bluuebunny/crossref_metadata_2025_split huggingface dataset:
Filamentary pattern in the cosmic web: galaxy filaments as pearl necklaces
Authors: Tempel Elmo , Bussov Maarja 
Published: October 2016

AbstractGalaxies form chains (filaments) that connect groups and clusters of galaxies. The filamentary network includes nearly half of the galaxies and is visually the most striking feature in cosmological maps. We study the distribution of galaxies along such a filamentary network, trying to find specific patterns. Our galaxy filaments are defined using the Bisous process. We use the two-point correlation function and the Rayleigh $Z$-squared statistic to study how the galaxies are distributed along the filaments. We show that galaxies and galaxy groups are not uniformly distributed along filaments, but tend to form a regular pattern. The characteristic length of the pattern is 7~$h^{-1}$Mpc. A slightly smaller characteristic length 4~$h^{-1}$Mpc can also be found, using the $Z$-squared statistic. One can say that galaxy filaments are like pearl necklaces, where the pearls are galaxy groups distributed more or less regularly along the filaments. We propose that this well defined characteristic scale could be used as a cosmological test.
Adaptive density estimator for galaxy surveys
Authors: Saar Enn 
Published: October 2016

AbstractGalaxy number or luminosity density serves as a basis for many structure classification algorithms. Several methods are used to estimate this density. Among them kernel methods have probably the best statistical properties and allow also to estimate the local sample errors of the estimate. We introduce a kernel density estimator with an adaptive data-driven anisotropic kernel, describe its properties and demonstrate the wealth of additional information it gives us about the local properties of the galaxy distribution.
Bayesian inference of the initial conditions from large-scale structure surveys
Authors: Leclercq Florent 
Published: October 2016

AbstractAnalysis of three-dimensional cosmological surveys has the potential to answer outstanding questions on the initial conditions from which structure appeared, and therefore on the very high energy physics at play in the early Universe. We report on recently proposed statistical data analysis methods designed to study the primordial large-scale structure via physical inference of the initial conditions in a fully Bayesian framework, and applications to the Sloan Digital Sky Survey data release 7. We illustrate how this approach led to a detailed characterization of the dynamic cosmic web underlying the observed galaxy distribution, based on the tidal environment.
Bayesian Cosmic Web Reconstruction: BARCODE for Clusters
Authors: Patrick Bos E. G. , van de Weygaert Rien , Kitaura Francisco , Cautun Marius 
Published: October 2016

AbstractWe describe the Bayesian \barcode\ formalism that has been designed towards the reconstruction of the Cosmic Web in a given volume on the basis of the sampled galaxy cluster distribution. Based on the realization that the massive compact clusters are responsible for the major share of the large scale tidal force field shaping the anisotropic and in particular filamentary features in the Cosmic Web. Given the nonlinearity of the constraints imposed by the cluster configurations, we resort to a state-of-the-art constrained reconstruction technique to find a proper statistically sampled realization of the original initial density and velocity field in the same cosmic region. Ultimately, the subsequent gravitational evolution of these initial conditions towards the implied Cosmic Web configuration can be followed on the basis of a proper analytical model or an N-body computer simulation. The BARCODE formalism includes an implicit treatment for redshift space distortions. This enables a direct reconstruction on the basis of observational data, without the need for a correction of redshift space artifacts. In this contribution we provide a general overview of the the Cosmic Web connection with clusters and a description of the Bayesian BARCODE formalism. We conclude with a presentation of its successful workings with respect to test runs based on a simulated large scale matter distribution, in physical space as well as in redshift space.
Dynamics of pairwise motions in the Cosmic Web
Authors: Hellwing Wojciech A. 
Published: October 2016

