Visual Extinction Research Articles

Modelling methanol and hydride formation in the JWST Ice Age era

Recent JWST observations have measured the ice chemical composition towards two highly extinguished background stars, NIR38 and J110621, in the Chamaeleon I molecular cloud. The observed excess of extinction on the long-wavelength side of the H_2O ice band at 3$,$μm has been attributed to a mixture of CH_3OH with ammonia hydrates (NH_3⋅H_2O), which suggests that CH_3OH ice in this cloud could have formed in a water-rich environment with little CO depletion. Laboratory experiments and quantum chemical calculations suggest that CH_3OH could form via the grain surface reactions CH_3 + OH and/or C + H_2O in water-rich ices. However, no dedicated chemical modelling has been carried out thus far to test their efficiency. In addition, it remains unexplored how the efficiencies of the proposed mechanisms depend on the astrochemical code employed. We modelled the ice chemistry in the Chamaeleon I cloud to establish the dominant formation processes of CH_3OH, CO, CO_2, and of the hydrides CH_4 and NH_3 (in addition to H_2O). By using a set of state-of-the-art astrochemical codes (MAGICKAL, MONACO, Nautilus Uclchem and KMC simulations), we can test the effects of the different code architectures (rate equation vs. stochastic codes) and of the assumed ice chemistry (diffusive vs. non-diffusive). We consider a grid of models with different gas densities, dust temperatures, visual extinctions, and cloud-collapse length scales. In addition to the successive hydrogenation of CO, the codes' chemical networks have been augmented to include the alternative processes for CH_3OH ice formation in water-rich environments (i.e. the reactions CH_3 + OH → CH_3OH and C + H_2O → H_2CO). Our models show that the JWST ice observations are better reproduced for gas densities ≥10^5 cm^-3 and collapse timescales ≥10^5 yr. CH_3OH ice formation occurs predominantly ($>$99%) via CO hydrogenation. The contribution of reactions CH_3 + OH and C + H_2O is negligible. The CO_2 ice may form either via CO + OH or CO + O depending on the code. However, KMC simulations reveal that both mechanisms are efficient despite the low rate of the CO + O surface reaction. CH_4 is largely underproduced for all codes except for Uclchem for which a higher amount of atomic C is available during the translucent cloud phase of the models. Large differences in the predicted abundances are found at very low dust temperatures (T_ dust$<$12 K) between diffusive and non-diffusive chemistry codes. This is due to the fact that non-diffusive chemistry takes over diffusive chemistry at such low T_ dust. This could explain the rather constant ice chemical composition found in Chamaeleon I and other dense cores despite the different visual extinctions probed.

Ionized Carbon in Galaxies: The [C ii] 158 μm Line as a Total Molecular Gas Mass Tracer Revisited

In this paper, we present a statistical study of the [C ii] 158 μm line and the CO(1−0) emission for a sample of ∼200 local and high-z (32 sources with z > 1) galaxies with very different physical conditions. We explore the correlation between the luminosities of [C ii] and CO(1−0) lines and obtain a strong linear relationship, confirming that [C ii] is able to trace total molecular gas mass, with a small difference between (U)LIRGs and less-luminous galaxies. The tight and linear relation between [C ii] and CO(1−0) is likely determined by the average value of the observed visual extinction A V and the range of G 0/n in galaxies. Further investigations into the dependence of L [C ii]/L CO(1−0) on different physical properties show that L [C ii]/L CO(1−0) (1) anticorrelates with ΣIR, and the correlation becomes steeper when ΣIR ≳ 1011 L ⊙ kpc−2; (2) correlates positively with the distance from the main sequence Δ(MS) when Δ(MS) ≲ 0; and (3) tends to show a systematically smaller value in systems where the [C ii] emission is dominated by ionized gas. Our results imply that caution needs to be taken when applying a constant [C ii]-to-M mol conversion factor to estimate the molecular gas content in extreme cases, such as galaxies having low-level star formation activity or high star formation rate surface density.

