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Discovery of an extended ultraviolet disk in the nearby galaxy NGC4625

A. Gil de Paz·B. F. Madore·S. Boissier·R. Swaters·C. C. Popescu·R. J. Tuffs·K. Sheth·R. C. Kennicutt·L. Bianchi·D. Thilker·D. C. Martin
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Abstract

Recent far-UV (FUV) and near-UV (NUV) observations of the nearby galaxy NGC4625 made by the Galaxy Evolution Explorer (GALEX) show the presence of an extended UV disk reaching 4 times the optical radius of the galaxy. The UV-to-optical colors suggest that the bulk of the stars in the disk of NGC4625 are currently being formed, providing a unique opportunity to study today the physics of star formation under conditions similar to those when the normal disks of spiral galaxies like the Milky Way first formed. In the case of NGC4625, the star formation in the extended disk is likely to be triggered by interaction with NGC4618 and possibly also with the newly discovered galaxy NGC4625A. The positions of the FUV complexes in the extended disk coincide with peaks in the H I distribution. The masses of these complexes are in the range 10^3-10^4 Msun with their Halpha emission (when present) being dominated by ionization from single stars.

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A. Gil de Paz, B. F. Madore, S. Boissier, R. Swaters, C. C. Popescu, R. J. Tuffs, K. Sheth, R. C. Kennicutt, L. Bianchi, D. Thilker, D. C. Martin. 2005-06-15. Discovery of an extended ultraviolet disk in the nearby galaxy NGC4625. https://doi.org/10.1086/432054

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