Tuesday 3/26/13

Just one paper today, and not even that long (ApJ letter). Anyways, it’s by Zahid et al., on the evolution of the galaxy mass-metallicity relationship with redshift. They have 3 redshift bins under z=1 that they have some confidence in (but yes, using just the R23 metallicity indicator). And there is clear evolution seen with redshift. One interesting thing that hasn’t made it completely to my radar before this paper is the idea of metallicity ‘saturation’ of massive galaxies at low redshifts. Anyways, easy to look at the two main figures and the conclusions if you’re interested! Alison

The Chemical Evolution of Star-Forming Galaxies Over the Last 11 Billion Years

Jabran Zahid (IfA, University of Hawaii), Margaret Geller (SAO), Lisa Kewley (ANU), Ho Seong Hwang (SAO), Daniel Fabricant (SAO), Michael Kurtz(SAO)
(Submitted on 24 Mar 2013)

We measure the stellar mass-metallicity relation at five epochs ranging to z~2.3. We quantify, for the first time, evolution in the shape of the mass-metallicity relation as a function of redshift; the mass-metallicity relation flattens at late times. There is an empirical upper limit to the gas-phase oxygen abundance in star-forming galaxies that is independent of redshift. From examination of the mass-metallicity relation and its observed scatter we show that the flattening at late times is a consequence of evolution in the stellar mass where galaxies enrich to this empirical upper metallicity limit; there is also evolution in the fraction of galaxies at a fixed stellar mass that enrich to this limit. The stellar mass where metallicities begin to saturate is ~0.7 dex smaller in the local universe than it is at z~0.8. These observations provide a benchmark for theoretical and observational studies of the chemical evolution of star-forming galaxies.

Comments: 6 pages, 2 figures. Submitted to ApJ Letters. Comments are welcome
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Cite as: arXiv:1303.5987 [astro-ph.CO]
(or arXiv:1303.5987v1 [astro-ph.CO] for this version)
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