541 research outputs found
Review of Big Bang Nucleosynthesis and Primordial Abundances
Big Bang Nucleosynthesis (BBN) is the synthesis of the light nuclei,
Deuterium, He3, He4 and Li7, during the first few minutes of the universe. This
review concentrates on recent improvements in the measurement of the primordial
(after BBN, and prior to modification) abundances of these nuclei. We mention
improvement in the standard theory, and the non-standard extensions which are
limited by the data. (abridged)Comment: 61 pages, to appear in Physica Script
Re-calibration of SDF/SXDS Photometric Catalogs of Suprime-Cam with SDSS Data Release 8
We present photometric recalibration of the Subaru Deep Field (SDF) and
Subaru/XMM-Newton Deep Survey (SXDS). Recently, Yamanoi et al. (2012) suggested
the existence of a discrepancy between the SDF and SXDS catalogs. We have used
the Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8) catalog and compared
stars in common between SDF/SXDS and SDSS. We confirmed that there exists a
0.12 mag offset in B-band between the SDF and SXDS catalogs. Moreover, we found
that significant zero point offsets in i-band (~ 0.10 mag) and z-band (~ 0.14
mag) need to be introduced to the SDF/SXDS catalogs to make it consistent with
the SDSS catalog. We report the measured zero point offsets of five filter
bands of SDF/SXDS catalogs. We studied the potential cause of these offsets,
but the origins are yet to be understood.Comment: 36 pages, 19 figures(128 EPS files), PASJ accepte
Relative Flux Calibration of Keck HIRES Echelle Spectra
We describe a new method to calibrate the relative flux levels in spectra
from the HIRES echelle spectrograph on the Keck-I telescope. Standard data
reduction techniques that transfer the instrument response between HIRES
integrations leave errors in the flux of 5 - 10%, because the effective
response varies. The flux errors are most severe near the ends of each spectral
order, where there can be discontinuous jumps. The source of these errors is
uncertain, but may include changes in the vignetting connected to the optical
alignment. Our new flux calibration method uses a calibrated reference spectrum
of each target to calibrate individual HIRES integrations. We determine the
instrument response independently for each integration, and hence we avoid the
need to transfer the instrument response between HIRES integrations. The
procedure can be applied to any HIRES spectrum, or any other spectrum. While
the accuracy of the method depends upon many factors, we have been able to flux
calibrate a HIRES spectrum to 1% over scales of 200 A that include order joins.
We illustrate the method with spectra of Q1243+3047 towards which we have
measured the deuterium to hydrogen abundance ratio.Comment: 24 pages, 17 figures, submitted to PAS
Predicting QSO Continua in the Ly Alpha Forest
We present a method to make predictions with sets of correlated data values,
in this case QSO flux spectra. We predict the continuum in the Lyman-Alpha
forest of a QSO, from 1020 -- 1216 A, using the spectrum of that QSO from 1216
-- 1600 A . We find correlations between the unabsorbed flux in these two
wavelengths regions in the HST spectra of 50 QSOs. We use principal component
analysis (PCA) to summarize the variety of these spectra and we relate the
weights of the principal components for 1020 -- 1600 A to the weights for 1216
-- 1600 A, and we apply this relation to make predictions. We test the method
on the HST spectra, and we find an average absolute flux error of 9%, with a
range 3 -- 30%, where individual predictions are systematically too low or too
high. We mention several ways in which the predictions might be improved.Comment: 17 pages, 4 figures, submitted to Ap
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