AbstractWe present results of analysis of the dark matter (DM) pairwise velocity statistics in different Cosmic Web environments. We use the DM velocity and density field from the Millennium 2 simulation together with the NEXUS+ algorithm to segment the simulation volume into voxels uniquely identifying one of the four possible environments: nodes, filaments, walls or cosmic voids. We show that the PDFs of the mean infall velocities v12 as well as its spatial dependence together with the perpendicular and parallel velocity dispersions bear a significant signal of the large-scale structure environment in which DM particle pairs are embedded. The pairwise flows are notably colder and have smaller mean magnitude in wall and voids, when compared to much denser environments of filaments and nodes. We discuss on our results, indicating that they are consistent with a simple theoretical predictions for pairwise motions as induced by gravitational instability mechanism. Our results indicate that the Cosmic Web elements are coherent dynamical entities rather than just temporal geometrical associations. In addition it should be possible to observationally test various Cosmic Web finding algorithms by segmenting available peculiar velocity data and studying resulting pairwise velocity statistics.
Measuring the cosmic bulk flow with 6dFGSv
Authors: Magoulas Christina , Springob Christopher , Colless Matthew , Mould Jeremy , Lucey John , Erdoğdu Pirin , Jones D. Heath 
Published: October 2016

AbstractWhile recent years have seen rapid growth in the number of galaxy peculiar velocity measurements, disagreements remain about the extent to which the peculiar velocity field - a tracer of the large-scale distribution of mass - agrees with both ΛCDM expectations and with velocity field models derived from redshift surveys. The 6dF Galaxy Survey includes peculiar velocities for nearly 9 000 early-type galaxies (6dFGSv), making it the largest and most homogeneous galaxy peculiar velocity sample to date. We have used the 6dFGS velocity field to determine the amplitude and scale of large-scale cosmic flows in the local universe and test standard cosmological models. We also compare the galaxy density and peculiar velocity fields to establish the distribution of dark and luminous matter and better constrain key cosmological parameters such as the redshift-space distortion parameter.
Lyα Forest Tomography of the z > 2 Cosmic Web
Authors: Lee Khee-Gan 
Published: October 2016

AbstractThe hydrogen Lyα forest is an important probe of the z > 2 Universe that is otherwise challenging to observe with galaxy redshift surveys, but this technique has traditionally been limited to 1D studies in front of bright quasars. However, by pushing to faint magnitudes (g > 23) with 8-10m large telescopes it becomes possible to exploit the high area density of high-redshift star-forming galaxies to create 3D tomographic maps of large-scale structure in the foreground. I describe the first pilot observations using this technique, as well discuss future surveys and the resulting science possibilities for galaxy evolution and cosmology.
Radiative Feedback Effects during Cosmic Reionization
Authors: Sullivan David , Iliev Ilian T. 
Published: October 2016

AbstractWe present coupled radiation hydrodynamical simulations of the epoch of reionization, aimed at probing self-feedback on galactic scales. Unlike previous works, which assume a (quasi) homogeneous UV background, we self-consistently evolve both the radiation field and the gas to model the impact of previously unresolved processes such as spectral hardening and self-shielding. We find that the characteristic halo mass with a gas fraction half the cosmic mean,Mc(z), a quantity frequently used in semi-analytical models of galaxy formation, is significantly larger than previously assumed. While this results in an increased suppression of star formation in the early Universe, our results are consistent with the extrapolated stellar abundance matching models from Mosteret al.2013.
Zeldovich and the Missing Baryons, Results from Gravitational Lensing
Authors: Schild Rudolph E. 
Published: October 2016

AbstractCentral to Zeldovich's attempts to understand the origin of cosmological structure was his exploration of the fluid dynamical effects in the primordial gas, and how the baryonic dark matter formed. Unfortunately microlensing searches for condensed objects in the foreground of the Magellanic Clouds were flawed by the assumption that the objects would be uniformly (Gaussian) distributed, and because the cadence of daily observations strongly disfavored detection of planet mass microlenses. But quasar microlensing showed them to exist at planetary mass at the same time that a hydro-gravitational theory predicted the planet-mass population as fossils of turbulence at the time of recombination (z = 1100; Gibson 1996, 2001). Where the population has now been detected from MACHO searches to the LMC (Sumi et al. 2011) we compare the quasar microlensing results to the recent determination of the mass distribution function measured for the planetary mass function, and show that the population can account for the baryonic dark matter.
The origin of the galaxy color bimodality
Authors: Aragón-Calvo M. A. , Neyrinck Mark C. , Silk Joseph 
Published: October 2016

