Day 529

Wednesday.

1310.3038
Reconstruction of brad features in the primordial spectrum and inflation potential from Planck
Hazra, Shafieloo, Smoot

Address the optimized binning of the primordial PS; also allowing the position of the bins to vary.  This allows addressing the location of the possible broad physical features in the primordial spectrum with relatively smaller number of bins compared to earlier analysis; avoids noise fitting.  MCMC analysis, present samples of the allowed primordial spectra with broad features consistent with Planck.  Test likelihood of step-like feature in the primordial spectra; revisit an inflationary model, which can address the similar features obtained from the binning of the spectrum; numerically calculate the local fNL for this model in equilateral and arbitrary triangular configurations of wavevectors and show that the obtained non-Guassianity for this model is consistent with Planck results.  Also consider different spectral tilts at different bins to identify the cosmological scale that the spectral index needs to have a red tilt; spectral index cannot be well constrained up to k~0.01 Mpc^-1.

1310.3278
Constraints on large-scale dark acoustic oscillations from cosmology
Racine, de Putter, Raccanelli, Sigurdson

If DM is coupled to DR (dark radiation), dark acoustic oscillations (DAO) will imprint a characteristic scale---a sound horizon of DM, on the matter PS.  Compute DAO effects; use cosmological data from CMB, BAO and LSS to constrain the possible fraction of interaction DM as well as the strength of its interaction with DR.  Constraint rests on the betrayal by gravity of the location of otherwise invisible DM.  Find: linear cosmological data and CMB lensing put strong constraints on existence of DAO features in the CMB and the LSS of the universe.  Find that at most ~5% of all DM can be very strongly interacting with DR.  Show that results are surprisingly constraining for the recently proposed Double-disk DM model, a novel example of how large-scale precision cosmological data can be used to constrain galactic physics and sub-galactic structure.

1310.3280
Dry mergers do not explain the observed evolution of massive early-type galaxies since z=1
Sonnenfeld, Nipoti, Treu

Some suggest: observed size evolution of massive ETGs can be explained as a combination of dry mergers and progenitor bias, at least since z=1.  Carry out a new test of the dry-merger scenario based on recent lensing measurements of the evolution of the mass density profile of ETGs.  Construct a theoretical model for the joint evolution of the size and density slope gamma' driven by dry mergers occurring at rates given by cosmological simulations.  Show that a dry-merger scenario cannot reproduce the almost constant gamma' in the range 0<z<1, being ruled out at >99 CL.  Then show with a simple toy model that a modest amount of cold gas in the mergers - consistent with the upper limits on recent SF in ETGs - is sufficient to reconcile the model with the observations.  Thus suggest a scenario where the outer regions of massive ETGs grow by dry-merger accretion while small amounts of dissipation and nuclear SF conspire to keep the mass density profile constant and approximately isothermal.

1310.3339
Weak gravitational lensing systematics from image combination
Shapiro, Rowe, Goodsall, Hirata, Fucik, Rhodes, Seshadri, Smith

WFIRST and Euclid uses undersampled and aliased pixels, but oversampled, unaliased images can be obtained by combining multiple, dithered exposures of the same source with a suitable reconstruction algorithm.  Any such reconstruction must minimally distort the reconstructed images for WL analysis to be unbaised.  In this paper, use IMCOM algorithm of Rowe, Hirata, and Rhodes to investigate the effect of image combination on shape measurements (size and ellipticity).  Simulate dithered images of sources with varying amounts of ellipticity and undersampling, reconstruct oversampled output images from them using IMCOM, and measure shape distortions in the output.  Simulations show that IMCOM creates no significant distortions when the relative offsets between dithered images are precisely known.  Distortions increase with the uncertainty in those offsets but become problematic only with relatively poor astrometric precision.  For images similar to those from AFTA implementation of WFIRST, combining eight undersampaled images (sampling ratio Q=1) with highly pessimistic uncertainty in astrometric registration (sigma_d~1e-3 pixels) yields an RMS shear error of O(1e-4).  Analysis pipeline is adapted from that of the Precision Projector Laboratory (NASA JPL and Caltech) which characterizes image sensors using laboratory emulations of astronomical data.

