1303.1176
Mid-infrared microlensing of accretion disc and dusty torus in quasars: effects on flux ratio anomalies
Sluse, Kishimoto, Anguita, Wucknitz, Wambsganss
Investigate whether the assumption "multiply-imaged quasars and AGNs in MIR are unaffected by the microlensing produced by the stars in the lensing galaxy". This premise disregards microlensing of the accretion disk in the MIR range, and does not account for recent progress in the knowledge of the dusty torus. To simulate microlensing, first build a simplified image of the quasar composed of an accretion disc, and of a larger ring-like torus. The mock quasars are then microlensed using an inverse ray-shooting code. Simulate wavelength and size dependence of microlensing for different lensed image types and fraction of compact objects projected in the lens; allows derivation of magnification probabilities as a function of wavelength, and calculate the microlensing-induced deformation of the SED of the lensed images. Find that microlensing variations as large as 0.1 mag are very common at 11 microns (observer-frame). The main signal comes from microlensing of the accretion disc, which may be significant even when the fraction of flux from the disc is as small as 5% of the total flux. Also show that the torus of sources with Lbol < 1e45 erg/s is expected to be noticeably microlensed. [why are these things microlensed? because they are small in size?] Microlensing may thus be used to get insight into the rest NER inner structure of AGNs. Investigate whether microlensing in the MIR can alter the so-called Rcusp relation that inks the fluxes of the lensed images triplet produced when the source lies close to a cusp macro-caustic. This relation is commonly used to identify massive (DM) substructures in lensing galaxies. Find that significant deviations from Rcusp may be expected, which means that microlensing can explain part of the flux ratio problem.
1303.1183
The impact of starbursts on the circumgalactic medium
Borthakur et al
Impact of SB on the properties of the surrounding CGM (gas located beyond the galaxy's stellar body and extending out to the virial radius (200 kpc). Obtain UV spectra of 20 low-z FG galaxies using BG QSOs. Sample consists of SB and control galaxies. Latter comprises normal SF and passive galaxies with similar stellar masses and impact parameters as the SBs. Use optical spectra from SDSS to setimate properties of SBs, inferring average ages of 200 Myrs and burst fraction involving ~10% of their stellar mass. Reveal highly ionized gas traced by CIV in 80% (4/5) of SB and 17% (2/12) of control. The 2 control galaxies with CIV absorbers differed from the 4 SBs in showing multiple low-ionization transitions and strong saturated Ly-a lines. They appear to be physically different systems. Show that the CIV absorbers in the SB CGM represent a significant baryon repository. The high detection rate of this highly ionized material in the SB suggests that SB-driven winds can affect the CGM out to radii as large as 200 kpc. This is plausible given the inferred properties of the SBs and the known properties of SB-driven winds. This would represent the first direct observational evidence that local SBs can impact the bulk of the gaseous halos of their host galaxies, and as such provides new evidence of the importance of this kind of feedback in evolution of galaxies.
1303.1213
Optical counterparts of the nearest ultraluminous X-ray sources
Gladstone, Copperwheat, .. Cartwright, et al
33 ULXs observed with Hubble & Chandra, 9 have no visible counterpart (O-type companions ruled out for 4 cases.) 2 ULSx place them in the nucleus of their host galaxy, removed from sample. Of the remaining 22 ULXs, 13 have on possible optical counterpart, while multiple are visible within the error regions of other ULXs. Calculate the number of chance coincidences; estimate that 13 pm 5 are true counterparts. Constrain nature of companions by fitting SED and M_V; can rule out O-type in 20 cases, while one excludes all OB-type companions. For 7 ULXs, able to impose inclination-dependent upper and/or lower imits on the BH mass, if extinction to the assumed companion star is not larger than the Galactic column. Suggests that 10 ULXs do not have O compnions, while none of the 18 fitted rule out B-type companions. [are these all assumed to be extragalactic? What are typical x-ray sources like?]
