STELLAR POPULATIONS IN THE CENTRAL 0.5 pc OF THE GALAXY. II. THE INITIAL MASS FUNCTION
By Jessica R. Lu, T. Do, A. Ghez, Mark R. Morris, S. Yelda, K. Matthews. 2013
181 citations recorded by the source corpus.
The supermassive black hole at the center of the Milky Way plays host to a massive, young cluster that may have formed in one of the most inhospitable environments in the Galaxy. We present new measurements of the global properties of this cluster, including the initial mass function (IMF), age, and cluster mass. These results are based on Keck laser-guide-star adaptive optics observations used to identify the young stars and measure their Kp-band luminosity function as presented in Do et al. A Bayesian inference methodology is developed to simultaneously fit the global properties of the cluster utilizing the observations and extensive simulations of synthetic star clusters. We find that the slope of the mass function for this cluster is α = 1.7 ± 0.2, which is steeper than previously reported, but still flatter than the traditional Salpeter slope of 2.35. The age of the cluster is between 2.5 and 5.8 Myr with 95% confidence, which is a younger age than typically adopted but consistent within the uncertainties of past measurements. The exact age of the cluster is difficult to determine since our results show two distinct age solutions (3.9 Myr and 2.8 Myr) due to model degeneracies in the relative number of Wolf–Rayet and OB stars. The total cluster mass is between 14,000 and 37,000 M☉ above 1 M☉ and it is necessary to include multiple star systems in order to fit the observed luminosity function and the number of observed Wolf–Rayet stars. The new IMF slope measurement is now consistent with X-ray observations indicating a factor of 10 fewer X-ray emitting pre-main-sequence stars than expected when compared with a Salpeter IMF. The young cluster at the Galactic center is one of the few definitive examples of an IMF that deviates significantly from the near-universal IMFs found in the solar neighborhood.
Subfields: Astronomy and Astrophysics, Instrumentation
View Paper: https://www.semanticscholar.org/paper/2a55349d8a6e13a1aa1457246a4827dc91204aef
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Citations in the corpus
- Eccentric Black Hole Gravitational-wave Capture Sources in Galactic Nuclei: Distribution of Binary Parameters (2017, background): “Lu et al. (2013) infer that the mass function of these young stars is proportional to m−1.7±0.2, which implies that the number of massive stars is currently higher than that for a standard Salpeter mass function.”
- Greatly Enhanced Merger Rates of Compact-object Binaries in Non-spherical Nuclear Star Clusters (2017, methodology): “Merger rate estimates The total mass of the young stars currently observed in the inner ≈ 1pc region is a few times 104 M⊙ (Lu et al. 2013).”
- Global hierarchical collapse in molecular clouds. Towards a comprehensive scenario (2019, background): “…al. 2016), the apparent excess of massive stars in regions of extremely high SFRs, such as the Galactic Center cluster and the Arches cluster (e.g., Lu et al. 2013; Hosek et al. 2019), and the observed correlation between the mass of the most massive star in a cluster and the cluster mass (e.g.,…”
- The big problems in star formation: The star formation rate, stellar clustering, and the initial mass function (2014, background): “…based on resolved stellar populations are for the clusters forming near the Galactic center, including the Quintuplet cluster (Hußmann et al. 2012) and the nuclear star cluster (Lu et al. 2013) do appear to have IMFs where the highmass slope is somewhat flatter than the Salpeter value α = 2.35.”
- Merging Binaries in the Galactic Center: The eccentric Kozai-Lidov mechanism with stellar evolution (2016, background): “…may form rejuvenated products that appear young, which could explain the unexpected population of young stars in the GC (Ghez et al. 2005) and it may change the initial mass function (IMF) of the GC stellar population, which could explain the observed top-heavy IMF in the GC (Lu et al. 2013).”
- Assisted inspirals of stellar mass black holes embedded in AGN discs: solving the ‘final au problem’ (2016, background): “1.35−1.7 (Paumard et al. 2006; Alexander, Begelman & Armitage 2007; Lu et al. 2013) - or an even more radical IMF with dN/dM?”
- Stellar Dynamics and Stellar Phenomena Near a Massive Black Hole (2017, background): “…and appear to have been formed ∼ 6 Myr ago from a fragmenting, self-gravitating circumnuclear gas disk, with an unusually flat topheavy initial mass function, quite unlike that observed in star forming regions in the galactic bulk (Nayakshin & Sunyaev 2005; Bartko et al. 2010; Lu et al. 2013).”
- Surface brightness profile of the Milky Way’s nuclear star cluster (2014, background): “Of particular interest is that at least 50% of the stars that formed in the most recent star formation event (between 2−6 Ma ago, Lu et al. 2013) appear to have formed in situ in a disc around Sgr A* (Levin & Beloborodov 2003; Paumard et al. 2006; Lu et al. 2009).”
- STARS, GAS, AND DARK MATTER IN THE SOLAR NEIGHBORHOOD (2015, background): “…have been established are in massive elliptical galaxies (e.g., Conroy et al. 2013, but see Smith et al. 2015) and near the Galactic Center (e.g., Lu et al. 2013), although it should be noted that there is no evidence for deviations from a universal IMF in the old nuclear star cluster at the…”
- Nuclear star clusters (2009, methodology): “The total mass in young stars is between 14,000–37,000M (measured via the K-band luminosity function, Lu et al. 2013); the measurement of photometric masses of the O/B stars gives a consistent lower limit ≥ 12000M (Feldmeier-Krause et al. 2015).”