1202.1279
The x-ray reflector in NGC 4945: a time and space resolved portrait
Marinucci, Risaliti, Wang, Nardini, Elvis, Fabbiano, Bianchi, Matt
Time, spectral and imaging analysis of the x-ray reflector in NGC 2925, reveal its geometrical and physical structure. Hosts one of the brightest AGN above 10keV, but is only visible through its reflected/scattered emission below 10keV, due to absorption by a column density of 4e24 cm^-2. New Suzaku observation show a remarkable constancy (within 30-50pc) [...of what? over time, it seems, over 6 months]. Chandra imaging show resolved, flattened, ~150 pc-long clumpy structure, with spectrum due to cold reflection of the primary AGN emission. Clumpiness may explain the small covering factor derived from the spectral and variability properties.
1202.1292
Cores in WDM haloes: a Catch 22 problem
Maccio, Paduroiu, Anderalden, Schneider, Moore
WDM free streaming dampens the fluctuation spectrum, flattens the mass function of haloes, and imprints a fine grained phase density limit for DM structures. This limit is expected to imprint a constant density core at the halo center on the contrary to what happens for CDM. Explore using high-res sims with different WDM scenarios. Find size of core in good agreement with theoretical expectations based on Liouville's theorem [what? which one? "phase space distribution is constant along a path of the system"]. However, sims show that in order to create a significant core (r_c~1kpc) in a dwarf galaxy (M~1e10 Msun), a thermal candidate with a mass as low as 0.1 keV is required [talking about the WDM particle mass?]. Would fully prevent the formation of the dwarf galaxy in the first place. For candidates satisfying LSS constrains (m_wdm>1-2keV), the expected size of the core is of the order of 40 (80) pc for a DM halo with mass of 1e10 (8) Msun. Conclude that "standard" WDM is not viable solution for explaining the presence of cored density profiles in low mass galaxies.
1202.1283
Gravitational fragmentation in galaxy mergers: a stability criteria
Escala, Becerra, del Valle, Castillo
Study gravitational stability of gaseous streams in a galaxy merger; mergers occur on ongoing massive cluster formation and bursts of SF. Find an analytic parameter for gaseous streams orbiting around the merger remnant. Test stability criteria using hydrosims. Criteria successfully predicts streams that will be gravitationally unstable to fragment into clumps.
1202.1284
A new probe of the small-scale primordial power spectrum: astrometric microlensing by ultracompact minihaloes
Li, Erickcek, Law
DM enclosed in a large initial amplitude fluctuation (delta>1e-3) collapses shortly after recombination and forms a ultracompact minihalo (UCMH). Their high central densities make UCMHs suitable for detection via astrometric microlensing: as the UCMH moves, i t changes the apparent position of background stars. A UCMH with a mass larger than a few solar masses can produce a distinctive astrometric microlensing signal that is detectable by Gaia. If Gaia does not detect graviataional lensing by any UCMHs, then establishes an upper limit on their abundance and constrains the amplitude of the primordial power spectrum for k~3500 Mpc^-1. These constraints complement the upper bound on the amplitude of the primordial power spectrum derived from limits on gamma-ray emission from UCMHs because the astrometric microlensing signal produced by an UCMH is maximized if the DM annihilation rate is too low to affect the UCMH's density profile. If DM annihilation within UCMHs is not detectable, a search for UCMHs by Gaia could constrain the amplitude of the primordial power spectrum to be <1e-5, this bound is 3 orders of magnitude stronger than the bound derived from the absence of primordial black holes.
1202.1304
Homogeneous metallicities and radial velocities for Galactic globular clusters
Saviane, et al
New spectro observations of metallicity and radial velocities of MW globular clusters. Most GCs have uniform metallicities, but some have internal metallicity [Fe/H] spreads.
1202.1306
Nonlinear behavior of BAO from the Zeldovich approximation using a non-Fourier perturbation appraoch
McCullaugh, Szalay
* Zeldovich approximation: simple approximation to derive the non-linear stage of gravitational evolution.
BAO characterize the DE EoS: must understand the effects of both the non-linearities and z-space distortions on the location and shape of the acoustic peak. Consider these effects using the Zeldovich approximation and a novel approach to 2nd order perturbation theory; the 2nd term of the Z power spectrum is built from convolutions of the linear power spectrum with polynomial kernels in Fourier space, suggesting hat the corresponding term of the Z correlation function can be written as a sum of quadratic products of a broader class of correlation functions, expressed through simple spherical Bessel transforms of the linear power spectrum. [?] Highlight the advantages of writing the nonlinear expansion in configuration space, as this calculation is easily extended to redshift space, and the higher order terms are mathematically simpler than their Fourier counterparts.