Toward a robust physical and chemical characterization of heterogeneous lines of sight: The case of the Horsehead nebula

Context. Dense and cold molecular cores and filaments are surrounded by an envelope of translucent gas. Some of the low-J emission lines of CO and HCO+ isotopologues are more sensitive to the conditions either in the translucent environment or in the dense and cold one because their intensities result from a complex interplay of radiative transfer and chemical properties of these heterogeneous lines of sight (LoSs). Aims. We extend our previous single-zone modeling with a more realistic approach that introduces multiple layers to take account of possibly varying conditions along the LoS. We used the IRAM-30m data from the ORION-B large program toward the Horsehead nebula in order to demonstrate our method’s capability and effectiveness. Methods. We propose a cloud model composed of three homogeneous slabs of gas along each LoS, representing an outer envelope and a more shielded inner layer. We used the non-LTE radiative transfer code RADEX to model the line profiles from the kinetic temperature (Tkin), the volume density (nH2), kinematics, and chemical properties of the different layers. We then used a fast and robust maximum likelihood estimator to simultaneously fit the observed lines of the CO and HCO+ isotopologues. To limit the variance on the estimates, we propose a simple chemical model by constraining the column densities. Results. A single-layer model cannot reproduce the spectral line asymmetries that result from a combination of different radial velocities and absorption effects among layers. A minimal heterogeneous model (three layers only) is sufficient for the Horsehead application, as it provides good fits of the seven fitted lines over a large part of the studied field of view. The decomposition of the intensity into three layers allowed us to discuss the distribution of the estimated physical or chemical properties along the LoS. About 80% of the 12CO integrated intensity comes from the outer envelope, while ~55% of the integrated intensity of the (1 − 0) and (2 − 1) lines of C18O comes from the inner layer. For the lines of the 13CO and the HCO+ isotopologues, integrated intensities are more equally distributed over the cloud layers. The estimated column density ratio N(13CO)/N(C18O) in the envelope increases with decreasing visual extinction, and it reaches 25 in the pillar outskirts. While the inferred Tkin of the envelope varies from 25 to 40 K, that of the inner layer drops to ~15 K in the western dense core. The estimated nH2 in the inner layer is ~3 × 104 cm−3 toward the filament, and it increases by a factor of ten toward dense cores. Conclusions. Our proposed method correctly retrieves the physical and chemical properties of the Horsehead nebula. It also offers promising prospects for less supervised model fits of wider-field datasets.

Star formation in the high-extinction Planck cold clump PGCC G120.69+2.66

We investigate the star formation occurring in the Planck Galactic cold clump PGCC 120.69+2.66. Near-infrared JHKs images and K-band spectroscopy obtained with NOTCam at the Nordic Optical Telescope complemented with archive data are used to study the stellar content. In addition, millimetre line CO and CS spectra were obtained with the Onsala 20 m telescope, and sub-millimetre continuum SCUBA archive data are used to characterise the host molecular cloud. We identify a molecular cloud core traced by CO and CS emission at a distance of 1.1 kpc. In the region studied, we identify 5 submm continuum cores. Embedded in and around these dense submm cores, we find 38 young stellar objects, classified as 9 Class I, 8 Class II, and 21 near-IR excess or variability sources, accompanied by bipolar nebulosities and signs of protostellar jets. Furthermore, a very bright and reddened source is found towards this molecular cloud core. Even though its location appears to suggest its association to the star formation region, its infrared spectral type is compatible with a red supergiant, hidden behind 36 mag of visual extinction.

JWST Observations of Young protoStars (JOYS)

