Context.
Planets form in protoplanetary disks and inherit their chemical composition. It is therefore crucial to understand the molecular content of protoplanetary disks in their gaseous and solid ...components.
Aims.
We aim to characterize the distribution and abundance of molecules in the protoplanetary disk of DG Tau and to compare them with its dust distribution.
Methods.
In the context of the ALMA chemical survey of Disk-Outflow sources in the Taurus star forming region (ALMA-DOT) we analyze ALMA observations of the nearby disk-outflow system around the T Tauri star DG Tau in H
2
CO 3
1,2
−2
1,1
, CS 5−4, and CN 2−1 emission at an unprecedented resolution of ~0′′.15, which means ~18 au at a distance of 121 pc.
Results.
Both H
2
CO and CS emission originate from a disk ring located at the edge of the 1.3 mm dust continuum. CS probes a disk region that is slightly further out with respect to H
2
CO; their peaks in emission are found at ~70 and ~60 au, with an outer edge at ~130 and ~120 au, respectively. CN originates from an outermost and more extended disk/envelope region with a peak at ~80 au and extends out to ~500 au. H
2
CO is dominated by disk emission, while CS also probes two streams of material possibly accreting onto the disk with a peak in emission at the location where the stream connects to the disk. CN emission is barely detected and both the disk and the envelope could contribute to the emission. Assuming that all the lines are optically thin and emitted by the disk molecular layer in local thermodynamic equilibrium at temperatures of 20−100 K, the ring- and disk-height-averaged column density of H
2
CO is 2.4−8.6 × 10
13
cm
−2
, that of CS is ~1.7−2.5 × 10
13
cm
−2
, while that of CN is ~1.9−4.7 × 10
13
cm
−2
. Unsharp masking reveals a ring of enhanced dust emission at ~40 au, which is located just outside the CO snowline (~30 au).
Conclusions.
Our finding that the CS and H
2
CO emission is co-spatial in the disk suggests that the two molecules are chemically linked. Both H
2
CO and CS may be formed in the gas phase from simple radicals and/or desorbed from grains. The observed rings of molecular emission at the edge of the 1.3 mm continuum may be due to dust opacity effects and/or continuum over-subtraction in the inner disk, as well as to increased UV penetration and/or temperature inversion at the edge of the millimeter(mm)-dust which would cause enhanced gas-phase formation and desorption of these molecules. CN emission originates only from outside the dusty disk, and is therefore even more strongly anti-correlated with the continuum, suggesting that this molecule is a good probe of UV irradiation. The H
2
CO and CS emission originate from outside the ring of enhanced dust emission, which also coincides with a change in the linear polarization orientation at 0.87 mm. This suggests that outside the CO snowline there could be a change in the dust properties that manifests itself as an increase in the intensity (and change of polarization) of the continuum and of the molecular emission.
SOLIS Codella, C.; Bianchi, E.; Podio, L. ...
Astronomy and astrophysics (Berlin),
10/2021, Volume:
654
Journal Article
Peer reviewed
Open access
Context.
Recent results in astrochemistry have revealed that some molecules, such as interstellar complex organic species and deuterated species, can serve as valuable tools in the investigation of ...star-forming regions. Sulphuretted species can also be used to follow the chemical evolution of the early stages of a Sun-like star formation process.
Aims.
The goal is to obtain a census of S-bearing species using interferometric images towards SVS13-A, a Class I object associated with a hot corino that is rich in interstellar complex organic molecules.
Methods.
To this end, we used the NGC 1333 SVS13-A data at 3 mm and 1.4 mm obtained with the IRAM-NOEMA interferometer in the framework of the SOLIS (Seeds of Life in Space) Large Program. The line emission of S-bearing species was imaged and analyzed using local thermodynamic equilibrium (LTE) and large velocity gradient (LVG) approaches.
Results.
