Day 734

Monday.

1408.6842
The Illustris simulation: evolving population of black holes across cosmic time
Sijacki, Voglsberger, Genel, Springel, Torrey, Snyder, Nelson, Hernquist

Study the properties of BHs and their host galaxies across cosmic time in the Illustris simulation: (106.5Mpc)^3, 12e9 resolution elements, galaxy formation physics.  Find that the BH mass density for z=0-5 and the BH MF at z=0 predicted by Illustris are in excellent agreement with the most recent observational constraints.  Show that the bolometric and hard X-ray luminosity functions of AGN at z=0 reproduce observational data very well over the full dynamic range probed.  This requires radiative efficiencies to be on average low, epsilon_r<=0.1, unless the bolometric corrections are largely underestimated.  Cosmic downsizing of the AGN population is in broad agreement with the findings from X-ray surveys, but caution that obscuration effects may introduce systematic biases in the flux-limited samples at the faint end.  Also study black hole - host galaxy scaling relations as a function of galaxy morphology, color and sSFR.  Find that BHs and galaxies co-evolve at the massive end, but for low mass, blue and SF galaxies there is no tight relation with either their central BH masses or the nuclear AGN activity.

1408.6846
GALFIT-CORSAIR: implementing the core-Sersic model into GALFIT
Bonfini

Introduce GALFIT-CORSAIR: a publicly available, fully retro-compatible modification of the 2d fitting soft are GALFIT (v.3) which adds an implementation of the core-Sersic model.  

1408.6953
A new determination of the primordial He abundance using the HeI 10830A emission line: cosmological implications
Izotov, Thuan, Guseva

Present NIR spectro-observations of HeI emission line in 45 low-metallicity HII regions, combine with optical spectra to derive primordial He abundance.  HeI line intensity is very sensitive to the density of the HII region; improves determination of the conditions in the He+ zone.  He mass fraction Y derived with accuracy better than 3%.  Derived Yp = 0.2551 pm 0.0022, higher than predicted by standard BBN model.  Combine derived Yp with D/H=(2.53pm0.25)^e-5, find that the best agreement between these light element abundances is achieved in a cosmo model with a baryon mass density Omega_b h^2=0.024pm0.0017 and an effective number of neutrino species Neff=3.58pm0.25.  A non-standard value of Neff is preferred at the 99% CL, impinge the possible existence of additional types of neutrino species.

1408.7052
3D weak gravitational lensing of the CMB and galaxies
Kitching, Heavens, Das

Present a PS formalism that combines the full 3d information from the galaxy ellipticity field, with information from the CMB.  Include in this approach galaxy cosmic shear and galaxy IA, CMB deflection, CMB T and CMB polarization data; including the inter-datm PS between all quantitates.  Apply this to forecasting cosmological parameter errors for CMB and imaging surveys and show that the additional covariance between the CMB and ellitpicity measurements can improve galaxy IA measurements by a factor of two, and DE EoS measurements by 30 %.  Present predictions for Euclid-like, KiDS, ACTPoL, and CoRE-like experience and show that the combination of cosmic shear and the CMB, from Euclid-like and CoRE-like experiments, can measure the sum of neutrino masses with an error of 0.02 eV,and the DE EoS with an error on w0 of less than 0.01.

1408.5388
The Milky Way Tomography with SDSS.  V.  Mapping the Dark Matter halo
Loebman, Ivezic, ... et al

Use the number density distribution and kinematics of SDSS halo stars, probe the DM distribution to heliocentric distances exceeding 10 kpc and galactocentric distances exceeding 20 kpc.  Analysis utilizes Jeans equations to generate 2d acceleration maps throughout the volume; this approach is thoroughly tested on N-body+SPH sim of a MW-like galaxy.  Show that the known accelerations (gradients of the gravitational potential) can be successfully recovered in such a realistic system.  Show that the gravitational potential implied by SDS observations cannot be explained, assuming Newtonian gravity, by visible matter alone: the gravitational force experienced by stars at galactocentric distances of 20 kpc is as much as 3 times stronger than what can be attributed to purely visible matter.  Show that SDSS data provide a strong constraint on the shape of the DM halo potential.  Within galactocentric distances of 20 kpc, the DM halo potential is well described as an oblate halo with axis ratio qDM=0.7pm0.1; corresponds to an axis ratio qDM=0.4pm0.1 for the DM density distribution.  Because of the precise 2d measurements of the acceleration of the halo stars, MOND models can be rejected as the explanation of the observed behavior.

Day 733

Friday.

1408.6608
Detection of the universal effect of the large scale velocity shear on they fall directions of the galactic satellites
Lee, Choi

Report a detection of the universal effect on the large-scale velocity shear on the infall directions of the galactic satellites into their hosts.  Identifying the isolated galactic systems each of which consists of a single host galaxy and its satellites from SDSS DR7 and using the velocity shear field recently reconstructed by Lee+ in the local universe, investigate the alignments between the relative positions of the satellites from their isolated haloes and the principal axes of the local velocity shear tensors.  Find a clear signal that the galactic satellites in isolated systems are located preferentially along the directions of the minor principal axes of the local velocity shears smoothed on the scale of 10 Mpc/h.  Those galactic satellites which are fainter and located at larger distances from the hosts are shown to yield stronger alignments.  It is also shown that the alignment strength is quite insensitive to the cosmic web environment as well as to the luminosity, mass, richness sand a morphology of the isolated hosts and their satellites, which is consistent with the recent prediction of Libeskind+ based on a N-body sim that the velocity shear effect on the satellite infall direction is universal.

1408.6611
The effective cross-sections of a lensing-galaxy: singular isothermal sphere with external shear
Lee, Kim

Numerical studies on the imaging and caustic properties of the SIS under a wide range of external shear (from 0.0 to 2.0) are presented.  Using a direct inverse-mapping formula for this lens system, investigate various lensing properties under both a low and high shear case: image separations, total or individual magnifications, flux ratios of 2 images, maximum number of images, and lensing cross-sections.  Systematically analyze the effective lending cross-sections of double-lensing and quad-lensing systems based on the radio luminosity function obtained by JVAS and CLASS.  Find that the limit of a survey selection bias (i.e., between a brighter- and a fainter-image) preferentially reduces the effective lensing cross-sections of 2-image lensing systems.  By considering the effects of survey selection bias, demonstrate that the long standing anomaly on the high Quads-to-Doubles ratios (JVAS & CLASS : 50-70%) can be explained by the moderate effective shear of 0.16-0.18, which is half of previous estimates.  The derived inverse mapping formula could facilitate the SIS+shear lens model to be useful for galaxy-lensing simulations.

Day 732

Thursday.

1408.6284
Weak lensing corrections to tSZ-lensing cross correlation
Tröster, Van Waerbeke

The cross correlation between the thermal tSZ effect and gravitational lensing in the wide field has recently been measured.  It can be used to probe the distribution of the diffuse gas in large scale structure, as well as inform us about the missing baryons.  As for any lensing -based quantity, higher order lensing effects can potentially affect the signal.  Extend previous higher order lensing calculations to the case of tSZ-lensing cross correlations.  Derive terms analogous to corrections due to the Born approximation, lens-lens coupling, and reduced shear up to fourth order in the Newtonian potential.  Redshift distortions and vector modes are shown to be negligible at this order.  Find that the dominant correction due to the reduced shear exceeds percent-level only at multipoles of ell>3000.