1303.1227
Fast diffusion of magnetic field in turbulence and origin of cosmic magnetism
Cho
Turbulence is believed to play important roles in the origin of cosmic magnetism. Turbulence can efficiently amplify a uniform or spatially homogeneous seed B-field, but not clear whether or not we can draw a similar conclusion for a localized seed B-field. Main uncertainty is the rate of B-field diffusion on scales larger than the outer scale of turbulence. To measure the diffusion rate of B-field on those large scales, perform a numerical sim where the outer scale of turbulence is much smaller than the size of the system. Numerically compare diffusion of a localized seed B-field and a localized passive scalar. Find that diffusion of the B-field can be much faster than that of the passive scalar and that turbulence can efficiently amplify the localized seed B-field. Based on the simulation, construct a model for fast diffusion of B-field. Model suggests that a localized seed B-field can fill the how system in L_sys/L times the large-eddy turnover time and that growht of the B-field stops in max (15,Lsys/L) times the large-eddy turnover time, where L_sys is the size of the system and L is the driving scale. Finding implies that regardless of the shape of the seed field, fast magnetization is possible in turbulent systems, such as large-scale structure of the universe or galaxies.
1303.1301
Observational upper bound on the cosmic abundances of negative-mass compact objects and Ellis wormholes from the Sloan digital sky survey quasar lens search
Takahashi, Asada
No such exotic objects for ~50k distant quasars in SQLS data, set upper bounds on cosmic abundances of these lenses.
1303.1349
Improved primordial non-guasisanity constraints from measurements of galaxy clustering and the integrated Sachs-Wolfe effect
Giannantonio, Ross, Percival, Crittenden, Bacher, Kilbinger, Nichol, Weller
Strongest constraint on PNG from galaxy surveys, combine large-scale clustering and their cross-correlations with the CMB. Prior analysis by Giannantonio+ (2012), boraden analysis to include the full set of 2-pt correlation functions between all surveys. Advocate the use of X-correlations between the catalogs as a robust estimator; perform extended analysis of the possible systematics to reduce their impact on the results. To minimize the impact of stellar contamination in LRG sample, use the BOSS catalog of Ross+2011. Find evidence for a new systematic n the NVSS radio galaxy survey similar to, but smaller than, the known declination-dependent issue; by weighting the observed data with randomized catalogs in right ascension and declination, such problems can be moderated significantly. Find no evidence of primordial non-G; for the local type configuration, obtain -37<fNL<25 at 95% cl when using the most conservative part of the dataset, improving results by 30%; also find no evidence for significant kurtosis (gNL). In addition to PNG, simultaneously constrain DE and find that it is required with a form consistent with a cosmological constant. [how does ISW constrain NG?]
1303.1521
Double-disk dark matter
Fan, Katz, Randall, Reece
DDDM, in which self-interactions allow the DM to lose enough energy to lead to dynamics similar to those in the baryonic sector [i.e., the DM "cools"]. Most prominent signal of such a scenario could be an enhanced indirect detection signature with a distinctive spatial distribution.
1303.1534
Measuring the slopes of mass profiles for dwarf spheroidals in triaxial CDM potentials
Laporte et al
Generate stellar DMs in triaxial haloes to examine the reliability of slopes inferred by applying mass estimators of the form M ~ R_e sigma^2 (luminous effective radius times global velocity dispersion) to two stellar sub-populations independently tracing the same gravitational potential. The DFs take the form f(E) are dynamically stable, and are generated withing triaxial potentials corresponding directly to subhaloes formed in cosmo DM-only simulations of MW and galaxy cluster haloes. Also consider the effect of different tracer number density profiles (cuspy and cored) on the inferred slopes of mass profiles. Find that halo triaxiality tends to introduce an anti-correlation between R_e and sigma when estimated for a variety of viewing angles. The net effect is a negligible contribution to the systematic error associated with the slope of the mass profile, which continues to be dominated by a bias toward greater overestimation of masses for more-concentrated tracer populations. Demonstrate that simple mass estimates for two distinct tracer populations can give reliable (and cosmologically meaningful) lower limits for the slope, irrespective of the degree of triaxiality or shape of the tracer number density profile.
1303.1590
The hierarchical nature of the spin alignment of dark matter haloes in filaments
Aragon-Calvo
DM haloes in cosmo filaments and walls have their spin vector aligned (in average) with their host structure. While haloes in walls are aligned with the plane of the wall independently of their mass, haloes in filaments present a mass dependent two-regime orientation. Show that the transition mass determining the change in the alignment regime (from parallel to perpendicular) depends on the hierarchical level in which the halo is located, reflecting the hierarchical nature of the Cosmic Web. By explicitly exposing this hierarchy, able to identify the contributions of different components of the filament network to the spin alignment signal. Discuss a unifying picture to describe the alignment of haloes in filaments and walls consistent with previous results and these findings based on a two-phase angular momentum acquisition, first via tidal torquening and later via anisotropic mass accretion. The hierarchical identification and characterization of cosmic structures was done with a new implementation of the multiscale morphlogy filter. The MMF-2 represents a significant improvement over its predecessor in terms of robustness and by explicitly describing the hierarchical relations between the elements of the Cosmic Web.
