Sunday. Catching up on Wed, Thu, Fri.
1211.7007
Reionization history and CMB parameter estimation
Dizgah, Gnedin, Kinney
Study how uncertainty in the reionization history of the universe affects estimates of other cosmological parameters from the CMB. Analyze WMAP7 data and synthetic Planck-quality data generated using a realistic scenario for the reionization history of the universe obtained from high-res sims. Run parameter estimation using a simple sudden reionization approximation, and using PCA technique. Two main conclusions: (1) adopting a simple sudden reionization model does not introduce measurable bias into value for other parameters (detailed modeling of reionization is not necessary for parameter estimation from future CMB datasets as PLANCK. (2) PCA analysis does not allow accurate reconstruction of the actual reionization history of the universe in a realistic case.
1211.7040
X-ray morphological estimators
Rasia, Meneghetti, Ettori
Classification of clusters according to their X-ray appearance: discriminates between regular clusters (relaxed objects) and disturbed ones (dynamically active). Need both for cosmological (virialized, spherical) and astrophysical studies (turbulence, particle re-acceleration, magneto-astrophysics). Review several morphological parameters: asymmetry and fluctuation of the X-ray surface brightness, hardness ratios, X-ray surface-brightness concentration, centroid shift, and third-order power ratio. Test them against 60 Chandra-like images obtained from hydrodynamical simulations through the X-ray map simulator and visually classified as regular and disturbed. The best performances are computed using the largest possible region (within R500 or 1000 kpc). The best indicators are the third-order power ratio, the asymmetry parameter, and the X-ray-SB concentration. All their combinations offer an efficient way to distinguish between the two morphological classes achieving values of purity extremely close to 1. A new parameter, M, is defined. It combines the strengths of the aforementioned indicators and, therefore, resulted to be the most effective parameter analyzed.
1211.6110
The Wigner-Eckart Theorem in Cosmology
Dai, Jeong (Donghui!), Kamionkowski
* W-E theory: theorem of representation theory and quantum mechanics; states that matrix elements of spherical tensor operators on the basis of angular momentum eigenstates can be expressed as the product of two factors, one of which is independent of angular momentum orientation, and the other a Clebsch-Gordan coefficient. Formalism as a link between the symmetry transformation groups of space (applied to the Schrödinger equations) and the laws of conservation of energy, momentum, and angular momentum.
Total angular momentum (TAM) waves provide a set of basis functions for scalar, vector, and tensor fields that can be used in place of plane waves and that reflect the rotational symmetry of the spherical sky. Discuss 3-pt correlation functions (bispectra) for scalar, vector and tensor fields in terms of TAM waves. The WE theorem dictates that the expectation value, assuming statistical isotropy, of the product of 3 TAM waves is the product of a CG coefficient times a function times a function onfly of the total-angular-momentum quantum numbers. Show how this works, and provide explicit expressions relating the bispectra for TAM waves in terms of the more commonly used Fourier-space bispectra. This formalism will be useful to simplify calculations of projections of 3-d bispectra onto the spherical sky.
1211.6115
Towards a physical picture of star-formation quenching: the photometric properties of recently-quenched galaxies in the Sloan Digital Sky Survey
Mendel, Simard, Ellison, Patton
Study the processes that quench SF in the local universe; quenched galaxies identified based on the contribution of A-type stars to their observed (central) spectra and relative lack of ongoing SF. Find that such systems account for ~2.5% of all galaxies with >= 1e9.5 Msun, and have a space density of 2.2e-4 /Mpc^3. Show that quenched galaxies span a range of morphologies, but that visual classifications suggest that they are predominantly early-type systems. Their visual early-type classification is supported by quantitative structural measurements (Sersic indicies) that show a notable lack of disk-dominated galaxies, suggesting that any morphological transformation associated with galaxies' transition from SF to passive (formation of a stellar bulge) occurs contemporaneously with the decline of their SF activity. Show taht there is no clear excess of optical AGN in quenched galaxies, suggesting that (i) AGN feedback is not associated with the majority of quenched systems, or (ii) that the observability of quenched galaxies is such that the quenching phase in general outlives any associated nuclear activity. Comparison with classical post-starburst galaxies shows that both populations show similar signatures of bulge growth, and suggest that the defining characteristic of post-SB galaxies is the efficiency of their bulge growth rather than a particular formation mechanism.