1202.1314
Quantifying Jupiter's influence on the Earth's impact flux: implications for planetary habiability
Horner, Jones
It was thought that, w/o Jupiter, Earth would have been subject to a punishing impact regime, making Earth inhabitable. Little research has previously been carried out to support it. Present results of several suites of dynamical integrations to model the influence of Jupiter's mass and orbit on the impact rate that would be experienced by the Earth. Find: far from being a simple shield, Jupiter's role in determining the terrestrial impact flux is significantly more complicated than previously thought; such giant planets are perhaps more likely imperil the development of life on otherwise habitable planets.
1202.1339
One thousand and one clusters: measuring the bulk flow with the Planck ESZ and X-ray selected galaxy cluster catalogs
Mody, Hajian
Use Planck ESZ and ROSAT LSS cluster catalog to measure the bulk flow using kSZ in WMAP7. Build a full-sky kSZ template and fit to the WMAP data in W-band. Using a wiener filter, maximize the signal to noise ratio of the kSZ cluster signal in the data. Find no significant detection of the bulk flow, consistent with LCDM prediction.
1202.1345
Dust growth in the interstellar medium: how do accretion and coagulation interplay?
Hirashita
Dust grains grow in interstellar clouds by accretion and coagulation. Focus on these two grain growth processes and numerically investigate how they interplay to increase the grain radii. Show that accretion efficiently depletes grains with radii 0.001 um on a time scale of 10 Myr in solar-metallicity molecular clouds. Coagulation further pushes the grains to larger sizes after a major part of the gas phase metals are used up. Similar grain sizes are achieved by coagulation regardless of whether accretion takes place or not; in this sense, accretion and coagulation modify the grain size distribution independently. The increase of the total dust mass in a cloud is also investigated; show that coagulation slightly suppresses dust mass growth by accretion, but that this effect is slight enough to be neglected in considering the grain mass budget in galaxies. Finally, examine how accretion and coagulation affect the extinction curve: the UV slope and the carbon bump are enhanced by accretion, while they are flattened by coagulation.
1202.1346
Early structure formation from cosmic string loops
Shlaer, Vilenkin, Loeb
Effects of cosmic strings: highly non-G, and can produce NL structures at very early times, leading to early SF and reionization of the universe. String energy scales Gmu>1e-7 would be detectable in CMB by Planck.
1202.1371
The mass-richness relation of MaxBCG clusters from quasar lensing magnification using variability
Bauer, Baltay, Ellman, Jerke, Rabinowitz, Scalzo
Accurate measurement of galaxy cluster masses is important. MaxBCG mass constrained using WL, SZ, and X-ray measurements. THe mass normalization of the clusters as measured by WL is ~25% higher than SZ and x-ray, larger than measurement errors. Constrain MaxBCG cluster catalog by measuring gravitational lensing magnification of type I quasars in the BG of the clusters. The magnification is determined using the quasars variability and the correlation between quasars' variability amplitude and intrinsic luminosity. The mass-richness relation determined through magnification is in agreement with that measured using shear, confirming that the lensing strength of clusters implies a high mass normalization, and that the discrepancy with other methods is not due to a shear-related systematic measurement error. Study the dependence of the measured mass normalization on the cluster halo orientation. LoS clusters yield a higher normalization; however, this minority of haloes does not significantly bias the average mass-richness relation of the catalog.
1202.1417
Ionisation-induced SF III: effects of external triggering on the IMF in clusters
Dale, Bonnell
SPH sims of the impact of turbulent 2e3 M_sun SF molecular cloud of irradiation by an external source of ionizing photons. Find: affects gas morphology, with a less important role in triggering stars [not SF?]. The rate and morphology of SF are largely governed by the structure in the gas generated by the turbulent velocity field, and feedback has no discernible effect on the stellar initial mass function. Although many young stars are found in dense gas located near an ionization front, most of these objects also form when feedback is absent. Ionization has a stronger effect in diffuse regions of the cloud by sweeping up low-density gas that would not otherwise form stars into gravitationally-unstable clumps. However, dynamical interactions between the stars rapidly erase the correlations between their positions and velocities and that of the ionization front.