AbstractThe star formation history of galaxies is a complex process usually considered to be stochastic in nature, for which we can only give average descriptions such as the color-density relation. In this work we follow star-forming gas particles in a hydrodynamical N-body simulation back in time in order to study their initial spatial configuration. By keeping record of the time when a gas particle started forming stars we can produce Lagrangian gas-star isochrone surfaces delineating the surfaces of accreting gas that begin producing stars at different times. These surfaces form a complex a network of filaments in Eulerian space from which galaxies accrete cold gas. Lagrangian accretion surfaces are closely packed inside dense regions, intersecting each other, and as a result galaxies inside proto-clusters stop accreting gas early, naturally explaining the color dependence on density. The process described here has a purely gravitational / geometrical origin, arguably operating at a more fundamental level than complex processes such as AGN and supernovae, and providing a conceptual origin for the color-density relation.
The role of cold and hot gas flows in feeding early-type galaxy formation
Authors: Johansson Peter H. 
Published: October 2016

AbstractWe study the evolution of the gaseous components in massive simulated galaxies and show that their early formation is fuelled by cold, low entropy gas streams. At lower redshifts of z ≲ 3 the simulated galaxies are massive enough to support stable virial shocks resulting in a transition from cold to hot gas accretion. The gas accretion history of early-type galaxies is directly linked to the formation of their stellar component in the two phased formation scenario, in which the central parts of the galaxy assemble rapidly through in situ star formation and the later assembly is dominated primarily by minor stellar mergers.
Large-scale structure and the intrinsic alignment of galaxies
Authors: Blazek Jonathan , Seljak Uroš , Mandelbaum Rachel 
Published: October 2016

AbstractCoherent alignments of galaxy shapes, often called“intrinsic alignments” (IA), are the most significant source of astrophysical uncertainty in weak lensing measurements. We develop the tidal alignment model of IA and demonstrate its success in describing observational data. We also describe a technique to separate IA from galaxy-galaxy lensing measurements. Applying this technique to luminous red galaxy lenses in the Sloan Digital Sky Survey, we constrain potential IA contamination from associated sources to be below a few percent.
The beaming of subhalo accretion
Authors: Libeskind Noam I. 
Published: October 2016

AbstractWe examine the infall pattern of subhaloes onto hosts in the context of the large-scale structure. We find that the infall pattern is essentially driven by the shear tensor of the ambient velocity field. Dark matter subhaloes are preferentially accreted along the principal axis of the shear tensor which corresponds to the direction of weakest collapse. We examine the dependence of this preferential infall on subhalo mass, host halo mass and redshift. Although strongest for the most massive hosts and the most massive subhaloes at high redshift, the preferential infall of subhaloes is effectively universal in the sense that its always aligned with the axis of weakest collapse of the velocity shear tensor. It is the same shear tensor that dictates the structure of the cosmic web and hence the shear field emerges as the key factor that governs the local anisotropic pattern of structure formation. Since the small (sub-Mpc) scale is strongly correlated with the mid-range (∼ 10 Mpc) scale - a scale accessible by current surveys of peculiar velocities - it follows that findings presented here open a new window into the relation between the observed large scale structure unveiled by current surveys of peculiar velocities and the preferential infall direction of the Local Group. This may shed light on the unexpected alignments of dwarf galaxies seen in the Local Group.
Kinematics, structure and environment of three dwarf spheroidal galaxies
Authors: Sharina M. E. , Karachentsev I. D. , Karachentseva V. E. 
Published: October 2016

AbstractWe explore the environmental status of three low surface brightness
dwarf spheroidal galaxies (dSphs) KKH65, KK180 and KK227 using the results of our long slit
spectroscopic observations at the 6m telescope of the Russian Academy of Sciences and surface
photometry on the Sloan Digital Sky Survey (SDSS) images.
The objects were selected by Karachentseva in 2010 as presumably isolated galaxies.
The obtained surface brightness profiles demonstrate that our sample dSphs are less
centrally concentrated than the objects of the same morphological type in the Virgo cluster (VC).
Using the derived kinematic data we searched for possible neighbours of the dSphs within
the projected distances from them Rproj > 500 kpc and with the differences in radial velocities |Δ V| > 500 kms−1. We applied the group finding algorithm by
Makarov and Karachentsev to the selected sample.
Our analysis shows that the dwarf galaxies of our study are not isolated.
KKH65 and KK227 belong to the groups NGC3414
and NGC5371, respectively. KK180 is in the VC infall region. We conclude that
it is not possible at the moment to justify the existence of isolated dSphs outside
the Local Volume. The searches are complicated due to the lack of the accurate
distances to the galaxies farther than 10 Mpc.
The Binggeli effect
Authors: Biernacka M. , Panko E. , Godłowski W. , Bajan K. , Flin P. 
Published: October 2016