1211.6122
Systematic effects on the size-luminosity relation: dependence on model fitting and morphology
Bernardi, ... Mei ... Sheth, et al
Analysis confirms that two mass scales are special for early-type galaxies: M*=3e10 and 2e11 Msun. These same mass scales are also special for late types: there is almost no correlation between R and M* below the former, and almost no late-types above the latter.
1211.6123
Simulations of single and two-component galaxy decompositions for spectroscopically selected galaxies from the Sloan Digital Sky Survey
Meert, Vikram, Bernardi
Simulations used to test the 2d decompositions of SDSS galaxies utilizing the fitting routine GALFIT and analysis pipeline PyMorph. Fitting a 2-component Sersic + exponential model to what is a single Sersic results in a noisier recovery of the input parameters, but these are not biased; fitting a single Sersic to what is truly a 2-component system results in significant biases. These biases, for total magnitude and halflight radius in particular, should be useful in correcting other automatic fitting routines.
1211.6128
Model independent tests of cosmic growth vs expansion
Shafieloo, Kim, Linder
Use Gaussian processes to map the expansion history of the universe in a model independent manner from the Union2.1 SNe data, then apply these reconstructed results to solve for the growth history. By comparing this to BOSS and WiggleZ LSS data, examine whether growth is determined wholly by expansion, with the measured gravitational growth index testing gravity without assuming a model for DE. A further model independent analysis looks for z dependent deviations of growth from the GR solution without assuming the growth index form. Both approaches give results consistent with GR.
1211.6131
A substantial mass of cool, metal-enriched gas surrounding the progenitors of modern-day ellipticals
Prochaska, Hennawi, Simcoe
Hosts of luminous z~2 quasars evolve into todays massive elliptical galaxies. Current theories predict that the circum galactic medium (CGM) of these massive DM haloes (M~1e12.5 Msun) should be dominated by a T~1e7K virialized plasma. Test this hypothesis with observations of 74 close-projected quasar pairs, using spectra of the BG QSO to characterize the CGM of the FG one. Surprisingly, measurements reveal a cool (T~1e4 K), massive (M_CGM > 1e10 Msun), and metal-enriched (Z>~0.1 Zsun) medium extending to at least the expected virial radius (r_vir = 160 kpc). The average equivalent widths of HI Lya and CII 1334 exceed the corresponding CGM measurements of these transitions from all galaxy populations studied previously. Furthermore, conservatively estimate that the quasar CGM has a 64% covering fraction of optically thick gas within r_vir; this covering factor is twice that of the contemporaneous LBG population. This unexpected reservoir of cool gas is rarely detected "down-the-barrel" to quasars, and hence it is likely that the BG sightlines intercept gas which is shadowed from the quasar ionizing radiation by the same obscuring medium often invoked in models of AGN unification. Because the high-z halos inhabited by quasars predate modern groups and clusters, these observations are also relevant to the formation and enrichment history of the intragroup/intracluster medium.
1211.6213
Non-gaussian error bars in galaxy surveys -- 2
Harnois-Deraps, Pen
As the title says; a new method to get the error bars directly from the galaxy survey data.
1211.6215
THe JHU-SDSS metal absorption line catalog: redshift evolution and properties of Mg II absorbers
Zhu, Menard
A generic and fully-automatic method aimed at detecting absorption lines in the spectra of astronomical objects. Estimate the source continuum flux; then detects and identifies metal absorption lines. Apply to a sample of 100k quasar spectra from SDSS and compile a sample of 40k MgII & Fe II absorber systems, spanning 0.4<z<2.3. Corresponding catalog publicly available. Find: redshift evolution of strong Mg II absorbers to be remarkably similar to the cosmic SFH over 0.4<z<5.5 (the entire redshift range covered by observations), suggesting a physical link between these 2 quantities.
