Day 229

Tuesday.  Not doing a good job reading, but did finish Subaru reduction up to SCAMP astrometry.  Had a cake made by Sandra this morning, was Philip's birthday yesterday.  Edo is on a diet, and didn't have any cake.  Prepare for Journal Club!


Wednesday.  Journal Club reviewed HOD, but I'm not sure if Cris and I did a good job.  Cris seemed somewhat sad yesterday.  Gah!  I missed Cris' email last night!


1203.5777
What are special about Ground-level events?  Flares, CMEs, active regions and magnetic field connection
Nitta, Liu, DeRosa, Nightingale


Ground level events (GLEs): associated with CME and solar flares; occupy high-energy end of gradual solar energetic particle events.  Special conditions that produce these rare events still not understood.  Identification?  Eruptions and active regions (ARs): magnitudes of the CMEs and flares nor the complexities give sufficient conditions for GLEs.  Importance of B-field connection with AR?  50%, but onset time not correlated to the connection.  GLE onset behavior may be largely determined by when and where the CME-driven shock develops.  Find GLE has no solar-image evidence of onset, but STEREO and SDO may change that.


* would like a better description of the event that they're talking about.


1203.5785
Estimating CDM particle trajectories in the mildly non-linear regime of structure formation.  Implications for the density field in real and redshift space
Tassev, Zaldarriaga


Approximations for the CDM particle trajectories starting from Lagrangian perturbation theory: better approximation for the density in real and redshift space, as well as momentum density.  Gives good correlation with the NL density down to scales twice smaller than the NL scale; 6x smaller than the corresponding scale obtained using linear theory.  Speed-up of >10x in scanning of cosmo parameter space with N-body simulations for BAO.  Application: BAO peak reconstruction, building mock galaxy catalogs, momentum field reconstruction.


1203.5787
Present-day cosmic abundances.  A comprehensive study of nearby early B-type stars and implications for stellar and Galactic evolution and interstellar dust models
Nieva, Przbilla


Study early B-type stars in OB associations near solar neighborhood, derive present-day abundances for a few chemical elements with high-res spectra.  Derive atmospheric parameters (multiple ionization equilibria and hydrogen Balmer lines).  Results: constraint T_eff and log(g).  Determine absolute values for metal abundances to better than 25% uncertainty; establish present-day cosmic abundance standard.  (i) resolves discrepancy between a chemical homogeneous local gas-phase ISM and a chemically inhomogeneous young stellar component, (ii) facilitate the amount of heavy elements locked up in the interstellar dust to be constrained precisely (C dust destroyed but not silicates, graphite minority species), (iii) mixing of CNO-burning products follows tightly the predicted nuclear path, (iv) provide present day reference points for Galactic chemical evolution (v) imply sun has migrated outwards from the inner galactic disk by about 5-6 kpc from Galactic center (cancels effects of galactic chemical evolution and abundance gradients), signature of the Sun's origin left in the C/O ratio.