Context. Due to the high visual extinction and lack of sensitive mid-infrared (MIR) telescopes, the origin and properties of outflows and jets from embedded Class 0 protostars are still poorly constrained. Aims. We aim to characterise the physical, kinematic, and dynamical properties of the HH 211 jet and outflow, one of the youngest protostellar flows. Methods. We used the James Webb Space Telescope (JWST) and its Mid-InfraRed Instrument (MIRI) in the 5–28 µm range to study the embedded HH 211 flow. We mapped a 0′.95 × 0′.22 region, covering the full extent of the blueshifted lobe, the central protostellar region, and a small portion of the redshifted lobe. We extracted spectra along the jet and outflow and constructed line and excitation maps of both atomic and molecular lines. Additional JWST NIRCam H2 narrow-band images (at 2.122 and 3.235 µm) provide a visualextinction map of the whole flow, and are used to deredden our data. Results. The jet-driving source is not detected even at the longest MIR wavelengths. The overall morphology of the flow consists of a highly collimated jet, which is mostly molecular (H2, HD) with an inner atomic ([Fe I], [Fe II], [S I], [Ni II]) structure. The jet shocks the ambient medium, producing several large bow shocks (BSs) that are rich in forbidden atomic ([Fe II], [S I], [Ni II], [Cl I], [Cl II], [Ar II], [Co II], [Ne II], [S III]) and molecular lines (H2, HD, CO, OH, H2O, CO2, HCO+), and is driving an H2 molecular outflow that is mostly traced by low- J, v = 0 transitions. Moreover, H2 0-0 S(1) uncollimated emission is also detected down to 2″-3″ (~650–1000 au) from the source, tracing a cold (T=200–400 K), less dense, and poorly collimated molecular wind. Two H2 components (warm, T =300–1000 K, and hot, T =1000–3500 K) are detected along the jet and outflow. The atomic jet ([Fe II] at 26 µm) is detected down to ~130 au from the source, whereas the lack of H2 emission (at 17 µm) close to the source is likely due to the large visual extinction (AV > 80 mag). Dust-continuum emission is detected at the terminal BSs and in the blue- and redshifted jet, and is likely attributable to dust lifted from the disc. Conclusions. The jet shows an onion-like structure, with layers of different size, velocity, temperature, and chemical composition. Moreover, moving from the inner jet to the outer BSs, different physical, kinematic, and excitation conditions for both molecular and atomic gas are observed. The mass-flux rate and momentum of the jet, as well as the momentum flux of the warm H2 component, are up to one order of magnitude higher than those inferred from the atomic jet component. Our findings indicate that the warm H2 red component is the main driver of the outflow, that is to say it is the most significant dynamical component of the jet, in contrast to jets from more evolved YSOs, where the atomic component is dominant.

Quantifying the informativity of emission lines to infer physical conditions in giant molecular clouds

Context. Observations of ionic, atomic, or molecular lines are performed to improve our understanding of the interstellar medium (ISM). However, the potential of a line to constrain the physical conditions of the ISM is difficult to assess quantitatively, because of the complexity of the ISM physics. The situation is even more complex when trying to assess which combinations of lines are the most useful. Therefore, observation campaigns usually try to observe as many lines as possible for as much time as possible. Aims. We have searched for a quantitative statistical criterion to evaluate the full constraining power of a (combination of) tracer(s) with respect to physical conditions. Our goal with such a criterion is twofold. First, we want to improve our understanding of the statistical relationships between ISM tracers and physical conditions. Secondly, by exploiting this criterion, we aim to propose a method that helps observers to make their observation proposals; for example, by choosing to observe the lines with the highest constraining power given limited resources and time. Methods. We propose an approach based on information theory, in particular the concepts of conditional differential entropy and mutual information. The best (combination of) tracer(s) is obtained by comparing the mutual information between a physical parameter and different sets of lines. The presented analysis is independent of the choice of the estimation algorithm (e.g., neural network or χ2 minimization). We applied this method to simulations of radio molecular lines emitted by a photodissociation region similar to the Horsehead Nebula. In this simulated data, we considered the noise properties of a state-of-the-art single dish telescope such as the IRAM 30m telescope. We searched for the best lines to constrain the visual extinction, AVtot, or the ultraviolet illumination field, G0. We ran this search for different gas regimes, namely translucent gas, filamentary gas, and dense cores. Results. The most informative lines change with the physical regime (e.g., cloud extinction). However, the determination of the optimal (combination of) line(s) to constrain a physical parameter such as the visual extinction depends not only on the radiative transfer of the lines and chemistry of the associated species, but also on the achieved mean signal-to-noise ratio. The short integration time of the CO isotopologue J = 1 − 0 lines already yields much information on the total column density for a large range of (AVtot, G0) space. The best set of lines to constrain the visual extinction does not necessarily combine the most informative individual lines. Precise constraints on the radiation field are more difficult to achieve with molecular lines. They require spectral lines emitted at the cloud surface (e.g., [CII] and [CI] lines). Conclusions. This approach allows one to better explore the knowledge provided by ISM codes, and to guide future observation campaigns.

