23 research outputs found
HST/COS Observations of the Quasar Q0302-003: Probing the He II Reionization Epoch and QSO Proximity Effects
Q0302-003 () was the first quasar discovered that showed
a He II Gunn-Peterson trough, a sign of incomplete helium reionization at . We present its HST/Cosmic Origins Spectrograph far-UV medium-resolution
spectrum, which resolves many spectral features for the first time, allowing
study of the quasar itself, the intergalactic medium, and quasar proximity
effects. Q0302-003 has a harder intrinsic extreme-UV spectral index than
previously claimed, as determined from both a direct fit to the spectrum
(yielding ) and the helium-to-hydrogen ion ratio in the
quasar's line-of-sight proximity zone. Intergalactic absorption along this
sightline shows that the helium Gunn-Peterson trough is largely black in the
range , apart from ionization due to local sources, indicating
that helium reionization has not completed at these redshifts. However, we
tentatively report a detection of nonzero flux in the high-redshift trough when
looking at low-density regions, but zero flux in higher-density regions. This
constrains the He II fraction to be a few percent, suggesting helium
reionization has progressed substantially by . The Gunn-Peterson
trough recovers to a He II Ly forest at . We confirm a
transmission feature due to the ionization zone around a quasar just
off the sightline, and resolve the feature for the first time. We discover a
similar such feature possibly caused by a luminous quasar further
from the sightline, which suggests that this quasar has been luminous for >34
Myr.Comment: ApJ accepted version; 20 pages, 16 figure
He II Ly{\beta} Gunn-Peterson Absorption: New HST Observations, and Theoretical Expectations
Observations of He II Ly{\alpha} Gunn-Peterson troughs have proved to be a
valuable probe of the epoch of helium reionization at z~3. Since this optical
depth can become unmeasurably large even for modest He II fractions, various
alternate techniques have been proposed to push to higher redshift, and among
the more promising is looking at higher order Lyman-series troughs. We here
report four new observations of the He II Ly{\beta} trough, including new data
on the only sightline with a prior Ly{\beta} observation. However, the
effective optical depth ratio {\tau}_eff,{\beta}/{\tau}_eff,{\alpha} is not
simply predicted by (f_{\beta} {\lambda}_{\beta})/(f_{\alpha}
{\lambda}_{\alpha})=0.16, and we analyze cosmological simulations to find that
the correct ratio for helium at z~3 is ~0.35. In one case we infer
{\tau}_eff,{\alpha} > 8.8, strong evidence that helium was not fully reionized
at z=3.2--3.5, in agreement with previous measurements suggesting a later
completion of reionization.Comment: ApJ accepted. 25 pages, 3 figures, 4 table
Accelerator performance analysis of the Fermilab Muon Campus
Fermilab is dedicated to hosting world-class experiments in search of new
physics that will operate in the coming years. The Muon g-2 Experiment is one
such experiment that will determine with unprecedented precision the muon
anomalous magnetic moment, which offers an important test of the Standard
Model. We describe in this study the accelerator facility that will deliver a
muon beam to this experiment. We first present the lattice design that allows
for efficient capture, transport, and delivery of polarized muon beams. We then
numerically examine its performance by simulating pion production in the
target, muon collection by the downstream beam line optics, as well as
transport of muon polarization. We finally establish the conditions required
for the safe removal of unwanted secondary particles that minimizes
contamination of the final beam.Comment: 10 p
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A Large, Uniform Sample of X-Ray-emitting Active Galactic Nuclei from the ROSAT All Sky and Sloan Digital Sky Surveys: The Data Release 5 Sample
We describe further results of a program aimed at yielding ~104 fully characterized optical identifications of ROSAT X-ray sources. Our program employs X-ray data from the ROSAT All Sky Survey (RASS) and both optical imaging and spectroscopic data from the Sloan Digital Sky Survey (SDSS). RASS/SDSS data from 5740 deg² of sky spectroscopically covered in SDSS Data Release 5 provide an expanded catalog of 7000 confirmed quasars and other active galactic nuclei (AGNs) that are probable RASS identifications. Again, in our expanded catalog the identifications as X-ray sources are statistically secure, with only a few percent of the SDSS AGNs likely to be randomly superposed on unrelated RASS X-ray sources. Most identifications continue to be quasars and Seyfert 1 galaxies with 15 < m < 21 and 0.01 < z < 4, but the total sample size has grown to include very substantial numbers of even quite rare AGNs, e.g., it now includes several hundreds of candidate X-ray-emitting BL Lac objects and narrow-line Seyfert 1 galaxies. In addition to exploring rare subpopulations, such a large total sample may be useful when considering correlations between the X-ray and the optical and may also serve as a resource list from which to select the "best" object (e.g., X-ray-brightest AGN of a certain subclass at a preferred redshift or luminosity) for follow-up X-ray spectral or alternate detailed studies
A Large, Uniform Sample of X-ray Emitting AGN from the ROSAT All-Sky and Sloan Digital Sky Surveys: the Data Release 5 Sample
We describe further results of a program aimed to yield ~10^4 fully
characterized optical identifications of ROSAT X-ray sources. Our program
employs X-ray data from the ROSAT All-Sky Survey (RASS), and both optical
imaging and spectroscopic data from the Sloan Digital Sky Survey (SDSS).
