Day 843

Monday.

1411.4359
Homogeneous cosmology with aggressively expanding civilizations
Olson

In the context of a homogeneous universe, note that the appearance of aggressively expanding advanced life is geometrically similar to the process of nucleation and bubble growth in a first-order cosmological phase transition.  Exploit this similarity to describe the dynamics of life saturating the universe on a cosmic scale, adapting the phase transition model to incorporate probability distributions of expansion and resource consumption strategies.  Through a series of numerical solutions covering several orders of magnitude in in the input assumption parameters, the resulting cosmo model is used to address basic questions related to the intergalactic spreading of life, dealing with issues such as timescales, observability, competition between strategies, and first-mover advantage.  Finally, examine physical effects in the universe itself, such as reheating and the back reaction on the evolution of the scale factor, if such life is ale to control and convert a significant fraction of the available pressures matter into radiation.  Conclude that the existence of life, if certain advanced technologies are practical, could have a significant influence on the future large-scale evolution of the universe.


1502.07747
Galaxy morphology and star formation in the Illustris simulation at z=0
Snyder, ... Genel, Vogelsberger, ... Hernquist, Springel

Study how galaxy morphology depends on mass and SFR in the Illustris Sim.  Measure automated diagnostics of galaxy structure in 10808 simulated galaxies at z=0 with stellar masses 1e9.7<M*/Msun<1e12.3.  Add observational realism to idealized synthetic images and measure non-parametric statistics in rest frame u, g, i, and H band images from 4 directions.  Find that the Illustrious sim creates a morphologically diverse population of galaxies, occupying roughly the observed bulge strength locus, and reproducing median morphology trends vs. stellar mass, SFR and compactness.  Optical morphology correlates realistically with rotational structure, following qualitative classification schemes put forth by kinematic surveys.  Relative type fractions as a function of environment agree roughly with data.  These results imply that connections among mass, SF, and galaxy structure arise naturally from models matching global SF and halo occupation functions when simulated with accurate numerical methods.  This raises a question of how to construct the best experiments on large galaxy surveys to better distinguish between models.  Predict that at fixed halo mass near 1e12 Msun, galaxies with relatively more disc-like morphologies have higher stellar mass than those with bulge-like morphologies, a possible consequence of the Illustris feedback model acting on massive galaxies.  While Illustris galaxies at M*~1e11 Msun have a reasonable size distribution, those at M*~1e10 Msun have HLR larger than observed by roughly a factor of 2.  Furthermore, at M*~1e10.5 through 1e11 Msun, a relevant fraction of Illustris galaxies have distinct "ring-like" features, such that the bright pixels have an unusually wide spatial extent (M_20>-1).  


1502.07751
sCOLA: the N-body COLA method extend to the spatial domain
Tassev, Eisenstein, Wandelt, Zaldarriaga

sCOLA: an extension of the N-body COmoving Lagrangian Acceleration (COLA) method to the spatial domain.  Similar to the original temporal-domain COLA< sCOLA is an N-body method for solving for LSS in a frame that is an coming with observers following trajectories calculated in Lagrangian Perturbation Theory.  Incorporating the sCOLA method in an N-body code allows one to gain computational speed by capturing the gravitational potential from the far field using perturbative techniques, while letting the N-body code solve only for the near field.  The far and near fields are completely decoupled, effectively localizing gravity for the N-body side of the code.  Thus, running an N-body code for a small simulation volume using sCOLA can reproduce the results of a standard N-body run for the same small volume embedded inside a much larger simulation.  Demonstrate that sCOLA can be safely combined with the original temporal-domain COLA.  sCOLA can be used as a method for performing zoom-in simulations.  It also allows N-body codes to be made embarrassingly parallel, thus allowing for efficiently tiling a volume of interest using grid computing.  Moreover, sCOLA can be useful for cheaply generating large ensembles of accurate mock halo catalogs required to study galaxy clustering.  Surveys that will benefit the most are ones with large aspect ratios, such as pencil beam surveys, where sCOLA can easily capture the effects of LS transverse modes without the need to substantially increase the simulated volume.  As an illustration of the method, present proof-of-concept zoom-in simulations using a freely available sCOLA-based N-body code.


