Abstract
Although neural-network-based emulators enable efficient parameter estimation in 21 cm cosmology, the accuracy of such constraints is poorly understood. We employ nested sampling to fit mock ...data of the global 21 cm signal and high-
z
galaxy ultraviolet luminosity function (UVLF) and compare for the first time the emulated posteriors obtained using the global signal emulator
globalemu
to the “true” posteriors obtained using the full model on which the emulator is trained using
ARES
. Of the eight model parameters we employ, four control the star formation efficiency (SFE) and thus can be constrained by UVLF data, while the remaining four control UV and X-ray photon production and the minimum virial temperature of star-forming halos (
T
min
) and thus are uniquely probed by reionization and 21 cm measurements. For noise levels of 50 and 250 mK in the 21 cm data being jointly fit, the emulated and “true” posteriors are consistent to within 1
σ
. However, at lower noise levels of 10 and 25 mK,
globalemu
overpredicts
T
min
and underpredicts
γ
lo
, an SFE parameter, by ≈3
σ
–4
σ
, while the “true”
ARES
posteriors capture their fiducial values within 1
σ
. We find that jointly fitting the mock UVLF and 21 cm data significantly improves constraints on the SFE parameters by breaking degeneracies in the
ARES
parameter space. Our results demonstrate the astrophysical constraints that can be expected for global 21 cm experiments for a range of noise levels from pessimistic to optimistic, as well as the potential for probing redshift evolution of SFE parameters by including UVLF data.
Abstract
Accurate detection of the cosmological 21 cm global signal requires galactic foreground models that can remove power over 10
6
. Although foreground and global signal models unavoidably ...exhibit overlap in their vector spaces inducing bias error in the extracted signal, a second source of bias and error arises from inadequate foreground models, i.e., models that cannot fit spectra down to the noise level of the signal. We therefore test the level to which seven commonly employed foreground models—including nonlinear and linear forward models, polynomials, and maximally smooth polynomials—fit realistic simulated mock foreground spectra, as well as their dependence upon model inputs. The mock spectra are synthesized for an EDGES-like experiment and we compare all models’ goodness of fit and preference using a Kolmogorov–Smirnov (K-S) test of the noise-normalized residuals in order to compare models with differing, and sometimes indeterminable, degrees of freedom. For a single local sidereal time (LST) bin spectrum and
p
-value threshold of
p
= 0.05, the nonlinear forward model with four parameters is preferred (
p
= 0.99), while the linear forward model fits well with six to seven parameters (
p
= 0.94, 0.97, respectively). The polynomials and maximally smooth polynomials, like those employed by the EDGES and SARAS3 experiments, cannot produce good fits with five parameters for the experimental simulations in this work (
p
< 10
−6
). However, we find that polynomials with six parameters pass the K-S test (
p
= 0.4), although a nine-parameter fit produces the highest
p
-value (
p
∼ 0.67). When fitting multiple LST bins simultaneously, we find that the linear forward model outperforms (a higher
p
-value) the nonlinear model for 2, 5, and 10 LST bins. Importantly, the K-S test consistently identifies best-fit
and
preferred models.
Some formation scenarios that have been put forward to explain multiple populations within globular clusters (GCs) require that the young massive cluster have large reservoirs of cold gas within ...them, which is necessary to form future generations of stars. In this paper, we use deep observations taken with Atacama Large Millimeter/submillimeter Array (ALMA) to assess the amount of molecular gas within three young (50–200 Myr) massive (∼106 M⊙) clusters in the Antennae galaxies. No significant CO(3–2) emission was found associated with any of the three clusters. We place upper limits for the molecular gas within these clusters of ∼1 × 105 M⊙ (or <9 per cent of the current stellar mass). We briefly review different scenarios that propose multiple episodes of star formation and discuss some of their assumptions and implications. Our results are in tension with the predictions of GC formation scenarios that expect large reservoirs of cool gas within young massive clusters at these ages.
