1111.6970
A Second Kelvin-Helmholtz timescale of post helium-flash evolution
Gould
* Kelvin-Helmholtz instability: occurs when velocity shear is present within a continuous fluid, or when there is sufficient velocity difference across the interface between two fluids. Theory can be used to predict the onset of instability and transition to turbulent flow in fluids of different densities moving at various speeds.
* Rayleigh-Taylor instability: occurs when the lighter fluid is pushing the heavier fluid--case with interstellar cloud and shock system.
* Kelvin-Helmholtz mechanism: astronomical process that occurs when the surface of a star or planet cools. The cooling causes the pressure to drop and the star or planet shrinks as a result. This compression, in turn, heats up the core of the star/planet.
* Helium flash: runaway fusion of He in the core of low mass stars 0.5Msun<M<2.25 Msun, or on the surface of an accreting WD. May also occur in the outer layers of larger stars in shell flashes.
* red clump: core He-burning phase (main sequence=core H-burning phase)
* red giant: thermonuclear fusion of hydrogen in a shell surrounding the core.
After the "helium flash" abruptly ends the first ascent red giant evolution, a solar-type star is powered primarily by gravitational contraction of its He core, rather than by nuclear fusion. Because this energy is released in the core rather than the envelope, the overall structure of the star, and so its luminosity, is driven toward that of a red clump star from its initial position at the tip of the RGB (TRGB). This occurs on a first KH timescale E_env/L_TRGB~1e4 yrs, where E_env is the thermal energy stored in the envelope and L_TRGB is the luminosity of a clump star. However, once the star ssumes the approximate structure of a clumb star, it remains powered primarily by contraction for a second KH timescale ~ 1e6 years. It is this second KH timescale that determines the overall pace of the moderately violent processes by which the star returns to nuclear-power generation as a full-fledged clump star. The reservoir of gravitational energy acts as ultimate regulator, providing whatever supplemental energy is needed to power L_clump and occasionally absorbing the large momentary excesses from He mini-flashes. As this reservour is gradually exhausted, helium fusion approaches the level of stead-state clump stars.
* wow, I learned a lot here.
1111.6971
Galaxy triplets in SDSS-DR7: I. Catalogue
O'Mill, et al
Final catalog comprises of 1092 isolated triplets of galaxies of 0.01<z<0.40.
1111.6973
Evidence for three accreting black holes in a galaxy at z~1.35: A snapshot of recently formed BH seeds?
Schawinski, Urry, Treister, Simmons, Natarajan, Glikman
Discovery of multiple SMBH (1e6-1e7 Msun) in a single galaxy: merger, or in-situ formation?
1111.6974
WL predictions for coupled dark energy cosmologies at NL scales
Beynon... Koyama, et al
Coupled DE models using CoDECS simulations, WL predictions.
1111.6977
Formation times, mass growth histories and concentrations of DM haloes
Giocoli, Tormen, Sheth
Simple model for estimating the mass growth histories of DM haloes. The models is based on a fit to the formation time distribution, where formation is defined as the earliest time that the main branch of the merger tree contains a fraction f of the final mass M. Exploits the fact that the median formation time as a function of f is the same as the median of the main progenitor mass distribution as a function of time. Previous work: concentration c of the final halo is related to the formation time t_f associated with f~0.04. Simple algorithm for estimating how the distribution of halo concentrations may be expected to depend on mass, redshift and the expansion history of the BG cosmology. Show that one can predict c with 0.12 dex precision if mass is known; conversely, predict formation time from mass or c, approximately independent of f. C-based estimate may be useful for studies which seek to compare the age of the stars in the central galaxy in a halo with the time the core was first assembled.
1111.6981
A deep view of the Virgo cluster core
Lieder, et al
Analyze color magnitude relation (CMR) and structural scaling relations down to faint magnitudes, of early-type galaxies in Virgo cluster, and by constructing the luminosity function. New elliptical member galaxies (~70) found. CMR slope changes between dEs to dSphs. Scaling relations given by the dEs appear to be continued by the dSphs indicating a similar origin. The observed change in the CMR slope may mark the point at which gas loss prevented significant metal enrichment. The constant scatter around the CMR possibly indicates a short formation period, resulting in similar stellar populations. Luminosity function show lack of galaxies related to the expected number of low-mass DM haloes from theoretical models. Suppressed star formation in low-mass DM haloes, or tidal disruption of dwarfs in the dense core region of the cluster suspected.