1502.07754
The "Green Bean" galaxy SDSS J224024.1--092748: Unravelling the emission signature of a quasar ionization echo
Davies, Schirmer, Turner

Gas are the most [OIII]-luminous type-2 AGN at z~0.3.  However, their IR luminosities reveal AGN in very low activity states, indicating that their gas reservoirs must be ionized by photons from a recent high activity episode - we are observing quasar ionization echos.  Use integral field spectroscopy from Gemini Multi-Object Spectrograph to analyze the 3d kinematics, ionization state, temperature and density of ionized gas in the GB SDSS J224024.1-092748.  Model the emission line spectrum of each spaxel as a superposition of up to 3 Gaussian components and analyze the physical properties of each component individually.  Two narrow components, tracing the velocity fields of the disc and an ionized gas cloud, are superimposed over the majority of the galaxy.  Fast shocks produce hot (Te>20,000K), dense (n_e>100cm^-3), turbulent (sigma>600km/s), [OIII]-bright regions with enhanced [NII]/Halpha and [SII]/Halpha ratios.  The most prominent such spot is consistent with a radio jet shock-heating the ISM.  However, the AGN is still responsible for >82% of the galaxy's total [OIII] luminosity, strengthening the case for previous quasar activity.  The ionized gas cloud has a strong kinematic link to the central AGN and is co-rotating with the main body of the galaxy, suggesting that it may be the remnant of a quasar-driven outflow.  Analysis of J224024.1-092748 indicates that GBs provide a unique fossil record of the transformation from the most luminous quasars to weak AGN.

1502.07757
Simultaneous estimation of photometric redshifts and SED parameters: improved techniques and a realistic error budget
Acquviva, Raichoor, Gawiser

Seek to improve the accuracy of joint galaxy photometric redshift estimation and SED fitting.  By simulating different sources of uncorrected systematic errors, demonstrate that if the uncertainties on the photo-z are estimated correctly, so are those on the other SED fitting parameters, such as stellar mass, stellar age, and dust reddening.  Furthermore, find that if the z uncertainties are over(under)-estimated, the uncertainties in SED parameters tend to be over (under)estimated by similar amounts.  These results hold even in the presence of severe systematics and provide, for the first time, a mechanism to validate the uncertainties on these parameters via comparison with spectroscopic z.  Propose a new technique (annealing) to re-calibrate the joint uncertainties in the photo-z and SED fitting + z parameter space, including all correlations.  While the performance of joint SED fitting and photo-z estimation might be hindered by template imcompleteness, demonstrate that the latter is "flagged" by a large fraction of outliers in z, and that significant improvements can be achieved by using flexible stellar populations synthesis models and more realistic SFHs.  In all cases, find that the median stellar age is better recovered than the time elapsed from the onset of SF.


1502.07767
Spatially resolving the kinematics of the <100 {\mu}as quasar broad line region using spectroastrometry
Stern, Hennawi, Pott

Analyze the possibility to measure the BLR size and study its kinematic structure using spectroastrometry, whereby one measures the spatial position centroid of emission line photos as a function of velocity.  Calculate the expected spectroastrometric signal of a rotation-dominated BLR for various assumptions about the ratio of random to rotational motions, and the radial distribution of the BLR gas.  Show that for hyper-luminous quasars at z<2.5, the size of the low-ionization BLR can already be constrained with existing telescopes and adaptive optics systems, thus providing a novel method to spatially resolve the kinematics of the accretion flow at 1e3-4 gravitational radii, and measure M_BH at the high-L end of the AGN family.  With a 30m-class telescope, BLR spectroastrometry should be routinely detectable for much fainter quasars out to z~6, and for various emission lines.  This will enable kinematic M_BH measurements as a function of luminosity and redshift, providing a compelling science as for next generation telescopes.


1502.07900
The Subaru FMOS galaxy redshift survey (FastSound). I. Overview of the survey targeting on H$\alpha$ emitters at $z\sim1.4$
Tonegawa, Totani, ... et al

FastSound is a galaxy z survey using the NIR FMOS mounted on Subaru, targeting Ha emitters at z~1.18-1.54 down to the sensitivity limit of Ha flux ~ 2e-16 erg/cm^2/s.  The primary goal of the survey is to detect RSD, to test GR by measuring the growth rate of LSS and to constrain modified gravity models for the origin of the accelerated expansion of the universe.  The target galaxies were selected based on photo-z and Ha flux estimates calculated by fitting SED models to the 5 optical magnitudes of CFHTLS Wide catalog.  The survey started in March 2012, and all the observations were completed in July 2014.  In total, achieved 121 pointings of FMOS (each pointing has a 30' diameter circular footprint) covering 20.6 sq deg by tiling the four fields of the CFHTLS Wide in a hexagonal pattern.  Emission lines were detected from 4k SF galaxies by an automatic line detection algorithm applied to 2d spectral images.  This is the first in a series of papers based on FastSound data.  Describe the details of the survey design, target selection, observations, data reduction, and emission line detections.