1202.1426
Approximate bayesian computation for astronomical model analysis: a case study in galaxy demographics and morphological transformation at high redshift
Cameron, Pettitt
ABC (approximate bayesian computation) used for cases when MCMC doesn't work well (complex stochastic systems [presumably with many variables]). Apply to galaxy morphology evolution and merger rate studies. Returns tight constraints on the evolving merger rate and reveals merging, rather than secular evolution, as the most important mechanism for building up the firs generation of bulges in early-type disks.
1202.1434
A deep search for the host galaxies of GRBs with no detected optical afterglow
Rossi, et al
From 17 GRBs: Bursts with optically dim afterglows trace a subpopulation of massive starburst galaxies, which are markedly different from the main body of the GRB host galaxy population, namely the blue, subluminous, compact galaxies.
1202.1435
Far IR LF of local galaxies in the AKARI deep field south
Sedgwick, et al
Present the first far-IR LF in the AKARI Deep field south, a premier deep field of the AKARI space telescope, using spectroscopic redshifts obtained with AAOmega. To date, found spectro redshifts for 389 galaxies in the field and have measured the local (z<0.25) 90 micron LF using about 1/3 of these redshifts. The results are in reasonable agreement with recent theoretical predictions.
1202.1450
Rotating disks and non-kinematic double peaks
Elitzur, Ramos, Ceccarelli
Double-peaked line profiles: commonly considered a hallmark of rotating disks (distance between peaks a measure of the rotation velocity), but can also arise from radiative transfer effects in optically thick non-rotating sources. Detailed study of line emission from geometrically thin Keplerian disks. Derive the conditions for emergence of kinematic double peaks in optically thin and thick disks, and find that it is generally impossible to disentangle the effects of kinematics and line opacity in observed double-peaked profiles. Unless supplemented by additional information, a double-peaked profile alone is not a reliable indicator of a rotating disk. In certain circumstances, triple and quadruple profiles might e better indicators of rotation in optically thick disks.
1202.1469
Observable non-G from gauge field production in slow roll inflation, and a challenging connection with magnetogenesis
Barnaby, Nanba, Peloso
In any realistic particle physics model of inflation, the inflaton can be expected to couple to other fields. Consider a model with a dilaton-like coupling between a U(1) gauge field and a scalar inflation. Show that this coupling can result in observable non-gausisianity of characterstic and nearly local shape, even in the conventional regime where inflation is supported by a single scalar slowly rolling on a smooth potential: the time dependent inflation condensate leads to amplification of the large-scale gauge field fluctuations, which can feedback into the scalar/tensor cosmo perturbations. ...
1202.1476
The fine structure constant and the CMB damping scale
Menegoni, Archidiacono, Calabrese, Galli, Martins, Melchiorri
Analysis of damping tail of CMB suggests the effective number of relativistic degrees of reedom is larger than the standard value of N_eff=3.04, and inconsistent with it by >2 std devs. In this paper, study the role of a mechanism that could affect the shape of CMB angular fluctuations at those scales, namely a change in the recombination process through variations in the fine structure constant. Show that the new CMB data significantly improve the prevous constraints on variations of alpha, with alpha/alpha0=0.984 pm 0.005, i.e., hinting also to a more than 2 std dev from the current, local value of alpha0. A significant degeneracy is present between alpha and N_eff, and when variations in the latter are allowed the constraints on alpha are relaxed and again consistent with the standard value. Deviations of either parameter from their std values would imply the presence of new, currently unknown physics.
Li, Erickcek, Law
DM enclosed in a large initial amplitude fluctuation (delta>1e-3) collapses shortly after recombination and forms a ultracompact minihalo (UCMH). Their high central densities make UCMHs suitable for detection via astrometric microlensing: as the UCMH moves, i t changes the apparent position of background stars. A UCMH with a mass larger than a few solar masses can produce a distinctive astrometric microlensing signal that is detectable by Gaia. If Gaia does not detect graviataional lensing by any UCMHs, then establishes an upper limit on their abundance and constrains the amplitude of the primordial power spectrum for k~3500 Mpc^-1. These constraints complement the upper bound on the amplitude of the primordial power spectrum derived from limits on gamma-ray emission from UCMHs because the astrometric microlensing signal produced by an UCMH is maximized if the DM annihilation rate is too low to affect the UCMH's density profile. If DM annihilation within UCMHs is not detectable, a search for UCMHs by Gaia could constrain the amplitude of the primordial power spectrum to be <1e-5, this bound is 3 orders of magnitude stronger than the bound derived from the absence of primordial black holes.
