Thursday June 28th, 2012

Gas-phase metallicity of 27 galaxies at intermediate redshift

Authors: L. Morelli, V. Calvi, A. Cardullo, A. Pizzella, E. M. Corsini, E. Dalla Bontà
(Submitted on 27 Jun 2012)

Abstract: The purpose of this work is to make available new gas-phase oxygen abundance measurements for a serendipitous sample of 27 galaxies with redshift 0.35\leqz\leq0.52. We measured the equivalent widths of the [O
II]{\lambda}3727, H{\beta}, and [O III]{\lambda}{\lambda}4959, 5007 emission lines observed in the galaxy spectra obtained with the Visible Multi-Object Spectrograph mounted at the Very Large Telescope. For each galaxy, we derived the metallicity-sensitive emission lines ratio R23, ionization-sensitive emission lines ratio O32, and gas-phase oxygen abundance 12+log(O/H). The values of gas-phase oxygen abundance 12+log(O/H) we obtained for the sample galaxies are consistent with previous findings for galaxies at intermediate redshift.

Comments: 5 pages, 3 postscript figures and 3 tables. A&A in press
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Cite as: arXiv:1206.6300v1 [astro-ph.CO]

An Empirical Relation between Sodium Absorption and Dust Extinction

Authors: Dovi Poznanski, J. Xavier Prochaska, Joshua S. Bloom
(Submitted on 26 Jun 2012)

Abstract: Dust extinction and reddening are ubiquitous in astronomical observations and are often a major source of systematic uncertainty. We present here a study of the correlation between extinction in the Milky Way and the equivalent width of the NaI D absorption doublet. Our sample includes more than 100 high resolution spectra from the KECK telescopes and nearly a million low resolution spectra from the Sloan Digital Sky Survey (SDSS). We measure the correlation to unprecedented precision, constrain its shape, and derive an empirical relation between these quantities with a dispersion of order 0.15 magnitude in E(B-V). From the shape of the curve of growth we further show that a typical sight line through the Galaxy crosses about three dust clouds. We provide a brief guide on how to best estimate extinction to extragalactic sources such as supernovae, using the NaI D absorption feature, under a variety of circumstances.

Comments: Submitted to MNRAS
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA)
Cite as: arXiv:1206.6107v1 [astro-ph.IM]
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