1211.6423
The metallicity evolution of star-forming galaxies from redshift 0 to 3: combining magnitude limited survey with gravitational lensing
Yuan, Kewley, Richard
Comprehensive observational study of the gas phase metallicity of SF galaxies from 0<z<3. Combine new sample of gravitationally lensed and non-lensed samples to conduct a large investigation into the mass-metallicity (MZ) relation at z>1. We apply a self-consistent metallicity calibration scheme to investigate the metallicity evolution of SF galaxies as a function of z. Lensing magnification ensures that sample spans an wide range of stellar mass 3e7-6e10 Msun. Find that at the median redshift of z=2.07, the median metallicity of the lensed sample is 0.35 dex lower than the local SDSS SF galaxies and 0.18 dex lower than the z~0.8 DEEP2 galaxies. The z~2 MZ relation with 19 lensed galaxies: a more rapid evolution is seen between z~1-3 than z~0-1. Compare this evolution with them ost recent cosmoloigcal hydrodynamics simulations with momentum driven winds. Find that the model metallicity is consistent with the observed metallicity within the observational error for the low mass bins. However, for higher masses, the model over-predicts the metallicity at all redshifts. The over-prediction is most significant in the highest mass bin of 1e10-11 Msun.
1211.6425
Implementation of Sink particles in the Athena code
Gong, Ostriker (Eve)
Describe implementation and tests of sink particle algorithms in the Eulerian grid-based code Athena. Introduction of sink particles enables long-term evolution of systems in which localized collapse occurs, and it is impractical (or unnecessary) to resolve the accretion shocks at the centers of collapsing regions. Criteria for sink creation are motivated by the properties of the Larson-Penston collapse solution. Use standard particle-mesh methods to compute particle and gas gravity together. Accretion of mass and moment onto sinks is computed using fluxes returned by the Riemann solver. A series of tests based on previous analytic and numerical collapse solutions is used to validate our method and implementation. Demonstrate use of code for applications with a simulation of planar converging supersonic turbulent flow, in which multiple cores form and collapse to create sinks; these sinks continue to interact and accrete from their surroundings over several Myr.
1211.6429
An over-massive black hole in the compact lenticular galaxy NGC1277
van den Bosch, ... van de Ven, ... et al
Nature paper. SMBH mass and bulge correlate: possible causes include the non-causal, statistical process of gg merging, direct feedback between the BH and its host galaxy, or gg merging and the subsequent violent relaxation and dissipation. Empirical scaling relations are important for distinguishing between various theoretical models of galaxy evolution, and they further form the basis for all BH mass measurements at large distances. Observations have shown that the mass of the BH is typically 0.1% of the stellar bulge mass of the galaxy. The small galaxy NGC4486B currently has the largst published fraction of its massin BH at 115. Report observations of stellar kinematics of NGC 1277, which is compact, disky galaxy with a mass of 1.2e11Msun. From the data, determine that the mass of the BH is 1.7e10 Msun, or 59% of tis bulge mass. 5 other compact galaxies have proeprties similar to NGC 1277 and therefore may also contain over-sized BHs. It is not yet known if these galaxies represent a tail of distribution, or if disk-dominated galaxies fail to follow the normal BH mass scaling relations.
1211.6434
Precision cosmology in muddy waters: cosmological constraints and N-body codes
Smith, Reed, Potter, Marian, Crocce, Moore
Need to understand the uncertainties associated with simulating structure formation, or the constraining power of future surveys can be significantly reduced. With n_s, h, Om_b, Om_m, this effect can be largely mitigated by adding info from a CMB experiment. In contrast, the amplitude of fluctuations sigma8 and the time-evolving equation of state of dark energy (w_0, w_a) the mitigation is mild; DE FoM can be degraded by a factor of 2. Strong motivation for rigorous convergence testing of N-body codes.
