1201.2172
Acoustic scale from the angular power spectra of SDSS III DR8 photometric luminous galaxies
Seo, Ho, White, Cuesta, Ross, Saito, Reid, Padmanabhan, Percival, de Putter, Schlegel, Eisenstein, Xu, Schneider, Skibba, Verde, Nichol, ... et al
Measure acoustic scale from angular power spectra of SDSS DR8 with 872k galaxies over 10k sq deg between 0.45<z<0.65. The extensive spectroscopic training set of the BOSS luminous galaxies allows precise estimates of the true redshift distributions of galaxies in the imaging catalog. Utilizing redshift distribution information, build templates and fit to power spectra of the data to derive the location of BAO while marginalizing over many free parameters to exclude nearly all of the non-BAO signal. Derive the ratio of the angular diameter distance to the sound horizon scale D_A(z)/rs = 9.2pm0.4 at z=0.54, and thus D_A=1411pm64 Mpc at z=0.54; the result is fairly independent of assumptions on the underlying cosmology. Measurement of D_A(z) is 1.4 sigma higher than expected for concordance LCDM, in accordance to the trend of other BAO measurements for z>0.35. Report constraints on cosmological parameters from this measurement, combined with WMAP7 data and previous BAO measurements of SDSS and WiggleZ.
1201.2174
Complex structure in Class 0 Protostellar envelopes III: Velocity gradients in non-axisymmetric envelopes, infall or rotation?
Tobin, Hartmann, ... et al
Interferometric kinematic study of morphologically complex protostellar envelopes based on observations of the dense gas tracers N2H+ and NH3. Interpreted as rotation, but given the complex morphology of these clouds, doubt that that is the correct interpretation. Developed a filamentary parameterization of the rotating collapse model, find that most envelopes in the sample have PV structures that can be reproduced by an infalling filamentary envelope projected at different angles within the plane of the sky; this can mimic rotation.
1201.2175
Planet-planet scattering alone cannot explain the free-floating planet population
Veras, Reymond
Gravitational microlensing observations predict a vast population of free-floating giant planets that outnumbers main sequence stars almost twofold. [!!!] Planet-planet scatter and the ejection of one or more planets in isolated MS planetary systems cannot explain all of these free-floating objects. Using quantitative arguments and N-body sims, argue that the observed number of exoplanets exceeds the plausible number from scattering. Other potential sources of free-floaters: planetary stripping in stellar clusters and post-MS ejection are candidates.
1201.2177
First science with SHARDS: emission line galaxies
Cava, Gonzalez, SHARDS team
GOODS-N field deep spectro-photometry survey on high-z absorption red & dead sources. Optimized for detection of Mg absorption (rest frame ~280nm) at z>1, a distinctive, necessary, and sufficient feature of evolved stellar populations. Also allows for emission line galaxy studies.
1201.2178
The dust & gas properties of M83
Foyle, et al
Examine the dust and gas properties of the nearby, barred galaxy M83 (Herschel PACS and SPIRE). Find: nuclear, bar and spiral arm regions exhibit higher dust temperatures and masses compared to interarm regions. Distribution of dust temperature and mass are not spatially coincident. Assuming a trailing spiral structure, the dust temperature peaks in the spiral lie ahead of the dust surface density peaks. Dust mass surface density correlates well with the distribution of molecular gas as traced by CO (J=3-2) images and the SFR as traced by H2 with a correction for obscured SF using 24um emission. Using HI images to trace the atomic gas component, make total gas mass surface density maps, calculate gas-to-dust ratio. Find a mean gas-to-dust ratio of 84pm4 with higher values in the inner region assuming a constant CO-to-H2 conversion factor. Examine the gas-to-dust ratio using CO-toH2 conversion factor that varies with metallicity.
1201.2182
On the spin-down of intermittent pulsars
Li, Spitkovsky, Tchekhovskoy
Magnetospheres of pulsars are thought to be filled with plasma, and variations in plasma supply can affect both pulsar emission properties and spin-down rates. Some pulsars switch between two distinct "on" and "off" (radio loud and quiet, respectively) states. Spin-down rates in the two states differ by a large factor (~1.5-2.5), which is not easily understood in the context of current models. Present self-consistent numerical solutions of on and off states of the "intermittent" pulsar magnetopheres. On state: nearly ideal force-free magnetosphere with abundant magnetospheric plasma supply. Off state: plasma supply disruption, resulting in lower plasma density on the open field lines; use nearly vacuum conditions on the open field lines and nearly ideal force-free conditions on the closed field lines, where plasma can remain trapped even in the absence of pair production. Toroidal advenction of plasma in the closed zone in the "off" state causes spin-downs that are a factor of 2 higher than vacuum values, naturally obtaining a range of spin-down ratios between the "on" and "off" states.
1201.2252
Morphology of galaxies
Wadadekar
Study of morphology of galaxies important to understand the formation and evolution of galaxies and their sub-components as a function of luminosity, environment, and SF and galaxy assembly over time.
1201.2302
Habitability of earth-type planets and moons in the Kepler-16 system
Quarles, Musielak, Cuntz
* Planets that orbit just one star in a binary pair are said to have "S-type" orbits, whereas those that orbit around both stars have "P-type" or "circumbinary" orbits. It is estimated that 50–60% of binary stars are capable of supporting habitable terrestrial planets within stable orbital ranges.
* Kepler-16 is a binary star system in the constellation of Cygnus[3] that was targeted by the Keplerspacecraft. Both stars are smaller than the Sun; the primary, Kepler-16A, is a class K orange dwarf, and the secondary, Kepler-16B, is a class M red dwarf. They are separated by 0.22 AU, and complete an orbit around a common center of mass every 41 days. The system is host to one known extrasolar planet in circumbinary orbit: the Saturn-sized Kepler-16b.
Study habitable Earth-type planets and moons can exist in the Kepler-16 system by investigating orbital stability in the standard and extended habitable zone (HZ). Find: Earth-type planets in S-type orbits are possible within the standard HZ in direct vicinity of Kepler-16b, thus constituting habitable exomoons. Earth-mass planets cannot exist in P-type orbits around the two-stellar components within the standard HZ. But P-type Earth-mass planets can exist superior to the giant planet in the extended HZ pertaining to considerably enhanced back-warming in the planetary atmosphere if facilitated. Discuss potential detectability of Earth-type moons and planets in S and P-type orbits.
1201.2336
Fringe science: defringing CCD images with Neon lamp flat fields
Howell
The fringe pattern observed in a CCD image for a given near-IR filter is dominated by small thickness variations across the detector with a second order effect caused by the wavelength extent of the emission lines within the bandpass which produce the interference pattern. Show: essentially any set of emission lines which generally match the wavelength coverage of the night sky emission lines within a bandpass will produce an identical fringe pattern. Present an easy, inexpensive, and efficient method which uses a neon lamp as a flat field source and produces high S/N fringe frames to use for defringing an image during the calibration process.
1201.2353
ORIGAMI: delineating halos using phase-space folds
Falck, Neyrinck, Szalay
ORIGAMI identifies structures, particularly halos, in cosmological N-body simulations: finds the outer folds that delineate structures. Halo particles are identified as those that have undergone shell-crossing along 3 orthogonal axes, providing a dynamical definition of halo regions that is independent of density. ORIGAMI also identifies other morphological structures: particles that have undergone shell-crossing along 2,1, or 0 orthogonal axes correspond to filaments, walls, and voids respectively. Compare with standard FoF and find ORIGAMI halos are somewhat larger and more diffuse, less spherical, though the global properties of ORIGAMI haloes are in good agreement with other modern halo-finding algorithms.
No comments:
Post a Comment