Day 569

Monday.  Tuesday. …. Sunday.

1312.3637
Line-of-sight structure toward strong lensing galaxy clusters
Bayliss, Johnson, Gladders, Sharon, Oguri

Present an analysis of the LoS structure toward a sample of 10 SL cluster cores.  Structure is  traced by groups that are identified spectroscopically in 0.1<z<0.9, and we measure the projected angular and comoving separations between each group and the primary SL clusters in each corresponding LoS.  From these data, measure the distribution of projected angular separations between the primary strong lensing clusters and uncorrelated LSS as traced by groups.  Then compare the observed distribution of angular separations for the SL selected LoS against the distribution of groups that is predicted for clusters lying along random LoS.  There is clear evidence for an excess of structure along the LoS at small angular separations (theta <= 6') along the SL selected LoS, indicating that uncorrelated structure is a significant systematic that contributes to producing galaxy clusters with large cross sections for strong leasing.  The prevalence of LoS structure is one of several biases in S clusters that can potentially be folded into cosmological measurements using galaxy cluster samples.  These results also have implications for current and future studies --- such as the HST Frontier Fields --- that make use of massive galaxy cluster lenses as precision cosmological telescopes; it is essential that the contribution of LoS structure be carefully accounted for in the SL modeling of the cluster lenses.

1312.3640
The spin temperature of high-redshift damped Lyman-$\alpha$ systems
Kanekar et al

From high-z DLA systems, measure spin temperature T_s from HI 21 cm absorption lines, and correlate with core fractions, DLA metallicities and velocity widths.  z>2.4 samples contain more systems with high T_s~1000K, due to low fractions of the cold neutral medium.  …  Low covering factors in high-z DLAs cannot account for the observed z evolution in spin temperatures.

1312.3650
The incidence of stellar mergers and mass gainers among massive stars
de Mink, Sana, Langer, Izzard, Schneider

Majority of massive stars born as members of close binary systems, populations of massive MS stars contain stellar mergers and products of binary mass transfers.  Simulate populations of massive stars accounting for all major binary evolution effects based on the most recent binary parameter statistics and extensively evaluate the effect of model uncertainties.  ~10% of early type stars are product of a merger resulting from a close binary system; in total ~30% of massive MS stars are the product of binary interaction.  Show that the commonly adapted approach to minimize the effects of binaries on an observe sample by excluding systems detected as binaries through radial velocity campaigns can be counterproductive.  …

1312.3698
Hoe typical is the coma cluster?
Pimbblet, Penny, Davies

Urge caution in using Coma as a z~0 baseline cluster in galaxy evolution studies; show that although Coma is typical against the control sample in terms of its internal kinematics (substructure and velocity dispersion profile), it has significantly high (~3 sigma) X-ray temperature set against clusters of comparable mass.  By de-redshifting the control sample cluster galaxies SFRs using a fit to the galaxy MS evolution at z<0.1, determine that the typical SFR of Coma galaxies as a function of mass is higher than for galaxies in the control sample at CL>99%.  

1312.3704
Inference of dispersion measure from coherent time-steady sources
Hirata, McQuinn

Several recent papers have proposed schemes by which a dispersion measure, and hence electron column, could be obtained from a time-steady, incoherent radio source at a cosmological distance (such as an active galactic nucleus).  If correct, this would open a new window on the distribution of intergalactic baryons.  These schemes are based on the statistical properties of the received radiation, such as the 2- or 4-point correlation function of the received electric field, and in one case on the quantum nature of the EM field.  Show, on the basis of general principles, that these schemes are not sensitive to dispersion measure (or have an extremely small S/N ratio), because (i) the classical 2pt correlation function is unaffected by dispersion; (ii) for a source with a large number of incoherently emitting electrons, the central limit theorem obliterates additional information in higher-order functions; and (iii) such an emitter produces a radiation density matrix that is equivalent to a statistical distribution of coherent states, which contains no information that is not already in the statistics of the classical waveforms.  Why the proposed observables do not depend on dispersion measure (or have extremely tiny dependencies) is discussed in detail.

