2006/01/01 by Anil C. Seth, Julianne J. Dalcanton, Paul W. Hodge +2 · 169 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Cluster (spacecraft) #Computer science #Enhanced Data Rates for GSM Evolution #Galaxies: Formation, Evolution, Phenomena #Gamma-ray bursts and supernovae #Operating system #Physics #Star (game theory) #Star cluster #Stars #Telecommunications #astro-ph
paper · pdf · doi:10.1086/508994
published in The Astronomical Journal 132(6), 2539-2555 (Institute of Physics) · Accepted for publication in the AJ
openalex publication_date 2006/01/01 · arxiv created 2006/09/11 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We find 9 nuclear cluster candidates in a sample of 14 edge-on, late-type galaxies observed with HST/ACS. These clusters have magnitudes (MI ~ -11) and sizes (reff ~ 3pc) similar to those found in previous studies of face-on, late-type spirals and dE galaxies. However, three of the nuclear clusters are significantly flattened and show evidence for multiple, coincident structural components. The elongations of these three clusters are aligned to within 10 degrees of the galaxies' major axes. Structurally, the flattened clusters are well fit by a combination of a spheroid and a disk or ring. The nuclear cluster disks/rings have F606W-F814W (~V-I) colors 0.3-0.6 magnitudes bluer than the spheroid components, suggesting that the stars in these components have ages < 1 Gyr. In NGC 4244, the nearest of the nuclear clusters, we further constrain the stellar populations and provide a lower limit on the dynamical mass via spectroscopy. We also present tentative evidence that another of the nuclear clusters (in NGC 4206) may also host a supermassive black hole. Based on our observational results we propose an in situ formation mechanism for nuclear clusters in which stars form episodically in compact nuclear disks, and then lose angular momentum or heat vertically to form an older spheroidal structure. We estimate the period between star formation episodes to be 0.5 Gyr and discuss possible mechanisms for tranforming the disk-like components into spheroids. We also note the connection between our objects and massive globular clusters (e.g. \ω Cen), UCDs, and SMBHs. (Abridged)