DUST PRODUCTION FACTORIES IN THE EARLY UNIVERSE: FORMATION OF CARBON GRAINS IN RED-SUPERGIANT WINDS OF VERY MASSIVE POPULATION III STARS

Nozawa, Takaya,Yoon, Sung-Chul,Maeda, Keiichi,Kozasa, Takashi,Nomoto, Ken'ichi,Langer, Norbert University of Chicago Press for the American Astro 2014 ASTROPHYSICAL JOURNAL LETTERS - Vol.787 No.2

We investigate the formation of dust in a stellar wind during the red-supergiant (RSG) phase of a very massive Population III star with a zero-age main sequence mass of 500 M-circle dot. We show that, in a carbon-rich wind with a constant velocity, carbon grains can form with a lognormal-like size distribution, and that all of the carbon available for dust formation finally condenses into dust for wide ranges of the mass-loss rate ((0.1-3) x 10(-3) M-circle dot yr(-1)) and wind velocity (1-100 km s(-1)). We also find that the acceleration of the wind, driven by newly formed dust, suppresses the grain growth but still allows more than half of the gas-phase carbon to finally be locked up in dust grains. These results indicate that, at most, 1.7 M-circle dot of carbon grains can form during the RSG phase of 500 M-circle dot Population III stars. Such a high dust yield could place very massive primordial stars as important sources of dust at the very early epoch of the universe if the initial mass function of Population III stars was top-heavy. We also briefly discuss a new formation scenario of carbon-rich ultra-metal-poor stars, considering feedback from very massive Population III stars.

CHANDRA DETECTION OF A NEW DIFFUSE X-RAY COMPONENT FROM THE GLOBULAR CLUSTER 47 TUCANAE

Wu, E. M. H.,Hui, C. Y.,Kong, A. K. H.,Tam, P. H. T.,Cheng, K. S.,Dogiel, V. A. University of Chicago Press for the American Astro 2014 ASTROPHYSICAL JOURNAL LETTERS - Vol.788 No.2

In re-analyzing the archival Chandra data of the globular cluster 47 Tucanae, we have detected a new diffuse X-ray emission feature within the half-mass radius of the cluster. The spectrum of the diffuse emission can be described by a power-law model plus a plasma component with photon index Gamma similar to 1.0 and plasma temperature kT similar to 0.2 keV. While the thermal component is apparently uniform, the non-thermal contribution falls off exponentially from the core. The observed properties could possibly be explained in the context of multiple shocks resulting from the collisions among the stellar wind in the cluster and the inverse Compton scattering between the pulsar wind and the relic photons.

Binary Black Hole Population Properties Inferred from the First and Second Observing Runs of Advanced LIGO and Advanced Virgo

Abbott, B.P.,Kim, W.S.,Oh, J.J.,Oh, S.H.,Son, E.J. University of Chicago Press for the American Astro 2019 ASTROPHYSICAL JOURNAL LETTERS - Vol.882 No.2

<P> We present results on the mass, spin, and redshift distributions with phenomenological population models using the 10 binary black hole (BBH) mergers detected in the first and second observing runs completed by Advanced LIGO and Advanced Virgo. We constrain properties of the BBH mass spectrum using models with a range of parameterizations of the BBH mass and spin distributions. We find that the mass distribution of the more massive BH in such binaries is well approximated by models with no more than 1% of BHs more massive than 45<I>M</I>⊙ and a power-law index of α =1.3_{-1.7}^{+1.4}(90% credibility). We also show that BBHs are unlikely to be composed of BHs with large spins aligned to the orbital angular momentum. Modeling the evolution of the BBH merger rate with redshift, we show that it is flat or increasing with redshift with 93% probability. Marginalizing over uncertainties in the BBH population, we find robust estimates of the BBH merger rate density of R= 53.2_{-28.2}^{+55.8} Gpc<SUP>-3</SUP>yr<SUP>-1</SUP>(90% credibility). As the BBH catalog grows in future observing runs, we expect that uncertainties in the population model parameters will shrink, potentially providing insights into the formation of BHs via supernovae, binary interactions of massive stars, stellar cluster dynamics, and the formation history of BHs across cosmic time. </P>

