Day 473

Thursday.

1307.5847
Evidence for Ubiquitous, high-EW nebular emission in z~7 galaxies: towards a clean measurement of the specific star formation rate using a sample of bright, magnified galaxies
Smit, ... Moustakas, Umetsu, Zitrin, Coe, Gonzalez, Bartelmann, Benitez, Broadhusrt, et al


Nebular line emission has significant impact on the rest-frame optical fluxes of z~5-7 galaxies observed with Spitzer.  The line emission makes z~5-7 galaxies appear more massive, with lower sSFRs.  But corrections for thie line emission have been very difficult to perform reliably due to huge uncertainties on the overall strength of such emission at z>~5.5.  Present the most direct observational evidence yet for ubiquitous high-EW [OIII]+Hbeta line emission in Lyman-break galaxies at z~7, while also presenting a strategy for an improved measurement of the sSFR at z~7.  Accomplish this through the selection of bright galaxies in the narrow redshift window z~6.6-7.0 where the IRAC 4.5 micron flux provides a clean measurement of the stellar continuum light. Observed 4.5 micron fluxes in this window contrast with the 3.6 micron fluxes which are contaminated by the prominent [OIII]+Hbeta lines.  To ensure a high S/N for the IRAC flux measurements, consider only the brightest (H_160<26 mag) magnified galaxies identified in CLASH and other programs targeting galaxy clusters.  Remarkably, the mean rest-frame optical color for the bright 7-source sample is very blue, [3.6]-[4.5]=-0.9pm0.3.  Such blue colors cannot be explained by the stellar continuum light and require that the rest-fram EW of [OIII]+Hbeta be greater than 637 Angstroms for the average source [blue = contaminated].  The bluest four sources from the 7-source sample require and even more extreme EW of 1582 Angstroms.  The derived lower limit for the mean [OIII]+Hbeta EW could underestimate the true EW by ~2x based on a simple modeling of the redshift distribution of the sources.  Can also set a robust lower limit of >~4 Gyr^-1 on the sSFR based on the mean SED of the 7-source sample.

1307.5854
The environment of bright QSOs at z~6: star forming galaxies and X-ray emission
Costa, Sijacki, Trenti, Haehnelt

Employ cosmo hydro-sims to investigate models in which the SMBHs powering luminous z~6 QSOs grow from massive seeds.  Simulate at high res 18 fields sampling regions with densities ranging from the mean cosmic density all the way to the highest sigma peaks in the Millennium sim volume.  Only in the most massive haloes, BHs can grow to masses up t o 1e9 Msun by z~6 without invoking super-Eddington accretion.  Accretion onto the most massive BHs becomes limited by thermal AGN feedback by z~9-8 with further BH growth proceeding in short Eddington limited bursts.  Modeling suggest that current flux-limited surveys of QSOs at high z preferentially detect objects at their peak luminosity and therefore miss a substantial population of QSOs powered by similarly massive BHs but with low accretion rates.  To test whether the required host halo masses are consistent with the observed galaxy environment of z~6 QSOs, produce a realistic rest-frame UV images of simulated galaxies.  Without strong stellar feedback, sims predict numbers of bright galaxies larger than observed by 10x or more.  SNe-driven galactic winds reduce the predicted numbers to a level consistent with observations indicating that stellar feedback was already very efficient at high z.  Further investigated the effect of thermal AGN feedback on the surrounding gas.  Adopted AGN feedback prescription drives mostly energy-driven highly anisotropic outflows with gas speeds of >1000 km/s to distances of >=10 kpc consistent with observations.  The spatially extended thermal X-ray emission around bright QSOs powered by these outflows can exceed by large factors the emission expected without AGN feedback and is an important diagnostic of the mechanism whereby AGN feedback energy couples to surrounding gas.

1307.5909
Empirical constraints for the magnitude and composition of galactic winds
Zahid, ... Vogelsberger, Hernquiest, Dave, et al

Galactic winds are a key physical mechanism for understanding galaxy formation and evolution, yet empirical and theoretical constraints for the character of winds are limited and discrepant.  Recent empirical models find that local SF galaxies have a deficit of oxygen that scales with galaxy stellar mass [more M*, less O outflow?  ...that sounds right.  deeper potential, less SNe outflow].  The oxygen deficit provides unique empirical constraints on the magnitude of mass loss, composition of outflowing material and metal reaccretion onto galaxies.  Formulate the oxygen deficit constraints, so they may be easily implemented into theoretical models of galaxy evolution.  Parameterize an effective metal loading factor which combines the uncertainties of metal outflows and metal reaccretion into a single function of galaxy virial velocity.  Determine the effective metal loading factor by forward-fitting the oxygen deficit.  The effective metal loading factor we derive has important implications for the implementation of mass loss in models of galaxy evolution.

