Day 466

Wednesday.

1307.4075
Establishing a relation between mass and spin of stellar mass black holes
Banerjee, Mukhopadhyay

SMBHs (stellar mass BHs), forming by the core collapse of very massive, rapidly rotating stars, are expected to exhibit a high density accretion disk around them developed from the spinning mantle of the collapsing star.  A wide class of such disks, due to their high density and temperature, are effective emitters of neutrinos and hence called neutrino cooled disks.  Tracking the physics relating the observed (neutrino) luminosity to the mass, spin of BHs and the accretion rate M_dot of such disks, establish a correlation between the spin and mass of SMBHs at their formation stage.  Show that spinning BHs are more massive than non-spinning BHs for a given M_dot.  However, slowly spinning BHs can turn out to be more massive than spinning BHs if M_dot at their formation stage was higher compared to faster spinning BHs.

1307.3285
Modeling Baryon Acoustic Oscillations with perturbation theory and stochastic halo biasing
Kitaura, Yepes, Prada

Investigate the generation of mock halo catalogs based on perturbations theory and NL stochastic biasing with the PATCHY-code.  Use Augmented Langrangian Perturbation Theory (ALPT) to generate a DM density field on a mesh starting from Gaussian fluctuations.  ALPT is based on a combination of second order LPT (2LPT) on large scales and the spherical collapse model on smaller scales.  Account for the systematic deviation of perturbative approaches from N-body simulations together with halo biasing adopting an exponential bias [what is an exponential bias?].  Then account for stochastic biasing by defining three regimes: a low, an intermediate and a high density regime, using a Poisson distribution in the intermediate regime and the negative binomial distribution including an additional parameter to model over-dispersion in the high density regime.  Since this study focuses on massive haloes, suppress the generation of haloes in the low density regime.  The various NL biasing parameters, stochastic biasing parameter and density thresholds are calibrated with the large BigMultiDark N-body sim to match the PS of the corresponding halo population.  Model effectively includes only 4 parameters, as they are additionally constrained by the number density.  Mock catalogs show PS which are compatible with N-body sims within about 2% up to k~1h/Mpc at z=0.577 for a sample of haloes with the typical BOSS CMASS galaxy density.  The corresponding correlation functions are compatible down to a few Mpc.  Also find that neglecting over-dispersion in high density regions produces PS with deviations of 10% at k~0.4 h/Mpc.  These results indicate the need to account for an accurate statistical description of the galaxy clustering for precise studies of large scale surveys.  

1307.3686
Solar neutrino analysis for Super-Kamiokande
Sekiya, for Super-K Collaboration

Super-Kamiokande-IV started taking data in September of 2008, and with upgraded electronics and improvements to water system dynamics, calibration and analysis techniques, a clear solar neutrino signal could be extracted at recoil electron kinetic energies as low as 3.5 MeV.  SK-IV extracted solar neutrino flux between 3.5 and 19.5 MeV as 2.36e6 cm^-2 s^-1.  The SK combined recoil electron energy spectrum favors distortions predicted by standard neutrino flavor oscillation parameters over a flat suppression at 1 sigma level.  A maximum likelihood fit to the amplitude of the expected solar zenith angle variation of the elastic neutrino-electron scattering rate in SK, results in a day/night asymmetry of -3.2%.  THe 2.7 sigma significance of non-zero asymmetry is the first indication of the regeneration of electron type solar neutrinos as they travel through Earth's matter.  A fit to all solar neutrino data and KamLAND yeidls sin^2 theta_12=0.304, sin^2 theta_13=0.031, and Delta m^2_21=7.45e-5 eV^2.

1307.4000
Filtergraph: an interactive web application for visualization of astronomy datasets
Burger et al

As the title says.

1307.4079
Colour gradients of high-redshift early-type galaxies from hydrodynamical monolithic models
Tortora et al

Analyze the evolution of color gradients predicted by hydro models of early type galaxies (ETGs) in Pipino+(2008), which reproduce the chemical abundance pattern and the metallicity gradients of local ETGs.  Convert the SF and metal content into colors by means of stellar population synthesis model and investigate the role of different physical ingredients, as the initial gas distribution and content, and eps_SF, the normalization of SFR.  From the comparison with high z data, a full agreement with optical rest-frame observations at z<1 s found, for models with low eps_SF, whereas some discrepancies emerge at 1<z<2, despite the models reproducing quite well the data scatter at these redshifts [scatter of what?].  To reconcile the prediction of these high eps_SF systems with the shallower color gradients observed at lower z, suggest intervention of 1-2 dry mergers.  Suggest that future studies should explore the impact of wet galaxy mergings, interactions with environment, dust content  and a variation of the IMF from the galactic centers to the peripheries.

