Day 320

Monday.

1210.6980
Finding {\eta} Car analogs in nearby galaxies using Spitzer: I. candidate selection
Khan, Stanek, Kochanek

Late-stage evolution of the most massive stars is controlled by the effects of mass loss, which may be dominated by poorly understood eruptive mass ejections.  Understanding this population is challenging, because no other examples other than eta Car have been clearly identified in MW or other galaxies.  User Spitzer image of 7 nearby (<= 4 Mpc) galaxies to search for such analogs.  Find 34 candidates with a flat or rising MIR SED distribution towards longer MIR wavelengths that emit 1e5 Lsun in the IRAC bands (3.6 to 8.0 um) and are not known to be BG sources.  Based on expected number of BG sources, expect that follow-up observations will show that most of these candidates are not dust enshrouded massive stars, with an expectation of only 6 pm 6 surviving candidates.  Since we can detect true analogs of eta Car for roughly 200 years post-eruption, this implies that the rate of eruptions like eta Car is less than the ccSN [?] rate.  It is possible, however, that every M>40 Msun star undergoes such eruptions given initial results.  In Paper II, characterize the candidates through further analysis and follow-up observations, and there is no barrier to increasing the galaxy sample by an order of magnitude.

1210.6988
Dwarf galaxies with ionizing radiation feedback. II: spatially-resolved star formation relation
Kim, Krumholz, ... Abel et al

Spatially-resolved SF relation in high-resolution (3.8 pc) galactic-disk simulation.   New stellar feedback includes: ionizing radiation, SNe explosions, solve the radiative transfer equation (not subgrid model).  Photoheating by stellar radiation stabilizes gas against Jeans fragmentation, reducing the SFR.  Self-consistently calculate the location of ionized gas---for the first time, able to make spatially resolved mock observations of SF tracers, such as Halpha emission.  Can also observe how stellar feedback manifests itself in the correlation between ionized and molecular gas.  Apply this technique to the disk in a galactic halo of 2.3e11 Msun, find that correlation between SFR density (estimated from mock H-alpha emission) and molecular hydrogen density shows large scatter, especially at high resolutions of <~75 pc that are comparable to the size of GMCs.  This is because an aperture of GMC size captures only particular stages of GMC evolution.  By examining the evolving environment around star clusters, demonstrate that the breakdown of the traditional SF laws of the Kennicutt-Schmidt type at small scales results from a combination of stars drifting from their birthplaces, and molecular clouds being dispersed via ionizing radiation and supernova feedback.

1210.6990
Evolution of star formation and gas
Scoville

Review of SF in local and high-z universe, most material from 20 years ago.  Develop intuitive model for the evolution of galaxy mass and luminosity functions of the early Universe.  Develop model for dust heating and radiative transfer to elucidate the observed IR emissions.

1210.7029
Pulsars as excellent probes for the magnetic structure in our Milky Way
Han

Many probes for B-fields of the MW; conclude that pulsars are the best probes.  B-field strength and directions can be derived from their dispersion and rotation measures.  B-field structures such as field reversals between the arms and interarm regions can be well revealed from the distribution of RM data.  RM and DM can provide field strengths on large scales and small scales.  RMs of extragalactic radio sources can be used as the indication of B-field directions in the spiral tangential regions, and can be used as probes for the B-fields in the regions farther away than pulsars when their median RMs are compared with pulsar RMs. 

1210.7100
The duty cycle of radio-mode feedback in complete samples of clusters
Birzan et al

Results imply that the duty cycle of AGN outbursts (generating x-ray bubbles) with the potential to heat the gas significantly in cooling flow clusters is at least 60 per cent and could approach 100 per cent.

1210.7231
A measurement of the cosmic microwave background damping tail from the 2500-square-degree SPT-SZ survey
Story et al

SPT-SZ survey CMB temperature power spectrum over 650 < ell < 3000.  Fit SPT bandpowers, combined with WMAP7 with a 6 parameter LCDM cosmological model, and find that the two datasets are consistent and well fit by the model.  Adding SPT measurements significantly improves LCDM parameter constraints: sound horizon theta_s by x2.7.  Impact of gravitational lensing on CMB detected with 8 sigma [!].  Amplitude of lensing spectrum consistent with LCDM.  Constrain mean curvature of the observable universe with CMB data alone to be Omega_K=-0.003 pm 0.015.  ns = 0.96 pm 0.01.  CMB damping tail breaks the degeneracy between r and ns in large-scale CMB measurements, leading to an upper limit of r<0.18 (95% CL) in LCDM+r model.  ...