Star Burst Research Articles

AstroSat observations of interacting galaxies NGC 7469 and IC 5283

Aims. We carry out deep near-ultrviolet (NUV) and far-ultrviolet (FUV) imaging of an interacting galaxy system, comprised of a Seyfert type 1 galaxy NGC 7469 and its companion IC 5283. Our aim is to resolve and map the star-forming regions in the outer arms and look for signs of interaction between the two galaxies. Methods. We used AstroSat Ultra Violet Imaging Telescope (UVIT) to obtain NUV and FUV images of NGC 7469 in a range of filters. We have carried out photometry of star-forming regions in the two galaxies and found their spatial distributions. We also obtained the distributions of star formation rates (SFR) in NGC 7469 and IC 5283 using the estimates obtained from the FUV and NUV bands. We also carried out Kolmogorov-Smirnov tests to look for differences in the SFRs in the two galaxies. We derived the spectral energy distribution (SED), leading to the determination of physical parameters, including the overall SFR, stellar mass (M*), dust mass (MDust), and specific star formation rates (sSFRs) in both the galaxies. Results. Our NUV and FUV images show the presence of an outer spiral arm that is better resolved. We have identified 33 new star-forming regions out of 51 total identified in the UVIT composite image. Enhanced star formation activity is observed to coincide with the interaction, and KS tests show that there are no significant differences in the SFR distributions of NGC 7469 and IC 5283, indicating that the interaction between the galaxies has not influenced their star formation processes differently. The SED plots and the photometric results demonstrate that most of the star formation activity is confined inside the central starburst (SB) ring.

Omnipolar mapping and vector mapping in premature ventricular contractions ablation: a comparison with bipolar mapping

Abstract Background Omnipolar Mapping, with HD Grid high-density mapping catheter, overcomes the dependency of EGM characteristics to wavefront orientation, reconstructing the highest peak-to-peak voltage attainable within the electric field and the real wavefront direction, displayed in the form of a local activation vector [1][2]. Methods Consecutive patients who underwent radiofrequency ablation of PVCs from October 2021 to August 2023 at the Hospital Clinic of Barcelona were included in the study. EAM was performed with EnsiteX mapping system, Advisor HDgrid was used as mapping catheter. An activation map was performed if enough PVC burden. The area of interest was determined by earliest activation time combined with the morphology of unipolar electrogram during activation mapping. RF was delivered at the area of interest with target temperature of 45°C and maximum power of 50W. Both bipolar and omnipolar maps were analysed retrospectively. The reviewer was blinded to the ablation set for this analysis. A window of interest was created uniformally for all maps by defining a caliper within 15 ms before the onset of PVC. Activation vectors were displayed on the map and visually analysed. Three specific patterns were identified: Starburst, Homogeneous and Chaotic. Area of the earliest activation was measured. Earliest site of bipolar and omnipolar maps and specific location of star burst pattern were tagged. The site of the effective RF ablation was identified and the distance between points was determined. Results 18 patients were included. Overall, 11(61%) were males; age: 57,9±15,2 ys, 6(33%) patients haven't structural heart disease, 4(22%) presented PVC-induced cardiomyopathy. Mean left ventricular ejection fraction was 46±10. Mean PVC burden was 27±10%. In 9(50%) patients, PVCs were ablated from RVOT, 4(22%) in LVOT, 1(5%) in the left superior fascicle, 1(5%) in the antero-lateral papillary muscle, 2(10%) in the perihissian area and 1(5%) in the aortomitral continuity. Compared with bipolar, omnipolar mapping showed a smaller area of earliest activation(2,13±1,9mm2 vs 3,34±2,1 mm2,p<0,001), a shorter distance of the earliest point to starburst region(4,2±4,1mm vs 7,8±4,2mm,p<0,001) and shorter distance to the effective ablation site(6,1±3,9 mm vs 8,33±4,2mm, p<0,07). No significative difference was found between the effective RF ablation site and the starburst area compared to the distance between the effective RF ablation site and the omnipolar earliest deflection (6,11±3,9mm vs 6,5±4,3mm, p=0,6). No statistical significative difference was found between the timing of the earliest deflection in both settings (33,2±12,5 ms vs 31,5±12 ms, p=0,2) Conclusions Omnipolar mapping allows a better identification of the area of interest in PVC’s ablation compared to bipolar mapping. Vector mapping is a valuable asset to identify the earliest activation point to guide PVCs catheter ablation.Retrospective EAM analysisArea/distance measurements

