Day 1728

Friday.

2007.00669

Constraining the charge-sign and rigidity-dependence of solar modulation

Cholis, et al

Our ability to identify the sources of cosmic rays and understand how these particles propagate through the interstellar medium is hindered by the combined effects of the solar wind and its embedded magnetic field, collectively known as solar modulation. In this paper, we build upon our previous work to model and constrain the effects of solar modulation on the cosmic-ray spectrum, using data from AMS-02 and BESS Polar II collected between 2007 and 2012, during which the heliospheric magnetic field was in a state of negative polarity. Our model uses measurements of the heliospheric magnetic field and the tilt angle of the heliospheric current sheet to accurately predict the effects of solar modulation as a function of time, charge, and rigidity. By incorporating data from a period of negative polarity, we have been able to robustly observe and constrain the charge-dependent effects of solar modulation.

2007.00675

x-cut Cosmic Shear: optimally removing sensitivity to baryonic and nonlinear physics with an application to the dark energy survey year 1 shear data

Taylor, Bernardeau, Huff

We present a new method, called x-cut cosmic shear, which optimally removes sensitivity to poorly modeled scales from the two-point cosmic shear signal. We show that the x-cut cosmic shear covariance matrix can be computed from the correlation function covariance matrix in a few minutes, enabling a likelihood analysis at virtually no additional computational cost. Further we show how to generalize x-cut cosmic shear to galaxy-galaxy lensing. Performing an x-cut cosmic shear analysis of the Dark Energy Survey Year 1 (DESY1) shear data, we reduce the error on S8 by 20% relative to a correlation function analysis, while showing our constraints are robust to different baryonic feedback models. Largely driven by information at small angular scales, our result, S8 = 0.734 plus/minus 0.038, yields a 2.6 sigma tension with the Planck Legacy analysis of the cosmic microwave background. As well as alleviating baryonic modelling uncertainties, our method can be used to optimally constrain a large number of theories of modified gravity where computational limitations make it infeasible to model the power spectrum down to extremely small scales. The key parts of our code are made publicly available.

2007. 00847

Formation of mass-gap objects in highly asymmetric mergers

Safarzadeh, Loeb

The LIGO/Virgo Collaboration (LVC) recently reported the detection of GW190814, a merger of a $23^{+1.0}_{-0.9}~M_{\odot}$ primary black hole (BH), and a $2.6^{+0.08}_{-0.08}~M_{\odot}$ secondary. The secondary's mass falls into the mass-gap regime, which refers to the scarcity of compact objects in the mass range of 2-5 $M_{\odot}$. The first clue to the formation of the GW190814 lies in the fact that the primary is a very massive BH. We suggest that the secondary was born as a neutron star (NS) where a significant amount of the supernova ejecta mass from its formation remained bound to the binary due to the presence of the massive BH companion. The bound mass forms a circumbinary accretion disk, and its accretion onto the NS created a mass-gap object. In this scenario, LIGO/Virgo will only detect mass-gap objects in binary mergers with an extreme mass ratio. We also predict a correlation between the mass of the secondary and the mass of the primary in such asymmetric mergers. Our model can be tested with future data from the LVC's third-observing run.

2007.01211

Testing the accuracy of 3D-HST photometric redshift estimates as reference samples for deep weak lensing studies

Raihan, Shrabback, Hildebrandt, Applegate, Mahler

Accurate weak lensing mass estimates of clusters are needed in order to calibrate mass proxies for the cosmological exploitation of galaxy cluster surveys. Such measurements require accurate knowledge of the redshift distribution of the weak lensing source galaxies. In this context, we investigate the accuracy of photometric redshifts (photo-$z$s) computed by the 3D-HST team for the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey fields, which provide a relevant photometric reference data set for deep weak lensing studies. Through the comparison to spectroscopic redshifts and photo-$z$s based on very deep data from the Hubble Ultra Deep Field, we identify catastrophic redshift outliers in the 3D-HST/CANDELS catalogue. These would significantly bias weak lensing results if not accounted for. We investigate the cause of these outliers and demonstrate that the interpolation of spectral energy distribution (SED) templates and a well-selected combination of photometric data can reduce the net impact for weak lensing studies.