Spatial analysis of the Hα emission in the local star-forming UCM galaxies



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Pérez González, Pablo Guillermo and Zamorano Calvo, Jaime and Gallego Maestro, Jesús and Aragón Salamanca, A. and Gil de Paz, Armando (2003) Spatial analysis of the Hα emission in the local star-forming UCM galaxies. Astrophysical journal, 591 (2). pp. 827-842. ISSN 0004-637X

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We present a photometric study of the Halpha emission in the Universidad Complutense de Madrid (UCM) Survey galaxies. This work complements our previously published spectroscopic data. We study the location of the star-forming knots, their intensity and concentration, and the relationship of these properties with those of the host galaxy. We also estimate that the amount of Halpha emission that arises from the diffuse ionized gas is about 15% - 30% of the total Hα flux for a typical UCM galaxy. This percentage seems to be independent of the Hubble type. Conversely, we find that an "average'' UCM galaxy harbors a star formation event with 30% of its Hα luminosity arising from a nuclear component. The implications of these results for higher redshift studies are discussed, including the effects of galaxy size and the depth of the observations. A correlation between the star formation rate and the Balmer decrement is observed, but such correlation breaks down for large values of the extinction. Finally, we recalculate the Hα luminosity function and star formation rate density of the local universe using the new imaging data. Our results point out that, on average, spectroscopic observations detected about one-third of the total emission-line flux of a typical UCM galaxy. The new values obtained for the Halpha luminosity density and the star formation rate density of the local universe are 10^39.3±0.2 ergs s^-1 Mpc^-3 and ρ(SFR) = 0.016_-0.004^+0.007) M_⨀ yr-1 Mpc^-3 (H_0 = 50 km s^-1) Mpc^-1, Ω_M) = 1.0, Λ = 0). The corresponding values for the "concordance cosmology (H_0 = 70 km s^-1 Mpc^-1, Ω_M) = 0.3, Λ = 0.7) are 10^39.5±0.2 ergs s^-1 Mpc-3) and ρ_SFR = 0.029_-0.005^+0.008 M_⨀ yr^-1 Mpc^-3.

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© 2003. The American Astronomical Society.
P. G. P.-G. wishes to acknowledge the Spanish Ministry of Education and Culture for a Formación de Profesorado Universitario fellowship. A. A.-S. acknowledges generous financial support from the Royal Society. A. G. d. P. acknowledges financial support from NASA through a Long Term Space Astrophysics grant to B. F. Madore. Valuable discussion with Almudena Zurita is acknowledged. We are grateful to the anonymous referee for her/his helpful comments and suggestions. The present work was supported by the Spanish Programa Nacional de Astronomía y Astrofísica under grant AYA 2000-1790.

Uncontrolled Keywords:Diffuse ionized-gas; Nearby spiral galaxies; High-redshift galaxies; Madrid survey galaxies; Formation rate density; Digital sky survey; Universidad Complutense; Luminosity function; Line galaxies; Starburst galaxies
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:34282
Deposited On:12 Nov 2015 13:50
Last Modified:10 Dec 2018 15:05

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