Tuesday.
1304.1216
X-ray cluster constraints on non-Gaussianity
Shandera, Mantz, Rapetti, Allen
Constraints on primordial non-Gaussianity from abundance of X-ray detected clusters. Measure dimensionless skewness. When applied to standard local ansatz, the constraint corresponds to fNL=-2pm50. When applied to a model with a local-shape bispectrum but higher cumulants that are relatively more important, then the amplitude of the local-shape bispectrum is constrained to be fNL=-8pm14. This sensitivity implied that cluster counts could be used to distinguish qualitatively different models for the primordial fluctuations that have identical bispectra.
1304.1801
The PdBI arcsecond Whirlpool survey (PAWS). I. A cloud-scale/multi-wavelength view of the interstellar medium in a grand-design spiral galaxy
Schinnerer et al
Characterize the relation of molecular gas (CO emission) to other tracers of ISM, SF and stellar populations of varying ages. Find: (a) the distribution of molecular gas can be linked to different components of the gravitational potential, (b) evidence for a physical link between CO line emission and radio continuum that seems not to be caused by massive stars, but rather depend on the gas density, (c) close spatial relation between the PAH and molecular gas emission, but no predictive power of PAH emission for the molecular gas mass, (d) the I-H color map is an excellent predictor of the distribution (and to a lesser degree the brightness) of CO emission, and (e) that the impact of massive (UV-intense) young SF regions on the bulk of the molecular gas in central ~9kpc can not be significant due to a complex spatial relation between molecular gas and SF regions that ranges from co-spatial to spatially offset to absent. The last point, in particular, highlights the importance of galactic environment---and thus the underlying gravitational potential--- for the distribution of molecular gas and SF.
1304.1817
Non-Gaussian halo bias beyond the squeezed limit
Schmidt
Primordial non-G, in particular the coupling of modes with widely different wavelengths, can have a strong impact on the large-scale clustering of tracers through a scale-dependent bias with respect to matter. Demonstrate that the standard derivation of this non-G scale-dependent bias is in general valid only in the extreme squeezed limit of the primordial bispectrum, i.e., for clustering over very large scales. Further show how the treatment can be generalized to describe the scale-dependent bias on smaller scales, without making any assumptions on the nature of tracers apart from a dependence on the small-scale fluctuations within a finite region. If the leading scale-dependent bias \Delta b \propto k^alpha, then the first subleading term will scale as k^(alpha+2). This correction typically becomes relevant as one considers clustering over scales k>0.01 h/Mpc.
1304.1843
Bayesian lensing shear measuremen[t]
Bernstein, Armstrong
Derive estimator of WL lensing shear from BG galaxy images that avoids noise-induced biases through a rigorous Bayesian treatment of the measurement. The Bayesian formalism requires a prior describing the (noiseless) distribution of the target galaxy population over some parameter space; this prior can be constructed from low-noise images of a subsample of the target population, attainable from long integrations of a fraction of the survey field. Find two ways to combine this exact treatment of noise with rigorous treatment of the effects of the instrumental PSF and sampling. The Bayesian model fitting (BMF) method assigns a likelihood of the pixel data to galaxy models (e.g. Sersic ellipses), and requires the unlensed distribution of galaxies over the model parameters as a prior. The Bayesian Fourier domain (BFD) method compresses galaxies to a small set of weighted moments calculated after PSF correction in Fourier space. It requires the unlensed distribution of galaxy moments as a prior, plus derivatives of this prior under applied shear. BFD is the first shear measurement algorithm that is model-free and requires no approximations or ad hoc assumptions in correcting for the effects of PSF, noise, or sampling on the galaxy images. These algorithms are good candidates for attaining the part-per-thousand shear inference required for hemisphere-scale weak gravitational lensing surveys. [BMF has the drawback that shear biases will occur since galaxies do not fit any finite-parameter model, but has the advantage of being robust to missing data or non-stationary noise. Both BMF and BFD methods are readily extended to use data from multiple exposures and to inference of lensing magnification.]
1304.1894
The CDMS view on molecular data needs of Herschel, SOFIA, and ALMA
Müller et al
The catalog section of the Cologne Database for Molecular Spectroscopy (CDMS) contains mostly rotational transition frequencies of molecules observable in space. The lists are generated mostly from critically evaluated laboratory data employing established Hamiltonian models. The old version has been around for 12 years, a test version of the new CDMS is about to be released.
