A New Constraint on the Escape Fraction in Distant Galaxies Using Gamma-ray Burst Afterglow Spectroscopy

We describe a new method to measure the escape fraction fesc of ionizing radiation from distant star-forming galaxies using the afterglow spectra of long-duration gamma-ray bursts (GRBs). Optical spectra of GRB afterglows allow us to evaluate the optical depth of the host ISM, according to the neutral hydrogen column density N(HI) observed along the sightlines toward the star-forming regions where the GRBs are found. Different from previous effort in searching for faint, transmitted Lyman continuum photons, our method is not subject to background subtraction uncertainties and does not require prior knowledge of either the spectral shape of the host galaxy population or the IGM Lya forest absorption along these GRB sightlines. Because most GRBs occur in sub-L_* galaxies, our study also offers the first constraint on fesc for distant low-mass galaxies that dominate the cosmic luminosity density. We have compiled a sample of 27 GRBs at redshift z>2 for which the underlying N(HI) in the host ISM are known. These GRBs together offer a statistical sampling of the integrated optical depth to ionizing photons along random sightlines from star-forming regions in the host galaxies, and allow us to estimate the mean escape fraction averaged over different viewing angles. We find =0.02\pm 0.02 and place a 95% c.l. upper limit <= 0.075 for these hosts. We discuss possible biases of our approach and implications of the result. Finally, we propose to extend this technique for measuring at z~0.2 using spectra of core-collapse supernovae.Comment: Five journal pages, including one figure; ApJL in pres

Testing the E_p,i - L_p,iso - T_0.45 correlation on a BeppoSAX and Swift sample of gamma-ray bursts

Using a sample of 14 BeppoSAX and 74 Swift GRBs with measured redshift we tested the correlation between the intrinsic peak energy of the time-integrated spectrum, E_p,i, the isotropic-equivalent peak luminosity, L_p,iso, and the duration of the most intense parts of the GRB computed as T_0.45 ("Firmani correlation"). For 41 out of 88 GRBs we could estimate all of the three required properties. Apart from 980425, which appears to be a definite outlier and notoriously peculiar in many respects, we used 40 GRBs to fit the correlation with the maximum likelihood method discussed by D'Agostini, suitable to account for the extrinsic scatter in addition to the intrinsic uncertainties affecting every single GRB. We confirm the correlation. However, unlike the results by Firmani et al., we found that the correlation does have a logarithmic scatter comparable with that of the E_p,i-E_iso ("Amati") correlation. We also find that the slope of the product L_p,iso T_0.45 is equal to ~0.5, which is consistent with the hypothesis that the E_p,i-L_p,iso-T_0.45 correlation is equivalent to the E_p,i-E_iso correlation (slope ~0.5). We conclude that, based on presently available data, there is no clear evidence that the E_p,i-L_p,iso-T_0.45 correlation is different (both in terms of slope and dispersion) from the E_p,i-E_iso correlation.Comment: 9 pages, 4 figures, revised version submitted to MNRA

Evaluating Importation of Aquatic Ornamental Species for Biosecurity Purposes

The aquatic ornamental species (AOS) trade is a significant pathway for the introduction and establishment of non-indigenous species into aquatic environments. The likelihood of such occurrences is expected to increase worldwide as industry growth continues and warmer conditions emerge under future climate scenarios. This study used recent (2015 – 2019) New Zealand importation data to determine the composition, diversity, abundance, and arrival frequency of AOS. Our analysis revealed that ca. 300,000 aquatic ornamental individuals are imported annually to New Zealand, with freshwater fish comprising 98% of import quantities. Despite the relatively small market size, the estimated AOS diversity of 865 taxa (89 and 9.5% identified to species and genus level, respectively) is comparable to larger markets with ∼60% of taxa being of marine origin. Species (n = 20) for further investigation were prioritized based on quantity and frequency of import. These prioritized AOS were exclusively tropical and subtropical freshwater fish and align with the most frequently imported AOS globally, including the top three: neon tetra (Paracheirodon innesi), guppy (Poecilia reticulata), and tiger barb (Puntigrus tetrazona). Species distribution modeling of the 20 prioritized AOS predicted that 13 species are suitable for New Zealand’s current climate conditions, most notably sucker-belly loach (Pseudogastromyzon myersi), white cloud mountain minnow (Tanichthys albonubes), and golden otocinclus (Macrotocinclus affinis). Potential changes in habitat suitability were predicted under future climate scenarios, with largest increases (29%) for Po. reticulata. The described approach provides an adaptable framework to assess establishment likelihood of imported AOS to inform regulatory decision making