Linear to circular conversion in the polarized radio emission of a magnetar

AbstractRadio emission from magnetars provides a unique probe of the relativistic, magnetized plasma within the near-field environment of these ultra-magnetic neutron stars. The transmitted waves can undergo birefringent and dispersive propagation effects that result in frequency-dependent conversions of linear to circularly polarized radiation and vice versa, thus necessitating classification when relating the measured polarization to the intrinsic properties of neutron star and fast radio burst emission sites. We report the detection of such behaviour in 0.7–4 GHz observations of the P = 5.54 s radio magnetar XTE J1810−197 following its 2018 outburst. The phenomenon is restricted to a narrow range of pulse phase centred around the magnetic meridian. Its temporal evolution is closely coupled to large-scale variations in magnetic topology that originate from either plastic motion of an active region on the magnetar surface or free precession of the neutron star crust. Our model of the effect deviates from simple theoretical expectations for radio waves propagating through a magnetized plasma. Birefringent self-coupling between the transmitted wave modes, line-of-sight variations in the magnetic field direction and differences in particle charge or energy distributions above the magnetic pole are explored as possible explanations. We discuss potential links between the immediate magneto-ionic environments of magnetars and those of fast radio burst progenitors.

Homogeneous fine classification of Markarian galaxies based on SDSS medium-resolution spectroscopy

Context. Markarian (Mrk) galaxies, revealed due to their ultraviolet excess are very famous; they play a significant role in many astro-physical problems and come in a variety of types: Seyferts (Sys), low-ionization narrow emission-line regions (LINERs), starbursts (SBs), blue compact dwarf galaxies (BCDGs), as well as some quasars (QSOs) and blazars. They also appear as sources of non-optical radiation, such as gamma-ray, X-ray, ultraviolet (UV), infrared (IR), and radio, including some extremely high-energy gamma-ray sources (Mrk 421, Mrk 501) and very high-luminosity IR galaxies (Mrk 231). Aims. The classifications of Mrk galaxies for activity types have been carried out based on old mostly poor-quality and inhomoge-neous spectra (relatively low-resolution photographic spectra and low S/N spectra). The Sloan Digital Sky Surveys (SDSS) provides ~90% of the existing medium-resolution spectra, and is a relevant homogeneous database for classification of galaxies. Our aim was to obtain homogeneous classifications of Mrk galaxies by means of the SDSS spectra. Methods. Based on our work on the classification of newly revealed objects from various recent catalogs, we developed a fine classification scheme for activity types based on the homogeneous database of the SDSS spectroscopy. This scheme was applied to Mrk galaxies having spectra in the SDSS (779 out of 1544, 50.45%). Results. As a result, 779 Mrk galaxies now have homogeneous optical spectral classification that can be used for further studies and statistics of their physical and spatial properties. We revealed 2 QSOs, 49 classical Seyferts (broad-line Seyferts 1, BLS1s), 17 narrow-line Seyferts 1 (NLS1s), 4 Sy2s, 12 LINERs, 11 active galactic nuclei (AGN) without a definite type, 31 Composite spectrum objects, and 533 HII/Starbursts. Due to low-quality spectra, some objects were left without definite activity types and were classified as emission or absorption galaxies.