1312.3750
Bimodal distribution of sulfuric acid aerosols in the upper haze of Venus
Gao, Zhang, Crisp, Bardeen, Yung

The upper haze (UH) of Venus is variable on the order of days and it is populated by two particle modes.  Use CARMA (Community Aerosol and Radiation Model for Atmospheres) microphysics and vertical transport model to evaluate whether interaction of upwelled cloud particles and sulfuric acid particles nucleated in situ on meteoric dust are able to generate the two size modes, and whether their observed variability are due to cloud top vertical transient winds.  Droplets generated in the UH from nucleation of acid onto meteoric dust coagulate with the upwelled cloud particles and cannot reproduce the observed bimodal size distribution.  The mass transport enabled by cloud top transient winds are able to generate a bimodal size distribution in a time scale consistent with observations.  Sedimentation and convection in the middle and lower clouds causes the formation of large mode 2 and mode 3 particles.  Evaporation of these particles below the clouds creates a local sulfuric acid vapor maximum that causes upwelling of sulfuric acid back into the clouds.  If the polysulfur condensation nuclei are small and their production rate is high, coagulation of small droplets onto larger droplets in the middle cloud may result in sulfuric acid "rain" below the clouds once every few Earth months.  Reduction of the polysulfer condensation nuclei production rate destroys this oscillation and reduces the mode 1 particle abundance in the middle cloud by two orders of magnitude, though it better reproduces the sulfur-to-sulfuric-acid mass ratio in the cloud and haze droplets.  In general, find satisfactory agreement between results and observations, though improvements could be made by incorporating sulfur microphysics.

1312.3751
The coevolution of supermassive black holes and massive galaxies at high redshift
Lapi et al

From FIR studies of AGN, along with stellar LFs at z>1.5: (i) SF in the host galaxy proceeds within a heavily dust-enshrouded medium at an almost constant rate over a timescale ~0.5-1 Gyr, then abruptly declines due to quasar feedback.  Over the same timescale, (ii) part of the ISM loses angular momentum, reaches the circum-nuclear regions at a rate proportional to the SF and it temporarily stored into a massive reservoir/proto-torus wherefrom it can be properly accreted; (iii) the BH grows by accretion in a self-regulated regime with radiative power that can slightly exceed the Eddington limit L/L_Edd<4, particularly at the highest redshifts; (iv) for massive BHs the ensuing energy feedback at its maximum exceeds the stellar one and removes the interstellar gas, thus stopping the SF and the fueling of the reservoir; (v) afterwards, if the latter has retained enough gas, a phase of supply-limited accretion follows exponentially declining with a timescale of about 2 e-folding times.  Show that the ratio of the FIR luminosity of the host galaxy to the bolometric luminosity of the AGN maps the various stages of the above sequence.  Finally, discuss how the detailed properties and the specific evolution of the reservoir can be invest imaged via coordinated, high-res observations of SF-ing, SL galaxies in the (sub-)mm band with ALMA and in the X-ray band with Chandra and the next generation X-ray instruments.

1312.3817
Fast radial flows in transition disk holes
Rosenfeld, Chiang, Andrews

Protoplanetary "transition" disks have large,mass-depleted central cavities, yet also deliver gas onto their host stars at rates comparable to disks without holes: explain if gas flows inward at much higher radial speeds inside the cavity than outside the cavity.  Identify observational diagnostics of fast radial inflow in channel maps made in optically thick spectral lines.  Signatures include (1) twisted isophotes in maps made at low systemic velocities and (2) rotation of structures observed between maps made in high-velocity line wings.  Apply to archival ALMA data on a system; although the observed kinematics also consistent with a disk warp, the radial inflow scenario is preferred because it predicts low surface densities that appear consistent with recent observations of optically thin CO isotopologues in this disk.  How material in the disk cavity sheds its angular momentum wholesale to fall freely onto the star is an unsolved problem; gravitational torques exerted by giant planets or brown dwarfs are briefly discussed as a candidate mechanism.