[seminar] Astro Journal Club on 24 February

[Oskari Miettinen]

Dear all,

Our Astro Journal Club will be held again on Wednesday at 3:00 pm in the
seminar room F-201 of the Physics Department. This time we will discuss
about a curious, z=2.304 Lyman-alpha absorber seen towards the quasar
Q0453-423.

Presenter: Monika Herceg
Paper title: A high-redshift quasar absorber without CIV - a galactic
outflow caught in the act?
Authors: Fox, A., and Richter, P.

Summary:
We present a detailed analysis of a very unusual sub-damped Lyman alpha
(sub-DLA) system at redshift z=2.304 towards the quasar Q0453-423, based
on high signal-to-noise (S/N), high-resolution spectral data obtained with
VLT/UVES. With a neutral hydrogen column density of log N(HI)=19.23 and a
metallicity of -1.61 as indicated by [OI/HI] the sub-DLA mimics the
properties of many other optically thick absorbers at this redshift. A
very unusual feature of this system is, however, the lack of any CIV
absorption at the redshift of the neutral hydrogen absorption, although
the relevant spectral region is free of line blends and has very high S/N.
Instead, we find high-ion absorption from CIV and OVI in another metal
absorber at a velocity more than 220km/s redwards of the neutral gas
component. We explore the physical conditions in the two different
absorption systems using Cloudy photoionisation models. We find that the
weakly ionised absorber is dense and metal-poor while the highly ionised
system is thin and more metal-rich. The absorber pair towards Q0453-423
mimics the expected features of a galactic outflow with highly ionised
material that moves away with high radial velocities from a
(proto)galactic gas disk in which star-formation takes place. We discuss
our findings in the context of CIV absorption line statistics at high
redshift and compare our results to recent galactic-wind and outflow
models.

Link to the paper: http://adsabs.harvard.edu/abs/2016arXiv160205458F

Hope to see you all on Wednesday!

Cheers,
Oskari