1805.00021
Constraining non-cold dark matter models with the global 21-cm signal
Schneider
Any particle DM scenario featuring a suppressed power spectrum of astrophysical relevance results in a delay of galaxy formation. As a consequence, such scenarios can be constrained using the global 21-cm absorption signal initiated by the UV radiation of the first stars. The Experiment to Detect the Global Epoch of Reionization Signature (EDGES) recently reported the first detection of such an absorption signal at redshift ~17. While its amplitude might indicate the need for new physics, solely focus on the timing of the signal to test non-cold DM models. Assuming a conservative upper limit for star-formation based on radiation-hydrodynamics simulations, able to derive unprecedented constraints on a variety of non-cold DM models. For example, the mass of thermal warm DM is limited to m_TH>6.1 keV, while mixed DM scenarios (featuring a cold and hot component) are constrained to a hot DM fraction below 17 %. The ultra-light axion DM model is limited to masses m_a>8e-21 eV, a regime where its wave-like nature is pushed far below the kilo parsec scale. Finally, sterile neutrinos from resonant production can be fully disfavored as a dominant DM candidate. The results of this paper show that the 21cm absorption signal is a powerful discriminant of non-CDM, allowing for significant improvements over to the strongest current limits. Confirming the result from EDGES is paramount in this context.
1805.00159
Detecting galaxy-filament alignments in the Sloan Digital Sky Survey III
Chen, Ho, Blazek, He, Mandelbaum, Melchior, Singh
Previous studies have shown the filamentary structures in the cosmic web influence the alignments of nearby galaxies. Study this effect in the LOWZ sample of SDSS using the Cosmic Web Reconstruction filament catalogue of Chen+2016. Find that LOWZ galaxies exhibit a small but statistically significant alignment in the direction parallel to the orientation of nearby filaments. This effect is detectable even in the absence of nearby galaxy clusters, which suggests it is an effect from the matter distribution in the filament. A nonparametric regression model suggests that the alignment effect with filaments extends over separations of 30-40 Mpc. Find that galaxies that are bright and early-forming align more strongly with the directions of nearby filaments than those that are faint and late-forming; however, trends with stellar mass are less statistically significant, within the narrow range of stellar mass of this sample.
1804.11339
Ghostly tributaries to the Milky Way: Charting the Halo's stellar streams with the Gaia DR2 catalogue
Malhan, Ibata, Martin
Present a panoramic map of the stellar streams of the Milky Way based upon astrometric and photometric measurements from the Gaia DR2 catalogue. In this first contribution, concentrate on the halo at heliocentric distances beyond 5 kpc, and at Galactic latitudes |b|>30 deg, using the STREAMFINDER algorithm to detect structures along plausible orbits that are consistent with the Gaia proper motion measurements. Find a rich network of criss-crossing streams in the halo, often with striking kinematic coherence. Some of these structures were previously-known, several are new discoveries, but others are potentially artifacts of the Gaia scanning law and will require confirmation. With these initial discoveries, starting to unravel the complex formation of the halo of our Galaxy.
1805.00562
Studying galaxy roughs and ridges using weak gravitational lensing with the Kilo-Degree Survey
Brouwer, et al
Study projected under densities in the cosmic galaxy density field known as 'troughs', and their overdense counterparts, 'ridges'. Identify these regions using a bight sample of foreground galaxies from the photometric KiDS, specifically selected to mimic the spectroscopic GAMA survey. From an independent sample of KiDS background galaxies, measure the WL profiles of the troughs/ridges. Quantify their lensing strength A as a function of galaxy density percentile rank P and overdensity delta, and find that the skewness in the galaxy density distribution is reflected in the total mass distribution measured by WL. Interpret the results using the mock galaxy catalogue from MICE Grand Challenge light cone sim, and find a good agreement with observations. Using S/N weights derived from the Scinet LightCone Simulations (SLICS) mock catalogue, optimally stack the lensing signal of KiDS troughs with an angular radius theta_A={5,10,15,20} racmin, resulting in {16.8,14.9, 10.31, 7.55} sigma detections. Finally, select throughs using a volume-limited sample of galaxies, split into two redshift bins between 0.1<z<0.3. For troughs/ridges with transverse comoving radius R-A=1.9 Mpc/h, find no significant difference between the comoving A'(P) and A'(delta) relation of the low- and high-redshift sample. Using the MICE and SLICS mocks, predict that trough and ridge evolution could be detected with GL using deeper and wider lensing surveys, such as those from LSST and Euclid.
1805.01240
Statistical separation of weak gravitational lensing and intrinsic ellipticities based on galaxy color information
Tugendhat, Reischke, Schaefer
IA of galaxies are recognized as one of the most important systematic in WL surveys on small angular scales. In the paper, investigate ellipticity correlation functions that are remeasured separately on elliptical and spiral galaxies, for which it is assumed that the generic alignment mechanisms based on tidal shearing and tidal torquing, respectively. Including morphological information allows to find linear combinations of measured ellipticity correlation functions which suppress the gravitational lensing signal completely or which show a strongly boosted gravitational lensing signal relative to IA. Specifically, find that (i) intrinsic alignment spectra can be measured in a model-independent way at a significance of Sigma~60 with a wide-angle tomographic survey such as Euclid's, (ii) IA model parameters can be determined at %-level precision, (iii) this measurement is not impeded by misclassifying galaxies and assuming a wrong alignment model, (iv) parameter estimation from a cleaned WL spectrum is possible with almost no bias and (v) the misclassification would not strongly impact parameter estimation from the boosted WL spectrum.
No comments:
Post a Comment