The deepest Hubble Space Telescope far-ultraviolet observations in the Large Magellanic Cloud |
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Authors: | Elhanan Almoznino Noah Brosch Michael Shara David Zurek |
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Affiliation: | The Wise Observatory, and the School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel;Department of Astrophysics, American Museum of Natural History, New York, NY 10024, USA |
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Abstract: | We present a new analysis of the deepest pure-ultraviolet (UV) observations with the highest angular resolution ever performed. A set of 12 exposures with the Hubble Space Telescope ( HST ) WFPC2 and F160BW filter obtained in parallel observing mode, which cover ∼12 arcmin2 in the Large Magellanic Cloud (LMC), north of the bar and in the 'general field' region of the LMC, contain stars with far-UV monochromatic magnitudes as faint as 22 mag. The 198 detected UV sources represent an accumulated exposure of ≥ 2 × 104 s and reveal stars as faint as m UV≃ 20 mag . We combine these observations with deep UBVI charge-coupled device (CCD) imaging of the same region reaching as faint as V ≃ 26 mag , and reselect probable optical counterparts for the UV sources. After a two-stage search-and-analysis process, we detect robust counterparts for 129 stars. These are mostly upper main-sequence stars, from early B to early A spectral classes, with several F stars. We point out the lack of blue supergiants, which could have been easily detected in our survey. We measure a foreground extinction E ( B − V ) ≃ 0.08 mag by Galactic dust and a surface density of star formation rate twice the average Galactic value. These observations indicate that relatively recent star formation took place even off the bar of the LMC. |
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Keywords: | stars: formation galaxies: individual: Large Magellanic Cloud galaxies: irregular galaxies: stellar content |
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