1211.6722
The nature of filamentary cold gas in the core of the Virgo cluster
Werner, .. von der Linden, et al
Multi-wavelength study of the emission-line nebulae located SE of the nucleus of M87, the central dominant galaxy of Virgo cluster. FIR CII line emission from the nebula detected. Emission is extended an cospatial with optical Ha + NII, fUV CIV lines, and soft X-ray emission. The filamentary nebulae evidently contain multi-phase material spanning a temperature rage of at least 5 orders of magnitude, from 100K to 1e7K. This material has mostly likely been uplifter by the AGN from the center of M87. The thermal pressure of the 1e4K phase appears to be significantly lower than that of the surrounding hot ICM indicating the presence of additional turbulent and B pressure in the filaments. If the turbulence in the filaments is subsonic, then the B-field strength required to balance the pressure of the surrounding ICM is 30-70 micro-G. The spectral properties of the soft X-ray emission from the filaments indicate that it is due to thermal plasma with kT~0.5-1 keV, which is cooling by mixing with the cold gas and/or radiatively. Charge exchange can be ruled out as a significant source of soft X-rays. Bothe cooling and mixing scenarios predict gas with a range of temperatures. THis is at first glance inconsistent with the apparent lack of X-ray emitting gas with kT<0.5 keV. But show that the missing very soft X-ray emission could be absorbed b the cold gas in the filaments with an average absorption column density of 1e21 /cm^2, providing a natural explanation for the apparent temperature floor to the X-ray emission at kT~0.5 keV. The FIR through UV line emission is most likely primarily powered by the ICM particles penetrating the cold gas following a shearing induced mixing process.
1211.6723
Galaxy Zoo: a catalog of overlapping galaxy pairs for dust studies
Keel, et al
Overlapping galaxies: a direct way to probe the distribution of dust extinction and its effects on the BG light. Catalog of 1990 such pairs from SDSS.
1211.6804
THe abundance of star-forming galaxies in the redshift range 8.5 to 12: new results from the 2012 Hubble ultra deep field campaign
Ellis, et al
4 times the exposure in the key F105W filter used to locate distance galaxies. Combined with additional imaging in the F140W filter, the fidelity of high-z candidates is greatly improved. Using SED fitting, find 7 promising z>8.5 candidates. The robust 8.5<z<10 sample demonstrates a luminosity density that continues the smooth decline observed over 6<z<8. Such continuity has important implications for models of cosmic reionization and future searches for z>10 galaxies with JWST.
1211.7007
Reionization history and CMB parameter estimation
Dizgah, Gnedin, Kinney
Study how uncertainty in the reionization history of the universe affects estimates of other cosmological parameters from the CMB. Analyze WMAP7 data and synthetic Planck-quality data generated using a realistic scenario for the reionization history of the universe obtained from high-res sims. Run parameter estimation using a simple sudden reionization approximation, and using PCA technique. Two main conclusions: (1) adopting a simple sudden reionization model does not introduce measurable bias into value for other parameters (detailed modeling of reionization is not necessary for parameter estimation from future CMB datasets as PLANCK. (2) PCA analysis does not allow accurate reconstruction of the actual reionization history of the universe in a realistic case.
1211.7040
X-ray morphological estimators
Rasia, Meneghetti, Ettori
Classification of clusters according to their X-ray appearance: discriminates between regular clusters (relaxed objects) and disturbed ones (dynamically active). Need both for cosmological (virialized, spherical) and astrophysical studies (turbulence, particle re-acceleration, magneto-astrophysics). Review several morphological parameters: asymmetry and fluctuation of the X-ray surface brightness, hardness ratios, X-ray surface-brightness concentration, centroid shift, and third-order power ratio. Test them against 60 Chandra-like images obtained from hydrodynamical simulations through the X-ray map simulator and visually classified as regular and disturbed. The best performances are computed using the largest possible region (within R500 or 1000 kpc). The best indicators are the third-order power ratio, the asymmetry parameter, and the X-ray-SB concentration. All their combinations offer an efficient way to distinguish between the two morphological classes achieving values of purity extremely close to 1. A new parameter, M, is defined. It combines the strengths of the aforementioned indicators and, therefore, resulted to be the most effective parameter analyzed.
1211.6110
The Wigner-Eckart Theorem in Cosmology
Dai, Jeong (Donghui!), Kamionkowski
* W-E theory: theorem of representation theory and quantum mechanics; states that matrix elements of spherical tensor operators on the basis of angular momentum eigenstates can be expressed as the product of two factors, one of which is independent of angular momentum orientation, and the other a Clebsch-Gordan coefficient. Formalism as a link between the symmetry transformation groups of space (applied to the Schrödinger equations) and the laws of conservation of energy, momentum, and angular momentum.
