Went to Düsseldorf to pick up my sister, eat sushi, get a haircut with my sister, and do some Japanese grocery shopping; took the wrong train and ended up in Solingen on the way back! Pretty tired, Yoko fell asleep immediately. I can hear the upstairs neighbor playing music... they must be getting back at me for playing my Yoga video very loud this morning. (maybe)
1201.3919
A survey of MgII absorption at 2<z<6 with Magellan / FIRE: I: sample and evolution of the MgII frequency
Matejek, Simcoe
First systematic survey for Mg II quasar absorption lines at z>2.5. 111 Mg II systems over a path covering 1.9<z<6.3; 5 systems have z>5 with maximum at z=5.33 (the most distant Mg II system currently known). Comoving line density for weak systems has no evolution from z=0.4 to z=5.5; for stronger systems, increases 3 fold until z~3 before declining again toward higher redshifts. The EW distribution which fits and exponential, reflects this evolution by flattening as z->3 before steepening again. Rise and fall of the strong absorbers suggests a connection to the SFR density, as though they trace galactic outflows or other byproducts of SF. The weaker systems lack of evolution does not fit within this interpretation, but may be reproduced by extrapolating low z scaling relations between host galaxy luminosity and absorbing halo radius to earlier epochs. For the weak systems, luminosity-scaled models match the evolution better than similar models based on Mg II occupation of evolving CDM halo masses, which greatly underpredict dN/dz at early times unless the absorption efficiency of small haloes is significantly larger at early times. Taken together, these observations suggest that the general structure of Mg II bearing haloes was put into place early in the process of galaxy assembly. Except for a transient appearance of stronger systems near the peak epoch of cosmic star foramtion, the basic properties of Mg II absorbers have evolved fairly little even as the (presumably) associated galaxy populations grew substantially in stellar mass and half light radius.
* Mg II absorption lines: provide a luminosity-independent method for studying the distribution of gas in galactic haloes. Previous studies focused on z<2.3. Two theories: (1) Mg II traces cool clumps embedded in heated outflows from galaxies with high sSFR. (2) distribution of Mg II may reflect gravitational and gas accretion processes, as from dynamical mergers of cold accretion filaments. Anti-correlation between Mg II width and galaxy halo mass: individual Mg II systems are not virialized, and Mg II systems trace SF driven winds. Mg II correlate to galaxy color (to blue). But some MgII systems found around eraly-type systems.
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