Thursday, dinner with Uros and his posse tonight, to celebrate Lucas' completion of his Ph.D. Dinner last night with Laura and Robert was great--and I found out what a strange place Bonn will be.
1108.5734
What do gas-rich galaxies actually tell us about modified Newtonian dynamics?
Foremann, Scott
The baryonic Tully-Fisher relation that have been used to support MOND (challenging the existence of CDM) is based on poor collection and inconsistent use of data, and hence is invalid.
1108.5733
The evolution and environments of X-ray emitting AGN in high-redshift large-scale structures
Rumbaugh, Kocevski, Gal, Lemaux, Lubin, Fassnacht, McGrath, Squires
Check out the AGNs in LSS at z~0.7-0.9 with Keck 10m and deep Chandra. More than 36% of host galaxies are located in the 'green valley', which suggests that they are a transitional population. All AGN host galaxies indicate either on-going star formation, or a starburst within ~1Gyr (based on OII and Hd line strengths), indicating clear connection between starburst and nuclear activity. More evolved (determined by EW(OII) and EW(Hd)) AGN have lower rest-frame 0.5-8 keV X-ray luminosities and longer times since a starburst, indicating both SF and AGN activity occurred at earlier times. Analyze evolution of X-ray AGN and evaluate potential triggering mechanisms.
1108.5731
Ultra-faint dwarf galaxies as a test of early enrichment and metallicity-dependent star formation
Tassis, Gnedin, Kravtsov
Molecular H2 formed efficiently in the presence of metal (dust), which catalyzes H2 formation and shields from dissociating radiation. H2 based star formation is expected to leave bi-modality in the metallicity distribution among dwarf galaxies when there is no significant pre-enrichment by Pop III stars forming out of zero-metallicity gas, because when metallicity (and dust) abundance is low, formation of H2 is inefficient, the gas consumption time scale is long a,d SF and metal enrichment proceed slow; while when metallicity reaches a critical threshold value, SF and enrichment accelerate, which leads to rapid increase in stellar mass and metallicity of galaxies. Demonstrate via both analytical model and full cosmological simulations. In contrast, observed metallicity distributions of dwarf galaxies are not bimodal. This discrepancy points to substantial early stochastic pre-enrichment by Pop III stars to levels Z~0.01 Z_sun in dense, SF regions of early galaxies.
1108.5809
The shocking truth: the small contribution to hydrogen reionization from gravitational infall
Wyithe, Mould, Loeb
Deep searches for SF galaxies during the epoch of reionization have not yet found sufficient galaxies to provide the necessary ionising flux to reionize the universe. Perhaps fast accretion shocks associated with gravitational infall of baryons during the formation of galaxies can be an alternative method to generate the required ionising photons. Find shocks can ionize no more than a few percent of the cosmic hydrogen by z~6. Such ionization radiation would be significantly more biased than that from the first stars, leading to a modification of the luminosity weighted source clustering by 10%. This could be measurable using the 21cm line.
* how does the bias come into play? I guess one measures the clustering in 21cm...
1108.5982
Near-UV and visible spectroscopy of HAYABUSA spacecraft re-entry
Abe et al
Many atomic lines detected, Li coming from the onboard Li ion battery. FeO probably formed at the wake of the spacecraft. Excitation temperature varied from 4500K to 6000K. Fe I was 10 times more abundant than Mg I after the spacecraft explosion. N2+ band from a shock layer and CN violet bands from the sample return capsule's ablating head shield were dominant molecular bands in the near UV (3000-4000A). OH bands, N2+ bands.
* ablation: in spacecraft design, ablation is used to both cool and protect mechanical parts and/or payloads that would otherwise be damaged by extremely high temperatures. "removal of material from the surface of an object by vaporization, chipping, or other erosive processes"
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