Tuesday (gah!).
Wednesday (aaagh!). Reading for GalSim takes a loooong time. And the meeting minutes for various Euclid. Went climbing with Burke at Ironworks last night; that was fun. Climbed an easy 5.10A. My arms are still OK.
Thursday. Went running last night, and hurt my left knee. Arms -- OK. I guess the morning yoga helps with my arm muscle usage.
1205.4712
Orbit-based dynamical models of the Sculptor dSph galaxy
Breddels, Helmi, van den Bosch, van de Ven, Battaglia
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1205.4715
Principal component abundance analysis of microlensed bulge dwarf and subgiant stars
Andrews, Weinberg, Johnson, Bensby, Feltzing
First PC (PC1): strong contribution from alpha-elements (relative contributions of Type II and Type Ia SNe). PC2: Na-Ni correlation (likely product of metallicity-dependent Type II SNe yields). Distribution of PC1 is bimodal (recovered from bimodal [Fe/H] values). Enrichment history anomaly seen in outlier values of PCs. Thin and thick disk dwarfs yield a nearly identical PC1. Metal-rich and metal-poor bulge dwarfs track kinematically selected thin and thick disk dwarfs, respectively, suggesting broadly similar alpha-enrichment histories. Disk PC2 is dominated by a Y-Ba correlation (likely indicating a greater contribution of s-process enrichment from asymptotic giant branch stars in the disk, compared to the more rapidly forming bulge).
1205.4716
Chemical tracers of high-metallicity environments
Bayet, Davis, Bell, Viti
Properties of molecular gas in metal-rich environments (e.g., in ETGs). Photon-dominated region (PDR) chemistry in a wide range of physical conditions appropriate for these sources considered. Derive fractional abundances of 20 most chemically reactive species as a function of metallicity, optical depth, and various volume number gas densities, FUV radiation fields, and CR ionization rates. Also investigate the response of the chemistry to the changes in alpha-element enhancement as seen in ETGs. With increasing metallicity, CS, H2S, H2CS, H2O, H3O+, HCO+ and H2CN seem invariant, whereas C+, CO, C2H, CN, HCN, HNC and OCS appear to be the species most sensitive to change. The most sensitive species to the change in the fractional abundance of alpha-elements are C+, C, CN, HCN, HNC, SO, SO2, H2O and CS. Finally, provide line brightness ratios for the most abundant species, especially in the range observable with ALMA. Discussion of favorable line ratios to use for estimation of super-solar metallicities and alpha-elements are also provided.
1205.4724
The origin of the microlensing events observed towards the LMC and the stellar counterpart of the Magellanic stream
Besla, Hernquist, Loeb
Novel theory to explain the long-standing puzzle of the nature of the microlensing events reported towards the LMC by MACHO and OGLE collaborations. Propose: population of tidally stripped stars from SMC located 4-10 kpc behind a lensing population of LMC disk stars can naturally explain the observed event durations, event frequency and spatial distribution of the reported events. Favors scenario for the interaction history of MC where the clouds are on their first infall towards the MW and the SMC has recently collided with the LMC, leading to a large number of faint sources distributed non-uniformly behind the LMC disk. Owing to the tidal nature of the source population, the sources exhibit a range of distances and velocities wrt the LMC lenses, naturally explaining the observed range of event durations (30-220 days). Assuming a detection efficiency of 30-50%, find event frequencies of 1-2/yr in the central regions of the LMC disk; comparable to the observed rate for the MACHO survey, ~2/yr. A lower detection efficiency of 10% is comparable to OGLE results. Observational tests: SMC stars are low-metallicity; exhibit high velocities relative to LMC disk stars (detectable via proper motion studies); there should exist a stellar counterpart to the gaseous Magellanic Stream and Magellanic Bridge with a Vband surface brightness > 34 Mag/ arcsec^2.
1205.5028
Type Ia single degenerate survivors must be overluminous
Shappee, Kochanek, Stanek
In the SD channel of SN Ia explosion, a MS donor star survives the explosion but it is stripped of mass and shock heated. This results in a companion that becomes significantly more luminous (10-1e3 Lsun) for a long period of time (1e3-4 years). The lack of such a luminous "leftover" strain the LMC SNe remnant SNR 0609-67.5 provides another piece of evidence against the SD scenario, while also none of the proposed survivors of Tycho (including Tycho G) could plausibly be the donor star. Luminous donors closer than 10Mpc should be observable with the HST starting ~2years post-peak, and should be easily tested.
1205.5037
A huge reservoir of ionized gas around the Milky Way: accounting for the missing mass?
Gupta, Mathur, Krongold, Nicastro, Galeazzi
Many galaxies contain a large reservoir of ionized gas with temperatures of about 1e5K (HST observations). Reeert Chandra probing a hotter phase of CGM of MW at 1e6K. This phase of the CGM is massive, extending over a large region around the MW (radius of 100 kpc). The mass content of this phase is over 1e10 Msun, many times more than cooler gas phases and comparable to the total baryonic mass in the disk of the Galaxy. THe missing mass of the galaxy appears to be in this warm-hot gas phase.
1205.5223
Determination of neutrino mass hierarchy by 21cm line and CMB B-mode polarization observations
Oyama, Shimizu, Kohri
Ongoing and future observations for both the 21 cm line and the CMB B-mode polarization produced by a CMB lensing, and study their sensitivities to the effective number of neutrino species, the total neutrino mass, and the neutrino mass hierarchy. Find: combining the CMB observations with future squire kilometer arrays optimized for 21 cm line such as Omniscope can determine the neutrino mass hierarchy at 95% CL. Also show that the combination of Planck+ Polarbear and SKA can strongly improve the bounds of the total neutrino mass and the effective number of neutrino species to be Delta Sigma m_nu~0.15eV and Delta N_nu~0.35 at 95% CL, respectively.
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