Discovery of an extended ultraviolet disk in the nearby galaxy NGC 4625



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Gil de Paz, Armando and Madore, B. F. and Boissier, S. and Swaters, R. and Popescu, C. C. and Tuffs, R. J. and Sheth, K. and Kennicutt, R. C. and Bianchi, L. and Thilker, D. and Martin, D. C. (2005) Discovery of an extended ultraviolet disk in the nearby galaxy NGC 4625. Astrophysical journal, 627 (1). L29-L32. ISSN 0004-637X

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Recent far-UV (FUV) and near-UV (NUV) observations of the nearby galaxy NGC 4625 made by the Galaxy Evolution Explorer (GALEX) show the presence of an extended UV disk reaching to 4 times the optical radius of the galaxy. The UV-to-optical colors suggest that the bulk of the stars in the disk of NGC 4625 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 NGC 4625, the star formation in the extended disk is likely to be triggered by interaction with NGC 4618 and possibly also with the newly discovered galaxy NGC 4625A. 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 M_☉, with their Hα emission (when present) being dominated by ionization from single stars.

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© 2005. The American Astronomical Society. All rights reserved. GALEX is a NASA Small Explorer launched in 2003 April. We gratefully acknowledge NASA’s support for construction, operation, and scientific analysis of the GALEX mission. We thank Judith Cohen for kindly providing her Ha filter for COSMIC. R. C. K. is partially financed by NASA grant NAG5-8426.

Uncontrolled Keywords:Recent star-formation; Westerbork HI survey; B-type stars; Spiral galaxies; Surface photometry; Evolution-explorer; Irregular galaxies; Dwarf galaxies; Attenuation; Fluxes
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:35941
Deposited On:25 Feb 2016 16:23
Last Modified:10 Dec 2018 15:05

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