Total angular momentum (TAM) waves provide a set of basis functions for scalar, vector, and tensor fields that can be used in place of plane waves and that reflect the rotational symmetry of the spherical sky. Discuss 3-pt correlation functions (bispectra) for scalar, vector and tensor fields in terms of TAM waves. The WE theorem dictates that the expectation value, assuming statistical isotropy, of the product of 3 TAM waves is the product of a CG coefficient times a function times a function onfly of the total-angular-momentum quantum numbers. Show how this works, and provide explicit expressions relating the bispectra for TAM waves in terms of the more commonly used Fourier-space bispectra. This formalism will be useful to simplify calculations of projections of 3-d bispectra onto the spherical sky.
1211.6115
Towards a physical picture of star-formation quenching: the photometric properties of recently-quenched galaxies in the Sloan Digital Sky Survey
Mendel, Simard, Ellison, Patton
Study the processes that quench SF in the local universe; quenched galaxies identified based on the contribution of A-type stars to their observed (central) spectra and relative lack of ongoing SF. Find that such systems account for ~2.5% of all galaxies with >= 1e9.5 Msun, and have a space density of 2.2e-4 /Mpc^3. Show that quenched galaxies span a range of morphologies, but that visual classifications suggest that they are predominantly early-type systems. Their visual early-type classification is supported by quantitative structural measurements (Sersic indicies) that show a notable lack of disk-dominated galaxies, suggesting that any morphological transformation associated with galaxies' transition from SF to passive (formation of a stellar bulge) occurs contemporaneously with the decline of their SF activity. Show taht there is no clear excess of optical AGN in quenched galaxies, suggesting that (i) AGN feedback is not associated with the majority of quenched systems, or (ii) that the observability of quenched galaxies is such that the quenching phase in general outlives any associated nuclear activity. Comparison with classical post-starburst galaxies shows that both populations show similar signatures of bulge growth, and suggest that the defining characteristic of post-SB galaxies is the efficiency of their bulge growth rather than a particular formation mechanism.
1211.6122
Systematic effects on the size-luminosity relation: dependence on model fitting and morphology
Bernardi, ... Mei ... Sheth, et al
Analysis confirms that two mass scales are special for early-type galaxies: M*=3e10 and 2e11 Msun. These same mass scales are also special for late types: there is almost no correlation between R and M* below the former, and almost no late-types above the latter.
1211.6123
Simulations of single and two-component galaxy decompositions for spectroscopically selected galaxies from the Sloan Digital Sky Survey
Meert, Vikram, Bernardi
Simulations used to test the 2d decompositions of SDSS galaxies utilizing the fitting routine GALFIT and analysis pipeline PyMorph. Fitting a 2-component Sersic + exponential model to what is a single Sersic results in a noisier recovery of the input parameters, but these are not biased; fitting a single Sersic to what is truly a 2-component system results in significant biases. These biases, for total magnitude and halflight radius in particular, should be useful in correcting other automatic fitting routines.
1211.6128
Model independent tests of cosmic growth vs expansion
Shafieloo, Kim, Linder
Use Gaussian processes to map the expansion history of the universe in a model independent manner from the Union2.1 SNe data, then apply these reconstructed results to solve for the growth history. By comparing this to BOSS and WiggleZ LSS data, examine whether growth is determined wholly by expansion, with the measured gravitational growth index testing gravity without assuming a model for DE. A further model independent analysis looks for z dependent deviations of growth from the GR solution without assuming the growth index form. Both approaches give results consistent with GR.
