Day 1629

Monday.

1909.05898
The CFHT Large Area U-band Deep Survey (CLAUDS)
Sawicki, et al

The CFHT Large Area U-band Deep Survey (CLAUDS) uses data taken with the MegaCam mosaic imager on CFHT to produce images of 18.60 deg2 with median seeing of FWHM=0.92 arcsec and to a median depth of U = 27.1 AB (5 sigma in 2 arcsec apertures), with selected areas that total 1.36 deg2 reaching a median depth of U=27.7 AB. These are the deepest U-band images assembled to date over this large an area. These data are located in four fields also imaged to comparably faint levels in grizy and several narrowband filters as part of the Hyper Suprime-Cam (HSC) Subaru Strategic Program (HSC-SSP). These CFHT and Subaru datasets will remain unmatched in their combination of area and depth until the advent of the Large Synoptic Survey Telescope (LSST). This paper provides an overview of the scientific motivation for CLAUDS and gives details of the observing strategy, observations, data reduction, and data merging with the HSC-SSP. Three early applications of these deep data are used to illustrate the potential of the dataset: deep U-band galaxy number counts, z~3 Lyman break galaxy (LBG) selection, and photometric redshifts improved by adding CLAUDS U to the Subaru HSC grizy photometry.

1909.05940

The Urban Observatory: A multi-model imaging platform for the study of dynamics in complex urban systems

Dobler, et al

We describe an "Urban Observatory" facility designed for the study of complex urban systems via persistent, synoptic, and granular imaging of dynamical processes in cities. An initial deployment of the facility has been demonstrated in New York City and consists of a suite of imaging systems - both broadband and hyperspectral - sensitive to wavelengths from the visible (~400 nm) to the infrared (~13 micron) operating at cadences of ~0.01 - 30 Hz (characteristically ~0.1 Hz). Much like an astronomical survey, the facility generates a large imaging catalog from which we have extracted observables (e.g., time-dependent brightnesses, spectra, temperatures, chemical species, etc.), collecting them in a parallel source catalog. We have demonstrated that, in addition to the urban science of cities as systems, these data are applicable to a myriad of domain-specific scientific inquiries related to urban functioning including energy consumption and end use, environmental impacts of cities, and patterns of life and public health. We show that an Urban Observatory facility of this type has the potential to improve both a city's operations and the quality of life of its inhabitants.

1909.05947

NASA's Meteoroid Engineering Model (MEM) 3 and its ability to replicate spacecraft impact rates

Moorhead, et al

Meteoroids pose one of the largest risks to spacecraft outside of low Earth orbit. In order to correctly predict the rate at which meteoroids impact and damage spacecraft, environment models must describe the mass, directionality, velocity, and density distributions of meteoroids. NASA's Meteoroid Engineering Model (MEM) is one such model; MEM 3 is an updated version of the code that better captures the correlation between directionality and velocity and incorporates a bulk density distribution. This paper describes MEM 3 and compares its predictions with the rate of large particle impacts seen on the Long Duration Exposure Facility (LDEF) and the Pegasus II and III satellites.

1909.06190

How to measure galaxy-galaxy-galaxy lensing with higher precision and accuracy

Linke, Simon, Schneider, Hilbert

Galaxy-galaxy-galaxy lensing (G3L) is a powerful tool for constraining the three-point correlation between the galaxy and the matter field and thereby models of galaxy evolution. We propose three improvements to current measurements of G3L, designed to improve the precision and the accuracy by using the galaxies' redshifts and removing biases of the estimator. We further show how to account for lens galaxy magnification by the cosmic large-scale structure and how to convert the G3L signal from angular to physical scales. The improvements are tested on simple mock data and simulated data based on the Millennium Run with an implemented semi-analytic model of galaxies. Our improvements increase the signal-to-noise ratio by on average $35~\%$ at angular scales between $0.1'$ and $10'$ and physical scales between $0.02$ and $2 \, h^{-1}\,\textrm{Mpc}$. They also remove the bias of the G3L estimator at angular scales below $1'$, which was originally up to $40\,\%$. The signal due to lens magnification is approximately $10\,\%$ of the total signal.