Astronomical Surveys and Active Galaxies

Astronomical Surveys are the main source for discoveries in astronomy. We are giving the most important parameters the significance of the surveys, their main products: images, photometric, spectroscopic and other data. Among the surveys, namely extragalactic ones, most important are those for Active Galaxies (both Active Galactic Nuclei (AGN) and Starburst (SB) Galaxies), and particularly the AGN. These objects reveal many spatial and physical characteristics helping understanding the Universe. We give a brief review of our searches and studies for Active Galaxies.

Morphological Study of Active Galaxies based on SDSS Images. Preliminary Results

Activity in galaxies has mainly two major forms: Active Galactic Nuclei (AGN) and Starburst (SB). Moreover, different types of AGN have different morphology. However, this question has not yet been properly investigated and due to old low-quality images, the morphology of many galaxies is not well described. SDSS images give a good possibility to homogeneously classify galaxies and investigate differences by the activity types. The concentration of the central part and the ratio between the central bulge and the total flux is a subject for detailed study. We use SDSS images to classify different types of active galaxies (both AGN and Starburst) and understand differences between QSOs, Seyferts 1 and 2, LINERS and Composites, as well as Starburst galaxies. The best expectation from our study will be the preliminary classification of active galaxies into activity types based on the images and before having their spectral types.

Development of Hydrophilic Oxide/Polymer Composite Membranes for Polymer Electrolyte Fuel Cells Operating at Wide Temperature Range

Toward the wide-spread use of heavy-duty vehicles (HDVs) operated by polymer electrolyte fuel cells (PEFCs) should approach the higher temperature around 120oC besides normal temperature (60-80oC). Commercial perfluorosulfonic acid-based electrolyte (PFSA, e.g. NafionⓇ) shows better proton conductivity with chemical stability in wide temperatures range, though decreases under low back pressure at 100~120 oC. In order to improve the proton conductivity at the higher temperature range, composite membrane of NafionⓇ with a hydrophilic filler of Ta doped TiO2 (Ta-TiO2) was synthesized. The Ta-TiO2 nanoparticles fillers with fused-aggregate network microstructure were synthesized by the flame method, and were crushed by wet mill(Star Burst, :Sugino Machine Limited CO.). The fillers were mixed with NafionⓇsolution (20 wt.%：D2020 Chemours Co.) by use of a rotary ultrasonic dispersing processor (500 rpm, 60 min. PR-1 :Thnky Co.), a planetary ball mill (500 rpm、30 min.：PULVERISETTE 6：FRITSCH Co.), and a defoaming processor (500 rpm、5 min.：HM-400W: Kyouritu Seiki). The dispersion solution was coated in hot air by use of a die coating system (die coater: Taku-Dai Mini-50: Daimon Co., Ltd.), and were hot-pressed (140 ℃ 3 min. TCMD-2.5:TOHO KOGYO co.) to form composite membranes (9 cm×9 cm ×25 µmt).The cross-sectional backscattered electron image BSE) of the composite membrane observed by scanning electron microscope (SEM, acceleration voltage 2 kV, SU9000: Hitachi High-Tech Co.) and transmission electron microscope (TEM, H-9500: Hitachi High-Tech Co.). The proton conductivity of the composite membrane was measured by the AC four-probe method. The current-voltage (IV) polarization curves of Single cells using the prepared composite membrane (membrane thickness: 25 µm) were measured at 80 ℃ 100% RH and 120 ℃ 20% RH, back pressure 50 kPaG.The obtained composite membranes were well flexibility with softness. The BSE images indicated that the high contrast images of Ta-TiO2 parties were uniformly dispersed in composite membrane. The higher magnified of the cross-sectional TEM images also showed that the hydrophilic surface of Ta-TiO2 adhered to the Nafion® without any air pores. The proton conductivity of the composite membrane at 80% RH increased with increasing Ta-TiO2 content and showed maximum value of 0.13 S cm-1at 3 wt%, and then decreased. The maximum proton conductivity was 1.3 times higher than that of Nafion®. The IV performance of the single cell using composite membrane kept same performance to that using Nafion® membrane at 80 oC 100% RH, and then improved at 120 oC 20% RH. The water content at 120 oC 20% RH kept higher value by the effect of hydrophilicity of the Ta-TiO2, which would be one of the reasons to enhance the cell performance at 120 oC 20% RH. Figure 1

