Day 1500

Monday.

1811.06081
Measurement of splash back feature around SZ-selected galaxy clusters with DES, PST and ACT
Shin, et al

Present a detection of the splash back feature around galaxy clusters selected sing they rSZ signal.  Recent measurements of the splash back feature around optically selected galaxy clusters have found that the splash back radius, r_sp, is smaller than predicted by N-body simulations.  A possible explanation for this discrepancy is that r_sp inferred from the observed radial distrubiton of galaxies is affected by selection effects related to the optical cluster-finding algorithms.  Test this possibility by measuring the splash back feature in clusters selected via the SZ effect in data from the SPT SZ survey and ACT Polarimeter survey.  The measurement is accomplished by correlating these clusters with galaxies detected int the DES Y3 data.  The SZ observable used to select clusters in this analysis is expected to have a twitter correlation with halo mass and to be more immune to projection effects and aperture-induced biases than optically selected clusters.  Find that the measured r_sp for SZ-selected clusters is consistent with the expectations from simulations, although the small number of SZ-selected clusters make s a precise comparison difficult.  In agreement with previous work, when using optically selected redMaPPer clusters, r_sp is ~2 sigma smaller than in the simulations.  These results motivate detailed investigations of selection biases in optically selected cluster catalogs and exploration of the splash back feature as a function of galaxy color, finding that blue galaxies have profiles close to a power law with no discernible splashback feature, which is consistent with them being on their first infall into the cluster.


1811.06556
Biases in inferring dark matter profiles from dynamical and lensing measurements
Scibelli, Perna, Keeton

The degeneracy between disk and halo contributions in spiral galaxy rotation curves makes it difficult to obtain a full understanding of the distribution of baryons and DM in disc galaxies like our own MW.  Using mock data, study how constraints on DM profiles obtained from kinematics, strong lensing, or a combination of the two are affected by assumptions about the halo model.  Compare 4 different models: spherical isothermal and NFW haloes, along with spherical and elliptical Burkert haloes. For both kinematics and lensing, find examples where different models fit the data well but give enclosed masses that are inconsistent with the true (i.e., input) values.  This is especially notable when the input and fit models differ in having cored or cusp profiles (such as fitting an NFW model when the underlying DM distribution follows a different profiles).  Find that mass biases are more pronounced with lensing than with kinematics, and using both methods can help reduce the bias and provide stronger constraints on the DM distributions.


1811.06844
Paleo-detectors: searching for Dark Matter with Ancient Minerals
Drukier, et al

Thanks to the large integration time of paleo-detectors, relative small target masses suffice to obtain exposures, i.e. the product of integration time and target mass, much larger than what is feasible in the conventional direct detection approach.  Discuss the paleo-detector proposal in detail, in particular, a range of background sources.  For low-mass WIMPs with masses m_chi <~ 10 GeV, the largest contribution to the background budget comes for nuclear recoils induced by coherent scattering of solar neutrinos.  For heavier WIMPs, the largest background source is nuclear recoils induced by fast neutrons created by heavy radioactive contaminants, particularly ^238U; neutrons can arise in spontaneous fission or from alpha-particles created in ^238U decays.  Also discuss the challenges of mineral optimization, specifically the determination of readily available minerals from rocks in deep boreholes which are able to record persistent damage from nuclear recoils.  In order to suppress backgrounds induced by radioactive contaminants, propose to use minerals found in marine evaporites or in ultra-basic rocks.  Estimate the sensitivity of paleo-detectors to spin-independent and spin-dependent WIMP-nucleus interactions.  In all interaction cases considered here, the sensitivity of low-mass WIMPs with masses m_chi<~10GeV extends to WIMP-nucelaon cross sections many orders of magnitude smaller than current upper limits.  For heavier WIMPs with masses m_chi>~30 GeV cross elections a factor of few to ~100 smaller than current upper limits can be probed by paleo-detectors.