We imaged the spatial distribution on ≤300 au scale of the line emission of
32
SO,
34
SO, C
32
S, C
34
S, C
33
S, OCS, H
2
C
32
S, H
2
C
34
S, and NS. The low excitation (9 K)
32
SO line traces: (i) the low-velocity SVS13-A outflow and (ii) the fast (up to 100 km s
−1
away from the systemic velocity) collimated jet driven by the nearby SVS13-B Class 0 object. Conversely, the rest of the lines are confined in the inner SVS13-A region, where complex organics were previously imaged. More specifically, the non-LTE LVG analysis of SO, SO
2
, and H
2
CS indicates a hot corino origin (size in the 60–120 au range). Temperatures between 50 K and 300 K, as well as volume densities larger than 10
5
cm
−3
have been derived. The abundances of the sulphuretted are in the following ranges: 0.3–6 × 10
−6
(CS), 7 × 10
−9
–1 × 10
−7
(SO), 1–10 × 10
−7
(SO
2
), a few 10
−10
(H
2
CS and OCS), and 10
−10
–10
−9
(NS). The N(NS)/N(NS
+
) ratio is larger than 10, supporting the assessment that the NS
+
ion is mainly formed in the extended envelope.
Conclusions.
The H
2
CS/H
2
CO ratio, once measured at high-spatial resolutions, increases with time (from Class 0 to Class II objects) by more than one order of magnitude (from ≤10
−2
to a few 10
−1
). This suggests that S/O changes along the process of Sun-like star formation. Finally, the estimate of the S/H budget in SVS13-A is 2–17% of the Solar System value (1.8 × 10
−5
), which is consistent with what was previously measured towards Class 0 objects (1–8%). This finding supports the notion that the enrichment of the sulphuretted species with respect to dark clouds remains constant from the Class 0 to the Class I stages of low-mass star formation. The present findings stress the importance of investigating the chemistry of star-forming regions using large observational surveys as well as sampling regions on the scale of the Solar System.
Vanishing white matter (VWM) is an autosomal recessive leukoencephalopathy characterized by slowly progressive ataxia and spasticity with additional stress-provoked episodes of rapid and major ...deterioration. The disease is caused by mutations in the genes encoding the subunits of eukaryotic initiation factor 2B, which is pivotal in translation of mRNAs into proteins. The disease onset, clinical severity, and disease course of VWM vary greatly. The influence of genotype and gender on the phenotype is unclear.
From our database of 184 patients with VWM, we selected those with the following mutations in the gene EIF2B5: p.Arg113His in the homozygous state (n = 23), p.Arg113His in the compound-heterozygous state (n = 49), p.Thr91Ala in the homozygous state (n = 8), p.Arg113His/p.Arg339any (n = 9), and p.Thr91Ala/p.Arg339any (n = 7). We performed a cross-sectional observational study. Evaluated clinical characteristics were gender, age at onset, age at loss of walking without support, and age at death. Means, male/female ratios, and Kaplan-Meier curves were compared.
Patients homozygous for p.Arg113His had a milder disease than patients compound heterozygous for p.Arg113His and patients homozygous for p.Thr91Ala. Patients with p.Arg113His/p.Arg339any had a milder phenotype than patients with p.Thr91Ala/p.Arg339any. Overall, females tended to have a milder disease than males.
The clinical phenotype in VWM is influenced by the combination of both mutations. Females tend to do better than males.
Guanidinoactetate methyltransferase (GAMT) deficiency is an autosomal recessive disorder of creatine synthesis. The authors analyzed clinical, biochemical, and molecular findings in 27 patients.
The ...authors collected data from questionnaires and literature reports. A score including degree of intellectual disability, epileptic seizures, and movement disorder was developed and used to classify clinical phenotype as severe, moderate, or mild. Score and biochemical data were assessed before and during treatment with oral creatine substitution alone or with additional dietary arginine restriction and ornithine supplementation.
Intellectual disability, epileptic seizures, guanidinoacetate accumulation in body fluids, and deficiency of brain creatine were common in all 27 patients. Twelve patients had severe, 12 patients had moderate, and three patients had mild clinical phenotype. Twenty-one of 27 (78%) patients had severe intellectual disability (estimated IQ 20 to 34). There was no obvious correlation between severity of the clinical phenotype, guanidinoacetate accumulation in body fluids, and GAMT mutations. Treatment resulted in almost normalized cerebral creatine levels, reduced guanidinoacetate accumulation, and in improvement of epilepsy and movement disorder, whereas the degree of intellectual disability remained unchanged.
Guanidinoactetate methyltransferase deficiency should be considered in patients with unexplained intellectual disability, and urinary guanidinoacetate should be determined as an initial diagnostic approach.
Context.