1202.1304
Homogeneous metallicities and radial velocities for Galactic globular clusters
Saviane, et al
New spectro observations of metallicity and radial velocities of MW globular clusters. Most GCs have uniform metallicities, but some have internal metallicity [Fe/H] spreads.
1202.1306
Nonlinear behavior of BAO from the Zeldovich approximation using a non-Fourier perturbation appraoch
McCullaugh, Szalay
* Zeldovich approximation: simple approximation to derive the non-linear stage of gravitational evolution.
BAO characterize the DE EoS: must understand the effects of both the non-linearities and z-space distortions on the location and shape of the acoustic peak. Consider these effects using the Zeldovich approximation and a novel approach to 2nd order perturbation theory; the 2nd term of the Z power spectrum is built from convolutions of the linear power spectrum with polynomial kernels in Fourier space, suggesting hat the corresponding term of the Z correlation function can be written as a sum of quadratic products of a broader class of correlation functions, expressed through simple spherical Bessel transforms of the linear power spectrum. [?] Highlight the advantages of writing the nonlinear expansion in configuration space, as this calculation is easily extended to redshift space, and the higher order terms are mathematically simpler than their Fourier counterparts.
1202.1314
Quantifying Jupiter's influence on the Earth's impact flux: implications for planetary habiability
Horner, Jones
It was thought that, w/o Jupiter, Earth would have been subject to a punishing impact regime, making Earth inhabitable. Little research has previously been carried out to support it. Present results of several suites of dynamical integrations to model the influence of Jupiter's mass and orbit on the impact rate that would be experienced by the Earth. Find: far from being a simple shield, Jupiter's role in determining the terrestrial impact flux is significantly more complicated than previously thought; such giant planets are perhaps more likely imperil the development of life on otherwise habitable planets.
1202.1339
One thousand and one clusters: measuring the bulk flow with the Planck ESZ and X-ray selected galaxy cluster catalogs
Mody, Hajian
Use Planck ESZ and ROSAT LSS cluster catalog to measure the bulk flow using kSZ in WMAP7. Build a full-sky kSZ template and fit to the WMAP data in W-band. Using a wiener filter, maximize the signal to noise ratio of the kSZ cluster signal in the data. Find no significant detection of the bulk flow, consistent with LCDM prediction.
1202.1345
Dust growth in the interstellar medium: how do accretion and coagulation interplay?
Hirashita
Dust grains grow in interstellar clouds by accretion and coagulation. Focus on these two grain growth processes and numerically investigate how they interplay to increase the grain radii. Show that accretion efficiently depletes grains with radii 0.001 um on a time scale of 10 Myr in solar-metallicity molecular clouds. Coagulation further pushes the grains to larger sizes after a major part of the gas phase metals are used up. Similar grain sizes are achieved by coagulation regardless of whether accretion takes place or not; in this sense, accretion and coagulation modify the grain size distribution independently. The increase of the total dust mass in a cloud is also investigated; show that coagulation slightly suppresses dust mass growth by accretion, but that this effect is slight enough to be neglected in considering the grain mass budget in galaxies. Finally, examine how accretion and coagulation affect the extinction curve: the UV slope and the carbon bump are enhanced by accretion, while they are flattened by coagulation.
1202.1346
Early structure formation from cosmic string loops
Shlaer, Vilenkin, Loeb
Effects of cosmic strings: highly non-G, and can produce NL structures at very early times, leading to early SF and reionization of the universe. String energy scales Gmu>1e-7 would be detectable in CMB by Planck.
1202.1371
The mass-richness relation of MaxBCG clusters from quasar lensing magnification using variability
Bauer, Baltay, Ellman, Jerke, Rabinowitz, Scalzo
Accurate measurement of galaxy cluster masses is important. MaxBCG mass constrained using WL, SZ, and X-ray measurements. THe mass normalization of the clusters as measured by WL is ~25% higher than SZ and x-ray, larger than measurement errors. Constrain MaxBCG cluster catalog by measuring gravitational lensing magnification of type I quasars in the BG of the clusters. The magnification is determined using the quasars variability and the correlation between quasars' variability amplitude and intrinsic luminosity. The mass-richness relation determined through magnification is in agreement with that measured using shear, confirming that the lensing strength of clusters implies a high mass normalization, and that the discrepancy with other methods is not due to a shear-related systematic measurement error. Study the dependence of the measured mass normalization on the cluster halo orientation. LoS clusters yield a higher normalization; however, this minority of haloes does not significantly bias the average mass-richness relation of the catalog.
