The MUSE Hubble Ultra Deep Field Survey Feltre, Anna; Bacon, Roland; Tresse, Laurence ...
Astronomy and astrophysics (Berlin),
09/2018, Letnik:
617
Journal Article
Recenzirano
Odprti dostop
The physical origin of the near-ultraviolet Mg
II
emission remains an underexplored domain, unlike more typical emission lines that are detected in the spectra of star-forming galaxies. We explore ...the nebular and physical properties of a sample of 381 galaxies between 0.70 <
z
< 2.34 drawn from the MUSE
Hubble
Ultra Deep Survey. The spectra of these galaxies show a wide variety of profiles of the Mg
II
λλ
2796, 2803 resonant doublet, from absorption to emission. We present a study on the main drivers for the detection of Mg
II
emission in galaxy spectra. By exploiting photoionization models, we verified that the emission-line ratios observed in galaxies with Mg
II
in emission are consistent with nebular emission from H
II
regions. From a simultaneous analysis of MUSE spectra and ancillary
Hubble
Space Telescope information through spectral energy distribution fitting, we find that galaxies with Mg
II
in emission have lower stellar masses, smaller sizes, bluer spectral slopes, and lower optical depth than those with absorption. This leads us to suggest that Mg
II
emission is a potential tracer of physical conditions that are not merely related to those of the ionized gas. We show that these differences in Mg
II
emission and absorption can be explained in terms of a higher dust and neutral gas content in the interstellar medium (ISM) of galaxies showing Mg
II
in absorption, which confirms the extreme sensitivity of Mg
II
to the presence of the neutral ISM. We conclude with an analogy between the Mg
II
doublet and the Ly
α
line that lies in their resonant nature. Further investigations with current and future facilities, including the
James Webb
Space Telescope, are promising because the detection of Mg
II
emission and its potential connection with Ly
α
could provide new insights into the ISM content in the early Universe.
Abstract
Using an ultra-deep blind survey with the MUSE integral field spectrograph on the European Southern Observatory Very Large Telescope, we obtain spectroscopic redshifts to a depth never ...before explored: galaxies with observed magnitudes
m
AB
≳ 30–32. Specifically, we detect objects via Ly
α
emission at 2.9 <
z
< 6.7 without individual continuum counterparts in areas covered by the deepest optical/near-infrared imaging taken by the
Hubble Space Telescope
, the Hubble Ultra Deep Field. In total, we find 102 such objects in 9 square arcminutes at these redshifts. Detailed stacking analyses confirm the Ly
α
emission as well as the 1216 Å breaks and faint ultraviolet continua (
M
UV
∼ −15). This makes them the faintest spectroscopically confirmed objects at these redshifts, similar to the sources believed to reionize the universe. A simple model for the expected fraction of detected/undetected Ly
α
emitters as a function of luminosity is consistent with these objects being the high-equivalent width tail of the normal Ly
α
-emitter population at these redshifts.
By reducing carbohydrate intake, people with type 1 diabetes may reduce fluctuations in blood glucose, but the evidence in this area is sparse. The aim of this study was to investigate glucose ...metrics during a one-week low-carbohydrate-high-fat (HF) and a low-carbohydrate-high-protein (HP) diet compared with an isocaloric high-carbohydrate (HC) diet. In a randomized, three-period cross-over study, twelve adults with insulin-pump-treated type 1 diabetes followed an HC (energy provided by carbohydrate: 48%, fat: 33%, protein: 19%), HF (19%, 62%, 19%), and an HP (19%, 57%, 24%) diet for one week. Glucose values were obtained during intervention periods using a Dexcom G6 continuous glucose monitoring system. Participant characteristics were: 33% females, median (range) age 50 (22-70) years, diabetes duration 25 (11-52) years, HbA1c 7.3 (5.5-8.3)% (57 (37-67) mmol/mol), and BMI 27.3 (21.3-35.9) kg/m
. Glycemic variability was lower with HF (30.5 ± 6.2%) and HP (30.0 ± 5.5%) compared with HC (34.5 ± 4.1%) (P
= 0.009, P
= 0.003). There was no difference between groups in mean glucose (HF: 8.7 ± 1.1, HP: 8.2 ± 1.0, HC: 8.7 ± 1.0 mmol/L, P
= 0.08). Time > 10.0 mmol/L was lower with HP (22.3 ± 11.8%) compared with HF (29.4 ± 12.1%) and HC (29.5 ± 13.4%) (P
= 0.037, P
= 0.037). In conclusion, a one-week HF and, specifically, an HP diet improved glucose metrics compared with an isocaloric HC diet.
Abstract
Context
Current guidelines for exercise-related glucose management focus on reducing bolus and/or basal insulin doses and considering carbohydrate intake. Yet far less attention has been ...paid to the potential role of other macronutrients alongside carbohydrates on glucose dynamics around exercise.