Planet formation starts around Sun-like protostars with ages ≤1 Myr, but the chemical compositions of the surrounding discs remains unknown.
Aims.
We aim to trace the radial and vertical ...spatial distribution of a key species of S-bearing chemistry, namely H
2
CS, in protoplanetary discs. We also aim to analyse the observed distributions in light of the H
2
CS binding energy in order to discuss the role of thermal desorption in enriching the gas disc component.
Methods.
In the context of the ALMA chemical survey of disk-outflow sources in the Taurus star forming region (ALMA-DOT), we observed five Class I or early Class II sources with the o-H
2
CS(7
1,6
−6
1,5
) line. ALMA-Band 6 was used, reaching spatial resolutions ≃40 au, that is, Solar System spatial scales. We also estimated the binding energy of H
2
CS using quantum mechanical calculations, for the first time, for an extended, periodic, crystalline ice.
Results.
We imaged H
2
CS emission in two rotating molecular rings in the HL Tau and IRAS 04302+2247 discs, the outer radii of which are ~140 au (HL Tau) and 115 au (IRAS 04302+2247). The edge-on geometry of IRAS 04302+2247 allows us to reveal that H
2
CS emission peaks at radii of 60–115 au, at
z
= ±50 au from the equatorial plane. Assuming LTE conditions, the column densities are ~10
14
cm
−2
. We estimate upper limits of a few 10
13
cm
−2
for the H
2
CS column densities in DG Tau, DG Tau B, and Haro 6–13 discs. For HL Tau, we derive, for the first time, the H
2
CS/H abundance in a protoplanetary disc (≃10
−14
). The binding energy of H
2
CS computed for extended crystalline ice and amorphous ices is 4258 and 3000–4600 K, respectively, implying thermal evaporation where dust temperatures are ≥50–80 K.
Conclusions.
H
2
CS traces the so-called warm molecular layer, a region previously sampled using CS and H
2
CO. Thioformaldehyde peaks closer to the protostar than H
2
CO and CS, plausibly because of the relatively high excitation level of the observed 7
1,6
−6
1,5
line (60 K). The H
2
CS binding energy implies that thermal desorption dominates in thin, au-sized, inner and/or upper disc layers, indicating that the observed H
2
CS emitting up to radii larger than 100 au is likely injected in the gas phase due to non-thermal processes.
Twenty-three patients with late onset argininosuccinate lyase deficiency (ASLD) were identified during a 27-year period of newborn screening in Austria (1:95,600, 95% CI=1:68,036–1:162,531). One ...additional patient was identified outside the newborn screening with neonatal hyperammonemia. Long-term outcome data were available in 17 patients (median age 13years) ascertained by newborn screening. Patients were treated with protein restricted diet and oral arginine supplementation during infancy and childhood. IQ was average/above average in 11 (65%), low average in 5 (29%), and in the mild intellectual disability range in 1 (6%) patients. Four patients had an abnormal EEG without evidence of clinical seizures and three had abnormal liver function tests and/or evidence of hepatic steatosis. Plasma citrulline levels were elevated in four patients. Plasma ammonia levels were within normal range prior and after a protein load in all patients. Seven different mutations were identified in the 16 alleles investigated. Four mutations were novel (p.E189G, p.R168C, p.R126P, and p.D423H). All mutations were associated with low argininosuccinate lyase activities (0–15%) in red blood cells. Newborn screening might be beneficial in the prevention of chronic neurologic and intellectual sequelae in late onset ASLD, but a proportion of benign variants might have contributed to the overall favorable outcome as well.