1408.6297
Statistical and systematic uncertainties in pixel-based source reconstruction algorithms for gravitational lensing
Tagore, Keeton

Gravtiational lens modeling of spatially resolved sources is a challenging inverse problem with many observational constraints and model parameters.  Examine established pixel-based source reconstruction algorithms for de-lensing the source and constraining lens model parameters.  Using test data for four canonical lens configurations, explore statistical and systematic uncertainties associated with gridding, source regularization, interpolation errors, noise, and telescope pointing.  Specifically, compare two gridding schemes in the source plane: a fully adaptive grid that follows the lens mapping but is irregular, and an adaptive Cartesian grid.  Also consider regularization schemes that minimize derivatives of the source (using two finite difference methods) and introduce a scheme that minimizes deviations from an analytic source profile.  Careful choice of gridding and regularization can reduce "discreteness noise" in the chi2 surface that is inherent in the pixel-based methodology.  With a gridded source, some degree of interpolation is unavoidable, and errors due to interpolation need to be taken into account (especially for high SN data).  Different realizations of the noise and telescope pointing lead to slightly different values for lens model parameters, and the scatter between different "observations" can be comparable to or larger than the model uncertainties themselves.  The same effects create scatter in the lensing magnification at the level of a few percent for a peak SN ratio of 10, which decreases as the data quality improves.

Day 731

Wednesday.

1408.5407
The stellar-to-halo mass relations of local galaxies segregated by color
Rodriguez-Puebla et al

Derive the stellar-to-halo mass relations, SHMR, of local blue and red central galaxies separately, as well as the fraction of haloes hosting blue/red central galaxies.  Find that: 1) the SHMR of central galaxies is segregated by color, with blue centrals having a SHMR above the one of red centrals; at logMh~12, the Ms/Mh ratio of the blue centrals is ~0.05, which is ~1.7 times larger than the value of red centrals.  2) the intrinsic scatters of the SHMRs of red and blue centrals are ~0.14 and ~0.11 dex, respectively.  The intrinsic scatter of the average SHMR of all central galaxies changes from ~0.20 dex to ~0.14 dex in the 11.3<logMh<15 range.  3) the fraction of haloes hosting blue centrals at Mh=1e11 Msun is 87%, but at 2e12 Msun decays to ~20%, approaching to a few per cents at higher masses.  The characteristic mass at which this fraction is the same for blue and red galaxies is Mh~7e11 Msun.  Results suggest that at the SHMR of central galaxies at large masses is shaped by halo mass quenching (likely through shock virial heating and AGN feedback), but group richness also plays an important role: central galaxies living in less dense environments quenched their star formation later or did not quench it yet.  At low masses, processes that delay SF without invoking too strong SN-driven outflows could explain the high Ms/Mh ratios of blue centrals as compared to those of the scarce red centrals.

1408.5898
Strong lensing, time delays, and the value of H$_0$
Barnacka, Geller, Dell'antonio, Benbow

Why does the H0 value vary from 50-100 km/s/Mpc?  It may arise from different components of the quasar (e.g. the jet).  Misidentifying a variable emitting region in a jet with emission from the core region may introduce an error in the Hubble constant derived from a time delay.  Investigate the complex structure of sources as the underlying physical explanation of the wide spared in values of H0 based on gravitational lensing.  MC sims demonstrate the potentially large impact of the position of the variable emitting region on H0 determination.  The derived value of the Hubble constant is very sensitive to the offset between the center of the emission and the center of the variable emitting region.  Based on these simulations, propose using the value of H0 known from other techniques to spatially resolve the origin of the variable emission once the time delay is measured.  Advocate this method particularly for gamma-ray astronomy, where the angular resolution of detectors reaches approximately 0.1 degree; lensed blazers offer the only route for identify the origin of gamma-ray flares.  Large future samples of gravitationally lensed sources identified with Euclid, SKA, and LSST will enable a statistical determination of H0.  The method should also provide new insights into the structure of the sources and their cosmic evolution at different energies.

1408.5970
The Sloan Digital Sky Survey reverberation mapping project: technical overview
Shen et al

4 day cadence with SDSS with >30 epochs, plus 2 day cadence with CFHT or Steward, of 849 broad-line quasars.  SDSS-RM is the first major program to systematically explore the potential of RM for road-line quasars at z>0.3, and will investigate the prospects of RM with all major broad lines covered in optical spectroscopy.  It will provide guidance on future multi-object RM campaigns on larger scales, and is aiming to deliver more than tens of BLR lag detections for a homogeneous sample of quasars.  

Day 730

Tuesday.

1408.5435
Tests of streaming models for redshift-space distortions
White, Reid, Chuang, Tinker, McBride, Prada, Samushia

Observations of redshift-space distortions in spectroscopic galaxy surveys offer an attractive method for observing the build-up for cosmological structure, which depends both on the expansion rate of the Universe and our theory of gravity.  In preparation for analysis of BOSS final data release, compare a number of analytic and phenomenological 'streaming' models, specified in configuration space, to mock catalogs derived in different ways from several N-body simulations.  The galaxies in each mock analog have properties similar to those of the higher redshift galaxies measured by BOSS but differ in the details of how small-scale velocities and halo occupancy are determined.  Find that all of the analytic models fit the simulations over a limited range of scales while failing at small scales.  Discuss which models are most robust and on which scales they return reliable estimates of the rate of growth of structure: find that models based on some form of resumption can fit the N-body data for BOSS-like galaxies above 30 Mpc/h well enough to return unbiased parameter estimates.

1408.5633
Measuring cluster masses with CMB lensing: a statistical approach
Melin, Bartlett

Present a method for measuring the masses of galaxy clusters using the imprint of their gravitational lensing signal on the CMB temperature anisotropies.  The method first reconstructs the projected gravitational potential with a quadratic estimator and then applies a matched filter to extract cluster mass.  The approach is well-suited for statistical analyses that bin clusters according to other mass proxies.  Find that current experiments such as Planck, SPT and ACT, can practically implement such a statistical methodology, and that future experiments will reach sensitivities sufficient for individual measurements of massive systems.  As illustration, use simulations of Planck observations to demonstrate that it tis possible to constrain the mass scale of a set of 62 massive clusters with prior information from X-ray observations, similar to the published Planck ESZ-XMM sample.  Examine the effect of the tSZ and kSZ signals, finding that the impact of kSZ remains small in this context.  The stronger tSZ signal, however, must be actively removed from the CMB maps by component separation techniques prior to reconstruction of the gravitational potential.  Study of 2 such methods highlights the importance of broad frequency coverage for this purpose.  A companion paper presents application to the Planck data on the ESZ-XMM sample.

1408.5790
Accretion history of the Milky Way dark matter halo and the origin of its angular momentum
Peebles

The flow of Dm into the MW and LMC in a model for the gravitational field of the neighboring galaxies yields a growth history of the DM halo of the MW that ends up with angular momentum roughly in the observed direction, and it produces a DM stream around the LMC that resembles the Magellanic Stream.

Day 729

Monday.

1408.5133
On the radiation driven alignment of dust grains: detection of the polarization hole in a starless core
Alves, et al

Investigate the polarization properties of a starless core in a very early evolutionary stage.  Linear polarization data reveal the properties of the dust grains in the distinct phases of the ISM.  The goal is to investigate how the polarization degree and angle correlate with the cloud and core gas.  Use optical, NIR and sub millimeter polarization observations toward the starless object Pipe-109 in the Pipe nebula.  Data cover a physical scale range of 0.08 to 0.4 pc, comprising the dense gas, envelope and the surrounding cloud.  The cloud polarization is well traced by the optical data.  The NIR polarization is produced by a mixed population of grains from the core border and the cloud gas.  The optical and NIR polarization toward the cloud reach the maximum possible value and saturate wrt the visual extinction.  Modeling of the sub millimeter polarization indicate a magnetic field main direction projected onto the plane-of-sky and loss of grain alignment for densities higher than 6e4 cm^-3 (or A_V>30 mag).  Pipe-109 is immersed in a magnetized medium, with a very ordered magnetic field.  The absence of the internal source of radiation significantly affects the polarization efficiencies in the core, creating a polarization hole at the center of the starless core.  This result supports the theory of dust grain alignment via radiative torques.

