Browsing by Subject "photometric calibration"
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Item M Dwarf Metallicities And Giant Planet Occurrence: Ironing Out Uncertainties And Systematics(2014-08) Gaidos, Eric; Mann, Andrew W.; Mann, Andrew W.Comparisons between the planet populations around solar-type stars and those orbiting M dwarfs shed light on the possible dependence of planet formation and evolution on stellar mass. However, such analyses must control for other factors, i.e., metallicity, a stellar parameter that strongly influences the occurrence of gas giant planets. We obtained infrared spectra of 121 M dwarfs stars monitored by the California Planet Search and determined metallicities with an accuracy of 0.08 dex. The mean and standard deviation of the sample are -0.05 and 0.20 dex, respectively. We parameterized the metallicity dependence of the occurrence of giant planets on orbits with a period less than two years around solar-type stars and applied this to our M dwarf sample to estimate the expected number of giant planets. The number of detected planets (3) is lower than the predicted number (6.4), but the difference is not very significant (12% probability of finding as many or fewer planets). The three M dwarf planet hosts are not especially metal rich and the most likely value of the power-law index relating planet occurrence to metallicity is 1.06 dex per dex for M dwarfs compared to 1.80 for solar-type stars; this difference, however, is comparable to uncertainties. Giant planet occurrence around both types of stars allows, but does not necessarily require, a mass dependence of similar to 1 dex per dex. The actual planet-mass-metallicity relation may be complex, and elucidating it will require larger surveys like those to be conducted by ground-based infrared spectrographs and the Gaia space astrometry mission.Item Reconstructing Emission From Pre-Reionization Sources With Cosmic Infrared Background Fluctuation Measurements By The JWST(2015-05) Kashlinsky, A.; Mather, J. C.; Helgason, K.; Arendt, R. G.; Bromm, Volker; Moseley, S. H.; Bromm, VolkerWe present new methodology to use cosmic infrared background (CIB) fluctuations to probe sources at 10 less than or similar to z less than or similar to 30 from a James Webb Space Telescope (JWST)/NIRCam configuration that will isolate known galaxies to 28 AB mag at 0.5-5 mu m. At present significant mutually consistent source-subtracted CIB fluctuations have been identified in the Spitzer and AKARI data at similar to 2-5 mu m, but we demonstrate internal inconsistencies at shorter wavelengths in the recent CIBER data. We evaluate CIB contributions from remaining galaxies and show that the bulk of the high-z sources will be in the confusion noise of the NIRCam beam, requiring CIB studies. The accurate measurement of the angular spectrum of the fluctuations and probing the dependence of its clustering component on the remaining shot noise power would discriminate between the various currently proposed models for their origin and probe the flux distribution of its sources. We show that the contribution to CIB fluctuations from remaining galaxies is large at visible wavelengths for the current instruments precluding probing the putative Lyman-break of the CIB fluctuations. We demonstrate that with the proposed JWST configuration such measurements will enable probing the Lyman-break. We develop a Lyman-break tomography method to use the NIRCam wavelength coverage to identify or constrain, via the adjacent two-band subtraction, the history of emissions over 10 less than or similar to z less than or similar to 30 as the universe comes out of the "Dark Ages." We apply the proposed tomography to the current Spitzer/IRAC measurements at 3.6 and 4.5 mu m, to find that it already leads to interestingly low upper limit on emissions at z greater than or similar to 30.