1304.2046
Luminosity bias (II): the cosmic web of the first stars
Barkana
[invited review] Understanding the formation and evolution of the first stars and galaxies. Universe was filled with neutral H at early times, so most promising method for observing the epoch of first stars is using the prominent 21-cm spectral line of H atom. Current observational efforts concentrated on reionization era (cosmic age t~500Myr), with earlier times considered much more challenging . The next frontier of even earlier galaxy formation (t~200 Myr) is emerging as a promising observational target. This is made possible by a recently noticed effect of a significant relative velocity between the baryons and DM at early times. The velocity difference suppresses SF, causing a unique form of early luminosity bias. The spatial variation of this suppression enhances large-scale clustering and produces a prominent cosmic web on 100 comoving Mpc scales in the 21-cm intensity distribution. [really? wow] This structure makes it much more feasible for radio astronomers to detect these early stars, and should drive a new focus on this era, which is rich with little-explored astrophysics.
1304.2164
Effect of masks regions on weak lensing statistics
Shirasaki, Yoshida, Hamana
Study how masks affect the measurement of statistics of matter distribution probed by WL. Study impact of mask regions on WL Minkowski Functionals (MFs) with 1000 Gaussian simulations. Consider actual sky masks used for Subaru. Masks increase the variance of the convergence field and thus the expected values of the MFs are biased even for a Gaussian random field. The bias is caused by 2 effects. (1) One is owing to the reduced number of sampling Fourier modes, which can be accounted for analytically by considering the survey geometry appropriately. (2) The other is owing to variation of the variance of the convergence field for each field of view. Lensing MFs are biased systematically when the reconstructed convergence field is normalized by its variance. Then use a large number of cosmological ray-tracing simulations in order to address if the lensing MFs measured for a Subaru 2-deg^2 survey are consistent with those of the standard cosmology. The resulting chi^2/n_dof = 29.6/30 for combined 3 MFs, obtained by taking the mask effects into account, suggests that the observational data are indeed consistent with the standard LCDM model. Finally, ,explore how masked covariance matrices affect cosmological parameter estimation. Conclude that the lensing MFs are powerful probe of cosmology only if the effect of masking is correctly taken into account.
1304.2299
Fossile evidence for the two-phase formation of elliptical galaxies
Huang, Ho, Peng, Li, Barth
Massive early-type galaxies have undergone dramatic structural evolution over the last 10 Gyr. 3 photometric subcomponents: a compact inner component with effective radius Re<1 kpc, an intermediate-scale middle component with Re~2.5 kpc, and an extended outer envelope with Re~10 kpc. Attempt to relate these substructures with the properties of early type galaxies observed at higher z. Find that a hypothetical structure formed from combining the inner plus the middle components of local ellipticals follows a strikingly tight stellar mass-size relation, one that resembles the distribution of early-type galaxies at z~1.5. Outside of the central kpc, the median stellar mass surface density profiles of this composite structure agree closest with those of massive galaxies that have similar cumulative number density at 1.5<z<2.0 within the uncertainty. Propose that the central substructures in nearby ellipticals are the evolutionary descendants of the "red nuggets" formed under highly dissipative ("wet") conditions at high z, as envisioned in the initial stages of the two-phase formation scenario recently advocated for massive galaxies. Subsequent accretion, plausibly through dissipationless ("dry") minor mergers, builds the outer regions of the galaxy identified as the outer envelope in this decomposition. THe large scatter exhibited by this component on the stellar mass-size plane testifies to the stochastic nature of the accretion events.
1304.2321
Dark energy and neutrino constraints from a future EUCLID-like survey
Basse, ... Hannestad, et al
Forceast on constraining DE and neutrino parameters from combination of cosmic shear PS, galaxy PS, and cluster mass function measurements. Find: combination of these three probes vastly improves the survey's potential to measure the time evolution of DE. In terms of a DE FoM defined as (sigma(w_0) sigma(w_a))^-1, find a value of 454 for Euclid-like data combined with Planck-like measurements of CMB anisotropies in a fiducial LCDM cosmology, a number that is quite conservative compared with existing estimates because of the choice of model parameter space and analysis method, but still an improvement of x3 to x8 using either CMB+galaxy clustering+cosmic shear data, or CMB+cluster mass function alone. Consider also the survey's potential to measure DE perturbations in models wherein the DE is parameterized as a fluid with a nonstandard non-adiabatic sound speed, and find that in an optimistic scenario in which w_0 deviates by as much as is currently observationally allowed from -1, models with c_s^2 = 1e-6 and c_s^2 = 1 can be distinguished at more than 2 sigma significance. Under the same optimistic assumptions, if the Jeans mass associated with DE clustering falls within the cluster mass range observed by the survey, then the order of magnitude of the DE sound speed can potentially be pinned down. Find tha the sum of neutrino masses can be measured with 1 sigma precision of 0.01 eV, even in complex cosmological models in which the DE equation of state varies with time.
1304.2337
On inferring extinction laws in z~6 quasars at signatures of supernova dust
Hjorth et al
SNe dominate (probably) the dust budget at high redshift.
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