1408.5143
Next generation strong lensing time delay estimation with Gaussian processes
Hojjati, Linder

SL forms multiple, time delayed images of cosmological sources, with the "focal length" of the lens serving as a cosmological distance probe.  Robust estimation of the time delay distance can tightly constrain the Hubble constant as well as the matter density and DE.  Current and next generation surveys will find hundreds to thousands of lensed systems but accurate time delay estimation from noisy, gappy light curves is potentially a limiting systematic.  Using a large sample of blinded light curves from the SL TD challenge, develop and demonstrate a Gaussian Process cross correlation technique that delivers an average bias within 0.1% depending on the sampling, necessary for sub percent Hubble constant determination.  The fits are accurate (80% of them within 1 day) for delays from 5-100 days and robust against cadence variations shorted than 6 days.  Study the effects of survey characteristics such as cadence, season, and campaign length, and derive requirements for time delay cosmology: in order not to bias the cosmology determination by 0.5 sigma, the mean time delay fit accuracy must be better than 0.2%.

Day 728

Friday.

1408.4807
Connecting star formation quenching with galaxy structure and supermassive black holes through gravitational heating of cooling flows
Guo

SF quenching in galaxies is related to galaxy structure.  Propose a new mechanism to explain the physical origin of this correlation.  Assume that, while quiescent galaxies are maintained quenched by a  feedback mechanism, cooling flows in the hot halo gas can still develop intermittently.  Study cooling flows in a large suite of around 90 hydrodynamic sims of an isolated galaxy group, and find that the flow development depends significantly on the gravitational potential well in the central galaxy.  If the galaxy's gravity is not strong enough, cooling flows result in a central cooling catastrophe, supplying cold gas and feeding SF to galactic bulges.  When the bulge grows prominent enough, compressional heating starts to offset radiative cooling and maintains cooling flows in a long-term hot mode without producing cooling catastrophe.  The model thus describes a self-limited growth channel for galaxy bulges, and naturally explains the connection between quenching and bulge prominence.  In particular, explicitly demonstrate that M*/M_eff^1.5 is a good structural predictor of quenching. Further find that the gravity from the central SMBH also affects the bimodal fate of cooling flows, and predict a more general quenching predictor to be M_bh^1.6 M* / R_eff^1.5, which may be tested in future observational studies.

Day 727

Thursday.

1408.2720
The strongest gravitational lenses: IV. The order statistics of the largest Einstein radii with cluster mergers
Redlich, Waizmann, Bartelmann

Investigate the impact of galaxy-cluster mergers on the order statistics of the largest Einstein radii.  Show that the inclusion of mergers significantly shifts the extreme value distribution of the largest Einstein radius to higher values, typically increasing the expected value by ~10%.  A comparison with current data reveals that the largest observed Einstein radius agrees excellently well with the theoretical predictions of LCDM model at z>0.5.  At z<0.5, the results are somewhat more controversial.  Although cluster mergers also increase the expected values of the order statistics of the largest Einstein radii by ~10%, the theoretically expected values are notably lower (~3 sigma deviation for n=12) than the largest Einstein radii of a selected sample of SDSS clusters in the redshift range 0.1<z<0.55.  The uncertainties of the observed Einstein radii are still large, however, and thus the measurements need to be carefully revised in future works.  Therefore, given the premature state of current observational data, there is still no reliable statistical evidence for observed Einstein radii to exceed the theoretical expectations of the standard cosmological model.

1408.2907
Sailing under the Magellanic clouds: A DECam view of the Carina Dwarf
McMonigal, et al

Present deep optical photometry from the DECam imager on the 4m Blanco telescope of 12 deg^2 of the Carina dwarf spheroidal.

1408.4451
Black holes at the centers of nearby dwarf galaxies
Moran, et al

Identify 28 AGNs nearby (d<80 Mpc) low mass, low luminosity dwarf galaxies.  The accreting objects at the galaxy centers are expected to be intermediate-mass black holes (IMBHs) with M_BH<1e6 Msun.  The AGNS were selected using several optical emission-line diagnostics after careful modeling of the continuum present in the spectra.  Limited the survey to objects with spectral characteristics similar to those of Seyfert nuclei, excluding emission-line galaxies with ambiguous spectra that could be powered by stellar processes.  The his galaxies in the sample are thus the least massive objects in the very local universe certain to contain central BHs.  Given the focus on the nearest objects included in the SDSS, the survey is more sensitive to low-luminosity emission than previous optical searches for AGNs in low-mass galaxies.  The [O III] lambda 5007 luminosities of the Seyfert nuclei in the sample have a median value of L_5007=2e5 Lsun and extend down to 1e4 Lsun.  Using published data for broad-line IMBH candidates, have derived an [O III] bolometric correction of log (L_bol/L_5007) = 3.0pm0.3, which is significantly lower than values obtained for high-luminosity AGNs.  Applying this correction to the sample, obtain minimum black-hole mass estimates that fall mainly in the 1e3 Msun-1e4 Msun range, which is roughly where the predicted mass functions for different BH seed formation scenarios overlap the most.  In the stellar mass range that includes the bulk of the AGN host galaxies in the sample, derive a lower limit on the AGN fraction of a few percent, indicating that active nuclei in dwarf galaxies are not as rare as previously thought.

1408.4648
The redshift-space galaxy two-point correlation function and baryon acoustic oscillations
Jeong, Dai, Kamionkowski, Szalay

Describe the anisotropies that arise in the z-space galaxy 2PCF and elucidate the origin of features that arise in the dependence of the BAOs on the angle between the orientation of the galaxy pair and the line of sight.  Do so with a derivation of the configuration-space 2PCF using streaming model.  Find that, contrary to common belief, the locations of BAO peaks in the redshift-space 2PCF are anisotropic even in the linear theory.  Aniosotropies in BAO depend strongly on the method of extracting the peak, showing maximum 3% angular variation.  Also find that extracting the BAO peak of r^2 xi(r,mu) significantly reduces the anisotropy to sub-percent level angular variation.  When subtracting the tilt due to the broadband behavior of the 2PCF, the BAO bump is enhanced along the line of sight because of local infall velocities toward the BAO bump.  Precise measurement of the angular dependence of the z-space 2PCF will allow new geometrical tests of DE beyond the BAO.

1408.4742
Cosmic discordance: Are Planck CMB and CHFTLenS weak lensing measurements out of tune?
MacCrann, Zuntz, Bridle, Jain, Becker

Examine the level of agreement between low-z WL data and the CMB using CFHTLenS and Planck+WMAP polarization.  Perform an independent analysis of the CFHTLenS six bin tomography results of Heymans+ 2013.  Extend their systematics treatment and find the cosmological constraints to be relatively robust to the choice of NL modeling, extension to the AI model and inclusion of baryons.  Find that the 90% confidence contours of CFHTLenS and Planck+WP do not overlap even in the full 6D parameter space of LCDM, so the two datasets are discrepant.  Allowing a massive active neutrino or tensor modes does not significantly resolve the disagreement in the full n-dimensional parameter space.  Results differ from some i the literature because of the use of the full tomographic information in the WL data and marginalize over systematics.  Note that adding a sterile neutrino to LCDM does bring the 8D 64% contours to overlap, mainly due to the extra effective number of neutrino species, which is found to be 0.84pm0.35 (68%) greater than standard on combining the datasets.  Discuss why this is not a completely satisfactory resolution, leaving open the possibility of other new physics or observational systematics as contributing factors.  Provide updated cosmology fitting functions for the CFHTLenS constraints and discuss the differences from ones used in the literature.