1111.6993
Elliptical galaxies have only been the predominant morphological class for massive galaxies since only z~1
Buitrago, Trujillo, Conselice, Haeussler
Present-day massive galaxies are composed mostly of early-type objects. In hierarchical assembling scenario, the morphological content of the massive population is expected to change with time from disk-like objects in the early Universe to spheroid-like galaxies at present. 1082 objects of 0<z<3, with 639 having spectroscopic redshifts, find that the fraction of early-type galaxies among the massive galaxy population has changed from ~20-30% at z~3 to ~70% at z=0. Elliptical galaxies have been the predominant morphological class for massive galaxies since only z~1.
1111.7081
Magnetic fields and star formation as seen in edge-on galaxies
Krause
Radio continuum and polarization observations of several nearby galaxies allowed determination of their vertical scale heights, magnetic field strengths and large-scale magnetic field patterns. All show a similar large-scale magnetic field pattern, which is parallel to the galactic disk along the midplane and X-shaped further away from the disk plane, independent of their Hubble type or star formation in the disk or nuclear region. Conclude: though a high SFR in the disk increases the total magnetic field strength in the disk and the halo, the SFR does not significantly change the global field configuration nor influence the global scale heights of the radio emission. The observed similar scale heights indicate that star formation regulates the galactic wind velocities. The galactic wind itself may be essential for an effective dynamo action.
1111.7156
Modeling of weak lensing statistics. I. Power spectrum and bispectrum
Valageas, Sato, Nishimichi
Performance of an analytic model of the 3d matter distribution. Works well for power spectrum and bispectrum, recovers the dependence on cosmology.
1111.7245
The first public release of SPT data: Maps of a 95 sq deg. field from 2008 observations
Schaffer et al
SPT nearly completed a 2500 sq deg. survey of the southern sky in 3 frequency bands. Present the first public data release of SPT maps and associated data products. Arcminute-resolution maps at 150 GHz and 220 Ghz of 95 sq. deg. field, observed to a depth of approximately 17 uK arcmin at 150 GHz and 41 uK arcmin at 220 GHz. Two variations on map filtering and map projection presented, one tailored for producing catalogs of galaxy clusters detected through their SZ effect signature, and one tailored for producing catalogs of emissive sources.
1112.0561
Spherical 3d Isotropic wavelets
Lanusse, Rassat, Starck
3d large scale structure maps with large sky coverage, for which a 3d Spherical Fourier Bessel analysis (SFB) is natural. Wavelets are particularly well-suited to the analysis and denoising of cosmological data, but spherical 3d isotropic wavelet transform does not currently exist to analyse spherical 3d data. Present a new fast Discrete Spherical Fourier-Bessel Transform (DSFBT) based on both a discrete Bessel Transform and the HEALPIX angular pixelisation scheme. Find noise removal possible without much loss to the large scale structure.
1112.0495
Tomography and weak lensing statistics
Munshi, Coles, Kilbinger
Generic predictions for lower order cumulants and their correlators for individual tomographic bins as well as between two different bins. Derive the corresponding one- and two-point joint probability distribution function for the tomographic convergence maps from different bins as a function of angular smoothing scale. The modelling of weak lensing statistics is obtained by a detailed ... [I give up trying to understand what he's saying]
1111.6587
The X-ray cluster survey with eROSITA: forecasts for cosmology, cluster physics, and primordial non-Gaussianity
Pillepich, Porciani, ReipricheROSITA will go up in late 2013, survey X-ray sky with unprecedented sensitivity. Detection limit of 50 photons in the 0.5-2.0 keV band with ~1.6 ks exposure, eROSITA will detect ~9.3e4 clusters with M>5e13 Msun/h with the currently planned all-sky survey, median redshift z~0.35. Fisher analysis on LCDM cosmology and X-ray scaling relations for galaxy clusters. Possibility of detecting primordial non-Gaussianity. Use cluster number counts, and the angular clustering of a photo-count limited sample of clusters. Discuss how the cluster sample should be split to optimize the analysis; show that z information of the individual clusters is vital to break the strong degeneracies among the model parameters. Discuss how the cluster sample should be split to optimize the analysis, show that redshift information of the individual clusters is vital to break the strong degeneracies among the model parameters. Delta sigma8~0.036, DeltaOmega_m ~ 0.012 without priors, x3 improvement of the current estimates of the slope of luminosity-mass relation. Delta(f_NL)=9, 36, or 144 for local, orthogonal and equilateral model, respectively. Measure redshifts with spectroscopic redshifts will tighten constraints by ~40% (except f_NL). Combine temperature anisotropies in CMB by the Planck satellite should give sensational constraints on both the cosmology and the properties of the intracluster medium.