POWER ASYMMETRY IN WMAP AND PLANCK TEMPERATURE SKY MAPS AS MEASURED BY A LOCAL VARIANCE ESTIMATOR

Akrami, Y.,Fantaye, Y.,Shafieloo, A.,Eriksen, H. K.,Hansen, F. K.,Banday, A. J.,Gorski, K. M. University of Chicago Press for the American Astro 2014 ASTROPHYSICAL JOURNAL LETTERS - Vol.784 No.2

We revisit the question of hemispherical power asymmetry in the WMAP and Planck temperature sky maps by measuring the local variance over the sky and on disks of various sizes. For the 2013 Planck sky map we find that none of the 1000 available isotropic Planck 'Full Focal Plane' simulations have a larger variance asymmetry than that estimated from the data, suggesting the presence of an anisotropic signature formally significant at least at the 3.3 sigma level. For the WMAP 9 year data we find that 5 out of 1000 simulations have a larger asymmetry. The preferred direction for the asymmetry from the Planck data is (l, b) = (212 degrees, -13 degrees), in good agreement with previous reports of the same hemispherical power asymmetry.

DIFFUSE EXTRAPLANAR DUST IN NGC 891

Seon, Kwang-il,Witt, Adolf N.,Shinn, Jong-ho,Kim, Il-joong University of Chicago Press for the American Astro 2014 ASTROPHYSICAL JOURNAL LETTERS - Vol.785 No.1

We report the detection of vertically extended far-ultraviolet and near-UV emissions in an edge-on spiral galaxy NGC 891, which we interpret as being due to dust-scattered starlight. Three-dimensional radiative transfer models are used to investigate the content of the extraplanar dust that is required to explain the UV emission. The UV halos are well reproduced by a radiative transfer model with two exponential dust disks, one with a scale height of approximate to 0.2-0.25 kpc and the other with a scale height of approximate to 1.2-2.0 kpc. The central face-on optical depth of the geometrically thick disk is found to be tau(thick)(B) approximate to 0.3-0.5 at the B band. The results indicate that the dust mass at vertical bar z vertical bar > 2 kpc is approximate to 3%-5% of the total dust mass, which is in good accordance with the recent Herschel submillimeter observation. Our results, together with the recent discovery of the UV halos in other edge-on galaxies, suggest the widespread existence of a geometrically thick dust layer above the galactic plane in spirals.

A HOT MOLECULAR CIRCUMSTELLAR DISK AROUND THE MASSIVE PROTOSTAR ORION SOURCE I

Hirota, Tomoya,Kim, Mi Kyoung,Kurono, Yasutaka,Honma, Mareki University of Chicago Press for the American Astro 2014 ASTROPHYSICAL JOURNAL LETTERS - Vol.782 No.2

We report new Atacama Large Millimeter/Submillimeter Array (ALMA) observations of a circumstellar disk around Source I in Orion KL, an archetype of massive protostar candidates. We detected two ortho-H2O lines at 321 GHz (10(2,9)-9(3,6)) and 336 GHz (nu(2) = 1, 5(2,3)-6(1,6)) for the first time in Source I. The latter one is in a vibrationally excited state at the lower state energy of 2939 K, suggesting evidence of hot molecular gas close to Source I. The integrated intensity map of the 321 GHz line is elongated along the bipolar outflow while the 336 GHz line map is unresolved with a beam size of 0 ''.4. Both of these maps show velocity gradients perpendicular to the bipolar outflow. The velocity centroid map of the 321 GHz line implies a spatial and velocity structure similar to that of vibrationally excited SiO masers tracing the root of the outflow emanating from the disk surface. In contrast, the 336 GHz line is most likely emitting from the disk midplane with a diameter of 0 ''.2 (84 AU) as traced by radio continuum emission and a dark lane devoid of the vibrationally excited SiO maser emission. The observed velocity gradient and the spectral profile of the 336 GHz H2O line can be reconciled with a model of an edge-on ring-like structure with an enclosed mass of >7M(circle dot) and an excitation temperature of >3000 K. The present results provide further evidence of a hot and neutral circumstellar disk rotating around Source I with a diameter of similar to 100 AU scale.