On the accretion of a new group of galaxies onto Virgo – III. The stellar population radial gradients of dEs

ABSTRACT Using MUSE data, we investigate the radial gradients of stellar population properties (namely age, [M/H], and the abundance ratio of α elements [α/Fe]) for a sample of nine dwarf early-type (dE) galaxies with log(M⋆/M⊙) ∼ 9.0 and an infall time onto the Virgo cluster of 2–3 Gyr ago. We followed a similar approach as in Bidaran et al. to derive their stellar population properties and star formation histories (SFHs) through fitting observed spectral indices and full spectral fitting, respectively. We find that these nine dE galaxies have truncated [Mg/Fe] versus [Fe/H] profiles than equally massive Virgo dE galaxies with longer past infall times. Short profiles of three dE galaxies are the result of their intense star formation which has been quenched long before their accretion onto the Virgo cluster, possibly as a result of their group environment. In the remaining six dE galaxies, profiles mainly trace a recent episode of star burst within 0.4Re which results in higher light-weighted [α/Fe] values. The latter SFH peak can be due to ram pressure exerted by the Virgo cluster at the time of the accretion of the dE galaxies. Also, we show that younger, more metal-rich, and less α-enhanced stellar populations dominate their inner regions (i.e. < 0.4Re) resulting in mainly flat ∇age, negative ∇[M/H], and positive ∇[α/Fe]. We find that with increasing log(σRe) of dE galaxies, ∇age and ∇[α/Fe] flatten, and the latter correlation persists even after including early-type galaxies up to log(σRe ∼ 2.5), possibly due to the more extended star formation activity in the inner regions of dEs, as opposed to more massive early-type galaxies.

Main Sequence to Starburst Transitioning Galaxies: Gamma-Ray Burst Hosts at z ∼ 2

Star-forming galaxies populate a main sequence (MS), a well-defined relation between stellar mass (M *) and star formation rate (SFR). Starburst (SB) galaxies lie significantly above the relation, whereas quenched galaxies lie below the sequence. In order to study the evolution of galaxies on the SFR–M * plane and its connection to the gas content, we use the fact that recent episodes of star formation can be pinpointed by the existence of gamma-ray bursts (GRBs). Here we present sensitive [C i] nondetections of z ∼ 2 ultraluminous infrared (ULIRG) GRB host galaxies. We find that our GRB hosts have similar molecular masses to those of other ULIRGs. However, unlike other ULIRGs, the GRB hosts are located at the MS or only a factor of a few above it. Hence, our GRB hosts are caught in the transition toward the SB phase. This is further supported by the estimated depletion times, which are similar to those of other transitioning galaxies. The GRB hosts are [C i]-dark galaxies, defined as having a [C i]/CO temperature brightness ratio of <0.1. Such a low [C i]/CO ratio has been found in high-density environments (n H > 104 cm−3) where CO is shielded from photodissociation, leading to underabundances of [C i]. This is consistent with the merger process that is indeed suggested for our GRB hosts by their morphologies.

Mass–Metallicity Relationship of SDSS Star-forming Galaxies: Population Synthesis Analysis and Effects of Star Burst Length, Extinction Law, Initial Mass Function, and Star Formation Rate

We investigate the mass–metallicity relationship of star-forming galaxies by analyzing the absorption line spectra of ∼200,000 galaxies in the Sloan Digital Sky Survey. The galaxy spectra are stacked in bins of stellar mass, and a population synthesis technique is applied yielding the metallicities, ages, and star formation history of the young and old stellar population together with interstellar reddening and extinction. We adopt different lengths of the initial starbursts and different initial mass functions for the calculation of model spectra of the single stellar populations contributing to the total integrated spectrum. We also allow for deviations of the ratio of extinction to reddening R V from 3.1 and determine the value from the spectral fit. We find that burst length and R V have a significant influence on the determination of metallicities, whereas the effect of the initial mass function is small. The R V values are larger than 3.1. The metallicities of the young stellar population agree with extragalactic spectroscopic studies of individual massive supergiant stars and are significantly higher than those of the older stellar population. This confirms galaxy evolution models where metallicity depends on the ratio of gas to stellar mass and where this ratio decreases with time. Star formation history is found to depend on galaxy stellar mass. Massive galaxies are dominated by stars formed at early times.