1408.4758
Reconciling Planck cluster counts and cosmology: Chandra/XMM instrumental calibration and hydrostatic mass bias
Israel, Schellenberger, Nevalainen, Massey, Reiprich

Temperature of X-ray emitting gas T_X is often used to infer the total mass of galaxy clusters (under the assumption of hydrostatic equilibrium).  Unfortunately, XMM-Newton and Chandra observatories measure inconsistent temperatures for the same gas, due to uncertain instrumental calibration.  Translate the relative bias in T_X measurements of Schellenberger+ 2014 into a bias on inferred mass for a sample of clusters with homogeneous WL masses, to simultaneously examine the hydrostatic bias and instrument calibration.  Israel+2014 found consistent WL and Chandra hydrostatic X-ray masses for a sample of clusters at z~0.5 and masses of a few 1e14 Msun . Find their XMM-Newton masses to be lower by b^xcal=15-20% than their Chandra masses.  At the massive end (>5e14 Msun), the XMM-Newton masses are~35% lower than the WL masses.  Assuming that the true hydrostatic bias is 20%, as indicated by simulations, results for the massive end indicate that Chandra's calibration of the energy dependence of the effective area is more accurate than XMM-Newtons's.  However, the opposite appears to be true at the low mass end.  In addition, follow through how a bias in the T_X would affect the Planck cluster counts.  X-ray masses feature prominently in the apparent discrepancy between Planck measurement of the CMB and the number of clusters detected via the SZ effect.  The SZ masses were indirectly calibrated via XMM-Newton observations.  Assuming the Chandra calibration to be correct, and amplified residual calibration bias (up to ~30% in mass) could ease the tension in the cosmological interpretation, while keeping the bias due to departures from hydrostatic equilibrium b^hyd~0.2, as expected from simulations.

Day 726

Wednesday.

1408.4211
Signatures of a companion star in Type Ia Supernovae
Maeda, Kutsuna, Shigeyama

While SNe Ia have been used as precise cosmological distance indicators, their progenitor systems remain unresolved.  One of the key questions is if there is a non-degenerate companion star at the time of a thermonuclear explosion of a WD.  Investigate if an interaction between the SN ejecta and the companion star may result in observable footprints around the maximum brightness and thereafter, by performing multidimensional radiation transfer simulations based on hydro sims of the interaction.  Find that such systems result in variations in various observational characteristics due to different viewing directions, while the predicted behaviors (redder and fainter for the companion direction) are opposite to what were suggested by the previous study.  The variations are generally modest and within observed scatters.  However, the model predicts trends between some observables different from observationally derived, thus a large sample of SNe Ia with small calibration errors may be used to constrain the existence of such a companion star.  The variations in different colors in optical band passes can be mimicked by external extinctions, thus such an effect could be a source of a scatter in the peak luminosity and derived distance.  After the peak, hydrogen-rich materials expelled from the companion will manifest themselves in hydrogen lines.  Halpha is however extremely difficult to identify.  Alternatively, find that P_beta in post-maximum NIR spectra can potentially provide powerful diagnostics.

1408.4323
Kepler and the long period variables
Hartig et al

Track photometry of 8 SR AGB stars using 30 minute cadence over a period of 45 months.  Light curves are shown to be smooth at the millimagnitude level over shorter time intervals.  No flares or other rapid events detached on the sub-day time scale.  Shortest AGB period detected is on the order of 100 days.  All SR variables shown to have multiple modes, typically fundamental + first overtone.  A second common characteristic of SR variables is shown to be the simultaneous excitation of multiple closely separated periods for the same overtone mode.  Approximately half the sample had a much longer variation in the light curve, likely a long secondary period.  The light curves were all well represented by a combination of sinusoids.  However, the properties of the sinusoids are time variable with irregular variations present at low level.  No non-radial pulsations were detected. It is argued that the long secondary period variation seen in many SR variables is intrinsic to the star and linked to multiple mode pulsation.  

Day 725

Tuesday.

1408.3631
Prospects for measuring the mass of black holes at high redshifts with resolved kinematics using gravitational lensing
Hezaveh

Application of the most robust method of measuring black hole masses, spatially resolved kinematics of gas and stars, is presently limited to nearby galaxies.  ALMA and 30-m class telescopes with milli-arcsecond resolution are expected to extend such measurements to larger distances.  Study the possibility of exploiting the angular magnification provided by strong gravitational lensing to measure black hole masses at high z (z~1-6), using resolved gas kinematics with these instruments.  Show that in ~15% and 20% of strongly lensed galaxies, the inner 25 and 50 pc could be resolved, allowing the mass of 1e8 Msun BHs to be dynamically measured with ALMA, if moderately bright molecular gas is present at these small radii.  Given the large number of SLs discovered in current millimeter surveys and future optical surveys, this fraction could constitute a statistically significant population f0or studying the evolution of the M-sigma relation at high z.

1408.3832
Analytical models for non-thermal pressure in galaxy clusters II: comparison with cosmological hydrodynamics simulation
Shi, Komatsu, Nelson, Nagai

Turbulent gas motion inside galaxy clusters provides a non-negligible non-thermal pressure support to the intracluster gas.  If not corrected, it leads to a systematic bias in the estimation of cluster masses from X-ray and SZ observations assuming hydrostatic equilibrium, and affects interpretation of measurements of the SZ PS and observations of cluster outskirts from ongoing and upcoming large cluster surreys.  Recently, Shi & Komatsu 2014 developed an analytical model for predicting the radius, mass, and redshift dependence of the non-thermal pressure contributed by the kinetic random motions of intracluster gas sourced by the cluster mass growth.  In this paper, compare the predictions of this analytical model to a state-of-the-art cosmological hydro sim.  As different mass growth histories result in different non-thermal pressure, perform the comparison on 65 simulated galaxy clusters on a cluster-by-cluster basis.  Find excellent agreement between the modeled and simulated non-termal pressure profiles.  Results open up the possibility of using the analytical model to correct the systematic bias and the mass estimation of galaxy clusters.  Also discuss tests of the physical picture underlying the evolution of intracluster turbulence, as well as a way to further improve the analytical modeling, which may help achieve a unified understanding of non-thermal phenomena in galaxy clusters.

Day 724

Monday.

1408.3407
Massive star archeology in globular clusters
Chantereau, Charbonnel, Meynet

Globular clusters are among the oldest structures in the Universe and they host today low-mass stars and no gas.  However, there has been a time when they formed as gaseous objects hosting a large number of short-lived, massive stars.  Many details on this early epoch have been depicted recently through unprecedented dissection of low-mass globular cluster stars via spectroscopy and photometry.  In particular, multiple populations have been identified, which bear the nucleosynthetic fingerprints of the massive hot stars long disappeared.  Discuss here how massive star archeology can be done through the lens of these multiple populations.

1408.3408
Hubble space telescope proper motions along the Sagittarius Stream: I. Observations and results for stars in four fields
Sohn, van der Marel, ... Kallivayalil, et al

Present HST study of stellar proper motions (PMs) for four fields spanning 200 degrees along the Sgr stream: one field in the trailing arm, one field near the Sgr dSph tidal radius, and two fields in the leading arm.  From data with 6-9 year time baselines, determine absolute PMs of dozens of individual stars per field, using established techniques that use distant background galaxies to define a stationary reference frame.  Stream stars are identified based on combined color-magnitude diagram (CMD) and PM information.  The results are broadly consistent with the few existing PM measurements for the Sgr dSph and the trailing arm.  However, new results provide the highest PM accuracy for the stream to date, the first PM measurements for the leading arm, and the first PM measurements for individual stream stars [also serendipitously determine the PM of the globular cluster NGC 6652 to be (5.6,-4.5) mas/yr].  In the trailing-arm field, the individual PMs allow kinematical separation of the trailing-arm stars from leading-arm stars that are 360 degrees further ahead in their orbit around the MW.  Also, in three of the fields, find indications that two distinct kinematical components may exist within the same arm and wrap of the stream.  Qualitative comparison of the HST data to the predictions of the Law& Majewski N-body model of the stream show that the PM measurements closely follow the predicted trend with Sgr longitude.  While this does not necessarily indicate that the triaxial MW dark halo shape inferred from the N-body model is correct, it does provide a successful consistency check using PM data that the model was not tailored to reproduce.  Quantitative data-model comparisons will be presented in a companion paper.