1303.1791
Carbon-enhanced metal-poor stars: the most pristine objects?
Spite, etal
Carbon-enhanced metal poor stars (CEMP) form a significant proportion of the metal-poor stars, their origin is not well understood. Select 3 from SDSS, observe with ESO VLT to determine element abundances. In turnoff stars (unlike giants) the carbon abundance has not been affected by mixing with deep layers and is therefore easier to interpret. The analysis was performed with 1D LTE static model atmospheres. When available, non-LTE corrections were applied to the classical LTE abundances. 3D effects on CH and CN molecular bands were computed using hydrosims of the stellar atmosphere (CO5BOLD), found to be very important. Facilitate a comparison with previous results, only 1d abundances are used in the discussion. The abundances (or upper limits) of the elements enable placing of these stares in different CEMP classes. C abundances confirm the existence of a plateau for [Fe/H]>=-3.4. The most metal poor stars have significantly lower carbon abundances, suggesting a lower plateau. Detailed analysis of a large sample of very low metallicity C-rich stars are required to confirm (or refute) this possible second plateau and specify the behavior of the CEMP stars at very low metallicity.
1303.1796
The orbit of the Chelyabinsk event impactor as reconstructed from amateur and public footage
Zuluaga, Ferrin, Geens
1303.1806
CFHTLenS: mapping the large scale structure with gravitational lensing
Van Waerbeke, Benjamin, Erben, Heymans, Hildebrandt, Hoekstra, Kitching, Mellier, Miller, Coupon, harnois-Deraps, Fu, Hudson, Kilbinger, Kuijken, Rowe, Schrabback, Semboloni, Vafaei, Uitert, Valender
154 deg2 CFHTLenS, largest contiguous map of projected mass density from gravitational lensing. First attempt to quantitatively characterize the scientific value of lensing maps, which could serve in the future as a complementary approach to the study of the dark universe with gravitational lensing. Show that mass maps contain unique cosmological information beyond that of traditional 2-pt statistical analysis techniques. Use numerical sims to show that GL inversion provides a reliable probe of the projected matter distribution of large scale structure; validate analysis by quantifying the robustness of the maps with various statistical estimators. Same process applied to CFHTLenS data. Found that the statistical properties of the projected mass are fully consistent with the cosmo analysis performed on the shear signal discussed in CFHTLenS companion papers. Maps also lead to a significant measurement of the 3rd order moment of the projected mass in agreement with analytic predictions, and to a marginal detection of the 4th order moment. Tests for residual systematics are found to be consistent with zero for the statistical estimators used. New approach for the comparison of the reconstructed mass map to that predicted from the galaxy distribution reveals the existence of giant voids int the DM maps as large as 3 degrees on the sky. Analysis shows that lensing mass maps not only is consistent with the results obtained by the traditional shear approach, but also enable new analysis techniques such as peak statistics and the morphological analysis of the projected DM distribution.
1303.1808
CFHTLenS tomographic weak lensing cosmological parameter constraints: mitigating the impact of intrinsic galaxy alignments
Heymans, Grocutt, Heavens ... et al
Finely-binned tomographic WL analysis of CFHTLenS, mitigating contamination to the signal from the presence of IA via simultaneous fit of a cosmo model and an IA model. 154 deg2 in 5 optical bands, with accurate shear and photometric redshifts for a galaxy sample wit ha median z of 0.7. Estimate the 21 sets of cosmic shear correlation functions associated with 6 z bins, each spanning the angular range of 1.5<theta<35 arcmin. Combine this CHFTLenS data with auxiliary cosmo probles: WMAP7, BOSS, and HST H0. Sigma_8 = 0.799pm0.015, Omega_m = 0.271 pm 0.010 for flat LCDM. for flat wCDM, w = -1.02 pm 0.09. Also provie constraints for curved LCDM and wCDM cosmologies. Find the IA contamination to be galaxy-type dependent with a significant IA signal found for early-type galaxies, in contrast to late-type galaxy sample for which the IA is found to be consistent with zero.
No comments:
Post a Comment