1202.1417
Ionisation-induced SF III: effects of external triggering on the IMF in clusters
Dale, Bonnell
SPH sims of the impact of turbulent 2e3 M_sun SF molecular cloud of irradiation by an external source of ionizing photons. Find: affects gas morphology, with a less important role in triggering stars [not SF?]. The rate and morphology of SF are largely governed by the structure in the gas generated by the turbulent velocity field, and feedback has no discernible effect on the stellar initial mass function. Although many young stars are found in dense gas located near an ionization front, most of these objects also form when feedback is absent. Ionization has a stronger effect in diffuse regions of the cloud by sweeping up low-density gas that would not otherwise form stars into gravitationally-unstable clumps. However, dynamical interactions between the stars rapidly erase the correlations between their positions and velocities and that of the ionization front.
1202.1426
Approximate bayesian computation for astronomical model analysis: a case study in galaxy demographics and morphological transformation at high redshift
Cameron, Pettitt
ABC (approximate bayesian computation) used for cases when MCMC doesn't work well (complex stochastic systems [presumably with many variables]). Apply to galaxy morphology evolution and merger rate studies. Returns tight constraints on the evolving merger rate and reveals merging, rather than secular evolution, as the most important mechanism for building up the firs generation of bulges in early-type disks.
1202.1434
A deep search for the host galaxies of GRBs with no detected optical afterglow
Rossi, et al
From 17 GRBs: Bursts with optically dim afterglows trace a subpopulation of massive starburst galaxies, which are markedly different from the main body of the GRB host galaxy population, namely the blue, subluminous, compact galaxies.
1202.1435
Far IR LF of local galaxies in the AKARI deep field south
Sedgwick, et al
Present the first far-IR LF in the AKARI Deep field south, a premier deep field of the AKARI space telescope, using spectroscopic redshifts obtained with AAOmega. To date, found spectro redshifts for 389 galaxies in the field and have measured the local (z<0.25) 90 micron LF using about 1/3 of these redshifts. The results are in reasonable agreement with recent theoretical predictions.
1202.1450
Rotating disks and non-kinematic double peaks
Elitzur, Ramos, Ceccarelli
Double-peaked line profiles: commonly considered a hallmark of rotating disks (distance between peaks a measure of the rotation velocity), but can also arise from radiative transfer effects in optically thick non-rotating sources. Detailed study of line emission from geometrically thin Keplerian disks. Derive the conditions for emergence of kinematic double peaks in optically thin and thick disks, and find that it is generally impossible to disentangle the effects of kinematics and line opacity in observed double-peaked profiles. Unless supplemented by additional information, a double-peaked profile alone is not a reliable indicator of a rotating disk. In certain circumstances, triple and quadruple profiles might e better indicators of rotation in optically thick disks.
1202.1469
Observable non-G from gauge field production in slow roll inflation, and a challenging connection with magnetogenesis
Barnaby, Nanba, Peloso
In any realistic particle physics model of inflation, the inflaton can be expected to couple to other fields. Consider a model with a dilaton-like coupling between a U(1) gauge field and a scalar inflation. Show that this coupling can result in observable non-gausisianity of characterstic and nearly local shape, even in the conventional regime where inflation is supported by a single scalar slowly rolling on a smooth potential: the time dependent inflation condensate leads to amplification of the large-scale gauge field fluctuations, which can feedback into the scalar/tensor cosmo perturbations. ...
1202.1476
The fine structure constant and the CMB damping scale
Menegoni, Archidiacono, Calabrese, Galli, Martins, Melchiorri
Analysis of damping tail of CMB suggests the effective number of relativistic degrees of reedom is larger than the standard value of N_eff=3.04, and inconsistent with it by >2 std devs. In this paper, study the role of a mechanism that could affect the shape of CMB angular fluctuations at those scales, namely a change in the recombination process through variations in the fine structure constant. Show that the new CMB data significantly improve the prevous constraints on variations of alpha, with alpha/alpha0=0.984 pm 0.005, i.e., hinting also to a more than 2 std dev from the current, local value of alpha0. A significant degeneracy is present between alpha and N_eff, and when variations in the latter are allowed the constraints on alpha are relaxed and again consistent with the standard value. Deviations of either parameter from their std values would imply the presence of new, currently unknown physics.
No comments:
Post a Comment