Tuesday.
1402.3590
Clustering tomography: measuring cosmological distances through angular clustering in thin redshift shells
Salazar-Alboronoz, Sánchez, Padilla, Baugh
Test the cosmological implications of studying galaxy clustering using a tomographic approach, by computing the galaxy 2pt angular correlation function w(theta) in thin redshift shells using a spectroscopic-redshift galaxy survey. The advantages of this procedure are that it is not necessary to assume a fiducial cosmology in order to convert measured angular positions and redshifts into distances, and that it give several (less accurate) measurements of the angular diameter distance D_A(z) instead of only one (more precise) measurement of the effective average distance D_V(z), which results in better constraints on the expansion history of the Universe. Test model for w(theta) and its covariance matrix against a set of mock galaxy catalogues and show that this technique is able to extract unbiased cosmological constraints. Also, assuming the best-fit LCDM cosmology from the CMB measurements from the Planck satellite, forecast the result of applying this tomographic approach to the final BOSS catalog in combination with Planck for 3 flat cosmological models, and compare them with the expected results of the isotropic BAO measurements post-reconstrunction on the same galaxy catalogue combined with Planck. While BAOs are more accurate for constraining cosmological parameters of the standard LCDM model, the tomographic technique gives better results when we allow the DE EoS w_DE deviate from -1, resulting in a performance similar to BAOs in the case of a constant value of w_DE, and a significant improvement of the case of time-dependent value of w_DE, increasing the value of the FoM in the w0-wa plane by a factor of 1.4.
1402.3594
Galaxy properties in clusters. II. Backsplash galaxies
Muriel, Coenda
Explore properties of galaxies on the outskirts of clusters and their dependence on recent dynamical history in order to understand the real impact that the cluster core has on the evolution of galaxies. >1000 galaxies M_0.1r<-19.6 on outskirts of 90 clusters (1<r/rvir<2) in 0.05<z<0.10. Use LoS velocity, select high and low velocity subsamples. Theoretical predictions indicate that a significant fraction of the first subsample should be backsplash galaxies, that is, objects that have already orbited near the cluster center. A significant proportion of the sample of high relative velocity HV galaxies seems to be composed of in falling objects. Results suggest that, at fixed stellar mass, late type galaxies in the low velocity LV sample are systematically older, refer and have formed fewer stars ruling the last 3 Gyrs than galaxies in the HV sample. This result is consistent with models that assume that the central regions of clusters are effective in quenching the SF by means of processes such as ram pressure stripping or strangulation. At fixed stellar mass, LV galaxies show some evidence of having higher surface brightness and smaller size than HV galaxies. These results are consistent with the scenario where galaxies that have orbited the central regions of clusters are more likely to suffer tidal effect, producing loss of mass as well as redistribution of matter towards more compact configurations. Finally, found a higher fraction of ET galaxies in the LV sample, supporting the idea that the central region of clusters of galaxies may contribute to the transformation of morphological types towards earlier types.
1402.3674
New results on the exotic galaxy `Speca' and discovering many more Specas with RAD@home network
Hota et al
A citizen-science research lab built on free web-services (Facebook, Google, Skype, …). Present 10 newly found candidate episodic radio galaxies, and 10 more interesting cases which includes bent-lobe radio galaxies located in new M-c-scale filaments, likely tracing cosmological cluster accretion from the cosmic web. The new Speca-like rare spiral-host large radio galaxies also been reported. Early analysis from follow-up observations revealed that Speca is likely a new entry to the cluster and its a fast rotating, extremely massive SF disk galaxy. Speca-like massive galaxies with giant radio lobes are possibly remnants of luminous quasars in the early Universe or of first SMBHs with in first massive galaxies [?]. As discoveries of Speca-like galaxies did not require new data from big telescopes, but free archival radio-optical data, these early results demonstrate the potential of RAD@home and how it can help resource-rich professionals, as well as demonstrate a model of academic-growth for resource-poor people in the underdeveloped regions via Internet.
1402.3823
r-Java 2.0: the nuclear physics
Kostka et al
A nucleosynthesis code for open use that performs r-process calculations as well as a suite of other analysis tools. With GUI, it is capable of: simulating nuclear statistical equilibrium (NSE), calculating r-process abundances for a wide range of input parameters and astrophysical environments, computing the mass fragmentation from neutron-induced fission as well as the study of individual nucleosynthesis processes. New feature: ability to solve the full reaction network. 3 fission channels (beta-delayed, neutron-induced and spontaneous fission) as well as computation of the mass fragmentation; compared to the upper limit on mass fission approximation. The effects of including beta-delayed neutron emission on r-process yield is studied. The role of coulomb interactions in NSE abundances is shown to be significant, supporting previous foundlings. Comparative analysis undertaken, producing results in literature: high-entroy wind around a proto-neutron star, the ejecta from a NS merger or the relativistic ejecta from a quark nova.
1402.3824
r-Java 2.0: the astrophysics
Kostka et al
Astrophysics incorporated into the software described. Survey of the available parameters for each astrophysical site is undertaken and the effect on final r-process abundance is compared. Resulting abundances for each site are also compared to solar observations both independently and in concert. R-Java 2.0 available for download.
1402.0506
Scale-dependent bias in the BAO-scale intergalactic neutral hydrogen
Pontzen
Show that HI density of the z~2.3 IGM's relation to cosmic overdensity is strongly scale-dependent. This behavior arises from a linearized version of the well-known "proximity effect", in which bright sources suppress atomic hydrogen density. Demonstrate how HI density consequently anti-correlates with total matter density when averaged on scales exceeding the Ly-limint mean-free-path. The radiative transfer thumbprint is highly distinctive and should be measurable in the Lya forest. Effects extend to sufficiently small scales to generate significant distortion of the correlation function shape around the BAO peak, although the peak location shifts only by 1.2 % for a mean source bias of b_j=3. The distortion changes significantly with b_j and other astrophysical parameters; measuring it should provide a helpful observational constrain on the nature of ionizing photon sources in the near future.
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