ABSTRACT We present an analysis of the physical conditions in an extreme molecular cloud in the Antennae merging galaxies. This cloud has properties consistant with those required to form a globular ...cluster. We have obtained ALMA CO and 870 m observations of the Antennae galaxy system with ∼0 5 resolution. This cloud stands out in the data with a radius of 24 pc and mass of >5 × 106 M . The cloud appears capable of forming a globular cluster, but the lack of associated thermal radio emission indicates that star formation has not yet altered the environment. The lack of thermal radio emission places the cloud in an early stage of evolution, which we expect to be short-lived ( 1 Myr) and thus rare. Given its mass and kinetic energy, for the cloud to be confined (as its appearance strongly suggests) it must be subject to an external pressure of P/kB 108 K cm−3-10,000 times higher than typical interstellar pressure. This would support theories that high pressures are required to form globular clusters and may explain why extreme environments like the Antennae are preferred environments for generating such objects. Given the cloud temperature of ∼25 K, the internal pressure must be dominated by non-thermal processes, most likely turbulence. We expect the molecular cloud to collapse and begin star formation in 1 Myr.
We present dynamical models of four interacting systems: NGC 5257/8, The Mice, the Antennae, and NGC 2623. The parameter space of the encounters are constrained using the Identikit model-matching and ...visualization tool. Identikit utilizes hybrid N-body and test particle simulations to enable rapid exploration of the parameter space of galaxy mergers. The Identikit-derived matches of these systems are reproduced with self-consistent collisionless simulations which show very similar results. The models generally reproduce the observed morphology and H I kinematics of the tidal tails in these systems with reasonable properties inferred for the progenitor galaxies. The models presented here are the first to appear in the literature for NGC 5257/8 and NGC 2623, and The Mice and the Antennae are compared with previously published models. Based on the assumed mass model and our derived initial conditions, the models indicate that the four systems are currently being viewed 175-260 Myr after first passage and cover a wide range of merger stages. In some instances there are mismatches between the models and the data (e.g., in the length of a tail); these are likely due to our adoption of a single mass model for all galaxies. Despite the use of a single mass model, these results demonstrate the utility of Identikit in constraining the parameter space for galaxy mergers when applied to real data.
The diagnosis of peripartum cardiomyopathy is one of exclusion, made after careful search for an underlying cause. Research in this area is compromised by the reliance of some on clinical criteria ...alone without strict echocardiographic criteria. This article argues for uniform criteria that define peripartum cardiomyopathy, similar to the criteria for idiopathic dilated cardiomyopathy set forth by a National Heart, Lung, and Blood Institute-sponsored workshop and proposes that the new definition include heart failure within the last month of pregnancy or 5 months postpartum; absence of preexisting heart disease; no determinable etiology, the traditional definition; and strict echocardiographic criteria of left ventricular dysfunction: ejection fraction less than 45%, or M-mode fractional shortening less than 30%, or both, and end-diastolic dimension more than 2.7 cm/m2. Mortality from peripartum cardiomyopathy remains high, 25-50%, and a recent review related long-term prognosis to echocardiographic measures of left ventricular chamber dimension and function at diagnosis and recovery. We describe a modified pharmacologic echocardiographic stress test that might be useful in determining left ventricular contractile reserve in women believed to be recovered by routine echocardiographic studies. The test reproduces hemodynamic stress akin to pregnancy, and the data might be useful when counseling women on future childbearing. Women who respond with reduced cardiac reserve might be advised to avoid pregnancy.
Fecal calprotectin and indole were studied in 134 subjects with recurrent CDI before and after FMT. Reduced fecal calprotectin (p = 0.0353, 95% CI 0.1305–0.1439) and rising levels of indole ...(p < 0.0001, 95% CI < 0.0001–0.0003) predicted successful treatment. A ratio of recal calprotectin/indole may provide prognostic value for FMT (p = 0.0004, 95% CI 0.22–0.87).
•Fecal calprotectin (marker of inflammation), and indole (microbiome diversity) were used to predict success in FMT.•Fecal calprotectin before and 7 days after FMT were elevated in RCDI compared to donor stools.•Fecal indole was lower in RCDI compared with donors.•The concentration of fecal calprotectin at 7 days post-FMT, predicts response to FMT.•The ratio of calprotectin/indole should be evaluated for predicting outcome of FMT in RCDI.
