ABSTRACT
Early JWST spectroscopic campaigns have confirmed the presence of strong O iii line-emitting galaxies in the redshift interval 7 < z < 9. Although deduced earlier from Spitzer photometry as ...an indicative of young stellar populations, some studies suggested the relevant photometric excesses attributed to O iii emission could, in part, be due to Balmer breaks arising from older stars. We demonstrate that this is likely the case by exploiting medium-band near-infrared JWST photometry in the Hubble Ultra Deep Field. We locate a sample of six galaxies with redshifts 8.2<z <8.6 for which the relevant medium-band filters enables us to separate the contributions of O iii emission and a Balmer break, thereby breaking earlier degeneracies of interpretation. The technique is particularly valuable since it provides photometric redshifts whose precision, $\Delta \, z\simeq \, \pm 0.08$, approaches that of spectroscopic campaigns now underway with JWST. Although some sources are young, a third of our sample have prominent Balmer breaks consistent with stellar ages of ≥150 Myr. Our results indicate that even intense O iii emitters experienced episodes of earlier star formation to z ∼10 and beyond, as is now being independently deduced from direct detection of the progenitors of similar systems.
ABSTRACT
We study the ionizing photon production efficiency at the end of the Epoch of Reionization (z ∼ 5.4 − 6.6) for a sample of 30 Ly α emitters. This is a crucial quantity to infer the ionizing ...photon budget of the universe. These objects were selected to have reliable spectroscopic redshifts, assigned based on the profile of their Ly α emission line, detected in the MUSE deep fields. We exploit medium-band observations from the JWST Extragalactic Medium-band Survey (JEMS) to find the flux excess corresponding to the redshifted Hα emission line. We estimate the ultraviolet (UV) luminosity by fitting the full JEMS photometry, along with several HST photometric points, with Prospector. We find a median UV continuum slope of $\beta = -2.09^{+0.23}_{-0.21}$, indicating young stellar populations with little-to-no dust attenuation. Supported by this, we derive ξion,0 with no dust attenuation and find a median value of log$\frac{\xi _{ion,0}}{\text{Hz erg}^{-1}} = 25.44^{+0.21}_{-0.15}$. If we perform dust attenuation corrections and assume a Calzetti attenuation law, our values are lowered by ∼0.1 dex. Our results suggest Ly α emitters at the Epoch of Reionization have slightly enhanced ξion,0 compared to previous estimations from literature, in particular, when compared to the non-Ly α emitting population. This initial study provides a promising outlook on the characterization of ionizing photon production in the early universe. In the future, a more extensive study will be performed on the entire data set provided by the JWST Advanced Deep Extragalactic Survey (JADES). Thus, for the first time, allowing us to place constraints on the wider galaxy populations driving reionization.
Abstract
Although low-mass star-forming galaxies are the leading candidates of the reionization process, we cannot conclusively rule out high-mass star-forming galaxies as candidates. While most ...simulations indicate the former is the best candidate, some models suggest that at
z
≥ 6 massive, UV-bright galaxies – “oligarchs” – account for at least 80% of the ionizing budget. To test this hypothesis, we target massive (
log
10
(
M
⋆
M
⊙
)
>
10
), UV-bright (
M
UV
∼ −22) Ly
α
emitters at
z
> 7 in archival data, observed with similar resolution spectrographs (Very Large Telescope/X-shooter and Keck/MOSFIRE). To increase the reliability of our conclusions, we stack all spectra and obtain a deep-stacked spectrum of 24.75 hr. The stacked Ly
α
profile displays a clear asymmetric red peak and an absence of a blue peak. We additionally estimate the intrinsic stacked Ly
α
profile of our targets by correcting for intergalactic medium (IGM) transmission using a range of neutral hydrogen fractions, finding no significant change in the profile. We measure a velocity offset
V
red
> 300 km s
−1
and an asymmetry in our red peak
A
∼ 3. Using various models and estimators, such as the peak separation, the asymmetry of the red peak, the ratio between Ly
α
and H
β,
and the
β
slope, we conclude that the escape fraction in these three UV-bright, massive (∼10
10
M
⊙
),
z
≥ 7 galaxies is
f
esc
(LyC) ≤ 10%.
Information content of BP/RP spectra in Gaia DR3 Witten, Callum E C; Aguado, David S; Sanders, Jason L ...
