1,333 research outputs found
Emission Line Galaxies in the STIS Parallel Survey II: Star Formation Density
We present the luminosity function of [OII]-emitting galaxies at a median
redshift of z=0.9, as measured in the deep spectroscopic data in the STIS
Parallel Survey (SPS). The luminosity function shows strong evolution from the
local value, as expected. By using random lines of sight, the SPS measurement
complements previous deep single field studies. We calculate the density of
inferred star formation at this redshift by converting from [OII] to H-alpha
line flux as a function of absolute magnitude and find rho_dot=0.043 +/- 0.014
Msun/yr/Mpc^3 at a median redshift z~0.9 within the range 0.46<z<1.415 (H_0 =
70 km/s/Mpc, Omega_M=0.3, Omega_Lambda=0.7. This density is consistent with a
(1+z)^4 evolution in global star formation since z~1. To reconcile the density
with similar measurements made by surveys targeting H-alpha may require
substantial extinction correction.Comment: 16 preprint pages including 5 figures; accepted for publication in
Ap
A quest for frustration driven distortion in Y2Mo2O7
We investigated the nature of the freezing in the geometrically frustrated
Heisenberg spin-glass Y2Mo2O7 by measuring the temperature dependence of the
static internal magnetic field distribution above the spin-glass temperature,
Tg, using the muSR technique. The evolution of the field distribution cannot be
explained by changes in the spin susceptibility alone and suggests a lattice
deformation. This possibility is addressed by numerical simulations of the
Heisenberg Hamiltonian with magneto-elastic coupling at T>0.Comment: 5 pages 4 figures. Accepted for publication in PR
From Dish to Bedside: Lessons Learned While Translating Findings from a Stem Cell Model of Disease to a Clinical Trial
While iPSCs have created unprecedented opportunities for drug discovery, there remains uncertainty concerning the path to the clinic for candidate therapeutics discovered with their use. Here we share lessons that we learned, and believe are generalizable to similar efforts, while taking a discovery made using iPSCs into a clinical trial
Frustration driven lattice distortion; an NMR investigation of Y2Mo2O7
We have investigated the 89Y NMR spectrum and spin lattice relaxation, T1, in
the magnetically frustrated pyrochlore Y2Mo2O7. We find that upon cooling the
spectrum shifts, and broadens asymmetrically. A detailed examination of the low
T spectrum reveals that it is constructed from multiple peaks, each shifted by
a different amount. We argue that this spectrum is due to discrete lattice
distortions, and speculate that these distortions relieve the frustration and
reduce the system's energy.Comment: To be published in Phys. Rev. Let
Spectroscopic Confirmation of Two Massive Red-Sequence-Selected Galaxy Clusters at z ~ 1.2 in the SpARCS-North Cluster Survey
The Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) is a deep z'-band imaging survey covering the Spitzer Wide-Area Infrared Extragalactic Survey (SWIRE) Legacy fields designed to create the first large homogeneously selected sample of massive clusters at z > 1 using an infrared adaptation of the cluster red-sequence method. We present an overview of the northern component of the survey which has been observed with Canada-France-Hawaii Telescope (CFHT)/MegaCam and covers 28.3 deg^2. The southern component of the survey was observed with Cerro Tololo Inter-American Observatory (CTIO)/MOSAICII, covers 13.6 deg^2, and is summarized in a companion paper by Wilson et al. We also present spectroscopic confirmation of two rich cluster candidates at z ~ 1.2. Based on Nod-and-Shuffle spectroscopy from GMOS-N on Gemini, there are 17 and 28 confirmed cluster members in SpARCS J163435+402151 and SpARCS J163852+403843 which have spectroscopic redshifts of 1.1798 and 1.1963, respectively. The clusters have velocity dispersions of 490 ± 140 km s^(â1) and 650 ± 160 km s^(â1), respectively, which imply masses (M_(200)) of (1.0 ± 0.9) Ă 10^(14) M_â and (2.4 ± 1.8) Ă 10^(14) M_â. Confirmation of these candidates as bonafide massive clusters demonstrates that two-filter imaging is an effective, yet observationally efficient, method for selecting clusters at z > 1
Spectroscopic Confirmation of a Massive Red-Sequence-Selected Galaxy Cluster at z = 1.34 in the SpARCS-South Cluster Survey
The Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) is a
z'-passband imaging survey, consisting of deep (z' ~ 24 AB) observations made
from both hemispheres using the CFHT 3.6m and CTIO 4m telescopes. The survey
was designed with the primary aim of detecting galaxy clusters at z >~ 1. In
tandem with pre-existing 3.6um observations from the Spitzer Space Telescope
SWIRE Legacy Survey, SpARCS detects clusters using an infrared adaptation of
the two-filter red-sequence cluster technique. The total effective area of the
SpARCS cluster survey is 41.9 deg^2. In this paper, we provide an overview of
the 13.6 deg^2 Southern CTIO/MOSAICII observations. The 28.3 deg^2 Northern
CFHT/MegaCam observations are summarized in a companion paper by Muzzin et al.
