1306.4980
CANDELS: the correlation between galaxy morphology and star formation activity at z~2
Lee, ... Koekemoer, Grogin, Dekel, Bell, et al
Discuss the state of assembly of the Hubble Sequence in the mix of bright galaxies at 1.4<z<=2.5 with a sample of 1671 galaxies down to H_AB~26, selected from the HST/ACS and WFC3 images of the GOODS-South field obtained as part of the GOODS and CANDELS observations. Investigate the relationship between the SF properties and morphology using various parametric diagnostics, such as the Sersic light profile, Gini (G), M_20, Concentration (C), Asymmetry (A) and multiplicity parameters. The sample clearly separates into massive, red and passive galaxies versus less massive, blue and SF ones, and this dichotomy correlates very well with the galaxies' morphological properties. SF galaxies show a broad variety of morphological features, including clumpy structures and bulges mixed with faint low SB features, generally characterized by disky-type light profiles. Passively evolving galaxies, on the other hand, very often have compact light distribution and morphology typical of today's spheroidal systems. Also find that artificially redshifted local galaxies have a similar distribution with z~2 galaxies in a G-M_20 plane. [!!! useful info for shape measurements] Visual inspection between the rest-frame optical and UV images show that there is a generally weak morphological k-correction for galaxies at z~2, but the comparison with non-parametric measures show that galaxies in the rest-frame UV are somewhat clumpier than rest-frame optical. [more useful info!!] Similar trends are observed in the local universe among massive galaxies, suggesting that the backbone of the Hubble sequence was already in place at z~2.
1306.4984
Detectability of the first cosmic explosions
de Souza et al
Preset a fully self-consistent simulation of a synthetic survey from the furthermost cosmic explosions. The appearance of the first generation of stars (Pop III) in the Universe represents a critical point during cosmic evolution signaling the end of the dark ages, a period of absence of light sources. Despite their importance, there is no confirmed detection of Pop III stars so far. A fraction of these primordial stars are expected to die as a pair-instability SNe (PISN [can only happen in stars with a mass range from around 130 to 250 Msun and low to moderate metalicity]), and should be bright enough to be observed up to a few hundred million years after the Big Bang. While the quest for Pop III stars continues, detailed theoretical models and computer simulations serve as a testbed for their observability. With the upcoming NIR missions, estimates of the feasibility of detecting PISN are not only timely but imperative. Combine state of the art cosmo and radiative sims into a complete and self-consistent framework which includes detailed features of the observational process. Show that a dedicated observational strategy using <~8 [units?] of total allocation time of the JWST mission can provide up to 9-15 detectable PISN per year.
1306.4985
the case against large intensity fluctuations in the z~2.5 HeII Lyman-alpha forest
McQuinn, Worseck
Previous studies of the 2.2<z<2.7 HeII Lya forest measured much larger ionizing BG fluctuations than are anticipated theoretically. Re-analyize recent HST data from the two HeII sight-lines that have been used to make these measurements, and find that the vast majority of the absorption is actually consistent with a single HeII photoionization rate. Show that the data constrains the RMS fractional fluctuations level smoothed at 1 Mpc to be <2 and discuss why other studies had found larger fluctuations. Our measurement is consistent with models in which quasars dominate the z=2.5 metagalactic HeII-ionizing background (but it can accomodate less compelling models), and it suggests that quasars (rather than stars) are the dominant contributor to the HI-ionizing background. Detect a HeII transverse proximity effect that is slightly offfset in redshift from a known quasar. Its profile and offset may indicate that the quasar turned on 10 Myr ago.
1306.4998
Review of the anisotropy working group at UHECR-2012
Deligny et al
Report on the current status for anisotropy searches in the arrival directions of UHECRs.
1306.5131
Two-point correlation function of density perturbations in a large void universe
Nishikawa, Yoo, Nakao
Study the 2-pt correlation function of density perturbations in a spherically symmetric void universe model which does not employ the Copernican principle [i.e., no special place in the Universe]. First solve perturbation equations in the inhomogeneous universe model and obtain density fluctuations by using a method of NL perturbation theory which was adopted in the previous paper. From the obtained solutions, calculate the 2-pt correlation function and show that it has a local anisotropy at the off-center position differently from those in homogeneous and isotropic universes. This anisotropy is caused by the tidal force in the off-center region of the spherical void. Since no tidal force exists in homogeneous and isotropic universes, can test the inhomogeneous universe by observing statistical distortion of the 2-tp galaxy correlation function.
1306.5140
How well do we know the Halo Mass Function?
Murray, Power, Robotham
Halo mass function (HMF): a powerful probe of DM and DE models, informed by LCDM parameters. In this letter, trace how changes in the cosmological parameters over the last decade have influenced uncertainty in our knowledge of the HMF. Show that this uncertainty has reduced significantly since the WMAP3, but the rate of this reduction is slowing. This is limited by uncertainty in the normalization sigma_8, whose influence is most pronounced at the high mass end of the MF. Find that the accuracy with which we can constrain the HMF in terms of the cosmological parameters has now reached the point at which it is comparable to the scatter in HMF fitting functions. This suggests that the power of the HMF as a precision probe of DM and DE hinges on more accurate determination of the theoretical HMF. Assess prospects of using the HMF to differentiate between CDM and WDM models based on ongoing improvements in measurements of Omega_m, and comment briefly on optimal survey strategies for constraining DM and DE models using the HMF.
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