Monthly notices of the Royal Astronomical Society,
09/2022, Letnik:
516, Številka:
3
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
Gaia Data Release 3 has provided the astronomical community with the largest stellar spectroscopic survey to date (> 220 million sources). The low resolution (R∼50) blue photometer (BP) and ...red photometer (RP) spectra will allow for the estimation of stellar atmospheric parameters such as effective temperature, surface gravity, and metallicity. We create mock Gaia BP/RP spectra and use Fisher information matrices to probe the resolution limit of stellar parameter measurements using BP/RP spectra. The best-case scenario uncertainties that this analysis provides are then used to produce a mock-observed stellar population in order to evaluate the false positive rate (FPR) of identifying extremely metal-poor stars. We conclude that the community will be able to confidently identify metal-poor stars at magnitudes brighter than G = 16 using BP/RP spectra. At fainter magnitudes true detections will start to be overwhelmed by false positives. When adopting the commonly-used G < 14 limit for metal-poor star searches, we find a FPR for the low-metallicity regimes Fe/H < -2, -2.5, and -3 of just 14 ${{\ \rm per\ cent}}$, 33 ${{\ \rm per\ cent}}$, and 56 ${{\ \rm per\ cent}}$ respectively, offering the potential for significant improvements on previous targeting campaigns. Additionally, we explore the chemical sensitivity obtainable directly from BP/RP spectra for carbon and α-elements. We find an absolute carbon abundance uncertainty of σA(C) < 1 dex for carbon-enriched metal-poor (CEMP) stars, indicating the potential to identify a CEMP stellar population for follow-up confirmation with higher resolution spectroscopy. Finally, we find that large uncertainties in α-element abundance measurements using BP/RP spectra means that efficiently obtaining these abundances will be challenging.
Preterm birth is the leading cause of neonatal mortality, and is frequently associated with intra-amniotic infection hypothesized to arise from bacterial ascension across a dysfunctional cervical ...mucus plug. To study this dysfunction, we assessed the permeability of cervical mucus from non-pregnant ovulating (n = 20) and high- (n = 9) and low-risk (n = 16) pregnant women to probes of varying sizes and surface chemistries. We found that the motion of negatively charged, carboxylated microspheres in mucus from pregnant patients was significantly restricted compared to ovulating patients, but not significantly different between high- and low-risk pregnant women. In contrast, charged peptide probes small enough to avoid steric interactions, but sensitive to the biochemical modifications of mucus components exhibited significantly different transport profiles through mucus from high- and low-risk patients. Thus, although both microstructural rearrangements of the components of mucus as well as biochemical modifications to their adhesiveness may alter the overall permeability of the cervical mucus plug, our findings suggest that the latter mechanism plays a dominant role in the impairment of the function of this barrier during preterm birth. We expect that these probes may be readily adapted to study the mechanisms underlying disease progression on all mucosal epithelia, including those in the mouth, lungs, and gut.
Leiomyosarcoma (LMS) is a soft tissue tumor with a significant degree of morphologic and molecular heterogeneity. We used integrative molecular profiling to discover and characterize molecular ...subtypes of LMS. Gene expression profiling was performed on 51 LMS samples. Unsupervised clustering showed three reproducible LMS clusters. Array comparative genomic hybridization (aCGH) was performed on 20 LMS samples and showed that the molecular subtypes defined by gene expression showed distinct genomic changes. Tumors from the 'muscle-enriched' cluster showed significantly increased copy number changes (P=0.04). A majority of the muscle-enriched cases showed loss at 16q24, which contains Fanconi anemia, complementation group A, known to have an important role in DNA repair, and loss at 1p36, which contains PRDM16, of which loss promotes muscle differentiation. Immunohistochemistry (IHC) was performed on LMS tissue microarrays (n=377) for five markers with high levels of messenger RNA in the muscle-enriched cluster (ACTG2, CASQ2, SLMAP, CFL2 and MYLK) and showed significantly correlated expression of the five proteins (all pairwise P<0.005). Expression of the five markers was associated with improved disease-specific survival in a multivariate Cox regression analysis (P<0.04). In this analysis that combined gene expression profiling, aCGH and IHC, we characterized distinct molecular LMS subtypes, provided insight into their pathogenesis, and identified prognostic biomarkers.