1111.6590
The environmental history of group and cluster galaxies in a LCDM universe
De Lucia, ... Zaritsky, et al
Use galaxy merger trees in high resolution cosmo simulation to study the environmental history of group and cluster galaxies. Show (i) surviving massive satellites within clusters were accreted later than their less massive counterparts, from more massive halos; (ii) the mixing of galaxy populations is incomplete during cluster assembly, which creates a correlation between the time a galaxy becomes satellite and its present distance from the cluster core. A large fraction of the most massive cluster members are accreted onto the main progenitor of the final group/cluster as central galaxies, while about half of al cluster galaxies with low and intermediate stellar mass are accreted as satellites. Large fractions of group and cluster galaxies (in particular those of low stellar mass) have therefore been 'pre-processed' as satellites of groups with mass ~1e13 Msun. To quantify the relevance of hierarchical structure growth on the observed environmental trends, considered observational estimates of the passive galaxy fractions, and their variation as a function of halo mass and cluster-centric distance. Comparisons with theoretical predictons require relatively long times for the suppression of SF in group and cluster satellites.
The environmental history of group and cluster galaxies in a LCDM universe
De Lucia, ... Zaritsky, et al
Use galaxy merger trees in high resolution cosmo simulation to study the environmental history of group and cluster galaxies. Show (i) surviving massive satellites within clusters were accreted later than their less massive counterparts, from more massive halos; (ii) the mixing of galaxy populations is incomplete during cluster assembly, which creates a correlation between the time a galaxy becomes satellite and its present distance from the cluster core. A large fraction of the most massive cluster members are accreted onto the main progenitor of the final group/cluster as central galaxies, while about half of al cluster galaxies with low and intermediate stellar mass are accreted as satellites. Large fractions of group and cluster galaxies (in particular those of low stellar mass) have therefore been 'pre-processed' as satellites of groups with mass ~1e13 Msun. To quantify the relevance of hierarchical structure growth on the observed environmental trends, considered observational estimates of the passive galaxy fractions, and their variation as a function of halo mass and cluster-centric distance. Comparisons with theoretical predictons require relatively long times for the suppression of SF in group and cluster satellites.
1111.6591
Realistic stellar feedback & Bluge formation in clumpy disks
Hopkins, Keres, Murray, Quataert, Hernquist
Study the effects of realistic stellar feedback on the formation and evolution of giant star-forming gas 'clumps' in high-redshift, gas-rich galaxies. Such galactic disks are unstable to the formation of bound gas-rich clumps whose properties initially depend only on global disk properties, not the microphysics of feedback. Without stellar feedback, clumps turn an order-unity fraction of their mass into stars and sink to the center, forming a large bulge and kicking most of the stars out into a much more extended stellar envelope. Stellar feedback disrupts the most massive clumps after they turn 10~20% of their mass into stars in 10-100 Myr, ejecting some material into a super-wind and recycling the rest of the gas into the diffuse ISM. This suppresses the bulge formation rate be direct 'clump coalescence' by a factor of several. However, the galactic disks do undergo significant secular evolution in the absence of mergers: clumps form and disrupt continuously and torque gas to the galactic center. The resulting evolution is qualitatively similar to bar/spiral evolution in simulations with a more homogeneous ISM.
1111.6596
Thinking outside the box: effects of modes larger than the survey on matter power spectrum covariance
de Putter, Wagner, Mena, Verde, PercivalPotentially dominant effect on mildly non-linear scales due to power in modes of size equal to and larger than the survey volume: Beat coupling effect. Derived analytically in perturbation theory, and tested with simulations, but some questions remain. Additional effect of the estimated average density which enters the power spectrum estimate. Work out analytic, perturbation theory based expressions including both the beat coupling and the local average effect, and show that while beat coupling indeed causes large excess covariance in agreement with the literature, realistically this is compensated almost entirely by the local average effect, leaving only ~10 of the excess [percent?]. Test on simulations. Find excellent agreement for variances. The range of agreement increases towards higher redshift and decreases slighty towards z=0. Include the large-mode effects in a full covarance matrix description for arbitrary survey geometry and confirming its validity using simulations. Useful as a stepping stone towards building an actual galaxy power spectrum covariance matrix.
