Turning Back the Clock: Inferring the History of the Eight O'clock Arc - Astrophysics > Cosmology and Nongalactic AstrophysicsReportar como inadecuado

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Abstract: We present the results from an optical and near-infrared spectroscopic studyof the ultraviolet-luminous z = 2.73 galaxy, the 8 o-clock arc. Due togravitational lensing, this galaxy is magnified by a factor of > 10, allowingin-depth measurements which are usually unfeasible at such redshifts. In theoptical spectra, we measured the systemic redshift of the galaxy, z = 2.7322+- 0.0012, using stellar photospheric lines. This differs from the redshift ofabsorption lines in the interstellar medium, z = 2.7302 +- 0.0006, implyinggas outflows on the order of 160 km-s. With H and K-band near-infrared spectra,we have measured nebular emission lines of Halpha, Hbeta, Hgamma, N II and OIII, which have a redshift z = 2.7333 +- 0.0001, consistent with the derivedsystemic redshift. From the Balmer decrement, we measured the dust extinctionto be A 5500 = 1.17 +- 0.36 mag. Correcting Halpha for dust extinction and theassumed lensing factor, we measure a star-formation rate of ~ 270 Msol-yr,which is higher than ~ 85% of star-forming galaxies at z ~ 2-3. Usingcombinations of all detected emission lines, we find that the 8 o-clock arc hasa gas-phase metallicity of ~ 0.8 Zsol, showing that enrichment at high-redshiftis not rare, even in blue, star-forming galaxies. Studying spectra from two ofthe arc components separately, we find that one component dominates the dustextinction and star-formation rate, although the metallicities between the twocomponents are similar. We derive the mass via stellar population modeling, andfind that the arc has a total stellar mass of ~ 4 x 10^11 Msol, which falls onthe mass-metallicity relation at z ~ 2. Finally, we estimate the total gasmass, and find it to be only ~ 12% of the stellar mass, implying that the 8o-clock arc is likely nearing the end of a starburst.

Autor: Steven L. Finkelstein Texas AandM University, Casey Papovich Texas AandM University, Gregory Rudnick University of Kansas, Eiichi

Fuente: https://arxiv.org/

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