Early JWST spectroscopic campaigns have confirmed the presence of strong O III line-emitting galaxies in the redshift interval \(7<z<9\). Although deduced earlier from Spitzer photometry as ...indicative of young stellar populations, some studies suggested the relevant photometric excesses attributed to O III emission could, in part, be due to Balmer breaks arising from older stars. We demonstrate that this is likely the case by exploiting medium-band near-infrared JWST photometry in the Hubble Ultra Deep Field. We locate a sample of 6 galaxies with redshifts 8.2\(<z<\)8.6 for which the relevant medium-band filters enables us to separate the contributions of O III emission and a Balmer break, thereby breaking earlier degeneracies of interpretation. The technique is particularly valuable since it provides photometric redshifts whose precision, \(\Delta\,z\simeq\,\pm0.08\), approaches that of spectroscopic campaigns now underway with JWST. Although some sources are young, a third of our sample have prominent Balmer breaks consistent with stellar ages of \(\geq\)150 Myr. Our results indicate that even intense O III emitters experienced episodes of earlier star formation to \(z\sim\)10 and beyond, as is now being independently deduced from direct detection of the progenitors of similar systems.
A general measure of the rate of senescence is the acceleration of mortality rate, represented here by the time required for the mortality rate to double (MRD). Rhesus monkeys have an MRD close to ...that of humans, about 8 years; their shorter life-span results mainly from higher mortality at all ages. In contrast, some groups with short life-spans (rodents and galliform birds) have shorter MRDs and faster senescence. On the basis of the Gompertz mortality rate model, one may estimate the MRD from the maximum life-span (t$_{max}$) and the overall population mortality rate. Such calculations show that certain birds have MRDs that are as long as that of humans. These results show that high overall mortality rates or small body sizes do not preclude slow rates of senescence.
ABSTRACT
We use deep imaging from the JWST Advanced Deep Extragalactic Survey (JADES) to study the evolution of the ionizing photon production efficiency, ξion. We estimate ξion for a sample of 677 ...galaxies at z ∼ 4–9 using NIRCam (Near-Infrared Camera) photometry. Specifically, combinations of the medium and wide bands F335M–F356W and F410M–F444W to constrain emission lines that trace ξion: Hα and O iii. Additionally, we use the spectral energy distribution fitting code prospector to fit all available photometry and infer galaxy properties. The flux measurements obtained via photometry are consistent with FRESCO (First Reionisation Epoch Spectroscopic Complete Survey) and NIRSpec-derived fluxes. Moreover, the emission-line-inferred measurements are consistent with the prospector estimates. We also confirm the observed ξion trend with redshift and MUV, and find: log ξion(z, MUV) = (0.05 ± 0.02)z + (0.11 ± 0.02)MUV + (27.33 ± 0.37). We use prospector to investigate correlations of ξion with other galaxy properties. We see a clear correlation between ξion and burstiness in the star formation history of galaxies, given by the ratio of recent to older star formation, where burstiness is more prevalent at lower stellar masses. We also convolve our ξion relations with luminosity functions from the literature, and constant escape fractions of 10 per cent and 20 per cent, to place constraints on the cosmic ionizing photon budget. By combining our results, we find that if our sample is representative of the faint low-mass galaxy population, galaxies with bursty star formation are efficient enough in producing ionizing photons and could be responsible for the reionization of the Universe.
Reconstruction of the intervalvular fibrosa (IVF) for invasive double-valve infective endocarditis (IE) is a technically challenging operation. This study presents the long-term outcomes of two ...surgical techniques for IVF reconstruction.
From 1988 to 2017, 138 patients with invasive double-valve IE underwent surgical reconstruction of the IVF, along with double-valve replacement (Commando procedure, n = 86) or aortic valve replacement with mitral valve repair (hemi-Commando procedure, n = 52). Mean follow-up was 41 ± 5.9 months.
Reoperation was required in 82% of patients, and 34% underwent emergency surgery. Pathologic features included positive blood cultures (90%), prosthetic valve IE (75%), aortic root abscess (78%), mitral annular abscess (24%), and intracardiac fistula (12%). There were 28 hospital deaths: 21 (24%) in the Commando group and 7 (14%) in the hemi-Commando group (P = .12). Overall survival at 1, 5, and 10 years was 67%, 48%, and 37%, respectively. Coronary artery disease, native valve IE, and causative organism (Staphylococcus aureus, coagulase-negative Staphylococcus, and viridans streptococci) were risk factors for late mortality. Freedom from reoperation at 1, 5, and 8 years was 87%, 74%, and 55%, respectively. Freedom from recurrent IE at 1, 5, and 8 years was 90%, 78%, and 67%, respectively.
Although it is technically demanding, surgery for invasive IE involving IVF, which provides the only chance for cure, can be performed with reasonable clinical outcomes. In cases of IE invading the IVF and limited to the anterior mitral valve leaflet, a hemi-Commando procedure that includes mitral valve repair has improved early outcomes.
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