SOFIA/upGREAT far-infrared spectroscopy of bright rimmed pillars in IC 1848

Using the upGREAT instrument on SOFIA, we imaged the [C II] 158 µm fine structure line emission in bright-rimmed pillars located at the southern edge of the IC 1848 H II region, and carried out pointed observations of the [O I] 63 and 145 µm fine structure lines toward selected positions. The observations are used to characterize the morphology, velocity field, and the physical conditions in the G1–G3 filaments. The velocity-resolved [C II] spectra show evidence of a velocity shift at the head of the brightest G1 filament, possibly caused by radiation pressure from the impinging UV photons or the rocket effect of the evaporating gas. Archival Herschel PACS and SPIRE observations imply H2 column densities in the range 1021 –1022 cm−2 , corresponding to maximum visual extinction AV ≃ 10 mag, and average H2 volume density of ≃4500 cm−3 in the filaments. The [C II] emission traces ∼17% of the total H2 column density, as derived from dust SED fits. Photon-dominated region models are unable to explain the observed line intensities of the two [O I] fine structure lines in IC 1848, with the observed [O I] 145 µm line being too strong compared to the model predictions. The [O I] lines in IC 1848 are overall weak and the signal-to-noise ratio is limited. However, our observations suggest that the [O I] 63/145 µm intensity ratio is a sensitive probe of the physical conditions in photon-dominated regions such as IC 1848. These lines are thus excellent targets for future high-altitude balloon instruments, less affected by telluric absorption.

Peering into the Heart of the Giant Molecular Cloud G148.24+00.41: A Deep Near-infrared View of the Newly Hatched Cluster FSR 655

We present a detailed near-infrared study of an embedded cluster located in the hub of the giant molecular cloud G148.24+00.41 of mass ∼105 M ⊙, with the TANSPEC instrument mounted on the 3.6 m Devasthal Optical Telescope. The hub is located near the geometric center of the cloud and represents its most massive clump. We studied the central 2 pc × 2 pc area of the hub with 5σ limiting magnitudes of 20.5, 20.1, and 18.6 mag in the J, H, and K s bands, respectively. Using the K s -band luminosity function and comparing it with the synthetic clusters, we obtained the age of the cluster as ∼0.5 Myr, which was found to corroborate well with the visual extinction versus the age of nearby embedded clusters. We find that the present mass of the cluster is around ∼180 M ⊙, and the cluster is currently forming stars at a rate of ∼330 M ⊙ Myr−1, with an efficiency of ∼20%. The cluster is connected to an extended gas reservoir through a filamentary network; thus, we hypothesize that the cluster has the potential to become a richer cluster in a few Myr of time.

Peripheral and bimanual reaching in a stroke survivor with left visual neglect and extinction

Peripheral and bimanual reaching in a stroke survivor with left visual neglect and extinction

The CO-dark molecular gas in the cold H I arc

The CO-dark molecular gas (DMG), which refers to the molecular gas not traced by CO emission, is crucial for the evolution of the interstellar medium (ISM). While the gas properties of DMG have been widely explored in the Solar neighborhood, whether or not they are similar in the outer disk regions of the Milky Way is still not well understood. In this Letter, we confirm the existence of DMG toward a cold H I arc structure at 13 kpc away from the Galactic center with both OH emission and H I narrow self-absorption (HINSA). This is the first detection of HINSA in the outer disk region, in which the HINSA fraction (NHINSA/NH2 = 0.022 ± 0.011) is an order of magnitude higher than the average value observed in nearby evolved dark clouds, but is consistent with that of the early evolutionary stage of dark clouds. The inferred H2 column density from both extinction and OH emission (NH2 ≈ 1020 cm−2) is an order of magnitude higher than previously estimated. Although the ISM environmental parameters are expected to be different between the outer Galactic disk regions and the Solar neighborhood, we find that the visual extinction (AV = 0.19 ± 0.03 mag), H2-gas density (nH2 = 91 ± 46 cm−3), and molecular fraction (58% ± 28%) of the DMG are rather similar to those of nearby diffuse molecular clouds. The existence of DMG associated with the expanding H I supershell supports a scenario where the expansion of supershells may trigger the formation of molecular clouds within a crossing timescale of the shock wave (∼106 yr).