The obscured hyper-energetic GRB 120624B hosted by a luminous compact galaxy at z = 2.20

Gamma-ray bursts are the most luminous explosions that we can witness in the Universe. Studying the most extreme cases of these phenomena allows us to constrain the limits for the progenitor models. In this Letter, we study the prompt emission, afterglow, and host galaxy of GRB 120624B, one of the brightest GRBs detected by Fermi, to derive the energetics of the event and characterise the host galaxy in which it was produced. Following the high-energy detection we conducted a multi-wavelength follow-up campaign, including near-infrared imaging from HAWKI/VLT, optical from OSIRIS/GTC, X-ray observations from the Chandra X-ray Observatory and at sub-millimetre/millimetre wavelengths from SMA. Optical/nIR spectroscopy was performed with X-shooter/VLT. We detect the X-ray and nIR afterglow of the burst and determine a redshift of z = 2.1974 +/- 0.0002 through the identification of emission lines of [OII], [OIII] and H-alpha from the host galaxy of the GRB. This implies an energy release of Eiso = (3.0+/-0.2)x10^54 erg, amongst the most luminous ever detected. The observations of the afterglow indicate high obscuration with AV > 1.5. The host galaxy is compact, with R1/2 < 1.6 kpc, but luminous, at L ~ 1.5 L* and has a star formation rate of 91 +/- 6 Msol/yr as derived from H-alpha. As other highly obscured GRBs, GRB 120624B is hosted by a luminous galaxy, which we also proof to be compact, with a very intense star formation. It is one of the most luminous host galaxies associated with a GRB, showing that the host galaxies of long GRBs are not always blue dwarf galaxies, as previously thought.Comment: 6 pages, 4 figures, 4 tables; accepted for publication in A&

A simple method for determination of plasma and urinary biotin

Measurement of biotin in plasma and urine has been stimulated by recent descriptions of inborn errors of biotin metabolism and by newly recognized causes of biotin deficiency. Biotin determination in physiologic fluids to document these conditions has been hindered by lack of a widely useable assay. This paper presents a method which employs tritium-labelled biotin, avidin, and nitrocellulose filters to measure urinary and plasma biotin in a rapid and simple manner.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23871/1/0000110.pd

Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission line galaxies

Superluminous supernovae (SLSNe) are very bright explosions that were only discovered recently and that show a preference for occurring in faint dwarf galaxies. Understanding why stellar evolution yields different types of stellar explosions in these environments is fundamental in order to both uncover the elusive progenitors of SLSNe and to study star formation in dwarf galaxies. In this paper, we present the first results of our project to study SUperluminous Supernova Host galaxIES, focusing on the sample for which we have obtained spectroscopy. We show that SLSNe-I and SLSNe-R (hydrogen-poor) often (~50% in our sample) occur in a class of galaxies that is known as Extreme Emission Line Galaxies (EELGs). The probability of this happening by chance is negligible and we therefore conclude that the extreme environmental conditions and the SLSN phenomenon are related. In contrast, SLSNe-II (hydrogen-rich) occur in more massive, more metal-rich galaxies with softer radiation fields. Therefore, if SLSNe-II constitute a uniform class, their progenitor systems are likely different from those of H-poor SLSNe. Gamma-ray bursts (GRBs) are, on average, not found in as extreme environments as H-poor SLSNe. We propose that H-poor SLSNe result from the very first stars exploding in a starburst, even earlier than GRBs. This might indicate a bottom-light initial mass function in these systems. SLSNe present a novel method of selecting candidate EELGs independent of their luminosity.Comment: Published version, matches proofs. Accepted 2015 February 13. 23 pages, 8 figures, 4 tables. Minor changes with respect to previous versio