GOODS-ALMA 2.0: Last gigayear star formation histories of the so-called starbursts within the main sequence

Recently, a population of compact main sequence (MS) galaxies exhibiting starburst-like properties were identified in the GOODS-ALMA blind survey at 1.1 mm. Several evolution scenarios were proposed to explain their particular physical properties (e.g., compact size, low gas content, short depletion time). In this work, we aim to study the star formation history (SFH) of the GOODS-ALMA galaxies to understand whether or not the so-called ‘starbursts (SBs) in the MS’ galaxies exhibit a star formation activity over the last gigayear that is different from that of the MS galaxies and that could explain their specificity. We use the CIGALE SED modelling code to which we add nonparametric SFHs. To compare the recent SFHs of the galaxies quantitatively, we define a parameter, the star formation rate (SFR) gradient, which provides the angle showing the direction that a galaxy has followed in the SFR-versus-stellar-mass plane over a given period. We show that SB in the MS galaxies show positive or weak negative gradients over the last 100, 300, and 1000 Myr, which is at odds with a scenario where these galaxies would be transitioning from the SB region at the end of a strong starburst phase. Normal GOODS-ALMA galaxies and “SB in the MS” galaxies show the same SFR gradient distribution, meaning that they have similar recent SFHs despite their different properties (compactness, low depletion time). The “SBs in the MS” galaxies manage to maintain their star-formation activity, allowing them to stay within the MS. This points toward a diversity of galaxies within a complex MS.

Dermoscopic Features of Perilesional Skin of Unstable Vitiligo: A Cross-Sectional Study

Objectives: Dermoscopy is a very useful tool in determining stability in vitiligo. Dermoscopic features of unstable vitiligo are trichrome appearance, comet tail appearance, star burst appearance, amoeboid pattern, nebular pattern, tapioca sago pattern and perifollicular hypopigmentation. Most studies are done on determining features of vitiligo lesions; however, there is lack of studies on dermoscopy in normal appearing perilesional skin. This would give an insight into the extent of the disease process, beyond the borders of skin lesions. We conducted a study on 100 unstable lesions of vitiligo and studied dermoscopic features in its perilesional skin. The objective of this study was to observe dermoscopic features of apparently normal perilesional skin in patients of unstable vitiligo. Materials and Methods: A cross-sectional study was conducted in a tertiary care centre in New Delhi. We evaluated perilesional skin of 100 unstable vitiligo lesions over a span of 1 year. The perilesional skin has been defined as area within 5 cm of the lesion. Dermoscopy was performed using DERMLITE 4 Dermoscope at 10X magnification with inbuilt white light and polarised light. Polarised light was used to study changes in the pigmentary network and other patterns. We looked for features such as pigment network, perifollicular pigmentation, presence of leukotrichia, microkoebner phenomenon and satellite lesions in the perilesional skin. Results: The study included a total of 100 unstable lesions. Majority of patients belonged to the age group of 18−30 years. Females outnumbered males (1.8:1). All cases had progressive disease and mean duration of disease was 12.07 ± 10. 85 years. Dermoscopic features of vitiligo were observed in 56% of patients even in normal appearing perilesional skin. The most common dermoscopic finding observed was reduced pigment network which was seen in 33% of cases. Perifollicular hypopigmentation and depigmentation were observed in 23 and two sites, respectively, while leukotrichia was seen at ten sites. Eight sites showed microkoebners phenomenon. Conclusion: The perilesional apparently normal skin also shows signs of disease activity in cases of unstable vitiligo. Hence, perilesional skin should also be examined carefully with the dermoscope and topical treatment and targeted phototherapy should aim at covering the normal looking perilesional skin as well, at least within 5 cm of the borders of the skin lesions. Importantly, the perilesional skin should also be examined before surgery.