1408.3409
BONNSAI: a Bayesian tool for comparing stars with stellar evolution models
Schneider, Langer, ... Izzard, Lau

Powerful telescopes equipped with multi-fibre or IFS combined with detailed models of stellar atmospheres and automated fitting techniques allow for the analysis for large number of stars. These datasets contain a wealth of information that require new analysis techniques to bridge the gap between observations and stellar evolution models.  To that end, develop BONNSAI (BONN Stsellar Astrophyscis Interface), a Bayesian statistical method, that is capable of comparing all available observables simultaneously to stellar models while taking observed uncertainties and prior knowledge such as IMF and distributions of stellar rotational velocities into account.  BONNSAI can be used to (1) determine probability distributions of fundamental stellar parameters such as initial mass and stellar ages from complex datasets, (2) predict stellar parameters that were not yet observationally determined and (3) test stellar models to further advance the understanding of stellar evolution.  An important aspect of BONNSAI is that it singles out stars that cannot be reproduced by stellar models through chi^2 hypothesis tests and posterior predictive checks.  BONNSAI can be used with any set of stellar models and currently supports massive main-sequence single star models of MW and LMC and SMC composition.  Apply new method to mock stars to demonstrate its functionality and capabilities.  In a first application, use BONNSAI to test the stellar models of Brott+2011 by comparing the stellar ages inferred for the primary and secondary stars of eclipsing MW binaries.  Ages are determined from dynamical masses and radii that are known to better than 3%.  Find that the stellar models reproduce the MW binaries well.  BONNSAI is available through a web-interface.

1408.3524
Cosmic-ray exposure ages of fossil micrometeorites from mid-Ordovician sediments at Lynna River, Russia

Measure the He and Ne concentrations of 50 individual extraterrestrial chromite grains recovered from mid-Ordovician (lower Darriwilian) sediments from the Lynna River section near St. Petersburg, Russia.  High concentrations of solar wind-like He and Ne found in most grains indicate that they were delivered to Earth as micrometeoritic dust, while their abundance, stratigraphic position and major element composition indicate an origin related to the L chondrite parent body (LCPB) break-up even, 470 Ma ago.  Compared to sediment-dispersed extraterrestrial chromite (SEC) grains extracted from coeval sediments at other localities, the grains from Lynna River are both highly concentrated and well preserved.  As in previous work, in most grains from Lynna River, high concentrations of solar wind-derived He and Ne impede a clear quantification of cosmic-ray produced He and Ne.  However, we have found several SEC grains poor in solar wind Ne, showing a resolvable contribution of cosmogenic 21Ne.  This makes it possible, for the first time, to determine robust CR exposure (CRE) ages in these fossil micrometeorites, on the order of a few hundred-thousand years.  These ages are similar to the CRE ages measured in chromite grains from cm-sized fossil meteorites recovered from coeval sediments in Sweden.  As the CRE ages are shorted than the orbital decay time of grains of this size by Poynting-Robertson drag [solar radiation causing a dust grain orbiting a star to lose angular momentum, causing dusts that are small enough to be affected by this drag, but too large to be blown away from the star, to spiral into the star], this suggests that the grains were delivered to Earth through direct injection into an orbital resonance.  Demonstrate how CRE ages of fossil micrometeorites can be used, in principle, to determine sedimentation rates, and to correlate the sediments at Lynna River with the fossil meteorite-bearing sediment layers in Sweden.

1408.3531
Constraints on 3.55 keV line emission from stacked observations of dwarf spheroidal galaxies
Malyshev, Neronov, Eckert

Analysis shows no evidence for the presence of the line in the stacked spectra of the dwarf galaxies.

1408.3578
Unveiling the secrets of metallicity and massive star formation using DLAs along gamma-ray bursts
Cucchiara, Fumagalli, ... Prochaska, et al

GRB hosts are star-forming, and have, on average, higher metallicity than the general QSO-DLA population.  

Day 723

Friday.

1408.3126
Using large scale structure to test multi field inflation
Ferraro, Smith

Primordial non-Gaussianity of local type is known to produce a scale-dependent contribution to the galaxy bias.  Several classes of multi-field inflationary models predict non-Gaussian bias which is stochastic, in the sense that dark matter and haloes don't trace each other perfectly on large scales.  In this work, forecast the ability of next-generation LSS surveys to constrain common types of primordial non-Gaussianity like f_NL, g_NL and tau_NL using halo bias, including stochastic contributions.  Provide fitting functions for statistical errors on these parameters which can be used for rapid forecasting or survey optimization.  A next-generation survey with volume V=25 Mpc^3/h^3, median redshift z=0.7 and mean bias b_g=2.5, can achieve sigma(f_NL)=6, sigma(g_NL)=1e5 and sigma(tau_NL)=1e3 if no mass information is available.  If halo masses are available, show that optimal weighting the halo field in order to reduce sample variance can achieve sigma(f_NL)=1.5, sigma(g_NL)=1e4 and sigma(tau_NL)=100 if haloes with mass down to M_min=1e11 Msun/h are resolved, outperforming Planck by a factor of 4 on f_NL and nearly an order of magnitude on g_NL and tau_NL.  Finally, study the effect of photometric redshift errors and discuss degeneracies between different non-Gaussian parameters, as well as the impact of marginalizing Gaussian bias and shot noise.

Day 722

Thursday.

1408.2825
Progress with the Prime Focus Spectrograph for the Subaru telescope: a massively multiplexed optical and near-infrared fiber spectrograph
Sugai, et al

The PSF is an optical/NIR multi-fiber spectrograph with 2394 science fibers, which are distributed in 1.3 degree diameter FoV at the Subaru 8.2m telescope.  The simultaneous wide wavelength coverage from 0.38 um to 1.26 um, with the resolving power of 3000, strengthens its ability to target 3 main survey programs: cosmology, galactic archaeology, and galaxy/AGN evolution.  A medium resolution mode with resolving power of 5000 for 0.71um to 0.89 um also will be available by simply exchanging dispersers.  PFS takes the role for the spectroscopic part of the Subaru Measurement of Images and Redshifts project, while Hyper Suprime-Cam works on the imaging part.  To transform the telescope plus WFC focal ratio, a 3-mm thick broad-band coated glass-molded micro lens is glued to each fiber tip.  A higher transmission fiber is selected for the longest part of the cable system, while one with a better FRD performance is selected for the fiber-positioned and fiber-slit components, given the more frequent fiber movements and tightly curved structure.  Each Fiber positioned consists of two stages of piezo-electric rotary motors.  Its engineering model has been produced and tested.  Fiber positioning will be performed iteratively by taking an image of artificially back-illuminated fibers with the Metrology camera located in the Cassegrain container.  The camera is carefully designed so that fiber position measurements are unaffected by small amounts of high spatial-frequency inaccuracies in WFC lens surface shapes.  Target light carried through the fiber system reaches one of four identical fast-Schmidt spectrograph modules, each with three arms.  Prototype VPH gratings have been optically tested.  CCD production is complete, with standard fully-depleted CCDs for red arms and more-challenging thinner fully-depleted CCDs with blue-optimized coating for blue arms.