1211.6131
A substantial mass of cool, metal-enriched gas surrounding the progenitors of modern-day ellipticals
Prochaska, Hennawi, Simcoe
Hosts of luminous z~2 quasars evolve into todays massive elliptical galaxies. Current theories predict that the circum galactic medium (CGM) of these massive DM haloes (M~1e12.5 Msun) should be dominated by a T~1e7K virialized plasma. Test this hypothesis with observations of 74 close-projected quasar pairs, using spectra of the BG QSO to characterize the CGM of the FG one. Surprisingly, measurements reveal a cool (T~1e4 K), massive (M_CGM > 1e10 Msun), and metal-enriched (Z>~0.1 Zsun) medium extending to at least the expected virial radius (r_vir = 160 kpc). The average equivalent widths of HI Lya and CII 1334 exceed the corresponding CGM measurements of these transitions from all galaxy populations studied previously. Furthermore, conservatively estimate that the quasar CGM has a 64% covering fraction of optically thick gas within r_vir; this covering factor is twice that of the contemporaneous LBG population. This unexpected reservoir of cool gas is rarely detected "down-the-barrel" to quasars, and hence it is likely that the BG sightlines intercept gas which is shadowed from the quasar ionizing radiation by the same obscuring medium often invoked in models of AGN unification. Because the high-z halos inhabited by quasars predate modern groups and clusters, these observations are also relevant to the formation and enrichment history of the intragroup/intracluster medium.
1211.6213
Non-gaussian error bars in galaxy surveys -- 2
Harnois-Deraps, Pen
As the title says; a new method to get the error bars directly from the galaxy survey data.
1211.6215
THe JHU-SDSS metal absorption line catalog: redshift evolution and properties of Mg II absorbers
Zhu, Menard
A generic and fully-automatic method aimed at detecting absorption lines in the spectra of astronomical objects. Estimate the source continuum flux; then detects and identifies metal absorption lines. Apply to a sample of 100k quasar spectra from SDSS and compile a sample of 40k MgII & Fe II absorber systems, spanning 0.4<z<2.3. Corresponding catalog publicly available. Find: redshift evolution of strong Mg II absorbers to be remarkably similar to the cosmic SFH over 0.4<z<5.5 (the entire redshift range covered by observations), suggesting a physical link between these 2 quantities.
1211.6423
The metallicity evolution of star-forming galaxies from redshift 0 to 3: combining magnitude limited survey with gravitational lensing
Yuan, Kewley, Richard
Comprehensive observational study of the gas phase metallicity of SF galaxies from 0<z<3. Combine new sample of gravitationally lensed and non-lensed samples to conduct a large investigation into the mass-metallicity (MZ) relation at z>1. We apply a self-consistent metallicity calibration scheme to investigate the metallicity evolution of SF galaxies as a function of z. Lensing magnification ensures that sample spans an wide range of stellar mass 3e7-6e10 Msun. Find that at the median redshift of z=2.07, the median metallicity of the lensed sample is 0.35 dex lower than the local SDSS SF galaxies and 0.18 dex lower than the z~0.8 DEEP2 galaxies. The z~2 MZ relation with 19 lensed galaxies: a more rapid evolution is seen between z~1-3 than z~0-1. Compare this evolution with them ost recent cosmoloigcal hydrodynamics simulations with momentum driven winds. Find that the model metallicity is consistent with the observed metallicity within the observational error for the low mass bins. However, for higher masses, the model over-predicts the metallicity at all redshifts. The over-prediction is most significant in the highest mass bin of 1e10-11 Msun.
1211.6425
Implementation of Sink particles in the Athena code
Gong, Ostriker (Eve)
Describe implementation and tests of sink particle algorithms in the Eulerian grid-based code Athena. Introduction of sink particles enables long-term evolution of systems in which localized collapse occurs, and it is impractical (or unnecessary) to resolve the accretion shocks at the centers of collapsing regions. Criteria for sink creation are motivated by the properties of the Larson-Penston collapse solution. Use standard particle-mesh methods to compute particle and gas gravity together. Accretion of mass and moment onto sinks is computed using fluxes returned by the Riemann solver. A series of tests based on previous analytic and numerical collapse solutions is used to validate our method and implementation. Demonstrate use of code for applications with a simulation of planar converging supersonic turbulent flow, in which multiple cores form and collapse to create sinks; these sinks continue to interact and accrete from their surroundings over several Myr.