1310.3373
MOND and its bimetric formulation
Milgrom

(1) Succinct account of the MOND paradigm (emphasizing the centrality of scale invariance in the NR, deep MOND limit), and describing rudiments of its phenomenology.  The present his credo, some generalities, concerning existing MOND theories.  Then concentrate on one relativistic formation of MOND in the form of a bimetric theory (BIMOND).  Describe various limits: the weak field, with application to gravitational waves, the NR limit, and their further deep-MOND (low acceleration) limits, which are scale invariant.  Other aspects of BIMOND that have been explored are aspects of cosmology, matter fluctuations in cosmology, and matter-twoin-matter interactions.  BIMOND remains largely unexplored, despite its promise in several regards: it tends to GR for a0 goes to 0 (a0 is the MOND constant); it has a simple NR limit; it descries gravitational lensing correctly, and it has a generic appearance of a cosmological-constant term that is of order a0^2/c^4, as observed.

1310.3819
The progenitors of the compact early-type galaxies at high-redshift
Williams et al

Use GOODS and CANDELS images to identify progenitors of massive (logM/Msun > 10) compact ETGs at z~1.6.  Since merging and accretion increase the size of the stellar component of galaxies, if the progenitors are among known SF galaxies, these must be compact themselves.  Select candidate progenitors among compact Lyman-break galaxies at z~3 based on their mass, SFR and central stellar density and find that these account for a large fraction of, and possibly all, compact ETGs at z~1.6.  Find that the average far-UV SED of the candidates is redder than that of the non-candidates, but the optical and MIR SED are the same, implying that the redder UV of the candidates is inconsistent with larger dust obscuration, and consistent with more evolved (aging) SF.  This is in line with other evidence that compactness is a sensitive predictor of passivity among high-z massive galaxies.  Also find that the light distribution of both the compact ETGs and their candidate progenitors does not show any extended "haloes" surrounding the compact "core", both in individual images and in stacks.  Argue that this is generally inconsistent with the morphology of merger remnants, even if gas-rich, as predicted by N-body simulations.  This suggests that the compact ETGs formed via highly dissipative, mostly gaseous accretion of units whose stellar components are very small and undetected in the HST images, with their stellar mass assembling in-situ, and that they have not experienced any major merging until the epoch of observations at z~1.6.  

1310.3823
Galaxy size trends as a consequence of cosmology
Stringer, et al

Show: trends in galaxy sizes with mass and redshift can be understood in terms of the influence of underlying cosmic evolution; a holistic view which is complimentary to the usual interpretations involving the accumulation of discreet [discrete?] evolutionary processes acting on individual objects.  Using analytic predictions from standard cosmology theory, supported with the results of the Millennium simulations, begin by deriving the size trends in the population of collapsed cosmic structures, and emphasize the important distinction between these trends and the hierarchical assembly of individual structures.  Moving on to galaxies, argue that the observed variation in galactic stellar mass, as a function of inferred host structure mass, can be understood to first order in terms of natural limitations of cooling and feedback.  But while this fractional stellar mass content varies by orders of magnitude, the characteristic radius of galaxies has been found to correlate strongly and linearly with that of the host structure.  Using analytic arguments, illustrated with mock populations generated from the Millennium simulations, then explain how these two aspects will lead to galaxy sizes that closely follow recently observed trends and their evolution, and verify this with direct comparison to galaxies from the COSMOS and SDSS surveys.  Conclude that it may be possible to understand the observed minimum radius for galaxies, the evolving trend in size as a function of mass for intermediate systems, and the observed increase in the sizes of massive galaxies, as being an emergent consequence of the cosmic expansion.

