2004/05/05 by A. Alonso‐Herrero, Almudena Alonso-Herrero, Toshinobu Takagi +9
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Cluster (spacecraft) #Dwarf galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy merger #Initial mass function #Intergalactic star #Physics #Spectral energy distribution #Star cluster #Star formation #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/422448
published as Astrophys.J. 612 (2004) 222-237 · Accepted for publication in ApJ. High quality versions of Figures 1 and 2 are available upon request
arxiv created 2004/05/05 · openalex publication_date 2004/09/01 · arxiv updated 2009/12/01 · openalex created_date 2020/11/23 · openalex updated_date 2026/08/06
We present Hubble Space Telescope ( HST ) NICMOS observations (1.1-2.2 μm) and 1.9-4.1 μm spectroscopy of the central region of the dwarf galaxy NGC 5253. The HST NICMOS observations reveal the presence of a nuclear double star cluster separated by ≃0 3-0 4, or 6-8 pc (for a distance d = 4.1 Mpc). The double star cluster, also a bright double source of Paα emission, appears to be coincident with the double radio nebula detected at 1.3 cm. The eastern near-infrared star cluster (C1) is identified with the youngest optical cluster, whereas the western star cluster (C2), although it is almost completely obscured in the optical, becomes the brightest star cluster in the central region of NGC 5253 at wavelengths longer than 2 μm. Both clusters are extremely young, with ages of approximately 3.5 Myr. C2 is more massive than C1 by a factor of 6-20 ( M C2 = 7.7 × 10 5 -2.6 × 10 6 M ☉ , for a Salpeter initial mass function [IMF] in the mass range 0.1-100 M ☉ ). Analysis of the circumnuclear spectrum excluding C1 and C2, as well as of a number of other near-infrared-selected clusters with a range of (young) ages, suggests that the star formation was triggered across the central regions of the galaxy. We have also modeled the nuclear UV to mid-infrared spectral energy distribution (SED) of NGC 5253 and found that the infrared part is well modeled by a highly obscured ( A V = 17 mag) young starburst with a stellar mass consistent with our photometric estimates for C1 and C2. The SED model predicts a moderately bright polycyclic aromatic hydrocarbon (PAH) feature at 3.3 μm that is not detected in our nuclear L -band spectrum. NGC 5253's low metallicity and a top-heavy IMF likely combine to suppress the 3.3 μm PAH emission that is commonly seen in more massive starburst systems.