21,223 research outputs found
Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. II. Expanding the Metallicity Range for Old Clusters and Updated Analysis Techniques
We present abundances of globular clusters in the Milky Way and Fornax from
integrated light spectra. Our goal is to evaluate the consistency of the
integrated light analysis relative to standard abundance analysis for
individual stars in those same clusters. This sample includes an updated
analysis of 7 clusters from our previous publications and results for 5 new
clusters that expand the metallicity range over which our technique has been
tested. We find that the [Fe/H] measured from integrated light spectra agrees
to 0.1 dex for globular clusters with metallicities as high as
[Fe/H]=, but the abundances measured for more metal rich clusters may be
underestimated. In addition we systematically evaluate the accuracy of
abundance ratios, [X/Fe], for Na I, Mg I, Al I, Si I, Ca I, Ti I, Ti II, Sc II,
V I, Cr I, Mn I, Co I, Ni I, Cu I, Y II, Zr I, Ba II, La II, Nd II, and Eu II.
The elements for which the integrated light analysis gives results that are
most similar to analysis of individual stellar spectra are Fe I, Ca I, Si I, Ni
I, and Ba II. The elements that show the greatest differences include Mg I and
Zr I. Some elements show good agreement only over a limited range in
metallicity. More stellar abundance data in these clusters would enable more
complete evaluation of the integrated light results for other important
elements.Comment: Accepted for publication in ApJ, 37 pages, 13 tables, 29 figure
The Detailed Chemical Abundance Patterns of M31 Globular Clusters
We present detailed chemical abundances for 20 elements in 30
globular clusters in M31. These results have been obtained using high
resolution (24,000) spectra of their integrated
light and analyzed using our original method. The globular clusters have
galactocentric radii between 2.5 kpc and 117 kpc, and therefore provide
abundance patterns for different phases of galaxy formation recorded in the
inner and outer halo of M31. We find that the clusters in our survey have a
range in metallicity of [Fe/H]. The inner halo clusters cover
this full range, while the outer halo globular clusters at R20 kpc have a
small range in abundance of [Fe/H]. We also measure abundances
of alpha, r- and s-process elements. These results constitute the first
abundance pattern constraints for old populations in M31 that are comparable to
those known for the Milky Way halo.Comment: XII International Symposium on Nuclei in the Cosmos August 5-12, 2012
Cairns, Australia. To appear in Proceedings of Scienc
Fast quantum algorithm for numerical gradient estimation
Given a blackbox for f, a smooth real scalar function of d real variables,
one wants to estimate the gradient of f at a given point with n bits of
precision. On a classical computer this requires a minimum of d+1 blackbox
queries, whereas on a quantum computer it requires only one query regardless of
d. The number of bits of precision to which f must be evaluated matches the
classical requirement in the limit of large n.Comment: additional references and minor clarifications and corrections to
version
Constraints to Energy Spectra of Blazars based on Recent EBL Limits from Galaxy Counts
We combine the recent estimate of the contribution of galaxies to the 3.6
micron intensity of the extragalactic background light (EBL) with optical and
near-infrared (IR) galaxy counts to set new limits on intrinsic spectra of some
of the most distant TeV blazars 1ES 0229+200, 1ES 1218+30.4, and 1ES 1101-232,
located at redshifts 0.1396, 0.182, and 0.186, respectively. The new lower
limit on the 3.6 micron EBL intensity is significantly higher than the previous
one set by the cumulative emission from resolved Spitzer galaxies. Correcting
for attenuation by the revised EBL, we show that the differential spectral
index of the intrinsic spectrum of the three blazars is 1.28 +- 0.20 or harder.
These results present blazar emission models with the challenge of producing
extremely hard intrinsic spectra in the sub-TeV to multi-TeV regime. These
results also question the reliability of recently derived upper limits on the
near-IR EBL intensity that are solely based on the assumption that intrinsic
blazar spectra should not be harder than 1.5.Comment: 13 pages, 2 figures, submitted to the Astrophysical Journa
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