Discovery of the broad-lined Type Ic SN 2013cq associated with the very energetic GRB 130427A

Long-duration gamma-ray bursts (GRBs) at z < 1 are in most cases found to be accompanied by bright, broad-lined Type Ic supernovae (SNe Ic-BL). The highest-energy GRBs are mostly located at higher redshifts, where the associated SNe are hard to detect observationally. Here we present early and late observations of the optical counterpart of the very energetic GRB 130427A. Despite its moderate redshift z = 0.3399+/-0.0002, GRB 130427A is at the high end of the GRB energy distribution, with an isotropic-equivalent energy release of Eiso ~ 9.6x10^53 erg, more than an order of magnitude more energetic than other GRBs with spectroscopically confirmed SNe. In our dense photometric monitoring, we detect excess flux in the host-subtracted r-band light curve, consistent with what expected from an emerging SN, ~0.2 mag fainter than the prototypical SN 1998bw. A spectrum obtained around the time of the SN peak (16.7 days after the GRB) reveals broad undulations typical of SNe Ic-BL, confirming the presence of a SN, designated SN 2013cq. The spectral shape and early peak time are similar to those of the high expansion velocity SN 2010bh associated with GRB 100316D. Our findings demonstrate that high-energy long-duration GRBs, commonly detected at high redshift, can also be associated with SNe Ic-BL, pointing to a common progenitor mechanism.Comment: 12 pages, 4 figures, 1 table, accepted for publication in Ap

Maternal and Cord β-Carotene levels and Their Association with Newborn Hearing Screen Results

Background. β-carotene is one of the few carotenoids that can be endogenously converted to vitamin A, a nutrient essential for inner ear development. While previous studies have identified a protective effect of carotenoids on hearing in adults, the impact of β-carotene on hearing outcomes in neonates is not well understood. The purpose of this study is to investigate the relationship between maternal β-carotene intake, maternal plasma, and umbilical cord plasma β-carotene levels and abnormal Newborn Hearing Screen (NHS) results. Significance of Problem. The prenatal period is critical for auditory development; thus, effectors of auditory development may significantly impact long-term hearing ability. Because maternal nutrition is modifiable, an improved understanding of the relationship between β-carotene levels and hearing outcomes may be relevant for prenatal care recommendations. Hypothesis. We hypothesize that higher levels of β-carotene will be associated with decreased risk of abnormal NHS results. Experimental Design. An IRB-approved study enrolled mother-infant pairs (n=541) at the time of delivery. β-carotene plasma levels were analyzed with HPLC. Maternal intake of β-carotene over the past year was quantified using the validated Harvard Food Frequency Questionnaire. NHS results were obtained from the Electronic Medical Record. Statistical analysis was done using the Mann-Whitney U and logistic regression tests, with p\u3c0.05 considered statistically significant. Results. Of the 541 participants, 8.5% of infants had abnormal NHS results. Higher median maternal β-carotene intake was observed in infants who failed their NHS compared to those who passed (5924 vs. 4722 mcg/day, p=0.019). Higher median maternal plasma levels of both trans- (206 vs. 149 mcg/L, p=0.021) and cis-β-carotene (15.9 vs. 11.2 mcg/L, p=0.015) were observed in infants who failed their NHS. Higher median cord plasma trans β-carotene was observed in infants who failed their NHS (15.5 vs. 8.0 mcg/L, p=0.04). Associations between failed NHS and log-transformed β-carotene intake and serum levels remained in a logistic regression model after adjustment for NICU admission, race/ethnicity, smoking status, maternal age, corrected gestational age, infant sex, and log transformed maternal caloric intake. Conclusion. The observed relationship between higher β-carotene levels and abnormal NHS was unexpected. While other studies suggest both deficient and excessive levels of vitamin A can impact inner ear development, β-carotene levels in our study were not exceptionally high. One possible explanation is that higher maternal β-carotene levels may be indicative of impaired transfer of β-carotene to the fetus. Further study is warranted to better understand the relationship between β-carotene and NHS results.https://digitalcommons.unmc.edu/chri_forum/1063/thumbnail.jp