1111.6598
An accurate method to correct for fiber collisions in galaxy clustering statistics
Guo, Zehavi, Zheng
A superior method for correcting for fiber collision effects, to recover the two-point correlation functions.
1111.6599
Non-thermal DM mimicking an additional neutrino species in the early universe
Hooper, Queiroz, Gnedin
SPT, ACT and WMAP have each reported measurements of CMB which favor the existence of roughly one additional neutrino species in addition to the known three. Neutrinos influence the CMB by contributing to the radiation density which alters the expansion rate of the universe during the epoch leading up to recombination. Consider an alternative possibility that the excess kinetic energy implied by these measurements was possessed by DM particles that were produced through a non-thermal mechanism, such as late-time decays. in particular, find that if a small fraction (<1%) of the DM in the universe today were produced through decays of a heavy and relatively long-lived state, the expansion history of the universe can be indistinguishable from that predicted in the standard cosmological model with an additional neutrino. Furthermore, if these decays take place after the completion of big band nucleosynthesis, this scenario can avoid tension with the value of three neutrino species preferred by measurements of the light element abundances.
1111.6608
Tidal signatures in the faintest MW satellites: the detailed properties of Leo V, Pisces II and Canes Venatici II
Sand, Strader, Willman, Zaritzky, McLeod, Caldwell, Seth, Olszewski
Structure and star formation history of the dwarfs: low metallicity, but hard to tell when the satellites formed wrt cosmic reionization. Lack of observed younger stellar population possibly sets them apart from the other satellites at galactocentric distances of 150 kpc. The ellipticities tend to align to the galactic center, in rough agreement with predictions from simulations of dwarf galaxies that have lost a significant fraction of their dark matter haloes and are being tidally stripped.
1111.6609
The dark matter halos of dwarf galaxies: a challenge for the LCDM paradigm?
Ferrero, Abadi, Navarro, Sales, Gurovich
The CMD halo mass function is much steeper than the galaxy stellar mass function on galactic and subgalactic scales. This difference is usually reconciled by assuming that the galaxy formation efficiency drops sharply with decreasing halo mass, so that galaxy formation is effectively suppressed below a threshold mass, M~ 1e10Msun. A halo mass threshold implies that, at any given radius, the dark mass enclosed by a galaxy must exceed a certain minimum. Use rotation curves of dwarf galaxies compiled from the literature to explore whether their enclosed mass is consistent with this constraint. Find almost one half of the dwarfs in sample with stellar mass between 1e6-1.7 Msun violate this restriction: either they live in haloes with masses substantially below the threshold or there is a mechanism capable of reducing the DM enclosed by some of the faintest dwarfs. Neither possibility is easily accommodated within the standard LCDM scenario. Extending galaxy formation to haloes well below 1e10 Msun would lead to severe disagreement with the low mass end of the galaxy stellar mass function; the extremely low stellar mass of the systems involved make it unlikely that baryonic effects may be responsible for reducing their dark matter content. Resolving this challenge seems to require new insights into dwarf galaxy formation, or else a radical revision of the prevailing paradigm.
1111.6619
The SDSS coadd: 275 deg sq of deep sdss imaging on stripe 82
Annis .., Seo, et al
r~23.5 for galaxies. image processing of coaddition, modeling of the PSF, calibration, production of SDSS catalogs. median seeing of 11 arcsec.
1111.6620
The SDSS Coadd: a galaxy photometric redshift catalog
Reis, ... et al
Catalog of photo-z's for SDSS coadd data, all the way down to r<24.5. Trained on SDSS Main/LRG, CNOC2, DEEP2 DR3, BOSS, VVDS, and WiggleZ. 68% of galaxies in the validation set have photoz error < 0.038.