Testing the evolutionary pathways of galaxies and their supermassive black holes and the impact of feedback from active galactic nuclei via large multiwavelength data sets

ABSTRACT It is still a matter of intense debate how supermassive black holes (SMBHs) grow and the role played by feedback from active galactic nuclei (AGN) in the coevolution of SMBHs and galaxies. To test the coevolution proposed by theoretical models, we compile a large AGN sample of 5639 X-ray detected AGN, over a wide redshift range, spanning nearly three orders of magnitude in X-ray luminosity. The AGN have been detected in the COSMOS-Legacy, the Boötes, the XMM-XXL, and the eROSITA Final Equatorial Depth Survey (eFEDS) fields. Using the specific star formation rate estimates, we split the AGN host galaxies into star forming (SF), starburst (SB), and quiescent (Q). Our results show that the AGN accretion is increased in SB systems compared to SF and Q. Our analysis reveals a mild increase of LX with M*. The LX/star formation rate (SFR) ratio has a weak dependence on M* and at fixed M* it is highest in Q systems. The latter trend is mostly driven by the significant drop in SFR in the Q state. The measured strong variations in SFR from the SB/SF to Q mirror those predicted in merger models with AGN feedback. However, the observed mild variations in LX are at variance with the same models. We also study the evolution of SFR for a galaxy control sample and found that it is very similar to that of X-ray AGN. This suggests that either AGN play a minor role in the star formation quenching, or the relative timescales of the two processes are different.

High-Pressure Water Jet System Treatment of Argan Nut Shell and Enzymatic Hydrolysis for Bioethanol Production

Argan nut shell represents the most generated by-product during the process of the extraction of argan oil. For the first time, argan nut shell was characterized and assessed as a new potential feedstock for bioethanol production using a combination of mechanical and enzymatic pretreatment. Argan shell samples were first disintegrated using the Star Burst system, which involves a high-pressure water jet system. Then, the pretreated argan nut shell was subjected to enzymatic hydrolysis using Viscozyme L (30 FBGU/g). Afterwards, the fermentation of the hydrolysate by Saccharomyces cerevisiae was investigated. Argan nut shell, as a feedstock plentiful in carbohydrates, conferred a high yield of saccharification (90%) and an optimal ethanol bioconversion (45.25%) using Viscozyme L (30 FBGU/g) at 2%w/v of argan feedstock.

What powers galactic outflows: nuclear starbursts or AGN?

ABSTRACT Galactic outflows can be powered either by nuclear starbursts (SB) or active galactic nuclei (AGNs). It has been argued that extreme starbursts can power extreme outflows, without the need to invoke AGN feedback. However, contributions from past and/or hidden AGN activity cannot be ruled out. Here, we constrain the potential role of the central black hole in driving powerful outflows in starburst galaxies (with no sign of ongoing AGN activity). We examine whether the galactic outflows can be explained by AGN luminosity evolution in the framework of our AGN ‘radiative dusty feedback’ scenario. We show that the outflow energetics of starburst galaxies in the local Universe can be quantitatively reproduced by power-law and exponential luminosity decays, coupled with radiation trapping. Likewise, a combination of heavy obscuration and mild luminosity decay may account for the energetics of galactic outflows observed in dusty star-forming galaxies in the early Universe. We discuss different physical arguments for SB versus AGN outflow-driving, and conclude that the latter can have a major impact on the evolution of galaxies.

