1811.06989
Dark energy survey year 1 results: constraints on intrinsic alignments and their colour dependence from galaxy clustering and weak lensing
Samuroff, et al
Perform a joint analysis of intrinsic alignments and cosmology using tomographic weak lensing ,galaxy clustering and gg lensing measurements from Y1 of DES. Define ealry- and late-type subsamples, which are found to pass a series of systematics tests, including for spurious photometric redshift error and point spread function correlations. Analyse these spit data alongside the fiducial mixed Y1 sample using a range of IA models. In a fiducial NL Alignment (NLA) analysis, assuming a flat LCDM cosmology, find a significant difference in IA amplitude, with early-type galaxies favoring A_IA=2.38+0.32-0.31 and late-type galaxies consistent with no IA at 0.05+0.10-0.09. Find weak evidence of a diminishing alignment amplitude at higher z in the early-type sample. The analysis is repeated using a number of extended model spaces, including a physically motivated model that includes both tidal torquing and tidal alignment mechanisms. In multi probe likelihood chains in which cosmology, IA in both galaxy samples and all other relevant systematics are varied simultaneously, find the tidal alignment and tidal torquing parts of the IA signal have amplitudes A_1=2.7±0.7, A_2=-2.9±1.9, respectively, for early-type galaxies and A_1=0.6±0.4, A_2=-2.3±1.3 for late-type galaxies. In the full (mixed Y1 sample the best constraints are A_1=0.7±0.4, A_2=-1.4+1.0-1.4. For all galaxy splits and IA models considered, report cosmological parameter constraints that are consistent with the results of Troxel+2017 and DES 2017.
1811.07135
An orbital window into the ancient Sun's mass
Spalding, Fischer, Laughlin
Models of the Sun's long-term evolution suggest that its luminosity was substantial reduced 2-4 billion years ago, which is inconsistent with substantial evidence for warm and wet conditions in the geological records of both ancient Earth and Mars. Typical solutions to this co-called "faint young Sun paradox" consider changes in the atmospheric composition of Earth and Mars, and while attractive, geological verification of these ideas is generally lacking -- particularly for Mars. One possible under-explored solution to the faint young Sun paradox is that the Sun has simply lost a few percent of its mass during its lifetime. If correct, this would slow, or potentially even offset the increase in luminosity expected from a constant-mass model. However, this hypothesis is challenging to test. Here, propose a novel observational proxy of the Sun's ancient mass that may be readily measured from accumulation patterns in sedimentary rocks on Earth and Mars. Show that the orbital parameters of the Solar system planets undergo quasi-cyclic oscillations at a frequency, given by secular mode g_2-g_5, that scales approximately linearly with the Sun's mass. Thus by examining the cadence of sediment accumulation in ancient basins, it is possible to distinguish between the cases of a constant mass Sun and a more massive ancient Sun to a precision of greater than about 1%. This approach provide and avenue toward verification, or of falsification, of the massive early Sun hypothesis.
1811.07136
Accurate redshift determination of standard sirens by the luminosity distance space-redshift space large scale structure cross correlation
Zhang
Point out a new possibility to determine the average redshift distribution of a large sample of gravitational wave standard sirens, without spectroscopic follow-ups. It is based on the X-correlation between the luminosity-distance space LSS traced by standard sirens, and the z space LSS traced by galaxies in preexisting EM wave observations. Construct an unbiased and model independent estimator E_z to realize this possibility. Demonstrate with BBO and Euclid that, 0.1% accuracy in z determination can be achieved. This method can significantly alleviate the need of spectroscopic follow-up of standard sirens, and enhance their cosmological applications.
Perform a joint analysis of intrinsic alignments and cosmology using tomographic weak lensing ,galaxy clustering and gg lensing measurements from Y1 of DES. Define ealry- and late-type subsamples, which are found to pass a series of systematics tests, including for spurious photometric redshift error and point spread function correlations. Analyse these spit data alongside the fiducial mixed Y1 sample using a range of IA models. In a fiducial NL Alignment (NLA) analysis, assuming a flat LCDM cosmology, find a significant difference in IA amplitude, with early-type galaxies favoring A_IA=2.38+0.32-0.31 and late-type galaxies consistent with no IA at 0.05+0.10-0.09. Find weak evidence of a diminishing alignment amplitude at higher z in the early-type sample. The analysis is repeated using a number of extended model spaces, including a physically motivated model that includes both tidal torquing and tidal alignment mechanisms. In multi probe likelihood chains in which cosmology, IA in both galaxy samples and all other relevant systematics are varied simultaneously, find the tidal alignment and tidal torquing parts of the IA signal have amplitudes A_1=2.7±0.7, A_2=-2.9±1.9, respectively, for early-type galaxies and A_1=0.6±0.4, A_2=-2.3±1.3 for late-type galaxies. In the full (mixed Y1 sample the best constraints are A_1=0.7±0.4, A_2=-1.4+1.0-1.4. For all galaxy splits and IA models considered, report cosmological parameter constraints that are consistent with the results of Troxel+2017 and DES 2017.
1811.07135
An orbital window into the ancient Sun's mass
Spalding, Fischer, Laughlin
Models of the Sun's long-term evolution suggest that its luminosity was substantial reduced 2-4 billion years ago, which is inconsistent with substantial evidence for warm and wet conditions in the geological records of both ancient Earth and Mars. Typical solutions to this co-called "faint young Sun paradox" consider changes in the atmospheric composition of Earth and Mars, and while attractive, geological verification of these ideas is generally lacking -- particularly for Mars. One possible under-explored solution to the faint young Sun paradox is that the Sun has simply lost a few percent of its mass during its lifetime. If correct, this would slow, or potentially even offset the increase in luminosity expected from a constant-mass model. However, this hypothesis is challenging to test. Here, propose a novel observational proxy of the Sun's ancient mass that may be readily measured from accumulation patterns in sedimentary rocks on Earth and Mars. Show that the orbital parameters of the Solar system planets undergo quasi-cyclic oscillations at a frequency, given by secular mode g_2-g_5, that scales approximately linearly with the Sun's mass. Thus by examining the cadence of sediment accumulation in ancient basins, it is possible to distinguish between the cases of a constant mass Sun and a more massive ancient Sun to a precision of greater than about 1%. This approach provide and avenue toward verification, or of falsification, of the massive early Sun hypothesis.
1811.07136
Accurate redshift determination of standard sirens by the luminosity distance space-redshift space large scale structure cross correlation
Zhang
Point out a new possibility to determine the average redshift distribution of a large sample of gravitational wave standard sirens, without spectroscopic follow-ups. It is based on the X-correlation between the luminosity-distance space LSS traced by standard sirens, and the z space LSS traced by galaxies in preexisting EM wave observations. Construct an unbiased and model independent estimator E_z to realize this possibility. Demonstrate with BBO and Euclid that, 0.1% accuracy in z determination can be achieved. This method can significantly alleviate the need of spectroscopic follow-up of standard sirens, and enhance their cosmological applications.
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