1307.4081
Is there a metallicity ceiling to form carbon stars? - A novel technique reveals a scarcity ofC stars in the inner M31 disk
Boyer, ... Dalcanton, et al

Use medium-band NIR WFC3 photometry with model NIR spectra of AGB stars to develop a new tool for efficiently distinguishing C-type AGB stars from oxygen-rich (M-type)AGB stars in galaxies at the edge of and outside the Local Group.  Present the results of a test of this method on a region of the inner disk of M31, where lack of C stars found, contrary to the findings of previous C star searches in other regions of M31.  Find only 1 candidate C star (+ 6 maybes) resulting in an extremely low ratio of C to M stars (C/M=3.3e-4) that is 1-2 orders of magnitude lower than other C/M estimates in M31.  THe low C/M ratio is likely due to the high metallicity in this region which impedes stars from achieving C/O>1 in their atmospheres.  These observations provide stringent constraints [to] evolutionary models of metal-rich AGB stars and suggest that there is a metallicity threshold above which M stars are unable to make the transition to C stars, dramatically affecting AGB mass loss and dust production and, consequently, the observed global properties of metal-rich galaxies.

1307.4089
Keck-I MOSFIRE spectroscopy of the z~12 candidate galaxy UDFj-39546284
Capak et al

A z~12 H-band dropout galaxy candidate: Find a 2.2 sigma peak with a line that can indicate 2<z<3.5 or a luminous galaxy at z~12 (flux was lower than expected).  Also search for low-z emission lines in 10 other 7<z<10 z, Y, and J-dropout candidates in mask, and find no significant detections.

1307.4177
Direct model fitting to combine dithered ACS images
Mahmoudian, Wucknitz

Combined sub-pixel dithered images can produce high-quality images, their use as input to forward-modelling techniques in gravitational lensing is still not optimal, because the residual artifacts still affect the modeling results in unpredictable ways.  In this paper, argue for an overall modeling approach that takes into account the dithering and the lensing without the intermediate product of a combined image.  Introduce an alternative approach to combine dithered images by direct model fitting with a least-squares approach including a regularization constraint.  Present tests with simulated and real data that show the quality of the results.  The additional effects of gravitational lensing and the convolution with an instrumental PSF can be included in a natural way, avoiding the possible systematic errors of previous procedures.

1307.4181
A test of the Suyama-Yamagushi inequality from weak lensing
Grassi, et al

Investigate the WL signature of primordial non-Gaussianities of the local type by constraining the magnitude of the weak convergence bi- and trispectra expected for the EUCLID WL survey.  Starting from expressions for the weak convergence spectra, bispectra and trispectra, whose relative magnitudes is investigated as a function of scale, compute their respective signal to noise ratios by relating the polyspectra's amplitude to their Gaussian covariance using a Monte-Carlo technique for carrying out the configuration space integrations.  In computing the Fisher-matrix on the non-Gaussianity parameters f_nl, g_nl and tau_nl with a very similar technique, derive Bayesian evidences for a violation of the Suyama-Yamaguchi relation tau_nl>=(6 f_nl/5)^2 as a function of the true f_nl and tau_nl-values and show that the relation can be probed down to levels of f_nl~100 and tau_nl~1e5.  IN a related study, ,derive analytical expressions for the probability density that the SY-relation is exactly fulfilled, as required by models in which any one field generates the perturbations.  Conclude with an outlook on the levels of non-Gaussianity that cna be probed with tomographic lensing surveys.

1307.4220
How well can cold-dark-matter substructures account for the observed lensing flux-ratio anomalies?
Xu, Sluse, Gao, Wang, Frenk, Mao, Schneider

Lensing flux-ratio anomalies are most likely caused by gravitational lensing by small-scale DM structures.  These anomalies offer the prospect of testing a fundamental prediction of the CDM cosmological model: the existence of numerous substructures that are too small to host visible galaxies.  Previous studies found that the number of subhalos in the six high-resolution simulations of CDM galactic haloes of the Aquarius project is not sufficient to account for the observed frequency of flux ratio anomalies seen in selected quasars from the CLASS survey.  These studies were limited by the small number of haloes used, their narrow range of masses (1-2e12 Msun), and the small range of lens ellipticities considered.  Address these shortcomings by investigating the lensing properties of a large sample of haloes with a wide range of masses in two sets of high resolution simulations of cosmological volumes and comparing them to a currently best available sample of radio quasars.  Find that, as expected, substructures do not change the flux-ratio probability distribution of image pairs and triples with large separations, but they have a significant effect on the distribution at small separations.  For such systems, CDM substructures can account for a substantial fraction of the observed flux-ratio anomalies.  For large close-pair separation systems, the discrepancies existing between the observed flux ratios and predictions from smooth halo models are attributed to simplifications inherent in these models which do not take account of fine details in the lens mass distributions.