Foreground Dust Properties toward the Cluster NGC 7380

Using starlight polarization, we present the properties of foreground dust toward cluster NGC 7380 embedded in H ii region Sh 2-142. Observations of starlight polarization are carried out in four filters using an imaging polarimeter equipped with a 104 cm ARIES telescope. Polarization vectors of stars are aligned along the Galactic magnetic field. Toward the east and southeast regions, the dust structure appears much denser than in other regions (inferred from extinction contours and a color composite image) and is also reflected in polarization distribution. We find that the polarization degree and extinction tend to increase with distance and indication for the presence of a dust layer at a distance of around 1.2 kpc. We have identified eight potential candidates exhibiting intrinsic polarization by employing three distinct criteria to distinguish between stars of intrinsic polarization and interstellar polarized stars. For interstellar polarized stars, we find that the maximum polarization degree increases with the color excess and has a strong scatter, with the mean value of 1.71% ± 0.57%. The peak wavelength spans 0.40–0.88 μm, with a mean value of 0.56 ± 0.07 μm, suggesting similar grain sizes in the region to those in the average diffuse interstellar medium. The polarization efficiency is also found to decrease with visual extinction as Pmax/AV∝AV−0.61 . Our observational results are found to be consistent with the predictions by the radiative torque alignment theory.

The neuroanatomy of visual extinction following right hemisphere brain damage: Insights from multivariate and Bayesian lesion analyses in acute stroke.

Multi-target attention, that is, the ability to attend and respond to multiple visual targets presented simultaneously on the horizontal meridian across both visual fields, is essential for everyday real-world behaviour. Given the close link between the neuropsychological deficit of extinction and attentional limits in healthy subjects, investigating the anatomy that underlies extinction is uniquely capable of providing important insights concerning the anatomy critical for normal multi-target attention. Previous studies into the brain areas critical for multi-target attention and its failure in extinction patients have, however, produced heterogeneous results. In the current study, we used multivariate and Bayesian lesion analysis approaches to investigate the anatomical substrate of visual extinction in a large sample of 108 acute right hemisphere stroke patients. The use of acute stroke patient data and multivariate/Bayesian lesion analysis approaches allowed us to address limitations associated with previous studies and so obtain a more complete picture of the functional network associated with visual extinction. Our results demonstrate that the right temporo-parietal junction (TPJ) is critically associated with visual extinction. The Bayesian lesion analysis additionally implicated the right intraparietal sulcus (IPS), in line with the results of studies in neurologically healthy participants that highlighted the IPS as the area critical for multi-target attention. Our findings resolve the seemingly conflicting previous findings, and emphasise the urgent need for further research to clarify the precise cognitive role of the right TPJ in multi-target attention and its failure in extinction patients.

Silicate Extinction Profile Based on the Stellar Spectrum by Spitzer/IRS

The 9.7 and 18 μm interstellar spectral features, arising from the Si–O stretching and O–Si–O bending modes of amorphous silicate dust, are the strongest extinction features in the infrared. Here we use the “pair method” to determine the silicate extinction profile by comparing the Spitzer/IRS spectra of 49 target stars with obvious extinction with those of unreddened stars of the same spectral type. The 9.7 μm extinction profile is determined from all the 49 stars and the 18 μm profile is determined from six stars. It is found that the profile has a peak wavelength at ∼9.2–9.8 and ∼18–22 μm, respectively. The peak wavelength of the 9.7 μm feature seems to become shorter for stars of late spectral types; meanwhile the FWHM seems irrelevant to the spectral type, which may be related to circumstellar silicate emission. The silicate optical depth at 9.7 μm, Δτ 9.7, mostly increases with the color excess in J − K S ( EJKS ). The mean ratio of the visual extinction to the 9.7 μm silicate absorption optical depth is A V /Δτ 9.7 ≈ 17.8, in close agreement with that of the solar-neighborhood diffuse interstellar medium. When EJKS>4 , this proportionality changes. The correlation coefficient between the peak wavelength and the FWHM of the 9.7 μm feature is 0.4, which indicates a positive correlation considering the uncertainties of the parameters. The method is compared with replacing the reference star by an atmospheric model spectral energy distribution and no significant difference is observed.