(2008). In this paper, we also report spectroscopic confirmation of SpARCS
J003550-431224, a very rich galaxy cluster at z = 1.335, discovered in the
ELAIS-S1 field. To date, this is the highest spectroscopically confirmed
redshift for a galaxy cluster discovered using the red-sequence technique.
Based on nine confirmed members, SpARCS J003550-431224 has a preliminary
velocity dispersion of 1050 +/- 230 km/s. With its proven capability for
efficient cluster detection, SpARCS is a demonstration that we have entered an
era of large, homogeneously-selected z > 1 cluster surveys.Comment: 10 pages, 6 Figures, Submitted to the Ap
Measurement of Cosmic Shear with the Space Telescope Imaging Spectrograph
Weak lensing by large-scale structure allows a direct measure of the dark
matter distribution. We have used parallel images taken with the Space
Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope to measure
weak lensing, or cosmic shear. We measure the shapes of 26036 galaxies in 1292
STIS fields and measure the shear variance at a scale of 0.51 arcminutes. The
charge transfer efficiency (CTE) of STIS has degraded over time and introduces
a spurious ellipticity into galaxy shapes during the readout process. We
correct for this effect as a function of signal to noise and CCD position. We
further show that the detected cosmic shear signal is nearly constant in time
over the approximately four years of observation. We detect cosmic shear at the
5.1 sigma level, and our measurement of the shear variance is consistent with
theoretical predictions in a LambdaCDM universe. This provides a measure of the
normalization of the mass power spectrum sigma_8=(1.02 +- 0.16)
(0.3/Omega_m)^{0.46} (0.21/Gamma)^{0.18}$. The one-sigma error includes noise,
cosmic variance, systematics and the redshift uncertainty of the source
galaxies. This is consistent with previous cosmic shear measurements, but tends
to favor those with a high value of sigma_8. It is also consistent with the
recent determination of sigma_8 from the Wilkinson Microwave Anisotropy Probe
(WMAP) experiment.Comment: 9 pages, 5 figure, 1 table, Accepted to Ap
Uranium(III) coordination chemistry and oxidation in a flexible small-cavity macrocycle
U(III) complexes of the conformationally flexible, small-cavity macrocycle trans-calix[2]benzene[2]pyrrolide (L)2â, [U(L)X] (X = O-2,6-tBu2C6H3, N(SiMe3)2), have been synthesized from [U(L)BH4] and structurally characterized. These complexes show binding of the U(III) center in the bis(arene) pocket of the macrocycle, which flexes to accommodate the increase in the steric bulk of X, resulting in long UâX bonds to the ancillary ligands. Oxidation to the cationic U(IV) complex [U(L)X][B(C6F5)4] (X = BH4) results in ligand rearrangement to bind the smaller, harder cation in the bis(pyrrolide) pocket, in a conformation that has not been previously observed for (L)2â, with X located between the two ligand arene rings
Emission Line Galaxies in the STIS Parallel Survey I: Observations and Data Analysis
In the first three years of operation STIS obtained slitless spectra of
approximately 2500 fields in parallel to prime HST observations as part of the
STIS Parallel Survey (SPS). The archive contains almost 300 fields at high
galactic latitude (|b|>30) with spectroscopic exposure times greater than 3000
seconds. This sample contains 220 fields (excluding special regions and
requiring a consistent grating angle) observed between 6 June 1997 and 21
September 2000, with a total survey area of about 160 square arcminutes. At
this depth, the SPS detects an average of one emission line galaxy per three
fields. We present the analysis of these data, and the identification of 131
low to intermediate redshift galaxies detected by optical emission lines. The
sample contains 78 objects with emission lines that we infer to be redshifted
[OII]3727 emission at 0.43<z<1.7. The comoving number density of these objects
is comparable to that of H-alpha emitting galaxies in the NICMOS parallel
observations. One quasar and three probable Seyfert galaxies are detected. Many
of the emission-line objects show morphologies suggestive of mergers or
interactions. The reduced data are available upon request from the authors.Comment: 58 preprint pages, including 26 figures; accepted for publication in
ApJ
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