1111.6621
The SDSS Coadd: Cosmic shear measurement
Lin, Dodelson, Seo, ... et al
Emode detected in both real and Fourier space with >5 sigma significance on degree scales, while B-mode is consistent with zero. Amplitude of signal constraints the combination of the matter density Omega_m and fluctuation amplitude sigma_8 to be Omega_m^0.7 sigma8 = 0.276.
1111.6666
Probing planetary mass dark matter in galaxies: gravitational nanolensing of multiply imaged quasars
Garsden, Bate, Lewis
Gravitational microlensing of planetary-mass objects ("nanolensing") can be used to probe the distribution of mass in a galaxy that is acting as a gravitational lens. Size of the source will smooth out (the gravitational lensing) light curve if it is too big. In a mock quasar system, find that if variability of 0.1 mag in amplitude can be observed, a source size of ~0.1 Einstein radius would be needed to see the effect of 2.5e-5 Msun masses in the micorlensing light curve. Investigation into the temporal properties of nanolensing events fines that there are two scales of nanolensing that can be observed: one due to the crossing of nanlensing caustic bands, the other due to the crossing of nanolensing caustics themselves. Latter is small, and requires sources of size 1e-4 ER to resolve. For sources of the size on an accretion disk, the nanolensing caustics are slightly smoothed-out, but can be observed on time scales of a few days. Crossing of caustic bands can be observed on time scales of about 3 months.
1111.6680
Sub-millimeter brightness of early star-forming galaxies
Yajima, Umemura, Mori
Based on 3d model of an early SF galaxy, explore the evolution of sub-millimeter brightness. Model: chemodynamic simulation of a primordial galaxy, SFR is ~10 Msun/yr at 0.3 Gyr. The former phase well reproduces the observed properties of LAEs and the latter does LBGs. Solve the 3d radiative transfer in the clumpy interstellar media in the model galaxy, taking the size distributions of dust grains into account, and calculate the dust temperature as a function of galactic evolutionary time. Find the clumpiness of interstellar media plays an important role for the sub-millimeter brightness. In the LAE phase, dust grains are concentrated on clumpy SF regions that are distributed all over the galaxy, and the grains can effectively absorb UV radiation from stars. As a result, dust is heated up to T>35K. In the LBG phase, the continuous SNe drive dust grains far away from SF regions. Then the grains cannot absorb much radiation from stars, and becomes into a cold state close to the CMB temperature. Consequently, the dust T decreases with the evolutionary time, where the mass-weighted mean T is T=26K at 0.1Gyr and T=21K at 1.0 Gyr. The sub-millimeter brightness is higher in the LAE phase than that in the LBG phase, although the dust-to-gas ratio increases monotonically as a function of time. Derive the spectral energy distributions by placing the model galaxy at a given redshift. The peak flux at 850 um is found to be 0.2-0.9 mJy if the model galaxy is placed at 6>z>2. ALMA can detect an early Sf galaxy with SFR of ~10 Msun/yr by less than one hour integration with 16 antennas.
1111.6681
Testing QMOND in the solar system
Galianni, Feix, Zhao, Horne
Low-acceleration "bubbles": saddle points of the gravitational potential near the planets. MOND predict significant deviations from Newtons laws at these bubbles. Several of the Saturn's outermost satellites periodically intersect the Saturn-Sun bubble, providing the first example of Solar System objects that regularly undergo the intermediate MOND regime.
1111.6688
The curious case of lyman alpha emitters: growing younger from z~3 to z~2?
Acquaviva, Vargas, Gawiser, Guaita
LAE galaxies are thought to be progenitors of present-day L* galaxies. Clustering analysis suggests that LAEs at z~3 evolve into LAEs at z~2, but physical nature of galaxies may not be compatible with this hypothesis. Use consistent data analysis pipelin and SED fitting software on two stacked samples of LAEs at z=3.1 and z=2.1, and by eliminating several systematic uncertainties that might cause discrepancy, determine that physical properties of these two samples of galaxies are dramatically different. LAEs at z=3.1 are found to be old (age~1 Gyr) and metal-poor (Z~Z_Sun). Difference in the observed stellar ages makes it very unlikely that z=3.1 LAEs evolve directly into z=2.1 LAEs. Larger samples of galaxies, studies of individual objects and spectroscopic measurements of metallicity at these redshifts are needed to confirm this picture, which is difficult to reconcile with the effects of 1Gyr of cosmological evolution.