Chemical differences among collapsing low-mass protostellar cores

Context. Organic features lead to two distinct types of Class 0/I low-mass protostars: hot corino sources exhibiting abundant saturated complex organic molecules (COMs) and warm carbon-chain chemistry (WCCC) sources exhibiting abundant unsaturated carbon-chain molecules. Some observations suggest that the chemical variations between WCCC sources and hot corino sources are associated with local environments and the luminosity of protostars. Aims. We aim to investigate the physical conditions that significantly affect WCCC and hot corino chemistry, as well as to reproduce the chemical characteristics of prototypical WCCC sources and hybrid sources, where both carbon-chain molecules and COMs are abundant. Methods. We conducted a gas-grain chemical simulation in collapsing protostellar cores, adopting a selection of typical physical parameters for the fiducial model. By adjusting the values of certain physical parameters, such as the visual extinction of ambient clouds (AVamb), cosmic-ray ionization rate (ζ), maximum temperature during the warm-up phase (Tmax), and contraction timescale of protostars (tcont), we studied the dependence of WCCC and hot corino chemistry on these physical parameters. Subsequently, we ran a model with different physical parameters to reproduce scarce COMs in prototypical WCCC sources. Results. The fiducial model predicts abundant carbon-chain molecules and COMs. It also reproduces WCCC and hot corino chemistry in the hybrid source L483. This suggests that WCCC and hot corino chemistry can coexist in some hybrid sources. Ultraviolet (UV) photons and cosmic rays can boost WCCC features by accelerating the dissociation of CO and CH4 molecules. On the other hand, UV photons can weaken the hot corino chemistry by photodissociation reactions, while the dependence of hot corino chemistry on cosmic rays is relatively complex. The value of Tmax does not affect any WCCC features, while it can influence hot corino chemistry by changing the effective duration of two-body surface reactions for most COMs. The long tcont can boost WCCC and hot corino chemistry by prolonging the effective duration of WCCC reactions in the gas phase and surface formation reactions for COMs, respectively. The scarcity of COMs in prototypical WCCC sources can be explained by insufficient dust temperatures in the inner envelopes that are typically required to activate hot corino chemistry. Meanwhile, the high ζ and the long tcont favors the explanation for scarce COMs in these sources. Conclusions. The chemical differences between WCCC sources and hot corino sources can be attributed to the variations in local environments, such as AVamb and ζ, as well as the protostellar property, tcont.

Probing stellar populations and interstellar medium in early-type central galaxies

ABSTRACT In this study, we analyse the characteristics of stellar populations and the interstellar medium (ISM) in 15 107 early-type central galaxies from the SPIDER survey. Using optical spectra from the Sloan Digital Sky Survey (SDSS), we investigate stellar age (Age), metallicity (Z), visual extinction (AV), and H α equivalent width (EWH α) to understand the evolution of the baryonic content in these galaxies. Our analysis explores the relationship between these properties and central velocity dispersion (σ) and halo mass (Mhalo) for isolated centrals (ICs) and group centrals (GCs). Our results confirm that both ICs and GCs’ stellar populations and gas properties are mainly influenced by σ, with Mhalo playing a secondary role. Higher σ values correspond to older, more metal-rich stellar populations in both ICs and GCs. Moreover, fixed σ values we observe younger Ages at higher values of Mhalo, a consistent trend in both ICs and GCs. Furthermore, we investigate the ionization source of the warm gas and propose a scenario where the properties of ionized gas are shaped by a combination of cooling within the intracluster medium (ICM) and feedback from Active Galactic Nuclei (AGNs) assuming a Bondi accretion regime. We observe inherent differences between ICs and GCs, suggesting that the ratio between AGN kinetic power and ICM thermal energy influences EWH α in ICs. Meanwhile, gas deposition in GCs appears to involve a more complex interplay beyond a singular AGN–ICM interaction.