The chemical composition of planets is inherited from that of the natal protoplanetary disk at the time of planet formation. Increasing observational evidence suggests that planet formation occurs in ...less than 1−2 Myr. This motivates the need for spatially resolved spectral observations of young Class I disks, as carried out by the ALMA chemical survey of Disk-Outflow sources in Taurus (ALMA-DOT). In the context of ALMA-DOT, we observe the edge-on disk around the Class I source IRAS 04302+2247 (the butterfly star) in the 1.3 mm continuum and five molecular lines. We report the first tentative detection of methanol (CH
3
OH) in a Class I disk and resolve, for the first time, the vertical structure of a disk with multiple molecular tracers. The bulk of the emission in the CO 2−1, CS 5−4, and o–H
2
CO 3
1, 2
− 2
1, 1
lines originates from the warm molecular layer, with the line intensity peaking at increasing disk heights,
z
, for increasing radial distances,
r
. Molecular emission is vertically stratified, with CO observed at larger disk heights (aperture
z
/
r
∼ 0.41−0.45) compared to both CS and H
2
CO, which are nearly cospatial (
z
/
r
∼ 0.21−0.28). In the outer midplane, the line emission decreases due to molecular freeze-out onto dust grains (freeze-out layer) by a factor of > 100 (CO) and 15 (CS). The H
2
CO emission decreases by a factor of only about 2, which is possibly due to H
2
CO formation on icy grains, followed by a nonthermal release into the gas phase. The inferred CH
3
OH/H
2
CO abundance ratio is 0.5−0.6, which is 1−2 orders of magnitude lower than for Class 0 hot corinos, and a factor ∼2.5 lower than the only other value inferred for a protoplanetary disk (in TW Hya, 1.3−1.7). Additionally, it is at the lower edge but still consistent with the values in comets. This may indicate that some chemical reprocessing occurs in disks before the formation of planets and comets.
GAMT deficiency is an autosomal recessive disorder of creatine biosynthesis resulting in severe neurological complications in untreated patients. Currently available treatment is only successful to ...stop disease progression, but is not sufficient to reverse neurological complications occurring prior to diagnosis. Normal neurodevelopmental outcome in a patient, treated in the newborn period, highlights the importance of early diagnosis.
Targeted mutation analysis (c.59G>C and c.327G>A) in the GAMT gene by the QIAxcel system and GAA measurement by a novel two-tier method were performed in 3000 anonymized newborn blood dot spot cards.
None of the targeted mutations were detected in any newborn. Two novel heterozygous variants (c.283_285dupGTC; p.Val95dup and c.278_283delinsCTCGATGCAC; p.Asp93AlafsX35) were identified by coincidence. Carrier frequency for these insertion/deletion types of GAMT mutations was 1/1475 in this small cohort of newborns. GAA levels were at or above the 99th percentile (3.12μmol/l) in 4 newborns. Second-tier testing showed normal results for 4 newborns revealing 0.1% false positive rate. No GAMT mutations were identified in 4 of the newborns with elevated GAA levels in the first tier testing.
This is the first two-tier study to investigate carrier frequency of GAMT deficiency in the small cohort of newborn population to establish evidence base for the first steps toward newborn screening for this treatable neurometabolic disorder.
► This is first study for two-tier GAA measurements in the blood dot spots. ► Low false positive rate for GAA measurement in the blood dot spots. ► This is the first study to use QIAxcel system for targeted mutation analysis.
The ALMA interferometer, with its unprecedented combination of high-sensitivity and high-angular resolution, allows for (sub-)mm wavelength mapping of protostellar systems at Solar System scales. ...Astrochemistry has benefited from imaging interstellar complex organic molecules in these jet-disk systems. Here we report the first detection of methanol (CH3OH) and methyl formate (HCOOCH3) emission towards the triple protostellar system VLA1623-2417 A1+A2+B, obtained in the context of the ALMA Large Program FAUST. Compact methanol emission is detected in lines from Eu = 45 K up to 61 K and 537 K towards components A1 and B, respectively. LVG analysis of the CH3OH lines towards VLA1623-2417 B indicates a size of 0${_{.}^{\prime\prime}}$11-0${_{.}^{\prime\prime}}$34 (14-45 au), a column density N(CH3OH) = 1016-1017 cm-2, kinetic temperature ≥ 170 K, and volume density ≥ 108 cm-3. An LTE approach is used for VLA1623-2417 A1, given the limited Eu range, and yields Trot ≤ 135 K. The methanol emission around both VLA1623-2417 A1 and B shows velocity gradients along the main axis of each disk. Although the axial geometry of the two disks is similar, the observed velocity gradients are reversed. The CH3OH spectra from B shows two broad (4-5 km s-1) peaks, which are red- and blue-shifted by ~ 6-7 km s-1 from the systemic velocity. Assuming a chemically enriched ring within the accretion disk, close to the centrifugal barrier, its radius is calculated to be 33 au. The methanol spectra towards A1 are somewhat narrower (~ 4 km s-1), implying a radius of 12-24 au.
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