In order to characterize and model the beam-weighted foreground for global 21 cm signal experiments, we present a methodology for generating basis eigenvectors that combines analytical and ...observational models of both the galactic spectral index and sky brightness temperature with simulations of beams having various angular and spectral dependencies and pointings. Each combination creates a unique beam-weighted foreground. By generating optimal eigenvectors to fit each foreground model using singular value decomposition (SVD), we examine the effects of varying the components of the beam-weighted foreground. We find that the eigenvectors for modeling an achromatic, isotropic beam-the ideal case-are nearly identical regardless of the unweighted foreground model used, and are practicably indistinguishable from polynomial-based models. When anisotropic, chromatic beams weight the foreground; however, a coupling is introduced between the spatial and spectral structure of the foreground that distorts the eigenvectors away from the polynomial models and induces a dependence of the basis upon the exact features of the beam (chromaticity, pattern, pointing) and foreground (spectral index, sky brightness temperature map). We find that the beam has a greater impact upon the eigenvectors than the foreground models. Any model that does not account for its distortion may produce rms uncertainties on the order of K for six-parameter, single-spectrum fits. If the beam is incorporated directly using SVD and training sets, however, the resultant eigenvectors yield milli-Kelvin level uncertainties. Given a sufficiently detailed description of the sky, our methodology can be applied to any particular experiment with a suitably characterized beam for the purpose of generating accurate beam-weighted foreground models.
We have searched for compact stellar structures within 17 tidal tails in 13 different interacting galaxies using F606W- and F814W-band images from the Wide Field Planetary Camera 2 on the Hubble ...Space Telescope. The sample of tidal tails includes a diverse population of optical properties, merging galaxy mass ratios, H I content, and ages. Combining our tail sample with Knierman et al., we find evidence of star clusters formed in situ with M V < --8.5 and V -- I < 2.0 in 10 of 23 tidal tails; we are able to identify cluster candidates to M V = --6.5 in the closest tails. Three tails offer clear examples of 'beads on a string' star formation morphology in V -- I color maps. Two tails present both tidal dwarf galaxy candidates and cluster candidates. Statistical diagnostics indicate that clusters in tidal tails may be drawn from the same power-law luminosity functions (with logarithmic slopes --2 to --2.5) found in quiescent spiral galaxies and interiors of interacting systems. We find that the tail regions with the largest number of observable clusters are relatively young (250 Myr old) and bright (V 24 mag arcsec--2), probably attributed to the strong bursts of star formation in interacting systems soon after periapse. Otherwise, we find no statistical difference between cluster-rich and cluster-poor tails in terms of many observable characteristics, though this analysis suffers from complex, unresolved gas dynamics and projection effects.
High-resolution two-dimensional (2D) 1H−15N heteronuclear correlation (HETCOR) spectroscopy has been used to characterize the structure and dynamics of 15N-backbone labeled antimicrobial piscidin 1 ...(p1) oriented in “native-like” hydrated lipid bilayers. Piscidin belongs to a family of amphipatic cationic antimicrobial peptides, which are membrane-active and have broad spectrum antimicrobial activity on bacteria. When the 1H chemical shifts are encoded by the 1H−15N dipolar couplings, 2D dipolar-encoded HETCOR (i.e., de-HETCOR) solid-state NMR spectra yield high resolution 1H and 15N chemical shifts as well as 1H−15N heteronuclear dipolar couplings. Several advantages of HETCOR and de-HETCOR techniques that emerge from our investigations could facilitate the atomic-level investigations of structure−function relationships in membrane-active peptides and membrane-bound species. First, the de-HETCOR NMR spectrum of a ten-site 15N-labeled sample of p1 aligned in hydrated lipid bilayers can resolve resonances that are overlapped in the standard HETCOR spectrum. Second, the resolution in de-HETCOR spectra of p1 improves significantly at higher magnetic field due to an enhanced alignment that improves spectrum definition uniformly. Third, the HETCOR spectrum of 15N−K14 p1 oriented in hydrated lipid bilayers displays not only the expected crosscorrelation between the chemical shifts of bonded amide1H and 15N spins but also a cross peak between the 1H chemical shift from bulk water and the 15N chemical shift from the labeled amide nitrogen. This information provides new insights into the intermolecular interactions of an amphipathic antimicrobial peptide optimized to partition at the water-bilayer interface and may have implications at the biological level.
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