Looking Into the Fireball: ROTSE-III and Swift Observations of Early GRB Afterglows

We report on a complete set of early optical afterglows of gamma-ray bursts (GRBs) obtained with the ROTSE-III telescope network from March 2005 through June 2007. This set is comprised of 12 afterglows with early optical and Swift/XRT observations, with a median ROTSE-III response time of 45 s after the start of gamma-ray emission (8 s after the GCN notice time). These afterglows span four orders of magnitude in optical luminosity, and the contemporaneous X-ray detections allow multi-wavelength spectral analysis. Excluding X-ray flares, the broadband synchrotron spectra show that the optical and X-ray emission originate in a common region, consistent with predictions of the external forward shock in the fireball model. However, the fireball model is inadequate to predict the temporal decay indices of the early afterglows, even after accounting for possible long-duration continuous energy injection. We find that the optical afterglow is a clean tracer of the forward shock, and we use the peak time of the forward shock to estimate the initial bulk Lorentz factor of the GRB outflow, and find 100<Gamma_0<1000, consistent with expectations.Comment: 31 pages, 5 figures, submitted to Ap

Hypertensive Disorders of Pregnancy are Associated with Differences in Maternal Serum Concentrations of Arachidonic Acid Metabolites

Background: Hypertensive disorders of pregnancy (HDP), including gestational hypertension, chronic hypertension, and preeclampsia, are a significant cause of maternal morbidity and mortality in the United States. Dysregulation of inflammation is thought to play a role in the development of HDP. Maternal diet has the potential to alter the risk of HDP by modulating inflammation. Arachidonic acid (AA) is a dietary polyunsaturated fatty acid which can be metabolized into both pro- and anti-inflammatory bioactive metabolites. Significance of Problem: HDP places women and their infants at risk for potentially severe pregnancy complications including placental abruption, embolism, end-organ failure, or death. Few treatments are currently available for HDP. Question: The objective of this study was to describe how maternal AA metabolites serum concentrations are associated with diagnosis of HDP. Experimental Design: Serum was collected from 121 pregnant women admitted to the labor and delivery unit at Nebraska Medical Center. Women were divided into normotensive or hypertensive groups based on definitions from the American College of Obstetricians and Gynecologists (ACOG). Concentrations of AA metabolites were measured using liquid chromatography-mass spectrometry. Descriptive statistics were generated, and Mann-Whitney U tests were used to compare metabolite concentrations between groups. Results: Women with HDP had significant higher serum concentrations of PGF2α (p=0.02) and 15-HETE (p=0.04), two metabolites with known inflammatory and vasoconstrictive properties. Women with HDP had significantly lower serum concentrations of 8(9)-DiHET (p=0.04), 11(12)-DiHET (p=0.04), and 14(15)-DiHET (p=0.001), which are all associated with vasodilation. Unexpectantly, hypertensive mothers also had lower serum concentrations of 5-HETE (p=0.02), which is associated with vasoconstriction. Conclusion: Overall, our study reveals that mothers diagnosed with HDP had significantly higher serum concentrations of vasoconstrictive AA metabolites and significantly lower serum concentrations of vasodilating AA metabolites compared to normotensive mothers. Future directions include analyzing differences in maternal metabolite profile separately for mothers with chronic hypertension, gestational hypertension, and preeclampsia compared to normotensive mothers. Results from these analyses will guide nutritional recommendations for women at risk of developing HDP.https://digitalcommons.unmc.edu/chri_forum/1062/thumbnail.jp