower mass clusters. Hence, in our model, stars from the dissolved clusters form the field population. We note that a 90% infant mortality rate for each factor of 10 in τ (i.e., dN/dτ ∝ τ-1) is consistent with all measured young cluster populations, including those in the Antennae, the Small Magellanic Cloud, and the Milky Way. In fact, the population of clusters in the Antennae can be viewed as a scaled-up version of the Milky Way in many respects, with a scale factor of roughly 1000 times the Lada & Lada sample of embedded star clusters in the local Milky Way. We find no evidence for a truncation of the Antennae cluster mass function at the high-mass end.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/2bf6a31c09cd647ceffabc5e168c805e8ca3bcdb

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Citations in the corpus

Probing the role of the galactic environment in the formation of stellar clusters, using M83 as a test bench (2015, unknown): “…of an initial cluster mass and luminosity function (ICMF and ICLF, respectively) being described with good approximation by a single power-law slope of index close to −2 (e.g., ⋆ E-mail: adamo@astro.su.se Bik et al. 2003; de Grijs et al. 2003; Whitmore et al. 2007, 2014; Chandar et al. 2014).”
THE LONG-TERM EVOLUTION OF THE GALACTIC DISK TRACED BY DISSOLVING STAR CLUSTERS (2010, background): “…masses significantly larger than the typical Milky Way cluster) suggests that the survival fraction is nearly independent of mass until two-body relaxation becomes the dominant destruction process at times 100 Myr after cluster formation (Fall et al. 2005, 2009; Fall 2006; Whitmore et al. 2007).”
RADIATION PRESSURE FROM MASSIVE STAR CLUSTERS AS A LAUNCHING MECHANISM FOR SUPER-GALACTIC WINDS (2010, background): “Numerous observations of expanding bubbles in the Milky Way (Murray & Rahman 2010) and in nearby galaxies (Whitmore et al. 2007; Gilbert & Graham 2007) demonstrate that such outflows start before any supernovae occur.”
The mass function of young star clusters in spiral galaxies (2008, background): “…linear relation between the luminosity of the brightest cluster in a galaxy and the total number of clusters, as expected if luminosities are drawn at random from a power-law distribution with slope≈−2 (Billett et al. 2002; Larsen 2002; Weidner et al. 2004; Whitmore 2003; Whitmore et al. 2007).”
Ionized gas outflows and global kinematics of low-z luminous star-forming galaxies (2014, background): “In addition to the nuclear starburst, many interacting and merger galaxies exhibit extranuclear knots of star formation, which are more massive than star clusters in normal spiral galaxies (e.g., Super Star Clusters, SSC; Whitmore et al. 2007; Miralles-Caballero et al. 2012).”
THE DRIVING MECHANISM OF STARBURSTS IN GALAXY MERGERS (2010, background): “…and general observational fact about interacting galaxies is that their SF proceeds in giant molecular clouds and star clusters, which can be 10–100 times more massive than in normal spiral galaxies, leading in particular to the formation of super star clusters (SSCs; Whitmore et al. 2007).”