AbstractWe found the alignement of elongated clusters of BM type I and III (the excess of small values of the Δθ angles is observed), having range till about 60 h−1Mpc. The first one is probably connected with the origin of supergiant galaxy, while the second one with environmental effects in clusters, originated on the long filament or plane.
Co–evolution of black holes and galaxies: the role of selection biases
Authors: Portinari Laura 
Published: October 2016

AbstractQuasars are tracers of the cosmological evolution of the Black Hole mass
– host galaxy relation, and indicate that the formation of BH
anticipated that of the host galaxies. We find that selection effects and
statistical biases dominate the interpretation of the observational results;
and co-evolution (= constant BH/galaxy mass ratio) is still compatible
with observations.
Answers from the Void: VIDE and its Applications
Authors: Sutter P. M. , Hamaus N. , Pisani A. , Lavaux G. , Wandelt B. D. 
Published: October 2016

AbstractWe discuss various applications ofvide, the Void IDentification and Examination toolkit, an open-source Python/C++ code for finding cosmic voids in galaxy redshift surveys and $N$-body simulations. Based on a substantially enhanced version ofZOBOV,videnot only finds voids, but also summarizes their properties, extracts statistical information, and provides a Python-based platform for more detailed analysis, such as manipulating void catalogs and particle members, filtering, plotting, computing clustering statistics, stacking, comparing catalogs, and fitting density profiles.videalso provides significant additional functionality for pre-processing inputs: for example,videcan work with volume- or magnitude-limited galaxy samples with arbitrary survey geometries, or dark matter particles or halo catalogs in a variety of common formats. It can also randomly subsample inputs and includes a Halo Occupation Distribution model for constructing mock galaxy populations.videhas been used for a wide variety of applications, from discovering a universal density profile to estimating primordial magnetic fields, and is publicly available athttp://bitbucket.org/cosmicvoids/vide\_publicandhttp://www.cosmicvoids.net.
Void asymmetries in the cosmic web: a mechanism for bulk flows
Authors: Bland-Hawthorn J. , Sharma S. 
Published: October 2016

AbstractBulk flows of galaxies moving with respect to the cosmic microwave background are well established observationally and seen in the most recent ΛCDM simulations. With the aid of an idealised Gadget-2 simulation, we show that void asymmetries in the cosmic web can exacerbate local bulk flows of galaxies. The {\it Cosmicflows-2} survey, which has mapped in detail the 3D structure of the Local Universe, reveals that the Local Group resides in a “local sheet” of galaxies that borders a “local void” with a diameter of about 40 Mpc. The void is emptying out at a rate of 16 km s-1Mpc-1. In a co-moving frame, the Local Sheet is found to be moving away from the Local Void at ∼ 260 km s-1. Our model shows how asymmetric collapse due to unbalanced voids on either side of a developing sheet or wall can lead to a systematic movement of the sheet. We conjectured that asymmetries could lead to a large-scale separation of dark matter and baryons, thereby driving a dependence of galaxy properties with environment, but we do {\it not} find any evidence for this effect.
The cosmic web in CosmoGrid void regions
Authors: Rieder Steven , van de Weygaert Rien , Cautun Marius , Beygu Burcu , Zwart Simon Portegies 
Published: October 2016