1211.6429
An over-massive black hole in the compact lenticular galaxy NGC1277
van den Bosch, ... van de Ven, ... et al
Nature paper. SMBH mass and bulge correlate: possible causes include the non-causal, statistical process of gg merging, direct feedback between the BH and its host galaxy, or gg merging and the subsequent violent relaxation and dissipation. Empirical scaling relations are important for distinguishing between various theoretical models of galaxy evolution, and they further form the basis for all BH mass measurements at large distances. Observations have shown that the mass of the BH is typically 0.1% of the stellar bulge mass of the galaxy. The small galaxy NGC4486B currently has the largst published fraction of its massin BH at 115. Report observations of stellar kinematics of NGC 1277, which is compact, disky galaxy with a mass of 1.2e11Msun. From the data, determine that the mass of the BH is 1.7e10 Msun, or 59% of tis bulge mass. 5 other compact galaxies have proeprties similar to NGC 1277 and therefore may also contain over-sized BHs. It is not yet known if these galaxies represent a tail of distribution, or if disk-dominated galaxies fail to follow the normal BH mass scaling relations.
1211.6434
Precision cosmology in muddy waters: cosmological constraints and N-body codes
Smith, Reed, Potter, Marian, Crocce, Moore
Need to understand the uncertainties associated with simulating structure formation, or the constraining power of future surveys can be significantly reduced. With n_s, h, Om_b, Om_m, this effect can be largely mitigated by adding info from a CMB experiment. In contrast, the amplitude of fluctuations sigma8 and the time-evolving equation of state of dark energy (w_0, w_a) the mitigation is mild; DE FoM can be degraded by a factor of 2. Strong motivation for rigorous convergence testing of N-body codes.
1211.6722
The nature of filamentary cold gas in the core of the Virgo cluster
Werner, .. von der Linden, et al
Multi-wavelength study of the emission-line nebulae located SE of the nucleus of M87, the central dominant galaxy of Virgo cluster. FIR CII line emission from the nebula detected. Emission is extended an cospatial with optical Ha + NII, fUV CIV lines, and soft X-ray emission. The filamentary nebulae evidently contain multi-phase material spanning a temperature rage of at least 5 orders of magnitude, from 100K to 1e7K. This material has mostly likely been uplifter by the AGN from the center of M87. The thermal pressure of the 1e4K phase appears to be significantly lower than that of the surrounding hot ICM indicating the presence of additional turbulent and B pressure in the filaments. If the turbulence in the filaments is subsonic, then the B-field strength required to balance the pressure of the surrounding ICM is 30-70 micro-G. The spectral properties of the soft X-ray emission from the filaments indicate that it is due to thermal plasma with kT~0.5-1 keV, which is cooling by mixing with the cold gas and/or radiatively. Charge exchange can be ruled out as a significant source of soft X-rays. Bothe cooling and mixing scenarios predict gas with a range of temperatures. THis is at first glance inconsistent with the apparent lack of X-ray emitting gas with kT<0.5 keV. But show that the missing very soft X-ray emission could be absorbed b the cold gas in the filaments with an average absorption column density of 1e21 /cm^2, providing a natural explanation for the apparent temperature floor to the X-ray emission at kT~0.5 keV. The FIR through UV line emission is most likely primarily powered by the ICM particles penetrating the cold gas following a shearing induced mixing process.
1211.6723
Galaxy Zoo: a catalog of overlapping galaxy pairs for dust studies
Keel, et al
Overlapping galaxies: a direct way to probe the distribution of dust extinction and its effects on the BG light. Catalog of 1990 such pairs from SDSS.
1211.6804
THe abundance of star-forming galaxies in the redshift range 8.5 to 12: new results from the 2012 Hubble ultra deep field campaign
Ellis, et al
4 times the exposure in the key F105W filter used to locate distance galaxies. Combined with additional imaging in the F140W filter, the fidelity of high-z candidates is greatly improved. Using SED fitting, find 7 promising z>8.5 candidates. The robust 8.5<z<10 sample demonstrates a luminosity density that continues the smooth decline observed over 6<z<8. Such continuity has important implications for models of cosmic reionization and future searches for z>10 galaxies with JWST.
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