Nick J. Mostek

Investigating Emission Line Galaxy Surveys with the Sloan Digital Sky Survey Infrastructure

The Baryon Acoustic Oscillation (BAO) feature in the power spectrum of galaxies provides a standard ruler to probe the accelerated expansion of the Universe. The current surveys covering a comoving volume su cient to unveil the BAO scale are limited to redshift z . 0:7. In this paper, we study several galaxy selection schemes aiming at building an emission-linegalaxy (ELG) sample in the redshift range 0:6 < z < 1:7, that would be suitable for future BAO studies using the Baryonic Oscillation Spectroscopic Survey (BOSS) spectrograph on the Sloan Digital Sky Survey (SDSS) telescope. We explore two di erent colour selections using both the SDSS and the Canada France Hawai Telescope Legacy Survey (CFHT-LS) photometry in the u, g, r, and i bands and evaluate their performance selecting luminous ELG. From about 2,000 ELG, we identified a selection scheme that has a 75 percent redshift measurement e ciency. This result confirms the feasibility of massive ELG surveys using the BOSS spectrograph on the SDSS telescope for a BAO detection at redshift z 1, in particular the proposed eBOSS experiment, which plans to use the SDSS telescope to combine the use of the BAO ruler with redshift space distortions using emission line galaxies and quasars in the redshift 0:6 < z < 2:2.

Stochastic bias of colour-selected BAO tracers by joint clustering-weak lensing analysis

The baryon acoustic oscillation (BAO) feature in the two-point correlation function of galaxies supplies a standard ruler to probe the expansion history of the Universe. We study here several galaxy selection schemes, aiming at building an emission-line galaxy (ELG) sample in the redshift range 0.6 1.5), but we are limited by current data sets depth to derive precise values of the galaxy bias. A survey using such tracers of the mass field will guarantee a high significance detection of the BAO.

Charge trap identification for proton-irradiated p+ channel CCDs

Charge trapping in bulk silicon lattice structures is a source of charge transfer inefficiency (CTI) in CCDs. These traps can be introduced into the lattice by low-energy proton radiation in the space environment, decreasing the performance of the CCD detectors over time. Detailed knowledge of the inherent trap properties, including energy level and cross section, is important for understanding the impact of the defects on charge transfer as a function of operating parameters such as temperature and clocking speeds. This understanding is also important for mitigation of charge transfer inefficiency through annealing, software correction, or improved device fabrication techniques. In this paper, we measure the bulk trap properties created by 12.5 MeV proton irradiation on p+ channel, full-depletion CCDs developed at LBNL. Using the pocket pumping technique, we identify the majority trap populations responsible for CTI in both the parallel and serial transfer processes. We find the dominant parallel transfer trap properties are well described by the silicon lattice divacancy trap, in agreement with other studies. While the properties of the defects responsible for CTI in the serial transfer are more difficult to measure, we conclude that divacancy-oxygen defect centers would be efficient at our serial clocking rate and exhibit properties consistent with our serial pocket pumping data.

Reducing Zero-point Systematics in Dark Energy Supernova Experiments

We study the effect of filter zero-point uncertainties on future supernova dark energy missions. Fitting for calibration parameters using simultaneous analysis of all Type Ia supernova standard candles achieves a significant improvement over more traditional fit methods. This conclusion is robust under diverse experimental configurations (number of observed supernovae, maximum survey redshift, inclusion of additional systematics). This approach to supernova fitting considerably eases otherwise stringent mission calibration requirements. As an example we simulate a space-based mission based on the proposed JDEM satellite; however the method and conclusions are general and valid for any future supernova dark energy mission, ground or space-based.

Pass-band filter performance for space-flight dark energy missions

The nature of Dark Energy can by constrained by the precise determination of super-novae distance moduli in ultraviolet to near IR pass-bands. Space-based observations are required for these moduli to be measured with the scientifically required photometric accuracies. Consequently, robust pass-band filters operable at cryogenic temperatures (120-140K) are needed that have challenging performance attributes including high in-band transmission, low ripple, good out-ofband rejection, and moderate band-edge slope. We describe the requirements and performance of dielectric multi-layer filters with spectral profiles that are suitable for both achieving the science and for accurate calibration using plausible on-orbit measurement systems.

BigBOSS: The Ground-Based Stage IV BAO Experiment

The BigBOSS experiment is a proposed DOE-NSF Stage IV ground-based dark energy experiment to study baryon acoustic oscillations (BAO) and the growth of structure with an all-sky galaxy redshift survey. The project is designed to unlock the mystery of dark energy using existing ground-based facilities operated by NOAO. A new 4000-fiber R=5000 spectrograph covering a 3-degree diameter field will measure BAO and redshift space distortions in the distribution of galaxies and hydrogen gas spanning redshifts from 0.2< z< 3.5. The Dark Energy Task Force figure of merit (DETF FoM) for this experiment is expected to be equal to that of a JDEM mission for BAO with the lower risk and cost typical of a ground-based experiment.

Photodiode and inteference filter calibration using a monochromatic illumination and cryogenic calibration system

The SNAP mission will conduct a systematic error limited survey of Type Ia supernovae to measure dark energy in the universe. The final accuracy of the dark energy parameters will depend upon the calibration of the flight instrumentation. To perform ground-based characterizations of SNAP calibration hardware, we have built the Monochromatic Illumination and Cryogenic Calibration System (MICCS). There are two immediate purposes for MICCS. The first purpose is to transfer the NIST irradiance calibration of Si and InGaAs photodiodes to additional photodiodes that are operated at the nominal SNAP focal plane temperature of 140 K. These photodiodes will be used by detector characterization laboratories to measure the quantum efficiency of the SNAP flight detectors. The second purpose of MICCS is to characterize the transmission of interference filters at incident angles and temperature similar to that used on the SNAP focal plane. We examine periodic transmission variations in a set of commercial filters and develop an interpolation method to determine the filter bandpass at any angle relevant to the SNAP focal plane.