Objective
To investigate the effects of a low-carbohydrate-high-protein (LCHP) compared with a high-carbohydrate-low-protein (HCLP) pre-exercise meal on the metabolic, hormonal, and physiological responses to exercise in adults with insulin pump–treated type 1 diabetes.
Methods
Fourteen adults (11 women, 3 men) with insulin pump–treated type 1 diabetes (median range HbA1c of 50 43-59 mmol/mol (6.7% 6.1%-7.5%), age of 49 25-65 years, and body mass index of 24.0 19.3-27.1 kg/m2) completed an unblinded, 2-arm, randomized, crossover study. Participants ingested isocaloric meals that were either LCHP (carbohydrate 21%, protein 52%, fat 27%) or HCLP (carbohydrate 52%, protein 21%, fat 27%) 90 minutes prior to undertaking 45 minutes of cycling at moderate intensity. Meal insulin bolus was dosed according to meal carbohydrate content but reduced by 25%. Basal insulin rates were reduced by 35% from meal ingestion to end of exercise.
Results
Around exercise the coefficient of variability was lower during LCHP (LCHP: 14.5 ± 5.3 vs HCLP: 24.9 ± 7.7%, P = .001). Over exercise, LCHP was associated with a lesser drop (LCHP: Δ−1.49 ± 1.89 vs HCLP: Δ−3.78 ± 1.95 mmol/L, P = .001). Mean insulin concentration was 30% lower during exercise for LCHP compared with HCLP (LCHP: 25.5 ± 11.0 vs HCLP: 36.5 ± 15.9 mU/L, P < .001).
Conclusion
Ingesting a LCHP pre-exercise meal lowered plasma glucose variability around exercise and diminished the drop in plasma glucose over exercise.
Using deep Hubble Frontier Fields imaging and slitless spectroscopy from the Grism Survey from Space, we study 2200 cluster and 1748 field galaxies at to determine the impact of environment on galaxy ...size and structure at stellar masses , an unprecedented limit at these redshifts. Based on simple assumptions- -we find no significant differences in half-light radii (re) between equal-mass cluster or field systems. More complex analyses- -reveal local density ( ) to induce only a 7% 3% (95% confidence) reduction in re beyond what can be accounted for by U − V color, Sérsic index (n), and redshift (z) effects. Almost any size difference between galaxies in high- and low-density regions is thus attributable to their different distributions in properties other than environment. Indeed, we find a clear color-re correlation in low-mass passive cluster galaxies ( ) such that bluer systems have larger radii, with the bluest having sizes consistent with equal-mass star-forming galaxies. We take this as evidence that large-re low-mass passive cluster galaxies are recently acquired systems that have been environmentally quenched without significant structural transformation (e.g., by ram pressure stripping or starvation). Conversely, ∼20% of small-re low-mass passive cluster galaxies appear to have been in place since . Given the consistency of the small-re galaxies' stellar surface densities (and even colors) with those of systems more than ten times as massive, our findings suggest that clusters mark places where galaxy evolution is accelerated for an ancient base population spanning most masses, with late-time additions quenched by environment-specific mechanisms mainly restricted to the lowest masses.
ABSTRACT We report the detection of Ly emission at ∼9538 in the Keck/DEIMOS and Hubble Space Telescope WFC3 G102 grism data from a triply imaged galaxy at z = 6.846 0.001 behind galaxy cluster MACS ...J2129.4−0741. Combining the emission line wavelength with broadband photometry, line ratio upper limits, and lens modeling, we rule out the scenario that this emission line is O ii at z = 1.57. After accounting for magnification, we calculate the weighted average of the intrinsic Ly luminosity to be ∼ 1.3 × 10 42 erg s − 1 and Ly equivalent width to be 74 15 . Its intrinsic UV absolute magnitude at 1600 is −18.6 0.2 mag and stellar mass ( 1.5 0.3 ) × 10 7 M , making it one of the faintest (intrinsic L UV ∼ 0.14 L UV * ) galaxies with Ly detection at z ∼ 7 to date. Its stellar mass is in the typical range for the galaxies thought to dominate the reionization photon budget at z 7 ; the inferred Ly escape fraction is high ( 10 %), which could be common for sub-L* z 7 galaxies with Ly emission. This galaxy offers a glimpse of the galaxy population that is thought to drive reionization, and it shows that gravitational lensing is an important avenue for probing the sub-L* galaxy population.