RASS/SDSS data from 5740 deg^2 of sky spectroscopically covered in SDSS Data
Release 5 (DR5) provide an expanded catalog of 7000 confirmed quasars and other
AGN that are probable RASS identifications. Again in our expanded catalog, the
identifications as X-ray sources are statistically secure, with only a few
percent of the SDSS AGN likely to be randomly superposed on unrelated RASS
X-ray sources. Most identifications continue to be quasars and Seyfert 1s with
15<m<21 and 0.01<z<4; but the total sample size has grown to include very
substantial numbers of even quite rare AGN, e.g., now including several
hundreds of candidate X-ray emitting BL Lacs and narrow-line Seyfert 1
galaxies. In addition to exploring rare subpopulations, such a large total
sample may be useful when considering correlations between the X-ray and the
optical, and may also serve as a resource list from which to select the "best"
object (e.g., X-ray brightest AGN of a certain subclass, at a preferred
redshift or luminosity) for follow-on X-ray spectral or alternate detailed
studies.Comment: Accepted for publication in AJ; 32 pages, including 11 figures, and 6
example table
An HST/COS Survey of the Low-Redshift IGM. I. Survey, Methodology, & Overall Results
We use high-quality, medium-resolution {\it Hubble Space Telescope}/Cosmic
Origins Spectrograph (\HST/COS) observations of 82 UV-bright AGN at redshifts
to construct the largest survey of the low-redshift
intergalactic medium (IGM) to date: 5343 individual extragalactic absorption
lines in HI and 25 different metal-ion species grouped into 2610 distinct
redshift systems at covering total redshift pathlengths and . Our semi-automated line-finding and
measurement technique renders the catalog as objectively-defined as possible.
The cumulative column-density distribution of HI systems can be parametrized
, with and
. This distribution is seen to evolve both in amplitude,
, and slope for .
We observe metal lines in 427 systems, and find that the fraction of IGM
absorbers detected in metals is strongly dependent on N_{HI}. The distribution
of OVI absorbers appear to evolve in the same sense as the Lya forest. We
calculate contributions to from different components of the low-
IGM and determine the Lya decrement as a function of redshift. IGM absorbers
are analyzed via a two-point correlation function (TPCF) in velocity space. We
find substantial clustering of \HI\ absorbers on scales of
km/s with no significant clustering at km/s. Splitting the
sample into strong and weak absorbers, we see that most of the clustering
occurs in strong, , metal-bearing IGM systems. The
full catalog of absorption lines and fully-reduced spectra is available via
MAST as a high-level science product at http://archive.stsci.edu/prepds/igm/.Comment: This is the accepted version (v3) of the paper. Previous versions
(July 2015 and Feb. 2014) should be replaced by this one. In particular,
please note that the associated MAST high-level-science product has been
updated to reflect the of the final state of the paper. It is available at:
http://archive.stsci.edu/prepds/igm
REVIEW OF PARTICLE PHYSICS
The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 3,324 new measurements from 878 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 120 reviews are many that are new or heavily revised, including a new review on High Energy Soft QCD and Diffraction and one on the Determination of CKM Angles from B Hadrons. The Review is divided into two volumes. Volume 1 includes the Summary Tables and 98 review articles. Volume 2 consists of the Particle Listings and contains also 22 reviews that address specific aspects of the data presented in the Listings. The complete Review (both volumes) is published online on the website of the Particle Data Group (pdg.lbl.gov) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Booklet with the Summary Tables and essential tables, figures, and equations from selected review articles is available in print and as a web version optimized for use on phones as well as an Android app.Peer reviewe
Electric dipole moments and the search for new physics
Static electric dipole moments of nondegenerate systems probe mass scales for
physics beyond the Standard Model well beyond those reached directly at high
energy colliders. Discrimination between different physics models, however,
requires complementary searches in atomic-molecular-and-optical, nuclear and
particle physics. In this report, we discuss the current status and prospects
in the near future for a compelling suite of such experiments, along with
developments needed in the encompassing theoretical framework.Comment: Contribution to Snowmass 2021; updated with community edits and
endorsement