Astro Coffee

Suggested papers for
Tue, Sep 13, 2016 at 11:00 AM and Fri, Sep 16, 2016 at 11:00 AM

15 Sep 2016

Complete Reionization Constraints from Planck 2015 Polarization

We conduct an analysis of the Planck 2015 data that is complete in reionization observables from the large angle polarization $E$-mode spectrum in the redshift range $6 < z < 30$. Based on 5 principal components, all of which are constrained by the data, this single analysis can be used to infer constraints on any model for reionization in the same range; we develop an effective likelihood approach for applying these constraints to models. By allowing for an arbitrary ionization history, ...

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13 Sep 2016

Photometric and astrometric vagaries of the enigma star KIC 8462852

We apply a PCA-based pre-whitening method to the entire collection of main Kepler mission long-cadence data for KIC 8462852 spanning four years. This technique removes the correlated variations of instrumental origin in both the detected light curves and astrometry, resolving intrinsic changes in flux and image position of less than 100 ppm and 1 mas, respectively. Beside the major dips in the light curve during mission quarters 8 and 16, when the flux dropped by up to 20%, we confirm multiple ...

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14 Sep 2016

Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes

Gaia Data Release 1 (Gaia DR1) contains astrometric results for more than 1 billion stars brighter than magnitude 20.7 based on observations collected by the Gaia satellite during the first 14 months of its operational phase. We give a brief overview of the astrometric content of the data release and of the model assumptions, data processing, and validation of the results. For stars in common with the Hipparcos and Tycho-2 catalogues, complete astrometric single-star solutions are obtained by i...

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9 Sep 2016

The heart of the swarm: K2 photometry and rotational characteristics of 56 Jovian Trojan asteroids

We present fully covered phased light curves for 56 Jovian Trojan asteroids as acquired by the K2 mission of the Kepler space telescope. This set of objects has been monitored during Campaign 6 and represents a nearly unbiased subsample of the population of small Solar System bodies. We derived precise periods and amplitudes for all Trojans, and found their distributions to be compatible with the previous statistics. We point out, however, that ground-based rotation periods are often unreliable...

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7 Sep 2016

Boosting Lya and HeII 1640A Line Fluxes from Pop III Galaxies: Stochastic IMF Sampling and Departures from Case-B

We revisit calculations of nebular hydrogen Lya and HeII 1640A line strengths for population III galaxies, undergoing continuous and bursts of star formation. We focus on initial mass functions (IMFs) motivated by recent theoretical studies, which generally span a lower range of stellar masses than earlier works. We also account for case-B departures and the stochastic sampling of the IMF. In agreement with previous works, we find that departures from case-B can enhance the Lya flux by a factor...

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7 Sep 2016

Beyond Jcrit: a critical curve for suppression of H2-cooling in protogalaxies

Suppression of H2-cooling in early protogalaxies has important implications for the formation of supermassive black holes seeds, the first generation of stars, and the epoch of reionization. This suppression can occur via photodissociation of H2 (by ultraviolet Lyman-Werner [LW] photons) or by photodetachment of H, a precursor in H2 formation (by infrared [IR] photons). Previous studies have typically adopted idealised spectra, with a blackbody or a power-law shape, in modeling the chemistry of...

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7 Sep 2016

SDSS-IV MaNGA: A serendipitous observation of a potential gas accretion event

The nature of warm, ionized gas outside of galaxies may illuminate several key galaxy evolutionary processes. A serendipitous observation by the MaNGA survey has revealed a large, asymmetric H$\alpha$ complex with no optical counterpart that extends $\approx8"$ ($\approx6.3$ kpc) beyond the effective radius of a dusty, starbursting galaxy. This H$\alpha$ extension is approximately three times the effective radius of the host galaxy and displays a tail-like morphology. We analyze its gas-phase m...

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9 Sep 2016

Mass extinctions and supernova explosions

A nearby supernova (SN) explosion could have negatively influenced life on Earth, maybe even been responsible for mass extinctions. Mass extinction poses a significant extinction of numerous species on Earth, as recorded in the paleontologic, paleoclimatic, and geological record of our planet. Depending on the distance between the Sun and the SN, different types of threats have to be considered, such as ozone depletion on Earth, causing increased exposure to the Sun's ultraviolet radiation, or ...

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12 Sep 2016

Halo Histories vs. Galaxy Properties at z=0, I: The Quenching of Star Formation

We test whether halo age and galaxy age are correlated at fixed halo and galaxy mass. The formation histories, and thus ages, of dark matter halos correlate with their large-scale density $\rho$, an effect known as assembly bias. We test whether this correlation extends to galaxies by measuring the dependence of galaxy stellar age on $\rho$. To clarify the comparison between theory and observation, and to remove the strong environmental effects on satellites, we use galaxy group catalogs to ide...

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8 Sep 2016

Evidence from SOFIA Imaging of Polycyclic Aromatic Hydrocarbon Formation along a Recent Outflow in NGC 7027

We report spatially resolved (FWHM$\sim3.8-4.6"$) mid-IR imaging observations of the planetary nebula (PN) NGC 7027 taken with the 2.5-m telescope aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). Images of NGC 7027 were acquired at 6.3, 6.6, 11.1, 19.7, 24.2, 33.6, and 37.1 $\mu\mathrm{m}$ using the Faint Object Infrared Camera for the SOFIA Telescope (FORCAST).The observations reveal emission from Polycyclic Aromatic Hydrocarbon (PAH) and warm dust ($T_D\sim90$ K) from the ...

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The Official Home Page of the United States Army

Army announces 3rd Brigade Combat Team, 101st Airborne Division deployment September 6, 2016 Army launches Rapid Capabilities Office August 31, 2016 Huntsville Center signs contract, Army reaches $1 billion energy milestone August 11, 2016 Department of the Army announces 101st Airborne Division deployment August 5, 2016 Army researchers testing Zika vaccine July 6, 2016 Army outlines gender integration implementation plan March 10, 2016 Zika Virus - What is it? What can you do? February 5, 2016...

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