93 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
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
Solar Sail Orbit Operations at Asteroids: Exploring the Coupled Effect of an Imperfectly Reflecting Sail and a Nonspherical Asteroid
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77005/1/AIAA-2002-4991-208.pd
Solar sail orbit operations at asteroids
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77377/1/AIAA-2000-4420-378.pd
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
The Kast Ground Based UV Spectral Survey of 79 QSOs at Redshift 2 for Lyman Alpha Forest and Metal Absorption
We present a moderate resolution (~1.15 Angstroms/pixel) survey of 79 quasars
obtained using the Kast spectrograph on the Shane 3m telescope at Lick
observatory. The spectra span the wavelength range of 3175-5880 Angstroms, and
have typical signal to noise of 6-20 in the regions of the spectra showing
Lyman alpha forest absorption. The quasars have a mean emission redshift of
z=2.17, and nearly all cover the entire Lyman alpha forest between Lyman alpha
and Lyman beta. Although the quasars were selected to avoid BAL, two quasars in
the survey are BAL, one of which is a new discovery. We list the HI and metal
ions observed in a total of 140 absorption systems. We also identify 526
emission lines, and list their observed wavelengths, along with new redshifts
of the quasars. We determine the rest wavelengths of 3 emission lines or line
blends in the forest to be 1070.95 +/- 1.00, 1123.13 +/- 0.51, and 1175.88 +/-
0.30 Angstroms.Comment: Submitted to the Astronomical Journa
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