1307.5988
No evidence for planetary influence on solar activity
Cameron, Schüssler

Abreu+ (2012) proposed a long-term modulation of solar activity through tidal effects exerted by the planets.  This claim is based upon a comparison of pseudo-periodicities derived from records of cosmogenic isotopes [what are these?] with those arising from planetary torques on an ellipsoidally deformed Sun.  Examined the statistical significance of the reported similarity of the periods: the tests carried out were repeated with artificial records of solar activity in the form of white or red noise.  The tests were corrected for errors in the noise definition as well as in the apodization and filtering of the random series.  The corrected tests provide probabilities for chance coincidence that are higher than nose claimed by Abreu+(2012) by about 3 and 8 order of magnitude for white and red noise, respectively.  For an unbiased choice of the width of the frequency bins used for the test (a constant multiple of the frequency resolution) the probabilities increase by another two orders of magnitude to 7.5% for red noise and 22% for white noise.  The apparent agreement between the periodicities in records of cosmogenic isotopes as proxies for solar activity and planetary torques is statistically insignificant.  There is no evidence for a planetary influence on solar activity.

1307.6002
The biasing of baryons on the cluster mass function and cosmological parameter estimation
Martizzi, Mohammed, Teyssier, Moore

The DM halo MF will be measured to high precision by ongoing and next generation surveys.  It is crucial to determine which are the theoretical uncertainties that need to be taken into account when comparing the observed halo MF (HMF) to the predictions of theoretical cosmological models and numerical simulations.  In this paper, study the effect of baryonic processes on the HMF in the galaxy cluster mass range, using a catalogue of 153 high resolution cosmological hydrodynamical sims performed with the AMR code ramses.  Use the results of our simulations within a simple analytical model to gauge the effects of baryon physics on the HMF.  Find: neglect of AGN feedback leads to a significant boost in the cluster MF similar to that reported by others.  However, including AGN feedback not only gives rise to systems that are similar to observed, but they also reverse the global baryonic effects on the clusters.  The resulting MF is closer to the unmodified DM HMF but still contains a mass dependent bias at the 5-10% level.  Then explore how these effects are within the noise for current survey volumes, but forthcoming and planned large surveys will be highly biased by these processes.

1307.6091
A small survey of the magnetic fields of planet-host stars
Fares et al

The comparison shows that these giant planet-host stars tend to have similar B-field topologies to stars without detected hot-Jupiters.

1307.6210
Dwarf galaxy planes: the discovery of symmetric structures in the Local Group
Pawlowski, Kroupa, Jerjen

Both major galaxies [Andromeda and MW] in the LG are surrounded by thin planes of mostly co-orbiting satellite galaxies, the vast polar structure (VPOS) around the MW and Great Plane of Andromeda (GPoA) around M31.  Summarize the current knowledge concerning these structures and compare their relative orientations and properties in a common coordinate system.  The existence of coherent satellite structures motivates an investigation of the distribution of the more distant non-satellite galaxies in the LG.  This results in the discovery of two planes (with diameters of 1-2 Mpc) which contain almost all nearby non-statellite galaxies.  The two LG planes are surprisingly symmetric, inclined by only 20 deg relative to the galactic disc of M31, similarly thin (h~60 kpc) and have near-to-identical offsets from the MW and M31.  They are inclined relative to each other by 35 deg.  Comparing the plane orientations with each other and with additional features indicates an intimate connection between the VPOS and the GPoA.  They are both polar to the MW, have similar orbital directions and are inclined by ~45 deg relative to each other.  The Magellanic Stream approximately aligns with the VPOS and the GPoA.  The alignment with other features such as the Supergalactic Plane and the over-density in hypervelocity stars are discussed as well. End with a summary of proposed scenarios trying to explain the LG galaxy structures as either originating from cosmological structures or from tidal debris of a past galaxy encounter.  There currently exists no full detailed model which satisfactorily explain the existence of the thin symmetric LG planes.

1307.6212
Astropy: a community Python package for Astronomy
The Astropy Collaboration

Present the v0.2 public version of the open-source and community-developed Python package.  Provides core astronomy-related functionality to the community, including support for domain-specific file formats such as FITS fils, VO tables, and common ASCII table formats, unit and physical quantity conversions, physical constants specific to astronomy, celestial coordinate and time transformation, WCS support, generalized containers for representing gridded as well as tabular data, and a framework for cosmological transformations and conversions.  Significant functionality is under active development, such as a model fitting framework, VO client and server tools, and aperture and PSF photometry tools.  The core development team is actively making additions and enhancements to the current code base, and everyone is encouraged to participate in the development of future Astropy versions.

1307.6518
The VIMOS VLT Depp Survey: the redshift distribution N(z) of magnitude-limited samples down to iAB=24.75 and KsAB=22
Le Fevre et al

Study provides a comprehensive galaxy number counts N(z) from galaxies with spectroscopic redshifts over a large redshift domain 0<z<5, a solid basis for the measurement of volume-complete quantities.  Magnitude-selected surveys identify a higher number of galaxies at z>2 than in color-color selected samples [by ratio, in absolute numbers?  probably absolute number], and use the magnitude-selected VVDS to emphasize the large uncertainties associated to other surveys using color or color-color selected samples.  Results further demonstrate that SAMs on DM sims have yet to find the right balance of physical processes and time-scales to properly reproduce a fundamental galaxy population property like the observed N(z).