Abstract 205: Efficacy and Safety of Mechanical Thrombectomy for Primary MeVO with Disabling Deficit

Introduction We aimed to evaluate the efficacy and safety of mechanical thrombectomy (MT) for medium vessel occlusion (MeVO) with the disabling deficit. Methods The study period was from January 2011 to December 2022. Inclusion criteria were 1) within 24 hours of stroke onset, 2) prestroke mRS score ≤1, 3) NIHSS score ≥4 or disabling deficit (complete hemianopia (≥2 on NIHSS), severe aphasia (≥2 on NIHSS), visual sensory extinction (≥1 on NIHSS), significant weakness with NIHSS subscore of paralysis ≥2), 4) MeVO (MCA distal M2, M3, ACA A1, A2, A3, PCA P1, P2, and P3). Outcomes were compared between the MT and standard medical treatment (SMT) groups. Outcome was defined as the favorable outcome (mRS score 0‐2 at 90 days), death within 90 days, and symptomatic intracranial hemorrhage (SICH). Results Of all, 192 patients (72 women, median age 78 years, median NIHSS score 11 points) were enrolled, and 76.6% (n=147) had distal M2 occlusion. Compared to the SMT group (n=153), the MT group (n=39) had a significantly larger median Tmax>10 sec volume (median 25 mL vs. 5 mL, P<0.01) and Tmax> 6‐sec volume (61 mL vs. 44 mL, P<0.01), while median NIHSS score (13 vs. 11, P=0.69) and intravenous thrombus (51.6％ vs. 55.3%, P=0.72) were significantly lower in the MT group. There were significantly more patients in the MT group with a favorable outcome (73.7% vs. 54.1%, adjusted odds ratio 2.59 95% confidence interval 1.07‐6.24), death within 90 days (7.9% vs. 3.1%), SICH (5.3% vs. 4.4%) were not significantly different. In subgroup analysis, MT was independently associated with age (<80 years; 1.33, 1.21‐15.57, P=0.222) and neurological severity (NIHSS ≥10 points; 2.79, 1.07‐7.24, P=0.870) for a favorable outcome. Conclusion In MeVO with disabling deficits, MT was independently associated with more favorable outcomes than the SMT group.

Outflows from the youngest stars are mostly molecular

The formation of stars and planets is accompanied not only by the build-up of matter, namely accretion, but also by its expulsion in the form of highly supersonic jets that can stretch for several parsecs1,2. As accretion and jet activity are correlated and because young stars acquire most of their mass rapidly early on, the most powerful jets are associated with the youngest protostars3. This period, however, coincides with the time when the protostar and its surroundings are hidden behind many magnitudes of visual extinction. Millimetre interferometers can probe this stage but only for the coolest components3. No information is provided on the hottest (greater than 1,000 K) constituents of the jet, that is, the atomic, ionized and high-temperature molecular gases that are thought to make up the jet’s backbone. Detecting such a spine relies on observing in the infrared that can penetrate through the shroud of dust. Here we report near-infrared observations of Herbig-Haro 211 from the James Webb Space Telescope, an outflow from an analogue of our Sun when it was, at most, a few times 104 years old. These observations reveal copious emission from hot molecules, explaining the origin of the ‘green fuzzies’4–7 discovered nearly two decades ago by the Spitzer Space Telescope8. This outflow is found to be propagating slowly in comparison to its more evolved counterparts and, surprisingly, almost no trace of atomic or ionized emission is seen, suggesting its spine is almost purely molecular.

Distribution of dust color temperature, dust mass and planck’s function around C-rich AGB star: IRAS 19558+3333 using IRIS, AKARI, and WISE Surveys

The dust properties of C-rich AGB (Asymptotic giant branch) star IRAS 19558+3333 located at right ascension (R.A.) (J2000) = 19h 57m 48.440s and Declination (J2000) = +330 41h 21.250s was studied. The FITS image of this AGB star was obtained by SkyView Virtual Observatory in IRIS, AKARI, and WISE surveys respectively. The flux of ambient medium in the wavelength range of IRIS 60 μm and 100 μm, AKARI 90 μm and 140 μm and WISE 12 μm and 22 μm was calculated along with the physical properties like dust color temperature, dust mass, Planck’s function and visual extinction of the candidate at a distance of 3415.420 pc. The minimum and maximum dust mass is found to be 1.606× 1021 kg (8.030 × 10−10 M⊙), and 7.013 × 1020 kg (3.506× 10−10 M⊙) in IRIS, 2.739 × 1022 kg (1.369× 10−8 M⊙), and 1.292 × 1022 kg (6.460 × 10-9 M⊙) in AKARI and 2.297 × 1020 kg (1.148 × 10−10 M⊙) and 3.013 × 1019 kg (1.506 × 10−11 M⊙) in the WISE survey and the dust color temperature of the corresponding C-rich star average value was found to be 24.230 ± 0.229 K in IRIS, 16.780 ± 0.189 K in AKARI and 123.750 ± 0.430 K in WISE survey. The temperature in WISE was higher than that of the AKARI and WISE surveys.

