The Luminosity Function of Star Clusters in Spiral Galaxies

By S. Larsen. 2002

176 citations recorded by the source corpus.

Star clusters in six nearby spiral galaxies are examined using archive images from the Wide Field Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope (HST). The galaxies have previously been studied from the ground and some of them are known to possess rich populations of "young massive clusters." Comparison with the HST images indicates a success rate of ∼75% for the ground-based cluster detections, with typical contaminants being blends or loose groupings of several stars in crowded regions. The luminosity functions (LFs) of cluster candidates identified on the HST images are analyzed and compared with existing data for the Milky Way and the LMC. The LFs are well approximated by power laws of the form dN(L)/dL ∝ Lα, with slopes in the range -2.4 ≲ α≲-2.0. The steeper slopes tend to be found among fits covering brighter magnitude intervals, although direct hints of a variation in the LF slope with magnitude are seen only at low significance in two galaxies. The surface density of star clusters at a reference magnitude of MV = -8, Σ, scales with the mean star formation rate (SFR) per unit area, ΣSFR. Assuming that the LF can be generally expressed as dN(L)/dL = cAΣLα, where A is the galaxy area, γ ∼ 1.0–1.4, α = -2.4, and the normalization constant c is determined from the WFPC2 data analyzed here, the maximum cluster luminosity expected in a galaxy from random sampling of the LF is estimated as a function of ΣSFR and A. The predictions agree well with existing observations of galaxies spanning a wide range of ΣSFR values, suggesting that sampling statistics play an important role in determining the maximum observed luminosities of star clusters in galaxies.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/9fd909363c0bdc7f792ecb5687b32b93da670bce

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Citations in the corpus

Cluster Mass Functions in the Large and Small Magellanic Clouds: Fading and Size-of-Sample Effects (2003, methodology): “…between N and Mmax was observed directly by Whitmore (2003) using a large number of galaxy surveys, and it was used by Billett et al. (2002) and Larsen (2002) to help explain the Larsen & Richtler (2000) correlation between the fraction of star formation in the form of clusters and the star…”
The structure and environment of young stellar clusters in spiral galaxies (2003, background): “The original sample of 21 nearby spirals analysed in Papers I–III has since been augmented by an additional handful of galaxies observed with the 3-m Shane telescope at Lick Observatory (see Larsen 2002).”
Probing the role of the galactic environment in the formation of stellar clusters, using M83 as a test bench (2015, methodology): “More evidence of the role played by the galactic environment on the properties of their cluster population has indirectly been suggested by the so called TL(U) versus SFR relation (Larsen 2002; Adamo et al. 2011).”
The mass function of young star clusters in spiral galaxies (2008, methodology): “…luminosities to masses via age-dependent mass-to-light ratios, so it is not surprising that more information is available about LFs than MFs. Larsen (2002) fitted power-laws dN/dL ∝ LαL to the LFs of young clusters in 6 spiral galaxies with HST/WFPC2 imaging, and found slopes in the range…”
The big problems in star formation: The star formation rate, stellar clustering, and the initial mass function (2014, background): “…is welldescribed by a power law dN/dM ∝ M−β with β ≈ 2 over most of its range; the uncertainty on the value of β is roughly 0.1−0.2 (Williams & McKee 1997; Zhang & Fall 1999; Larsen 2002; Bik et al. 2003; de Grijs et al. 2003a; Goddard et al. 2010; Bastian et al. 2011; Fall & Chandar 2012).”
A Hubble Space Telescope Census of Nuclear Star Clusters in Late-Type Spiral Galaxies. II. Cluster Sizes and Structural Parameter Correlations (2003, background): “…of NCs are in the range 106–107 L (Paper I), which makes them much brighter than average stellar clusters in the disks of nearby spiral galaxies (Larsen 2002) and comparable to young ‘‘super star clusters’’ in luminous merger pairs (see, e.g., Whitmore et al. 1999) or circumnuclear…”
Star Cluster Demographics. I. A General Framework and Application to the Antennae Galaxies (2006, background): “One example of a potential anomaly, the very bright cluster in NGC 1569, has already been discussed extensively in the literature (e.g.,Whitmore 2003; Billet et al. 2002; Larsen 2002).”
Stellar Populations in the Nuclei of Late-Type Spiral Galaxies (2006, background): “…the upper limit of the cluster mass distribution depends on the star formation rate in the sense that higher star formation rates lead to the formation of a larger number of clusters, which then sample further into the high-mass tail of the cluster mass distribution function (Larsen 2002).”
Formation of Globular Clusters in Hierarchical Cosmology (2003, background): “A similar correlation exists for the observed nearby galaxies (Larsen 2002).”
The ACS Virgo Cluster Survey. XII. The Luminosity Function of Globular Clusters in Early-Type Galaxies (2007, background): “…(if more clusters are formed, it is statistically more likely to achieve higher masses by random sampling of an underlying mass distribution that might still be universal) or indicative of a real, physical limit to the initial cluster mass function (Larsen 2002; Weidner, Kroupa & Larsen 2004).”
Implications for the formation of star clusters from extragalactic star formation rates (2004, methodology): “The age spread between 6.0 and 8.0 (in logarithmic units) is used to estimate the mass errors for the individual clusters in the Larsen data set plotted in Fig.”
A Study of Cygnus OB2: Pointing the Way toward Finding Our Galaxy’s Super-Star Clusters (2003, methodology): “Perhaps for this reason, it has been assumed that our Galaxy’s cluster luminosity function steepened over the range 11 MV 8 (Larsen 2002).”
On the star formation rate – brightest cluster relation: estimating the peak star formation rate in post-merger galaxies (2008, methodology): “1 (e.g. Billett, Hunter & Elmegreen 2002; Larsen 2002), a fact which led Weidner et al. (2004) not to include them in their fit to the data (shown as a dashed line in Fig.”
An analytical description of the disruption of star clusters in tidal fields with an application to Galactic open clusters (2005, background): “Suppose that the CIMF is a power law with a slope −α = −2 (Zhang & Fall 1999; Larsen 2002; Bik et al. 2003; de Grijs et al. 2003) in the range of Mmin < Mcl < Mmax, Mmin ≈ 10 2M⊙ and Mmax ≈ 10 7M⊙, then the number of clusters with initial mass Mi formed at time t will be N(Mi, t) = S(t) ( Mi…”
Galactic-Field Initial Mass Functions of Massive Stars (2003, background): “Furthermore, fieldðm > 1 M Þ must vary from galaxy to galaxy, because the star-cluster MF varies with the star formation rate (SFR) in the sense of a correlation between Mecl;max and SFR (Larsen 2002).”
THE ANTENNAE GALAXIES (NGC 4038/4039) REVISITED: ADVANCED CAMERA FOR SURVEYS AND NICMOS OBSERVATIONS OF A PROTOTYPICAL MERGER (2010, result): “A version of this diagram for cluster populations in entire galaxies was first shown – 23 – by Whitmore (2003) and has been subsequently studied by several other authors (Larsen 2002; WCF07; Bastian 2008; Larsen 2009).”