PO-637-04 BEYOND ACTIVATION AND VECTOR ARROW MAPPING: POWER OF OMNIPOLAR VOLTAGE TO DETECT BREAKOUT SITES

Traditionally, LAT maps depicting earliest activation, derived star burst vector depictions, and QS patterns on unipoles have been used to detect breakout sites. In the ventricle such strategies may be limited due to indeterminate LAT annotation, myocardial thickness and tangential activation to the mapping surface.

Spatially resolved star-formation relations of dense molecular gas in NGC 1068

Context. According to the current understanding of star formation (SF), the regulation of this phenomenon in galaxy disks reflects a complex balance between processes that operate in molecular gas on local cloud scales as well as on global disk scales. Aims. We analyse the influence of the dynamical environment on the SF relations of the dense molecular gas in the starburst (SB) ring of the Seyfert 2 galaxy NGC 1068. Methods. We used ALMA to image the emission of the 1–0 transitions of HCN and HCO+, which trace dense molecular gas in the r ∼ 1.3 kpc SB ring of NGC 1068, with a resolution of 56 pc. We also used ancillary data of CO(1–0) as well as CO(3–2) and its underlying continuum emission at the resolutions of ∼100 pc and ∼40 pc, respectively. These observations allow us to probe a wide range of molecular gas densities (nH2 ∼ 103 − 5 cm−3). The star-formation rate (SFR) in the SB ring of NGC 1068 is derived from Paα line emission imaged by HST/NICMOS. We analyse how different formulations of SF relations change depending on the adopted aperture sizes and on the choice of molecular gas tracer. Results. The scatter in the Kennicutt–Schmidt relation, linking the SFR density (ΣSFR) with the (dense) molecular gas surface density (Σdense), is about a factor of two to three lower for the HCN and HCO+ lines compared to that derived from CO(1–0) for a common aperture. Correlations lose statistical significance below a critical spatial scale of ≈300−400 pc for all gas tracers. The SF efficiency of the dense molecular gas, defined as SFEdense ≡ ΣSFR/Σdense, shows a scattered distribution as a function of the HCN luminosity (L′(HCN)) around a mean value of ≃0.01 Myr−1. An alternative prescription for SF relations, which includes the dependence of SFEdense on the combination of Σdense and the velocity dispersion (σ), resolves the degeneracy associated with the SFEdense − L′(HCN) plot. The SFEdense values show a positive trend with the boundedness of the gas, measured by the parameter b ≡ Σdense/σ2. We identify two branches in the SFEdense − b plot that correspond to two dynamical environments within the SB ring; they are defined by their proximity to the region where the spiral structure is connected to the stellar bar. This region corresponds to the crossing of two overlapping density wave resonances, where an increased rate of cloud-cloud collisions would favour an enhanced compression of molecular gas. Conclusions. These results suggest that galactic dynamics plays a major role in the efficiency of the conversion of gas into stars. Our work adds supporting evidence that density-threshold SF models, which argue that the SFEdense should be roughly constant, fail to account for spatially resolved SF relations of dense gas in the SB ring of NGC 1068.

Production of Fungal Nanochitosan Using High-Pressure Water Jet System for Biomedical Applications.

In this present work, fungal nanochitosans, with very interesting particle size distribution of 22 µm, were efficiently generated in high-yield production using a high-pressure water jet system (Star Burst System, Sugino, Japan) after 10 passes of mechanical treatment under high pressure. The specific characterization of fungal chitosan nanofibers suspensions in water revealed a high viscosity of 1450 mPa.s and an estimated transparency of 43.5% after 10 passes of fibrillation mechanical treatment. The mechanical characterization of fungal nanochitosan (NC) film are very interesting for medical applications with a Young’s modulus (E), a tensile strength (TS), and elongation at break (e%) estimated at 2950 MPa, 50.5 MPa, and 5.5%, respectively. Furthermore, we exhibited that the fungal nanochitosan (NC) film presented very good long-term antioxidant effect (reached 82.4% after 96 h of contact with DPPH radical solution) and very interesting antimicrobial activity when the nanochitosan (NC) fibers are mainly activated as NC-NH3+ form at the surface of the film with 45% reduction and 75% reduction observed for S. aureus (Gram-positive) and E. coli (Gram-negative), respectively, after 6 h of treatment. These promising antimicrobial and antioxidant activities indicated the high potential of valorization toward biomedical applications.