Astrochemical models of interstellar ices: History matters

Context. Ice is ubiquitous in the interstellar medium. As soon as it becomes slightly opaque in the visible, it can be seen for visual extinctions (AV) above ~1.5. The James Webb Space Telescope (JWST) will observe the ice composition toward hundreds of lines of sight, covering a broad range of physical conditions in these extinct regions. Aims. We model the formation of the main constituents of interstellar ices, including H2O, CO2, CO, and CH3OH. We strive to understand what physical or chemical parameters influence the final composition of the ice and how they benchmark to what has already been observed, with the aim of applying these models to the preparation and analysis of JWST observations. Methods. We used the Nautilus gas-grain model, which computes the gas and ice composition as a function of time for a set of physical conditions, starting from an initial gas phase composition. All important processes (gas-phase reactions, gas-grain interactions, and grain surface processes) are included and solved with the rate equation approximation. Results. We first ran an astrochemical code for fixed conditions of temperature and density mapped in the cold core L429-C to benchmark the chemistry. One key parameter was revealed to be the dust temperature. When the dust temperature is higher than 12 K, CO2 will form efficiently at the expense of H2O, while at temperatures below 12 K, it will not form. Whatever hypothesis we assumed for the chemistry (within realistic conditions), the static simulations failed to reproduce the observed trends of interstellar ices in our target core. In a second step, we simulated the chemical evolution of parcels of gas undergoing different physical and chemical situations throughout the molecular cloud evolution and starting a few 107 yr prior to the core formation (dynamical simulations). We obtained a large sample of possible ice compositions. The ratio of the different ice components seems to be approximately constant for AV > 5, and in good agreement with the observations. Interestingly, we find that grain temperature and low AV conditions significantly affect the production of ice, especially for CO2, which shows the highest variability. Conclusions. Our dynamical simulations satisfactorily reproduce the main trends already observed for interstellar ices. Moreover, we predict that the apparent constant ratio of CO2/H2O observed to date is probably not true for regions of low AV, and that the history of the evolution of clouds plays an essential role, even prior to their formation.

The evolution of HCO+ in molecular clouds using a novel chemical post-processing algorithm

ABSTRACT Modelling the chemistry of molecular clouds is critical to accurately simulating their evolution. To reduce computational cost, 3D simulations generally restrict their chemistry to species with strong heating and cooling effects. Time-dependent information about the evolution of other species is therefore often neglected. We address this gap by post-processing tracer particles in the SILCC-Zoom molecular cloud simulations. Using a chemical network of 39 species and 301 reactions (including freeze-out of CO and H2O) and a novel algorithm to reconstruct a density grid from sparse tracer particle data, we produce time-dependent density distributions for various species. We focus upon the evolution of HCO+, which is a critical formation reactant of CO but is not typically modelled on the fly. We find that ∼ 90 per cent of the HCO+ content of the cold molecular gas forms in situ around nHCO+ ∼ 103–104 cm−3, over a time-scale of approximately 1 Myr. The remaining ∼ 10 per cent forms at high extinction sites, with minimal turbulent mixing out into the less dense gas. We further show that the dominant HCO+ formation pathway is dependent on the visual extinction, with the reaction H3+ + CO contributing 90 per cent of the total HCO+ production above AV, 3D = 3. We produce the very first maps of the HCO+ column density, N(HCO+), and show that it reaches values as high as 1015 cm−2. We find that 50 per cent of the HCO+ mass is located within AV ∼ 10–30 in a density range of 103.5–104.5 cm−3. Our maps of N(HCO+) are shown to be in good agreement with recent observations of the W49A star-forming region.