[seminar] Astro Journal Club on 27 January

[Oskari Miettinen]

Dear all,

Our Astro Journal Club will be held again on Wednesday at 3:00 pm (sharp)
in the seminar room F-201 of the Physics Department. This time we will
discuss about the metallicity of star-forming galaxies.

Presenter: Ivana Barišić
Paper title: Rest-UV Absorption Lines as Metallicity Estimator: the Metal
Content of Star-Forming Galaxies at z~5
Authors: Faisst, A. L., Capak, P. L., Davidzon, I., et al.

Summary:
We measure a relation between the depth of four prominent rest-UV
absorption complexes and metallicity for local galaxies and verify it up
to z~3. We then apply this relation to a sample of 224 galaxies at 3.5 < z
< 6.0 (<z> = 4.8) in COSMOS, for which unique UV spectra from DEIMOS and
accurate stellar masses from SPLASH are available. The average galaxy
population at z~5 and log(M/Msun) > 9 is characterized by 0.3-0.4 dex (in
units of 12+log(O/H)) lower metallicities than at z~2, but comparable to
z~3.5. We find galaxies with weak/no Ly-alpha emission to have
metallicities comparable to z~2 galaxies and therefore may represent an
evolved sub-population of z~5 galaxies. We find a correlation between
metallicity and dust in good agreement with local galaxies and an inverse
trend between metallicity and star-formation rate (SFR) consistent with
observations at z~2. The relation between stellar mass and metallicity (MZ
relation) is similar to z~3.5, however, there are indications of it being
slightly shallower, in particular for the young, Ly-alpha emitting
galaxies. We show that, within a "bathtub" approach, a shallower MZ
relation is expected in the case of a fast (exponential) build-up of
stellar mass with an e-folding time of 100-200 Myr. Due to this fast
evolution, the process of dust production and metal enrichment as a
function of mass could be more stochastic in the first billion years of
galaxy formation compared to later times.

Link to the paper: http://adsabs.harvard.edu/abs/2015arXiv151200018F

Hope to see you all on Wednesday!

Cheers,
Oskari