Star burst in W 49 N presumably induced by cloud–cloud collision

Abstract We present high-resolution observations of CS (J = 1–0), H13CO+ (J = 1–0), and SiO (v = 0: J = 1–0) lines, together with the 49 GHz and 86 GHz continuum emissions, toward W 49 N carried out with the Nobeyama Millimeter Array. We identified 11 CS, eight H13CO+, and six SiO clumps with radii of 0.1–0.5 pc. The CS and H13CO+ clumps are mainly divided into two velocity components, one at 4 km s−1 and the other at 12 km s−1, while the SiO clumps have velocities between the two components. The SiO emission is distributed toward the ultracompact H ii (UCHII) ring, where the 4 km s−1 component clumps of CS and H13CO+ also exist. The 12 km s−1 component clumps of CS are detected at the east and west of the UCHII ring with an apparent hole toward the ring. The clump masses vary from 4.4 × 102 M$_\odot$ to 4.9 × 104 M$_\odot$ with the mean values of 0.94 × 104 M$_\odot$, 0.88 × 104 M$_\odot$, and 2.2 × 104 M$_\odot$ for the CS, H13CO+, and SiO clumps, respectively. The total masses derived from CS, H13CO+, and SiO clumps are 1.0 × 105 M$_\odot$, 0.70 × 105 M$_\odot$, and 1.3 × 105 M$_\odot$, respectively, which agree well with the corresponding virial masses of 0.71 × 105 M$_\odot$, 1.3 × 105 M$_\odot$, and 0.88 × 105 M$_\odot$, respectively. The average molecular hydrogen densities of the clumps are 0.90 × 106 cm−3, 1.4 × 106 cm−3, and 7.6 × 106 cm−3 for the CS, H13CO+, and SiO clumps, respectively. The density derived from the SiO clumps seems significantly higher than those from the others, probably because the SiO emission is produced in high-density shocked regions. The free-fall time scale of the clumps is estimated to be ∼3 × 104 yr, which gives an accretion rate of 3 × 10−3–1 M$_\odot$ yr−1 on to a stellar core. The observed clumps are, if they are undergoing free-fall, capable of producing dozens of massive stars in the next 105 yr. We propose a view that two pre-existing clouds with radial velocities of 4 km s−1 and 12 km s−1 collided with each other almost face-on to produce the observed clumps with intermediate velocities and triggered the burst of massive star formation in W 49 N.

Transforming gas-rich low-mass disky galaxies into ultra-diffuse galaxies by ram pressure

Faint extended elliptically-shaped ultra-diffuse galaxies and slightly brighter and more compact dwarf elliptical and lenticular stellar systems are common in galaxy clusters. Their poorly constrained evolutionary paths can be studied by identifying young ultra-diffuse galaxy and dwarf elliptical analogs populated with bright, massive stars. Using data mining we identified 11 such low-mass ($2\times10^8<M_*<2\times10^9 M_{\odot}$) galaxies with large half-light radii ($2.0<r_e<5$ kpc) and recently quenched star formation in the Coma and Abell 2147 galaxy clusters. All galaxies happen to have ram-pressure-stripped tails with signs of current or recent star formation. Deep spectroscopic observations revealed rotating stellar discs containing 70-95% dark matter by mass. A large fraction of the disc stars (10-60%) formed in intense star bursts 180-970 Myr ago, probably triggered by ram pressure. Observed global gradients of stellar age corroborate this scenario. Passive evolution in the next 10 Gyr will transform 9 of the 11 galaxies into ultra-diffuse galaxies. If we assume a constant rate of galaxy infall, 44$\pm$16% of the most luminous present-day ultra-diffuse galaxies in Coma must have formed via ram pressure stripping of disky progenitors.