EXPLORING THE X-RAY AND gamma-RAY PROPERTIES OF THE REDBACK MILLISECOND PULSAR PSR J1723-2837

Hui, C. Y.,Tam, P. H. T.,Takata, J.,Kong, A. K. H.,Cheng, K. S.,Wu, J. H. K.,Lin, L. C. C.,Wu, E. M. H. University of Chicago Press for the American Astro 2014 ASTROPHYSICAL JOURNAL LETTERS - Vol.781 No.1

We have investigated the X-ray and gamma-ray properties of the redback millisecond pulsar PSR J1723-2837 with XMM-Newton, Chandra, and Fermi. We have discovered the X-ray orbital modulation of this binary system with a minimum that coincides with the phases of radio eclipse. The X-ray emission is clearly non-thermal in nature, which can be described well by a simple power law with a photon index of similar to 1.2. The phase-averaged luminosity is similar to 9 x 10(31) erg s(-1) in 0.3-10 keV, which consumes similar to 0.2% of the spin-down power. We have detected the gamma-ray emission in 0.1-300 GeV from this system at a significance of similar to 6 sigma for the first time. The gamma-rays in this energy range consume similar to 2% of the spin-down power and can be modeled by a power law with a photon index of similar to 2.6. We discuss the high energy properties of the new redback in the context of an intrabinary shock model.

First measurement of the hubble constant from a dark standard siren using the dark energy survey galaxies and the LIGO/Virgo binary?black-hole merger GW170814

Soares-Santos, M.,Kim, W.S.,Oh, J.J.,Oh, S.H.,Son, E.J. University of Chicago Press for the American Astro 2019 ASTROPHYSICAL JOURNAL LETTERS - Vol.876 No.1

<P> We present a multi-messenger measurement of the Hubble constant H<SUB>0</SUB> using the binary-black-hole merger GW170814 as a standard siren, combined with a photometric redshift catalog from the Dark Energy Survey (DES). The luminosity distance is obtained from the gravitational wave signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017 August 14, and the redshift information is provided by the DES Year 3 data. Black hole mergers such as GW170814 are expected to lack bright electromagnetic emission to uniquely identify their host galaxies and build an object-by-object Hubble diagram. However, they are suitable for a statistical measurement, provided that a galaxy catalog of adequate depth and redshift completion is available. Here we present the first Hubble parameter measurement using a black hole merger. Our analysis results in <I>H</><SUB>0</SUB>=75_{-32}^{+40}km s<SUP>-1</SUP>Mpc<SUP>-1</SUP>, which is consistent with both SN Ia and cosmic microwave background measurements of the Hubble constant. The quoted 68% credible region comprises 60% of the uniform prior range [20, 140] km s<SUP>-1</SUP> Mpc<SUP>-1</SUP>, and it depends on the assumed prior range. If we take a broader prior of [10, 220] km s<SUP>-1</SUP> Mpc<SUP>-1</SUP>, we find <I>H</I><SUB>0</SUB>=78_{-24}^{+96} km s<SUP>-1</SUP> Mpc<SUP>-1</SUP> (57% of the prior range). Although a weak constraint on the Hubble constant from a single event is expected using the dark siren method, a multifold increase in the LVC event rate is anticipated in the coming years and combinations of many sirens will lead to improved constraints on <I>H</I><SUB>0</SUB>. </P>