1408.2832
Finding rocky asteroids around white dwarfs by their periodic thermal emission
Lin, Leob

Since old WDs are exceptionally dim, the contrast between the thermal emission of an orbiting object and a WD is dramatically enhanced compared to a MS host.  Furthermore, rocky object much smaller than the moon have no atmospheres and are tidally locked to the WD if they orbit near the Roche zone.  Show that this leads to temperature contrasts between the is day and night side of order unity that should lead to temporal variations in IR flux over an orbital period of 0.2 to 2 days.  Ground based telescopes could detect objects with a mass as small as 1% of the lunar mass M_L around Sirius B with a few hours of exposure.  JWST may be able to detect objects as small as 1e-3 M_L around most nearby WDs.  The tightest constraints will typically be placed on 12k K WDs, whose Roche zone coincides with the dust sublimation zone.  Constraining the abundance of minor planets around WDs as a function of their surface temperatures (and therefore age) provides a novel probe for the physics of planetary formation.

Day 721

Wednesday.

1408.2511
The FUV to Near-IR morphologies of luminous infrared galaxies in the GOALS sample
Petty, et al

Compare the morphologies of 20 LIRGs in the FUV, B, I and H bands, using Gini (G) and M20 parameters to quantitatively estimate the distribution and concentration of flux as a function of wavelength.  HST images provide an average spatial resolution of ~80 pc.  While the LIRGs can be reliably classified as mergers across the entire range of wavelengths studied here, there is a clear shift toward more negative M20 (more bulge-dominated) and a less significant decrease in G values at longer wavelengths.  Find no correlation between the derived FUV G-M20 parameters and the global measures of the IR to FUV flux ratio, IRX.  Given the fine resolution in the HST data, this suggests either that the UV morphology and IRX are correlated on very small scales, or that the regions emitting the bulk of the IR emission emit almost no FUV light.  Use the multi-wavelength data to simulate how merging LIRGs would appear from z~0.5-3 in deep optical and NIR images such as the HUDF, and use these simulations to measure the G-M20 at these redshfits.  Simulations indicate a noticeable decrease in G, which flattens at z>=2 by as much as 40%, resulting in mis-classifying the LIRGs as disk-like, even in the rest-frame FUV.  The higher redshift values of M20 for the GOALS sources do not appear to change more than about 10% from the values at z~0.  The change in G-M20 is caused by the surface brightness dimming of extended tidal features and asymmetries, and also the decreased spatial resolution which reduced the number of individual clumps identified.  This effect, seen as early as z~0.5, could easily lead to an underestimate of the number of merging galaxies at high-redshift in the rest-frame FUV.

1408.2526
The first billion years project: gamma-ray bursts at z>5
Elliott, et al

LGRBs have been suggested as close tracers of the underlying SFR in the universe.  They could potentially be used to probe the cosmic SFH with high accuracy due to their high luminosities.  Utilise two cosmological simulations from the First Billion Years project to investigate the systematic biases between the CSFH and the LGRB rate at z>5.  Populate LGRBs using a Monte-Carlo technique and a sub-selection based on environmental metallicity, progenitor stellar mass and ante.  Using a physically motivated LGRB progenitor model, demonstrate that the LGRB rate should trace the CSFH to high redshifts z>5.  The measured LGRB rate suggests that LGRBs have opening angles of 0.1 degrees, although the degeneracy with the progenitor model cannot rule out an underlying bias.  Demonstrate that proxies that relate the LGRB rate with global LGRB host properties do not reflect the underlying LGRB environment, and are in fact a result of the host galaxy's spatial properties, such that LGRBs can easily exist in galaxies of solar metallicity. However, find a sub-class to host galaxies that have low stellar mass and are metal-rich, to the extent that their metallicity dispersions would not allow low-metallicity environments.  Detection of a host galaxy with this set of global properties would directly reflect the progenitor's environment without information on the progenitor's environment itself.  Predict that 10% of LGRBs per year are associated with this subset of host galaxies.  The forbidden line emission of these galaxies would be bright enough to be detected by instruments mounted on JWST.  Such a discovery would place strong constraints on the collapsar model and suggest other avenues to be investigated, e.g., binary progenitor models.  
1408.2543
Cupid is doomed: an analysis of the stability of the inner Uranian satellites
French, Showalter

Cupid and Belinda are the first satellite to cross orbits, and they do so on a time scale of 1e3-1e7 years.  Cressida and Desdemona are next, in 1e5 to 1e7 years.  Show that the crossing times are highly sensitive to ICs and that Cupid's instability is related to its resonant interactions with Belinda.  Show that a previously discovered power law, which relates orbit crossing time to satellite mass, is valid across a wide range of masses.  Generalize the power law to handle two unstable orbital pairs with overlapping lifetimes and show that it can be used to extend the time span of studies of orbital stability in a computationally efficient manner.  Results suggest that the current Uranian satellite system is in transition and that the moons will continue to collide and reaccrete for the foreseeable future.

1408.2553
Quenching of star formation in SDSS groups: centrals, satellites and galactic conformity
Knobel, Lilly, Woo, Kovac

Re-examine the fraction of low-z SDSS satellite and centrals in which SF has been quenched, using the environment quenching efficiency formalism that separates out the dependence of stellar mass.  Show that the centrals of the groups containing the satellites are responding to the environment in the same way as their satellites, and that the well known differences between satellite and the general set of centrals arises because the latter are overwhelmingly dominated by isolated galaxies.  The widespread concept of "satellite quenching" as the cause of environmental effects in the galaxy population can therefore be generalized to "group quenching".  Then explore the dependence of the quenching efficiency of satellites on overdensity, group-centric distance, halo mass, the stellar mass of the satellite, and the stellar mass and sSFR of its central, trying to isolate the effect of these often interdependent variables.  Emphasize the importance of the central sSFR in the quenching efficiency of the associated satellites, and develop the meaning of this "galactic conformity" effect in a probabilistic description of the quenching of galaxies.  Show that conformity is strong, and that it varies strongly across parameter space.  Several arguments then suggest that environmental quenching and mass quenching may be different manifestations of the same underlying process.  These include the fact that mass quenching of galaxies is associated with the same halo masses that apparently see the onset of environmental effects in the satellites.  The marked difference in the apparent mass dependencies of environment quenching and mass quenching which produces distinctive signatures in the mass functions of centrals and satellites will arise naturally, since the distribution of the environmental variables are essentially independent of the stellar mass of the satellite.

Day 720

Tuesday.

1408.2050
Stellar origin of the 182Hf cosmochronometer and the presolar history of solar system matter
Lugaro et al

Among the short-lived radioactive nuclei inferred to be present in the early solar system via meteoritic analyses, there are several heavier than iron whose stellar origin has been poorly understood.  In particular, the abundances inferred for 182Hf (half-life = 8.9Myr) and 129I (half-life=15.7Myr) are in disagreement with each other if both nuclei are produced by the rapid neutron-capture process.  Here, demonstrate that contrary to previous assumption, the slow neutron-capture process in asymptotic giant branch stars produces 182Hf.  This has allowed us to date the last rapid and slow neutron-capture events that contaminated the solar system material at roughly 100Myr and 30 Myr, respectively, before the formation of the Sun.

1408.2295
Measurement of differential magnification
Er

In gravitational lensing, the magnification effect changes the luminosity and size of a background galaxy.  If the image sizes are not small compared to the scale over which the magnification and shear vary, higher-order distortions occur which are termed differential magnification.  Give an approximation of the magnification gradient for several halo models.  Assuming a symmetric distribution of source brightness, estimate for the differential magnification are obtained and then tested with simulations.  One of the main uncertainties of the estimators comes from the finite resolution of the image.  Study the strength of the method with the resolution of current and future telescopes.  Point out that the method is a potential approach to estimate the first flexion, and can be used to study galaxy and cluster mass profiles.