AbstractWe study the formation and evolution of the cosmic web, using the high-resolution CosmoGrid ΛCDM simulation. In particular, we investigate the evolution of the large-scale structure around void halo groups, and compare this to observations of the VGS-31 galaxy group, which consists of three interacting galaxies inside a large void.The structure around such haloes shows a great deal of tenuous structure, with most of such systems being embedded in intra-void filaments and walls. We use the Nexus+} algorithm to detect walls and filaments in CosmoGrid, and find them to be present and detectable at every scale. The void regions embed tenuous walls, which in turn embed tenuous filaments. We hypothesize that the void galaxy group of VGS-31 formed in such an environment.
The ISW imprints of voids and superclusters on the CMB
Authors: Hotchkiss S. , Nadathur S. , Gottlöber S. , Iliev I. T. , Knebe A. , Watson W. A. , Yepes G. 
Published: October 2016

AbstractWe examine the stacked integrated Sachs-Wolfe (ISW) imprints on the CMB along the lines of sight of voids and superclusters in galaxy surveys, using the Jubilee ISW simulation and mock luminous red galaxy (LRG) catalogues. We show that the expected signal in the concordance \Lam CDM model is much smaller than the primary anisotropies arising at the last scattering surface and therefore any currently claimed detections of such an imprint cannot be caused by the ISW effect in \Lam CDM. We look for the existence of such a signal in the Planck CMB using a catalogue of voids and superclusters from the Sloan Digital Sky Survey (SDSS), but find a result completely consistent with \Lam CDM – i.e., a null detection.
The Void Galaxy Survey: Galaxy Evolution and Gas Accretion in Voids
Authors: Kreckel Kathryn , van Gorkom Jacqueline H. , Beygu Burcu , van de Weygaert Rien , van der Hulst J. M. , Aragon-Calvo Miguel A. , Peletier Reynier F. 
Published: October 2016

AbstractVoids represent a unique environment for the study of galaxy evolution, as the lower density environment is expected to result in shorter merger histories and slower evolution of galaxies. This provides an ideal opportunity to test theories of galaxy formation and evolution. Imaging of the neutral hydrogen, central in both driving and regulating star formation, directly traces the gas reservoir and can reveal interactions and signs of cold gas accretion. For a new Void Galaxy Survey (VGS), we have carefully selected a sample of 59 galaxies that reside in the deepest underdensities of geometrically identified voids within the SDSS at distances of ∼100 Mpc, and pursued deep UV, optical, Hα, IR, and HI imaging to study in detail the morphology and kinematics of both the stellar and gaseous components. This sample allows us to not only examine the global statistical properties of void galaxies, but also to explore the details of the dynamical properties. We present an overview of the VGS, and highlight key results on the HI content and individually interesting systems. In general, we find that the void galaxies are gas rich, low luminosity, blue disk galaxies, with optical and HI properties that are not unusual for their luminosity and morphology. We see evidence of both ongoing assembly, through the gas dynamics between interacting systems, and significant gas accretion, seen in extended gas disks and kinematic misalignments. The VGS establishes a local reference sample to be used in future HI surveys (CHILES, DINGO, LADUMA) that will directly observe the HI evolution of void galaxies over cosmic time.
Molecular Gas and Star Formation in Void Galaxies
Authors: Das M. , Saito T. , Iono D. , Honey M. , Ramya S. 
Published: October 2016

AbstractWe present the detection of molecular gas using CO(1–0) line emission and followup Hα imaging observations of galaxies located in nearby voids. The CO(1–0) observations were done using the 45m telescope of the Nobeyama Radio Observatory (NRO) and the optical observations were done using the Himalayan Chandra Telescope (HCT). Although void galaxies lie in the most underdense parts of our universe, a significant fraction of them are gas rich, spiral galaxies that show signatures of ongoing star formation. Not much is known about their cold gas content or star formation properties. In this study we searched for molecular gas in five void galaxies using the NRO. The galaxies were selected based on their relatively higher IRAS fluxes or Hα line luminosities. CO(1–0) emission was detected in four galaxies and the derived molecular gas masses lie between (1 - 8)×109M⊙. The Hα imaging observations of three galaxies detected in CO emission indicates ongoing star formation and the derived star formation rates vary between from 0.2 – 1.0 M7odot; yr-1, which is similar to that observed in local galaxies. Our study shows that although void galaxies reside in underdense regions, their disks may contain molecular gas and have star formation rates similar to galaxies in denser environments.