1304.4594
Real or Interloper? The redshift likelihoods of galaxies in the HUDF12
Pirzkal, ... Coe, ... et al
SED fitting has become the workhorse for identifying high-z galaxies. Present analysis of the most recent and possibly most distant galaxies discovered in HUDF using a more robust method of z estimation based on MCMC, rather than relying on "best fit" models obtained using common chi^2 minimization techniques. Advantage of MCMC fitting is the ability to accurately estimate the probability density function of the redshift, as well as any other input model parameters, allowing us to derive accurate credible intervals by properly marginalizing over all other input model parameters. Apply method to 13 recently identified sources and show that, despite claims based on chi^2 minimization, none of these sources can be securely ruled out as low z interlopers given the low signal-to-noise of currently available observations. Estimate that there is an average probability of 21% that these sources are low z interlopers.
1304.4601
The biggest explosions in the universe
Johnson, et al
SM primordial stars expected to form in small fraction of massive protogalaxies in early universe; generally concieved as the progenitors of the seeds of SMBHs at high z. SM stars with masses of 55k Msun have been found [in simulations?] to explode and completely disrupt in a SN with an energy of up to 1e55 erg, instead of collapsing to a BH. Such events, roughly 10k times more energetic than a typical SNe today, would be among the biggest explosions in the history of the universe. Carry out a simulation of such a SM star SN in 2 stages. Using the RAGE radiation hydrodynamics code, first evolve the explosion from the earliest stages, through the breakout of the shock from the surface of the star until the blast wave has propagated out to several parsecs from the explosion site, which lies deep within an atomic cooling DM halo at z~15. Then, using the GADGET cosmological hydrodynamics code, evolve the explosion out to several kpcs from the explosion site, far into the low-density IGM. The host DM halo, with a total mass of 4e7 Msun, much more massive than typical primordial star forming haloes, is completely evacuated of high density gas after < 10 Myr, although dense metal-enriched gas re-collapses into the halo, where it will likely form second-generation stars after > 70 Myr. The 20k Msun in metals that are released in the explosion are widely distributed, and enrich the dense re-collapsing gas to an average metallicity of ~0.05 Z_sun. Such a high level of enrichment suggests that the chemical signature of these SM star explosions may have been missed in previous surveys of metal-poor stars.
1304.4622
Serendipitous discovery of a massive cD galaxy at z=1.096: Implications for the early formation and late evolution of cD galaxies
Liu, ... Grogin, et al
As the title says. ... Such increases in size and stellar mass without being accompanied by significant increases in velocity dispersion are consistent with evolutionary scenarios driven by both major and minor dry mergers. Such high-z cDs may be more common that expected.
1304.4646
Constraints on the shape of the Milky Way dark matter halo from the Sagittarius stream
Vera-Ciro, Helmi
New model for the DM halo of MW that fits the properties of the stellar stream associated with the Sagittarius dwarf galaxy. It is oblate with q=0.9 for r<10kpc. The outer halo can be made mildly triaxial, with minor-to-major axis ratio (c/a)_\Phi=0.8 and (b/a)_Phi=0.9, if the effect of LMC is taken into account. Therefore this new model takes into account the flattening induced by the presence of the Galactic disk and is also more consistent with cosmological expectations.
1304.4656
Reducing systematic error in cluster scale weak lensing
Utsumi et al
2 procedures efficient in suppressing systematic error in the B-mode: (1) refinement of the mosaic CCD warping procedure to conform to absolute celestial coordinates and (2) truncation of the smoothing procedure on a scale of 10'. Application of these procedures reduces the systematic error to 20% of its original amplitude. Provide an analytic expression for the distribution of the highest peaks in noise maps that can be used to estimate the fraction of false peaks in the WL kappa-SN maps as a function of the detection threshold. Based on this analysis, select a threshold S/N=4.56 for identifying an uncontaminated set of WL peaks in two test fields covering a total area of ~3 deg^2. Taken together these fields contain 7 peaks above the threshold. Among these, 6 are probably systems of galaxies and one is a superposition. Confirm the reliability of these peaks with dense redshift surveys, x-ray and imaging observations. The systematic error reduction procedures applied are general and can be applied to future large-area W surveys. The high peak analysis suggests that with a S/N threshold of 4.5, there should be only 2.7 spurious WL peaks even in an area of 1000 deg^2 where ~2000 peaks are expected.
1304.4719
Host galaxies of Type Ia Supernovae from the Nearby Supernova Factory
Childress, et al
Analysis (M*, SFRs, dust reddening) indicates that SNIa host galaxies are on average, typical representatives of normal field galaxies.
1304.4720
Host galaxy properties and Hubble residuals of tyep Ia supernovae from the nearby supernova factory
Childress, et al
Although metallicity has been a favored interpretation for the origin of the Hubble residual trend with host mass, illustrate here how dust in SF galaxies and mean SNIa progenitor age both evolve along the galaxy mass sequence, thereby presenting equally viable explanations for some or all of the observed SNIa host bias.
1304.4781
A quasi-Gaussian approximation for the probability distribution of correlation functions
Wilking, Schneider
Likelihood function of correlation functions must be known, to infer cosmological parameters in the context of Bayesian analysis from correlation functions. Show how to calculate a better approximation for the probability distribution of correlation functions---dubbed "quasi-Gaussian". Use the exact univariate PDF and constraints on correlation functions previously derived, transform the correlation functions to an unconstrained variable for which the Gaussian approximation is well justified. From this Gaussian in the transformed space, obtain the quasi-Gaussian PDF. The two approximations for the probability distributions are compared to the "true" distribution as obtained from simulations. Test how the new approximation performs when used as likelihood in a toy-model Bayesian analysis. The quasi-Gaussian PDF agrees very well with the PDF obtained from simulations; in particular, it provides a significantly better description than a straightforward coupla approach. In a simple toy-model likelihood analysis, it yields noticeably different results than the Gaussian likelihood, indicating its possible impact on cosmological parameter estimation.
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