Day 693

Monday.  In Edinburgh.

1407.1047
A relationship between specific star formation rate and metallicity gradient within z=1 galaxies from KMOS-HiZELS
Stott, ... Bower, et al

Sample of typical z=1 SF galaxies; metallicity gradient consistent with being flat or negative (i.e. higher metallicity cores than outskirts).  Find a trend between metallicity gradient and sSFR, such that galaxies with a high sSFR tend to have relatively metal-poor centers, a results which is strengthened when combined with datasets from the literature.  This results appears to explain the discrepancies reported between different high z studies and varying claims for evolution.  From a galaxy evolution perspective, the trend we see would mean that a galaxy's sSFR is governed by the amount of metal poor gas that can be funneled into its core, triggered either by merging or through efficient accretion.  In fact merging may play a significant role as it is the starburst galaxies at all epochs, which have the more positive metallicity gradients.  Results may help to explain the origin of the fundamental metallicity relation, in which galaxies at a fixed mass are observed to have lower metallicities at higher SFRs, especially if the metallicity is measured in an aperture encompassing only the central regions of the galaxy.  Finally, note that this study demonstrate the power of KMOS as an efficient instrument for large scale resolved galaxy surveys.

1407.1054
The MASSIVE survey - I. A volume-limited integral-field spectroscopic study for the most massive early-type galaxies within 108 Mpc
Ma, Greene, McConnell, ... et al

Massive early-type galaxies represent the modern-day remnants of the earliest major SF episodes in the history of the universe.  These galaxies are central to the understanding of evolution of cosmic structure, stellar populations, and SMBHs, but the details of their complex formation histories remain uncertain.  To address this situation, the MASSIVE survey, a volume-limited multi-wavelength, integral-field spectroscopic (IFS) and photometric survey of the structure and dynamics of the ~100 most massive early-type galaxies within a distance of 108 Mpc.  This survey probes a stellar mass range M*>1e11.5 Msun and diverse galaxy environments that have not been systematically studied to date.  The wide-field IFS data cover ~two effective radii of individual galaxies, and for a subset of them, the survey is acquiring additional IFS observations on sub-arcsecond scales with adaptive optics.  Dynamical orbit modeling of the combined data will allow simultaneous determination of the stellar, BH, and DM halo masses.  The goals of the project are to constrain the BH scaling relations at high masses, investigate systematically the stellar IMF and DM distribution in massive galaxies, and probe the late-type assembly of ellipticals through stellar population and kinematical gradients.  In the present work, describe the MASSIVE sample selection, discuss the structural and environmental properties of the selected galaxies, and provide an overview of the basic observational program and science goals.

1407.1115
A terrestrial planet in a ~1 AU orbit around one member of a ~15 AU binary
Gould, et al

Detection of a cold, terrestrial planet in a binary-star system using gravitational microlensing.  The planet has low mass (2 M_E) and lies projected at a_perp,ph ~ 0.8 AU from its host star, similar to the Earth-Sun distance.  However, the planet temperature is much lower, T<60 Kelvin, because the host star is only 0.10-0.15 Msun and therefore more than 400 times less luminous than the Sun.  The host is itself orbiting a slightly more massive companion with projected separation a_perp,ch=10-15 AU.  Straightforward modification of current microlensing search strategies could increase their sensitivity to planets in binary systems.  With more detections, such binary-star/planetary systems could place constraints on models of planet formation and evolution.  This detection is consistent with such systems being very common.

1407.1128
Three-point galaxy-galaxy lensing as a probe of dark matter halo shapes
Adhikari, Chue, Dalal

Propose a method to measure the ellipticities of DM haloes using the lens-shear-shear 3pt correlation function.  This method is immune to effects of galaxy-halo misalignments that can potentially limit 2pt gg lensing measurements of halo anisotropy.  Using a simple model for the projected mass distributions of DM haloes, construct an ellipticity estimator that sums over all possible triangular configurations of the 3pt function.  By applying the estimator to haloes from N-body sims, find that systematic errors in the recovered ellipticity will be at the <5% fractional level.  Estimate that future imaging surveys like LSST will have sufficient statistics to detect halo ellipticities using 3pt lensing.

1407.1236
Constraining the halo bispectrum in real and redshift space from perturbation theory and nonlinear stochastic bias
Kitaura et al

Present a method to produce mock galaxy catalogues with efficient perturbation theory schemes, which match the number density, PS and bispectra in real and z-space from N-body simulations.  The essential contribution of this work is the way in which the bias parameters are constrained in the PATCHY-code.  In addition of aiming at reproducing the 2-pt statistics, seek the set of bias parameters which constrain the univariate halo probability distribution function (PDF) encoding higher-order correlation functions.  Demonstrate that halo catalogues based on the same underlying DM field with a fixed halo number density and accurately matching the PS (within 2%), can lead to very different bispectra depending on the adopted halo bias model.  A model ignoring the shape of the halo PDF can lead to deviations up to factors of 2.  The catalogues obtained by additionally constraining the shape of the halo PDF can significantly lower the discrepancy in the 3pt statistics, yielding closely unbiased bispectra both in real and redshift space; which are in general compatible with those corresponding to an N-body simulation within 10% (deviating at most up to 20%).  The calculations show that the constant linear bias of ~2 for LRG-like galaxies seen in the PS, mainly comes from sampling haloes in high density peaks, choosing a high density threshold rather than from a factor multiplying the DM density field.  The method contributes towards an efficient modeling of the halo/galaxy distribution required to estimate uncertainties in the clustering measurements form galaxy redshift surveys.  Also demonstrated that this method represents a powerful tool to test various bias models.