Day 414

Wednesday.

1304.3726
Are z~5 QSOs found in the most massive high redshift over-densities?
Husband, et al

High-z QSOs likely markers for biased, over-dense regions where early galaxies cluster, regions that eventually grow into the groups and clusters seen in the lower z universe.  Explore the clustering of galaxies around z~5 as traced by LBGs (Lyman break galaxies).  Target fields of 3 QSOs using optical imaging and spectroscopy techniques used in ESO remote galaxy survey, which was successful in identifying individual clustering structures of LBGs.  Use the statistics of the redshift clustering in ERGS to show that two of the 3 fields show significant clustering of LBGs at the QSO redshifts.  Neither of these fields is obviously over-dense in LBGs from the imaging alone; a possible reason why previous imaging-only studies of high-z QSO environments have given ambiguous results.  This result shows that luminous QSOs at z~5 are typically found in over-dense regions.  The richest QSO field contains at least 9 spectroscopically confirmed objects at the same z including the QSO itself, 7 LBGs and a second fainter QSO.  While this is a very strong observational signal of clustering at z~5, it is of similar strength to that seen in two structures identified in the 'blank sky' ERGS fields.  This indicates that, while over-dense, the QSO environments are not more extreme than other structures that can be identified at these redshifts.  The three richest structures discovered in this work and in ERGS have properties consistent with that expected for proto-clusters and likely represent the early stages in the build-up of massive current-day groups and clusters.

1304.3735
Kronoseismology: using density waves in Saturn's C ring to probe the planet's interior
Hedman, Nicholson

Investigate origin of 6 unidentified C-ring waves.  Measure differences in the wave's phases among the different occultations, determine both the number of arms in each spiral pattern and the speeds at which these patterns rotate around the planet.  Find all 6 waves have between 2 and 4 arms, and pattern speeds between 1660 deg/day and 1861 deg/day.  Speeds too large to be attributed to any satellite resonance; insteand they are comparable to the predicted pattern speeds of waves generated by low-order normal-mode oscillations within the planet.  Precise pattern speeds associated with these waves should therefore provide strong constraints on Saturn's internal structure.  Identify multiple waves with the same number of arms and very similar pattern speeds, indicating that multiple m=3 and 2 sectoral (l=m) modes may exist within the planet.

1304.4043
Constraints on early Mars atmospheric pressure inferred from small ancient craters
Kite, Williams, Luas, Aharonson

Thinner past atmosphere will yield smaller minimum-sized craters that form.  If Mars did not have a stable multibar atmosphere at the time that the rivers were flowing, it rules out warm-wet CO2 greenhouse model; long-term average temperatures were probably below freezing.  Implies exoplanet habitable-zone calculations using Mars as a reference point may need to be reconsidered.

1304.4227
Discovery of Lyman break galaxies at z~7 from the ZFOURGE survey
Tilvi, ... van Dokkum, ... Glazebrook, ... Koekemoer, et al

Present 3 candidates for z~7 LBGs from 155 arcmin^2 area in the CANDELS/COSMOS field imaged by the zFourGE survey.  The FourStar medium-band filters provide the equivalent of R~10 spectroscopy, which cleanly distinguishes between z~7 LBGs and brown dwarf stars.  The distinction between stars and galaxies based on an object's angular size can become unreliable even when using HST imaging; there exists at least one very compact z~7 candidate that is indistinguishable from a point source.  The medium-band filters provide narrower redshift distributions compared with borad-band-derived redshifts.  The UV luminosity function derived using the three z~7 candidates is consistent with previous studies, suggesting an evolution at the bright end (MUV -21.6 mag) from z~7 to 5.  Fitting the galaxies' SED, predict Lyman-alpha equivalent widths for the two brightest LBGs, and find that the presence of a Lyman-alpha line affects the medium-band flux thereby changing the constraints on stellar masses and UV spectral slopes.  This illustrates the limitations of deriving LBG properties using only broad-band photometry.  The derived specific star-formation rates for the bright LBGs are ~13 per Gyr, slightly higher than the lower-luminosity LBGs, implying that the star-formation rate increases with stellar mass for these galaxies.

