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Title: Stellar metallicity of the extended disk and distance of the spiral galaxy NGC 3621

Low resolution (∼4.5 Å) ESO VLT/FORS spectra of blue supergiant stars are analyzed to determine stellar metallicities (based on elements such as iron, titanium, and magnesium) in the extended disk of the spiral galaxy, NGC 3621. Mildly subsolar metallicity (–0.30 dex) is found for the outer objects beyond 7 kpc, independent of galactocentric radius and compatible with the absence of a metallicity gradient, confirming the results of a recent investigation of interstellar medium H II region gas oxygen abundances. The stellar metallicities are slightly higher than those from the H II regions when based on measurements of the weak forbidden auroral oxygen line at 4363 Å but lower than the ones obtained with the R {sub 23} strong line method. It is shown that the present level of metallicity in the extended disk cannot be the result of chemical evolution over the age of the disk with the present rate of in situ star formation. Additional mechanisms must be involved. In addition to metallicity, stellar effective temperatures, gravities, interstellar reddening, and bolometric magnitudes are determined. After the application of individual reddening corrections for each target, the flux-weighted gravity-luminosity relationship of blue supergiant stars is used to obtain a distance modulusmore » of 29.07 ± 0.09 mag (distance D = 6.52 ± 0.28 Mpc). This new distance is discussed in relation to Cepheid and the tip of the red giant branch distances.« less
Authors:
; ;  [1] ; ;  [2]
  1. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
  2. Institute for Astro- and Particle Physics, University of Innsbruck, Technikerstr. 25/8, A-6020 Innsbruck (Austria)
Publication Date:
OSTI Identifier:
22356671
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 788; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; BOLOMETERS; DISTANCE; EVOLUTION; GALAXIES; GRAVITATION; IRON; LUMINOSITY; MAGNESIUM; METALLICITY; OXYGEN; RED SHIFT; RESOLUTION; SPECTRA; SUPERGIANT STARS; TITANIUM