1408.2337
Supermassive black holes with high accretion rates in active galactic nuclei: II. the most luminous standard candles in the Universe
Wang, et al

Use reverberation mapping (RM) to measure BH mass; identify super-Eddington accreting massive black holes (SEAMBHs) and use their unique properties to construct a new method for measuring cosmological distances.  The saturated bolometric luminosity of such sources is proportional to the BH mass which can be used to obtain their distance.  Report on five new RM measurements and show that in four of the cases, can measure the BH mass and 3 of these sources are SEAMBHs.  Collect more samples.  The ratio of the newly measured distance s to the standard cosmological ones has a mean scatter of 0.14 dex, indicating that SEAMBHs can be used as cosmological distance probes.  With their high luminosity, long period of activity and large numbers at high redshifts, SEAMBs have a potential to extend the cosmic distance ladder beyond the range now explored by Type Ia SNe.

Day 719

Monday.

1408.1744
The impact of super-survey modes on cosmological constraints from cosmic shear fields
Carron, Szapudi

Owing to the mass-sheet degeneracy, cosmic shear maps do not probe directly the Fourier modes of the underlying mass distribution on scales comparable to the survey size and larger. To assess the corresponding effect on attainable cosmological parameter constraints, quantify the information on surper-survey modes in a lognormal model and, when interpreted as nuisance parameters, their degeneracies to cosmological parameters.  The analytical and numerical calculations clarify the central role of super-sample covariance (SSC) in shaping the statistical power of cosmological observables.  Reconstructing the background modes from their non-Gaussian statistical dependence to small scales modes yields the renormalized convergence.  The diagonalizes the spectrum covariance matrix, and the information content of the corresponding PS is increased by a factor of 2 over standard methods.  Unfortunately, careful calculation of the Cramer-Rao bound shows that the information recovery can never be made complete.  Any observable built from shear fields, including optimal sufficient statistics, are subject to severe information loss, typically 80 to 90% below ell~3000 for generic cosmological parameters.  The lost information can only be recovered from additional, non-shear based data.  Predictions hold just as well for tomographic analysis, and/or full sky surveys.

1408.1872
Probing spatial homogeneity with LTB models: a detailed discussion
Redlich, ... Bartelmann, et al

To address the question of any statistical evidence for deviations from spatial homogeneity on large scales, developed a flexible framework based on spherically symmetric, but radial inhomogeneous LTB models with synchronous Big Bang.  A Monte Carlo Technique in combination with recent observational data was used to systematically vary the shape of the profiles.  (i) Reconsider giant LTB voids without DE to investigate whether extremely fine-tuned mass profiles can reconcile models with current data.  It can, but requires a Hubble rate which is too low compared to observations.  (ii) explain why it seems natural to extend the framework by a non-zero cosmological constant, which then allows general tests of the cosmological principle.  These extended models facilitate explorating whether fluctuations in the local matter density profile might potentially alleviate the tension between local and global measurements of the Hubble rate, as derived from Cepheid-calibrated type Ia SNe and CMB experiments, respectively.  Show that current data provide no evidence for deviations from spatial homogeneity on large scales.  More accurate constraints are required to ultimately confirm the validity of the cosmological principle, however.

Day 718

Friday.

1408.1476
Galaxy and mass assembly (GAMA): galaxy close-pairs, mergers, and the future fate of stellar mass
Robotham, et al

Use a highly complete subset of the GAMA-II redshift sample to fully describe the stellar mass dependence of close-pairs and mergers between 1e8 Msun and 1e12 Msun.  Using the analytic form of this fit, investigate the total stellar mass accreting onto more massive galaxies across all mass ratios.  Depending on how conservatively the merging system are selected, the fraction of mass merging onto more massive companions is 2.0-5.6%.  Using the GAMA-II data, see no significant evidence for a change in the close-pair fraction between redshift z=0.05-0.2.  However, find a systematically higher fraction of galaxies in similar mass close-pairs compared to published results over a similar redshift baseline.  Using a compendium of data and the function gamma_M=A(1+z)m to predict the major close-pair fraction, find fitting parameters of A=0.021pm0.001 and m=1.53pm0.08, which represents a higher low-z normalization and shallower power-law slope than recent literature values.  Find that the relative importance of in-situ SF versus galaxy merging is inversely correlated, with SF dominating the addition of stellar material below Mstar and merger accretion events dominating beyond M*.  Find mergers to have measurable importance on the whole extend of the GSMF, manifest as a deepening of the dip in the GSMF over the next Gyr and an increase in Mstar by as much as 0.01-0.05 dex.

Day 717

Thursday.

1408.1097
Imfit: a fast, flexible new program for astronomical image fitting
Erwin

Fits to 2d surface-brightness functions, with the typical galaxy decompositions (Sersic, exponential, Gaussian) along with core-Sersic and broken-exponential profiles, elliptical rings, and 3 components which perform LoS integration through 3d luminosity density models of disks and rings seen at arbitrary inclinations.  Available minimization algorithms include Levenberg-Marquardt, Nelder-Mead simplex, and Differential Evolution, allowing trade-offs between speed and decreased sensitivity to local minima in the fit landscape.  Minimization can be done using the standard chi^2 statistic (using either data or model values to estimate per-pixel Gaussian errors, or else user-supplied error images) or the Cash statistic; the latter is particularly appropriate for cases of Poisson data in the low-count regime.  Show that fitting low-S/N galaxy images using chi^2 minimization can lead to significant biases in fitted parameter values, which are avoided if the Cash statistic is used; this is true even when Gaussian read noise is present.  [What about PSFs?  seems to be suited for fitting large, well resolved galaxies.]

1408.1099
The Atlas3D project - XXIV. The intrinsic shape distribution of early-type galaxies
Weijmans, et al

Use photometric and kinematic data from Atlas3D.  Based on their ellipticity measurements from SDSS DR7 and additional imaging, first invert the shape distribution of fast and slow rotators under the assumption of axisymmetry.  The so-obtained intrinsic shape distribution for the fast rotators can be described with a Gaussian with a mean flattening of q=0.25 and standard deviation sigma_q=0.14, and an additional tail towards rounder shapes.  The slow rotators are much rounder, and are well described with a Gaussian with mean q=0.63 and sigma_q=0.09 .  Then check that the realists are consistent when applying a different and independent method to obtain intrinsic shape distributions, by fitting the observed ellipticity distributions directly using Gaussian parameterizations for the intrinsic axis ratios.  Although both fast and slow rotators are identified as early-type galaxies in morphological studies, and in many previous shape studies are therefore grouped together, their shape distributions are significantly different, hinting at different formation scenarios.  The intrinsic shape distribution of the fast rotators shows similarities with the spiral galaxy population.  Including the observed kinematic misalignment in the intrinsic shape study shows that the fast rotators are predominantly axisymmetric, with only very little room for triaxiality.  For the slow rotators though there are very strong indications that they are (mildly) triaxial.

Day 716

Tuesday.  Wednesday.

1408.0797
Microlens masses from 1-D parallaxes and heliocentric proper motions
Gould

1D microlens parallaxes can be combined with heliocentric lens-source relative proper motion measurements to derive the lens mass and distance, as suggested by Ghosh+2004.  Present the first mathematical analysis of this procedure, which can be shown to be represented as a quadratic equation.  It is formally subject to a 2-fold degeneracy.  Show that this degeneracy can be broken in many cases using the relatively crude 2D parallax information that is often available for microlensing events.  Also develop an explicit formula for the region of parameter space where it is more difficult to break this degeneracy.  Although no mass/distance measurements have yet been made using this technique, it is likely to become quite common over the next decade.

1408.0799
Mapping the cosmic web with the largest all-sky surveys
Bilicki, Peacock, et al

In order to reliably map the Universe to cosmologically significant depth over the full celestial sphere, one must draw on multi wavelength datasets and photo-z techniques.  Cross-match the largest photometric all-sky surveys (2MASS, WISE and SuperCOSMOS) to obtain accurate redshift estimates of millions of galaxies.  The first is the 2MASS Photometric Redshift Catalog (2MPZ, Bilicki+2014) is public and includes almost 1e6 galaxies with <z>=0.08.  Summarize how this catalog was constructed, and how using the WISE MIR sample together with SuperCOSMOS optical data allows to push to redshift shells of z~0.2-0.3 on unprecedented angular scales.  The catalogs, with ~20M sources in total, provide access to cosmological volumes crucial for studies of local galaxy flows (clustering dipole, bulk flow) and cross-correlations with the CMB such as ISW or lensing.

