Day 746

Wednesday.

1409.4413
First CO(17-16) emission line detected in a z>6 quasar
Gallerani et al

CO(17-16) line possibly contaminated by OH+ emission that may account for 35-60% of the total flux observed.  Photo-dissociation and X-ray Dominated regions (PDRs and XDRs) models show that PDRs alone cannot reproduce the high luminosity of the CO line relative to the low-J CO transitions and that XDRs are required.  By adopting a composite PDR+XDR model, derive molecular cloud and radiation field properties in the nuclear region of J1148.  Results show that highly excited CO lines represent a sensitive and possibly unique tool to infer the presence of X-ray faint or obscured SMBH progenitors in high-z galaxies.

1409.4414
Magnetic flux of progenitor stars sets gamma-ray burst luminosity and variability
Tchekhovskoy, Giannios

LGRBs are though to come from core-collapse of WR stars; their stellar masses M* have a rather narrow distribution, but the population of GRBs is very diverse (gamma ray luminosities span several orders of magnitude).  Argue that the difference is the star's large-scale magnetic flux.  Shortly after the core collapse, most of stellar B flux accumulates near the BH and remains there.  The flux extracts BH rotational energy and powers jets of roughly a constant luminosity, Lj, However, once BH mass accretion rate Mdot falls below ~Lj/c2, the flux becomes dynamically important and diffuses outwards, with the jet luminosity set by the rapidly declining mass accretion rate, Lj~Mdot c2.  This provides a potential explanation for the sharp end of GRBs and the universal shape of their light curves.  During the GRB, gas infall translates spatial variation of stellar B flux into temporal variation of Lj.  Make use of the deviations from constancy in Lj to perform stellar B flux "tomography".  Using this method, infer the presence of magnetized tori in the outer layers of progenitor stars for GRB 920513 and GRB 940210.

1409.4422
Imprints of the quasar structure in time-delay light curves: microlensing-aided reverberation mapping
Sluse, Tewes

Owing to the advent of large photometric surveys, the possibility to use broad band photometric data instead of spectra to measure the size of the broad line region of AGN has raised a large interest.  Describe a new method using time-delay lensed quasars where one of several images are affected by microlensing due to stars in the lensing galaxy.  Because microlensing decreases (or increases) the flux of the continuum compared to the broad line region, it changes the contrast between these two emission components.  Show that this effect can be used to effectively disentangle the intrinsic variability of those two regions, offering the opportunity to perform reverberation mapping based on single band photometric data.  Based on simulated light curves generated using a damped random walk model of quasar variability, show that measurement of the size of the broad line region can be achieved using this method, provided one spectrum has been obtained independently during the monitoring.  This method is complementary to photometric reverberation mapping and could also be extended to multi-band data.  Because the effect described above produces a variability pattern in difference light curves between pairs of lensed images which is correlated with the time-lagged continuum variability, it can potentially produce systematic errors in measurement of time delays between pairs of lensed images.  Simple simulations indicate that time-delay measurement techniques which use a sufficiently flexible model for the extrinsic variability are not affected by this effect and produce accurate time delays.  

1409.4482
Splashback in accreting dark matter halos
Adhikari, Dala, Chamberlain

Recent work has shown that density profiles in the outskirts of DM haloes can become extremely steep over a narrow range of radius.  This behavior is produced by splash back material on its first apocentric passage after accretion.  Show that the location of this splash back feature may be understood quite simply, from first principles.   Present a simple model, based on spherical collapse, that accurately predicts the location of splash back without any free parameters.  The important quantities that determine the splash back radius are accretion rate and redshift.

1409.4650
Constraining dark sector perturbations I: cosmic shear and CMB lensing
Battye, Moss, Pearson

Present current and future constraints on EoS for dark sector perturbations.  EoS considered are those corresponding to a generalized scalar field model and time-diffeomorphism invariant L(g) theories that are equivalent to models of a relativistic elastic medium and also Lorentz violating massive gravity.  Develop a theoretical understanding of the observable impact of these models.  In order to constrain these models, use CMB temperature data from Planck, BAO measurements, CMB lensing data from Planck and the SPT, and weak galaxy lensing data from CFHTLenS.  Find non-trivial exclusions on the range of parameters, although the data remains compatible with w=-1.  Gauge how future experiments will help to constrain the parameters.  This is done via a likelihood analysis for CMB experiments such as CoRE and PRISM, and tomographic galaxy WL surveys, focusing on the potential discriminatory power of Euclid on mildly NL scales.

1409.4681
Galaxy and mass assembly (GAMA): the dependence of the galaxy luminosity function on environment, redshift and color
McNaught-Roberts, Norberg, Baugh, Lacey, Loveday, Peacock, ... et al

Use 80k galaxies in GAMA to measure galaxy LF in different environments in 0.04<z<0.26.  The depth and size of GAMA allows samples split by color and z to measure the dependence of LF on environment, z and color.  Find that the LF varies smoothly with overdensity, consistent with previous results, with little environmental dependent evolution over the last 3 Gyrs.  The modified GALFORM model predictions agree remarkable well with the LFs split by environment, particularly in the most over dense environments.  The LFs predicted by the model for both blue and red galaxies are consistent with GAMA for the environments and luminosities at which such galaxies dominate.  Discrepancies between the model and the data seen in the faint end of the LF suggest too many faint red galaxies are predicted, which is likely due to the over-quenching of satellite galaxies.  The excess of bright blue galaxies predicted in under dense regions could be due to the implementation of AGN feedback not being sufficiently effective in the lower mass haloes.