1111.6693
AKARI Observation of the North Ecliptic Pole (NEP) Supercluster at z=0.087: mid-IR view of transition galaxies
Ko et al
MIR properties of galaxies in the NEP supercluster. Red-sequence galaxies consist not only of passively evolving red early-type galaxies, but also of (1) "weak SFG" (disk dominated SF galaxies which have star formation rates lower by ~4 times than blue-cloud galaxies), and (2) "intermediate MXG" (bulge-dominated galaxies showing stronger MIR dust emission than normal red early-type galaxies). These two populations can be a set of transition galaxies from blue, star-forming, late-type galaxies evolving into red, quiescent, early-type ones. Weak SFG types are predominant at 1e10 Msun<M*<1e10.5 Msun, and find in local densities similar to the outskirts of the galaxy clusters. ~40% of member galaxies in this mass range are weak-SFGs, but their proportion decreases. Fraction of intermediate-MXG also decreases as density and mass increase. ~40% of the red-sequence galaxies with early-type morphologies are classified as intermediate-MXG at intermediate densities. Results suggest that SF activity is strongly dependent on the stellar mass, but that the morphological transformation is mainly controlled by the environment.
1111.6773
Star formation laws in luminous infrared galaxies. New observational constraints on models
Garcia-Burillo et al
SF relations in galaxies in extreme starbursts, represented by local LIRGs and ULIRGs, with high quality observations in the 1-0 line of HCN. New data proves efficiency of SF in the dense molecular gas of extreme SBs is afactor of 3-4 higher compared to normal galaxies. KS laws seem to be violated, even if you take into account the HCN conversion factors. ...
1111.6792
Astro-WISE processing of wide-field images and other data
Buddelmeiijer, Williams, McFarland, Belikov
Consists of HW and SW federated over ~dozen institutes throughout Europe. Demo explains the architecture of Astro-WISE information system and shows use of interfaces. Can be used for variety of different instruments.
1111.6806
Refractive convergent plasma lenses explain ESE and pulsar scintillation
Pen, King
Propose convergent plasma lenses, possibly from current sheets, as a generic solution to strong interstellar scattering. ....
1111.6835
Application of cross correlations between CMB and LSS to constraints on the primordial non-Gaussianity
Takeuchi, Ichiki, MatsubaraLocal-type primordial non-Gaussianity affects the clustering of DM haloes. CMB lensing potential and galaxy angular distribution correlation affected by non-G, include redshift slicing to follow the z-evolution of clustering. Constraint can be improved by a little by including gg lensing shear cross correlations expected from HSC.
1111.6958
Seeing in the dark -- I. Multi-epoch alchemy
Huff, Hirata, Mandelbaum, Schlegel, Seljak, Lupton
Demonstrate that point-spread function effects on measured galaxy shapes in current ground-based surveys can be corrected with existing analysis techniques. Co-add SDSS stripe 82 to build a data set with the statistical power to measure cosmic shear, while using a rounding kernel method to null out the effects of the anisotropic PSF. Build galaxy catalogue from the combined imaging, characterise photometric properties, and show spurious shear remaining in the catalog after the PSF correction is negligible compared to the expected cosmic shear signal. Identify a new source of systematic error in the shear-shear auto-correlations arising from selection biases related to masking. Discuss the circumstances in which this method is expected to be useful for upcoming ground-based surveys that have lensing as one of the science goals, and identify the systematic errors that can reduce its efficacy.
Seeing in the dark -- I. Multi-epoch alchemy
Huff, Hirata, Mandelbaum, Schlegel, Seljak, Lupton
Demonstrate that point-spread function effects on measured galaxy shapes in current ground-based surveys can be corrected with existing analysis techniques. Co-add SDSS stripe 82 to build a data set with the statistical power to measure cosmic shear, while using a rounding kernel method to null out the effects of the anisotropic PSF. Build galaxy catalogue from the combined imaging, characterise photometric properties, and show spurious shear remaining in the catalog after the PSF correction is negligible compared to the expected cosmic shear signal. Identify a new source of systematic error in the shear-shear auto-correlations arising from selection biases related to masking. Discuss the circumstances in which this method is expected to be useful for upcoming ground-based surveys that have lensing as one of the science goals, and identify the systematic errors that can reduce its efficacy.
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