1310.3828
Cosmological constraints from measurements of Type Ia Supernovae discovered during the first 1.5 years of the Pan-STARRS1 survey
Rest et al

Present griz light curves of 146 spectroscopically confirmed SNe Ia (0.03<z<0.65) during the first 1.5 years of PanSTARRS1 medium deep survey.  Systematic uncertainties in the photometric system are 1.2% without accounting for the uncertainty in the HST Calspec definition of the AB system.  Construct Hubble diagram with a subset of 112 SNe Ia that pass light curve quality cuts.  Cosmological fit to 313 SNe Ea (112 PS1 SNe Ia + 201 low-z SNe Ia) using only SNe and ssuming a constant DE EoS and flatness, yields w=-1.015pm0.3(stat)pm0.15(sys).  When combined with BAO+PlanckCMB+H0, the analysis yields Omega_m=0.277pm0.01, and w=-1.186pm0.07 including all identified systematics (in a separate paper by Scolnic+2013).  The value of w is inconsistent with -1 at 2.4 sigma; tension has been seen in other high-z SN surveys and endures after removing either the BAO or the H0 constraint.  Include WMAP9 CMB constraints instead from Planck, find w=-1.142pm0.07, which diminishes the discord to <2 sigma.  Cannot conclude whether the tension with flat LCDM is a feature of DE, new physics or a combination of chance and systematic errors.  The full PS1 SNe sample will be 3x larger than this initial sample, which should prove more conclusive results.

1310.3837
Demographics of Sloan digital sky survey galaxies along the Hubble sequence
Oh et al

Present statistical properties of 7k nearby 0.033<z<0.044 galaxies from DR7; database including morphology distribution as well as the structural and spectroscopic properties of each morphology type based on the recent re-measurements of spectral line strengths by Oh+ (2011).  Database does not include galaxies that are apparently smaller and flatter, because morphology classification of them was difficult.  Statistics confirmed recent knowledge of galaxy populations (correlations between morphology and line strengths as well as the derived ages, etc.).  [what exactly are the contents of this database (morphology, structural and spectroscopic properties)?]

1310.3913
Evolution of the radio remnant of supernova 1987A: Morphological changes from day 7000
Ng et al

Radio imaging of 1987 at 9 GHz over 21 years, from 1992 to 2013.  Show that the remnant structure has evolved significantly since mid-2006 (day 7000): the emission latitude has gradually decreased, such that the overall geometry has become more similar to a ring structure.  Around the same time, find a decreasing trend in the east-west asymmetry of the surface emissivity.  These results could reflect the increasing interaction of the forward shock with material around the circumstellar ring, and the relative weakening of the interaction with the lower-density material at higher latitudes.  The morphological evolution caused an apparent break in the remnant expansion measured with a torus model, from a velocity of 4600pm150 km/s between day 4000 and 7000 to 2400pm100 km/s after day 7000.  However, emphasize that there is no conclusive evidence for a physical slowing of the shock at any given latitude in the expanding remnant, and that a change of radio morphology alone appears to dominate the evolution; supported by ring-only fits which show a constant expansion of 3890pm50 km/s without deceleration between days 4000 and 9000.  Suggest that once the emission latitude no longer decreases, the expansion velocity obtained from the torus model should return to the same value as that measured with the ring model.  

1310.4147
The suppression of star formation by powerful active galactic nuclei
Page et al

(Nature paper) Suspected (but unproven) that the tight correlation in mass of the BH and stellar components results from the AGN quenching the surrounding SF as it approaches its peak luminosity.  X-rays trace emission from AGN unambiguously, while SF galaxies are usually dust-obscured and are brightest at IR to submillimetre wavelengths.  Report observations in the submillimetre and X-ray which show that rapid SF is not observed around BHs above an X-ray luminosity of 1e44 erg/s.  This suppression of SF in the host galaxies of powerful AGN is a key prediction of models in which the AGN drives a powerful outflow, expelling the interstellar medium of its host galaxy and transforming the galaxy's properties in a brief period of cosmic time.