GALEX ultraviolet observations of the interacting galaxy NGC 4438 in the Virgo Cluster



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Gil de Paz, Armando and otros, ... (2005) GALEX ultraviolet observations of the interacting galaxy NGC 4438 in the Virgo Cluster. Astrophysical journal, 623 (1). L13-L16. ISSN 0004-637X

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We present GALEX near-ultraviolet (2310 Å) and far-ultraviolet (1530 Å) images of the interacting galaxy NGC 4438 (Arp 120) in the center of the Virgo Cluster. These images show an extended (20 kpc) tidal tail at the northwest edge of the galaxy that was previously undetected at other wavelengths; this tail is 15-25 kpc from NGC 4438's nucleus. Except for in the nucleus, the UV morphology of NGC 4438 is totally different from the Hα + [N II] morphology, which is more similar to the X-ray emission, confirming its gas cooling origin. We study the star formation history of NGC 4438 by combining spectrophotometric data in the UV-visible-near-IR wavelength range with population synthesis and galaxy evolution models. The data are consistent with a recent (~10 Myr), instantaneous burst of star formation in the newly discovered UV northwestern tail that is significantly younger than the age of the tidal interaction with NGC 4435, dated by dynamical models at ~100 Myr ago. Recent star formation events are also present at the edge of the northern arm and in the southern tail, while totally lacking in the other regions, which are dominated by the old stellar population that was perturbed during the dynamical interaction with NGC 4435. The contribution of this recent starburst to the total galaxy stellar mass is lower than 0.1%, an extremely low value for such a violent interaction. High-velocity, off-center tidal encounters such as that observed in Arp 120 are thus not sufficient to significantly increase the star formation activity of cluster galaxies.

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© 2005. The American Astronomical Society. All rights reserved. Artículo firmado por 29 autores. GALEX (Galaxy Evolution Explorer) is a NASA Small Explorer, launched in 2003 April. We gratefully acknowledge NASA’s support for the construction, operation, and science analysis of the GALEX mission, which was developed in cooperation with the Centre National d’Etudes Spatiales of France and the Korean Ministry of Science and Technology. We wish to thank the referee, V. Charmandaris, for his precious comments that helped improve the quality of the manuscript.

Uncontrolled Keywords:Star-formation; Surface photometry; Evolution-explorer; Disc galaxies; Tidal tails; Gas; Emission; History; Atlas
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:35943
Deposited On:25 Feb 2016 16:24
Last Modified:10 Dec 2018 15:05

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