ABSTRACT
This paper presents multiwavelength photometric catalogues of the last two Hubble Frontier Fields (HFFs), the massive galaxy clusters Abell 370 and RXC J2248.7−4431. The photometry ranges ...from imaging performed on the Hubble Space Telescope to ground-based Very Large Telescope and Spitzer/Infrared Array Camera, in collaboration with the ASTRODEEP team, and using the ASTRODEEP pipeline. While the main purpose of this paper is to release the catalogues, we also perform, as a proof of concept, a brief analysis of z > 6 objects selected using dropout method, as well as spectroscopically confirmed sources and multiple images in both clusters. While dropout methods yield a sample of high-z galaxies, the addition of longer wavelength data reveals that as expected the samples have substantial contamination at the ∼30–45 per cent level by dusty galaxies at lower redshifts. Furthermore, we show that spectroscopic redshifts are still required to unambiguously determine redshifts of multiply imaged systems. Finally, the now publicly available ASTRODEEP catalogues were combined for all HFFs and used to explore stellar properties of a large sample of 20 000 galaxies across a large photometric redshift range. The powerful magnification provided by the HFF clusters allows for an exploration of the properties of galaxies with intrinsic stellar masses as low as M* ≳ 107 M⊙ and intrinsic star formation rates ∼0.1–1 M⊙ yr−1 at z > 6.
THE COLOR VARIABILITY OF QUASARS Schmidt, Kasper B; Rix, Hans-Walter; Shields, Joseph C ...
Astrophysical journal. Letters,
01/2012, Letnik:
744, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We quantify quasar color variability using an unprecedented variability database-ugriz photometry of 9093 quasars from Sloan Digital Sky Survey (SDSS) Stripe 82, observed over 8 years at ~60 epochs ...each. We confirm previous reports that quasars become bluer when brightening. We find a redshift dependence of this blueing in a given set of bands (e.g., g and r), but show that it is the result of the flux contribution from less-variable or delayed emission lines in the different SDSS bands at different redshifts. After correcting for this effect, quasar color variability is remarkably uniform, and independent not only of redshift, but also of quasar luminosity and black hole mass. The color variations of individual quasars, as they vary in brightness on year timescales, are much more pronounced than the ranges in color seen in samples of quasars across many orders of magnitude in luminosity. This indicates distinct physical mechanisms behind quasar variability and the observed range of quasar luminosities at a given black hole mass-quasar variations cannot be explained by changes in the mean accretion rate. We do find some dependence of the color variability on the characteristics of the flux variations themselves, with fast, low-amplitude, brightness variations producing more color variability. The observed behavior could arise if quasar variability results from flares or ephemeral hot spots in an accretion disk.
ABSTRACT We study the stellar population properties of the IRAC-detected 6 z 10 galaxy candidates from the Spitzer UltRa Faint SUrvey Program. Using the Lyman Break selection technique, we find a ...total of 17 galaxy candidates at 6 z 10 from Hubble Space Telescope images (including the full-depth images from the Hubble Frontier Fields program for MACS 1149 and MACS 0717) that have detections at signal-to-noise ratios ≥ 3 in at least one of the IRAC 3.6 and 4.5 m channels. According to the best mass models available for the surveyed galaxy clusters, these IRAC-detected galaxy candidates are magnified by factors of ∼1.2-5.5. Due to the magnification of the foreground galaxy clusters, the rest-frame UV absolute magnitudes M1600 are between −21.2 and −18.9 mag, while their intrinsic stellar masses are between 2 × 108M and 2.9 × 109M . We identify two Ly emitters in our sample from the Keck DEIMOS spectra, one at zLy = 6.76 (in RXJ 1347) and one at zLy = 6.32 (in MACS 0454). We find that 4 out of 17 z 6 galaxy candidates are favored by z 1 solutions when IRAC fluxes are included in photometric redshift fitting. We also show that IRAC 3.6-4.5 color, when combined with photometric redshift, can be used to identify galaxies which likely have strong nebular emission lines or obscured active galactic nucleus contributions within certain redshift windows.
The GluN2C subunit exists predominantly, but not exclusively in NMDA receptors within the cerebellum. Antagonists such as UBP1700 and positive allosteric modulators including PYD-106 and ...3-acylamino-2-aminopropionic acid derivatives such as UA3-10 ((
)-2-amino-3-{5-(2-bromophenyl)thiophen-2-ylcarboxamido}propionic acid) represent promising tool compounds to investigate the role of GluN2C-containing NMDA receptors in the signal transduction in the brain. However, due to its high polarity the bioavailability and CNS penetration of the amino acid UA3-10 are expected to be rather low. Herein, three ester prodrugs
of the NMDA receptor glycine site agonist UA3-10 were prepared and pharmacokinetically characterized. The esters
showed higher lipophilicity (higher log
values) than the acid UA3-10 but almost the same binding at human serum albumin. The acid UA3-10 was rather stable upon incubation with mouse liver microsomes and NADPH, but the esters
were fast hydrolyzed to afford the acid UA3-10. Incubation with pig liver esterase and mouse serum led to rapid hydrolysis of the esters
. The isopropyl ester
showed a promising log
value of 3.57 and the highest stability in the presence of pig liver esterase and mouse serum. These results demonstrate that ester prodrugs of UA3-10 can potentially afford improved bioavailability and CNS penetration.
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