1304.4228
Nonlinear stochastic biasing of haloes: analysis of cosmological N-body simulations and perturbation theories
Sato, Matsubara

Use 40 large cosmo N-body sims for standard LCDM, study the X-correlation coefficient between matter and halo density field, which is an indicator of stochasticity of bias, over a wide redshift range 0<z<3.  The cross-correlation coefficient is important to extract information on the matter density field, by e.g. combining galaxy clustering and gg-lensing measurements.  Compare the simulation results with integrated perturbation theory (iPT) and standard perturbation theory (SPT) combined with a phenomenological model of local bias.  The X-correlation coefficient derived from the iPT agrees with N-body sims results down to r~15(10) Mpc/h within 0.5%(1.0%) for all redshifts, while roughly reproduces general behavior of the X-correlation coefficient on fully NL scales.  The iPT is powerful to predict the X-correlation coefficient down to quasi-linear regimes with a high precision.

1304.4256
A dust-obscured massive maximum-starburst galaxy at a redshift of 6.34
Riechers, ... Aguirre, ... Cooray, et al

As the title says.

1304.4265
CFHTLenS: the relation between galaxy dark matter haloes and baryons from weak gravitational lensing
Valender, Uitert, Hoekstra, ... et al

G-g lensing halo model, constrain halo mass and satellite fraction; analysis is limited to lenses at redshifts between 0.2 and 0.4.  Express relationship between halo mass and baryonic observable as a power law.  Luminosity-halo mass relation, find a slope and normalization for red and blue galaxies.  Do it also for stellar mass -halo mass relation.  The satellite fractions are generally close to zero for blue lenses, irrespective of luminosity of stellar mass.  Blue galaxies reside in less clustered environments than red galaxies.  Also find that the halo model, while matching the lensing signal around red lenses, is prone to over-predicting the large-scale signal for faint and less massive blue lenses.  This could be a further indication that these galaxies tend to be more isolated than assumed.

1304.4399
Testing the local-void alternative to dark energy using galaxy pairs
Wang, Dai

The distribution of orientations of galaxy pairs can be used to test the Copernican principle that we are not in a central or special region of Universe.  The popular void models can not fit both the latest type Ia SNe, CMB data and the distribution of orientations of galaxy pairs simultaneously.  Results rule out the void models at the 4 sigma confidence level as the origin of cosmic acceleration and favor the Copernican principle.

1304.4446
What have we learned from observational cosmology?
Hamilton

Review observational foundations of LCDM model; Cosmological Principle is shown to be verified with increasing accuracy.  Hot BB supported by many probes.  Measurement of cosmological parameters. within FLRW cosmologies, leading to LCDM model: an apparently flat Universe, dominated by a cosmological constant, whose matter component is dominantly dark.  Describe and discuss the various observational probes that lead to this conclusion and conclude that the LCDM model, although leaving a number of open questions concerning the deep nature of the constituents of the Universe, provides the best theoretical framework to explain the observations.

1304.4474
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XII. Time delays of the doubly lensed quasars SDSS J1206+4332 and HS 2209+1914
Eulaers et al

4 different techniques used to determine time delay of light curves: dispersion method, spline fit, a regression difference technique, and a numerical model fit; minimizes bias.  111.3 days and 20.0 days for the two multiply lensed quasars.  

1304.4493
The Tully-Fisher relations for Hickson Compact Group galaxies
Torres-Flores et al

Most of Hickson compact group [merging, with complex morphologies] galaxies lie on the K-band Tully-Fisher relation defined by field galaxies with a few low-mass outliers, which appear to have had strong recent burst of SF.  Strong burst of SF can affect B and K-band luminosities (also AGN activity) without affecting their total mass.