1408.0816
Molecular gas content in strongly-lensed z~1.5-3 star-forming galaxies with low IR luminosities
Dessauges-Zavadsky, ...Egami, ... Rex, Kneib, ... et al

To extend the molecular gas measurements to typical SFGs with SFR<40Msun/yr and M*<2.5e10 Msun at z~1.5-3, observe CO emission for 5 strongly lensed galaxies selected from the Herschel Lensing Survey.  Combine with a compilation of CO measurements from the literature.  Infer luminosity correction factors of the CO rotational levels J=2 and 3, valid for SFGs and sub-mm galaxies at z>1.  The combined sample of CO-detected SFGs at z>1 shows a large spared in SF efficiency (SFE), such that SFE extend beyond the low values of local spirals and overlap the distribution of z>1 submm galaxies.  Find that the spread in SFE (or equivalently in molecular gas depletion timescale) is due to primarily the sSFR, but also stellar mass and redshift.  Correlations of SFE with the offset from the MS and the compactness of the starburst are less clear.  The increase of the molecular gas depletion timescale with M* now revealed by low M* SFGs at z>1 is opposed to the admitted constant molecular gas depletion timescale and the linear KS relation.  Confirm an increase of the molecular gas fraction (fgas) from z~0.2 to z~1.2, followed by a quasi non-evolution toward higher redshifts.  At each redshift fgas shows a large dispersion due to the dependence on fgas on M*, producing a gradient of increasing fgas with decreasing M*.  Provide the first measure of fgas of z>1 SFGs at the low-M* end (1e9.4 < M*/Msun < 1e9.9), reaching a mean fgas=0.67pm0.20 which shows a clear fgas upturn.  Finally, find evidence for a non-universal dust-to-gas ratio among high-z SFGs and sub-mm galaxies, local spirals and ULIRGs with near solar metallicities.

1408.1081
Super-sample signal
Li, Hu, Takada

PS measurements extracting cosmo params require consideration of the impact of super-sample density fluctuations, larger than the survey scale.  These modes contribute to the mean density fluctuations delta_b in the survey and change the PS in the same was as a change in the cosmological background.  They can be simply included in cosmo param estimation and forecasts by treating delta_b as an additional cosmological parameter enabling efficient exploration of its impact.  Verify that the minimum variance estimator of delta_b is both unbiased and has the predicted variance using sub-volumes of large-volume N-body sims for PS measured wrt either the global or local mean density, e.g., for WL or galaxy clustering.  Parameter degeneracies arise since the response of the PS to delta_b and cosmological parameters share similar properties in changing the growth of structure and dilating the scale of features, especially in the local case.  In the absence of external constraints in the variance of delta_b, degeneracies can lead to a factor of 4-5 degradation in the errors of certain combinations of LCDM cosmo params for a wide range of survey volumes when using info out to k<~2h/Mpc.  Even with perfect info on the variance, the degradation can be a factor of 2-3 for one combination in the global case though its impact on individual parameters is smaller.  These techniques can easily extended to other parameter spaces and cosmological observables or to include baryonic effects.

Day 715

Monday.

1408.0001
The bones of the Milky Way
Goodman, et al

The very long and think IR dark cloud "Nessie" is longer than previously claimed, and an analysis of its Galactic location suggests that it lies directly in the MW's mid-plane, tracing out a highly elongated bone-like feature within the prominent Scutum-Centaurus spiral arm.  Re-analysis of MIR imagery from Spitzer show that this IRDC is at least 2, and possibly as many as 5 times longer than had originally been claimed by Nessie's discoverers; its aspect ratio is therefore at least 300:1, and possibly as large as 800:1.  A careful accounting for both the Sun's offset form the Galactic plane (~25 pc) and the Galactic center's offset from the (l,b)^H=(0,0) position shows that the latitude of the true Galactic mid-lane at the 3.1 kpc distance to the Scutum-Centaurus Arm is not b=0, but instead closer to b=-0.4, which is the latitude of Nessie to within a few pc.  An analysis of the radial velocities of low-density (CO) and high-density (NH3) gas associated with the Nessie dust feature suggests that Nessie runs along the Scutum-Centaurus Arm in position-position-velocity space, which means it likely forms a dense 'spine' of the arm in real space as well.  The Scutum-Centaurus arm is the closest major spiral arm to the Sun toward the inner Galaxy, and, at the longitude of Nessie, it is almost perpendicular to our line of sight, making Nessie the easiest feature to see as a shadow elongated along the Galactic Plane from the location.  Future high-resolution dust mapping and molecular line observations of the harder-to-find Galactic "bones" should allow us to exploit the Sun's position above the plane to gain a (very foreshortened) view "from above" of the MW's structure.

Day 714

Sunday (Friday).

1407.8178
Velocity anti-correlation of diametrically opposed galaxy satellites in the low redshift universe
Ibata, Ibata, Famaey, Lewis

[covered in Day 708 as Nature paper]

1407.8181
X-ray bright active galactic nuclei in massive galaxy clusters III: New insights into the triggering mechanisms of cluster AGN
Ehlert, Allen, ... Mantz ... von der Linden, et al

Find evidence for evolution in the cluster AGN population beyond the expected evolution of field AGN.  Analysis show that overall number density of cluster AGN scales with the cluster mass as ~M500^-1.2 [less likely to find AGN for more massive clusters].  No evidence for overall number density depending on the cluster redshift in a manner different than field AGN, nor there is any evidence that the spatial distribution of cluster AGN (given in units of the cluster overdensity radius r500) strongly depends on the cluster mass or redshift.  The M^-1.2 scaling relation is consistent with theoretical predictions of the galaxy merger rate in clusters, which is expected to scale with the cluster velocity dispersion sigma as ~sigma^-3 or ~M^-1.  This consistency suggests that AGN in clusters may be predominantly triggered by galaxy mergers, a result that is further corroborated by visual inspection of Hubble images for 23 spectroscopically confirmed cluster member AGN in the sample.  A merger-driven scenario for the triggering of X-ray AGN is not strongly favored by studies of field galaxies, however, suggesting that different mechanisms may be primarily responsible for the triggering of cluster and field X-ray AGN.

1407.8184
Are scalar and tensor deviations related in modified gravity?
Linder

Modified gravity theories on cosmic scales have 3 key deviations from GR.  They can cause cosmic acceleration without a physical, highly negative pressure fluid, can cause a gravitational slip between the two metric potentials, and can cause gravitational waves to propagate differently, e.g., with a speed different from the speed of light.  Examine whether the deviations in the metric potentials as observable through modified Poisson equations for scalar density perturbations are related to or independent from deviations in the tensor gravitational waves.  Show analytically that they are independent instantaneously in covariant Galileon gravity -- e.g. at some time one of them can have the general relativity value while the other deviates -- through related globally -- if one deviates over a finite period, the other at some point shows a deviation.  Present expressions for the early time and late time de Sitter limits, and numerically illustrate their full evolution.  This in(ter)dependence of the scalar and sensor deviations highlights complementarity between cosmic structure surveys and future gravitational wave measurements.

1407.8279
A new method of CCD dark current correction via ext rating the dark information from scientific images
Ma, Shang, Hu, Liu, Wang, Wei

As the title says.  [Their observations did not allow them to obtain dark frames.  Method description not in abstract.  Uses image pairs to estimate the spatial variation in the dark current.]