Extinction Values Research Articles

JWST/NIRCam Paβ Narrowband Imaging Reveals Ordinary Dust Extinction for Hα Emitters within the Spiderweb Protocluster at z = 2.16

We combine JWST/NIRCam and Subaru/MOIRCS dual Paβ+Hα narrowband imaging to trace the dust attenuation and the star formation activities of a sample of 43 Hα emitters at the core of one of the most massive and best-studied clusters in formation at the cosmic noon: the Spiderweb protocluster at z = 2.16. We find that most Hα emitters display Paβ/Hα ratios compatible with Case B recombination conditions, which translates into nebular extinction values ranging at AV ≈ 0–3 mag, and dust corrected Paβ star formation rates consistent with coeval main sequence field galaxies at fixed stellar mass ( 9.4<logM*/M⊙<11.0 ) during this cosmic epoch. Furthermore, we investigate possible environmental impacts on dust extinction across the protocluster large-scale structure and find no correlation between the dustiness of its members and environmental proxies such as phase-space position, clustercentric radius, or local density. These results support the scenario for which dust production within the main galaxy population of this protocluster is driven by secular star formation activities fueled by smooth gas accretion across its large-scale structure. This downplays the role of gravitational interactions in boosting star formation and dust production within the Spiderweb protocluster, in contrast with observations in higher redshift and less evolved protocluster cores.

Spectroscopic and Photometric Confirmation of 3 Globular and 14 Intermediate-age Clusters in the Irr II Galaxy NGC 3077

We present the results from spectroscopic and photometric analysis of 17 globular cluster (GC) candidates in the Irr II galaxy NGC 3077. The GC candidates were selected on the Hubble Space Telescope images and were cleaned of foreground Galatic stars using the GAIA parameters. We carried out aperture photometry using the multiband archival images from the Sloan Digital Sky Survey, Two Micron All Sky Survey of all candidates, and low resolution (R = 1000) spectroscopic observations of 12 GC candidates and three suspected foreground stars using the Optical System for Imaging and Low-Intermediate-Resolution Integrated Spectroscopy/Multi-Object Spectra mode at the Gran Telescopio Canarias. Age, metallicity, and extinction values were determined using both spectroscopic and photometric data, independently. We find three of the 17 candidates are old (age > 10 Gyr), metal-poor ([Fe/H] < −1.0 dex), and massive (mass > 105 M ⊙) GCs with characteristics similar to the classical GCs in the Milky Way. The rest are intermediate-age clusters (IACs) with typical ages of 3–4 Gyr and in general metal-rich clusters. The radial velocities of both populations are within 100 km s−1 of the recessional velocity of the host galaxy. A relatively large population of IACs and low value of GC specific frequency (S N = 0.7) suggest that the preinteraction galaxy was actively forming stars and star clusters, and is unlikely to be a dwarf elliptical as suggested in some previous works.

Denoising Medium Resolution Stellar Spectra With Neural Networks

ABSTRACTWe trained denoiser autoencoding neural networks on medium resolution simulated optical spectra of late‐type stars to demonstrate that the reconstruction of the original flux is possible at a typical relative error of a fraction of a percent down to a typical signal‐to‐noise ratio of per pixel. We show that relatively simple networks are capable of learning the characteristics of stellar spectra while still flexible enough to adapt to different values of extinction and fluxing imperfections that modifies the overall shape of the continuum, as well as to different values of Doppler shift. Denoised spectra can be used to find initial values for traditional stellar template fitting algorithms and—since evaluation of pretrained neural networks is significantly faster than traditional template fitting—denoiser networks can be useful when a fast analysis of the noisy spectrum is necessary, for example during observations, between individual exposures.

Retrieval of the physical parameters of galaxies from WEAVE-StePS-like data using machine learning

Context. The William Herschel Telescope Enhanced Area Velocity Explorer (WEAVE) is a new, massively multiplexing spectrograph that allows us to collect about one thousand spectra over a 3 square degree field in one observation. The WEAVE Stellar Population Survey (WEAVE-StePS) in the next 5 years will exploit this new instrument to obtain high-S/N spectra for a magnitude-limited (IAB = 20.5) sample of ∼25 000 galaxies at moderate redshifts (z ≥ 0.3), providing insights into galaxy evolution in this as yet unexplored redshift range. Aims. We aim to test novel techniques for retrieving the key physical parameters of galaxies from WEAVE-StePS spectra using both photometric and spectroscopic (spectral indices) information for a range of noise levels and redshift values. Methods. We simulated ∼105 000 galaxy spectra assuming star formation histories with an exponentially declining star formation rate, covering a wide range of ages, stellar metallicities, specific star formation rates (sSFRs), and dust extinction values. We considered three redshifts (i.e. z = 0.3, 0.55, and 0.7), covering the redshift range that WEAVE-StePS will observe. We then evaluated the ability of the random forest and K-nearest neighbour algorithms to correctly predict the average age, metallicity, sSFR, dust attenuation, and time since the bulk of formation, assuming no measurement errors. We also checked how much the predictive ability deteriorates for different noise levels, with S/NI,obs = 10, 20, and 30, and at different redshifts. Finally, the retrieved sSFR was used to classify galaxies as part of the blue cloud, green valley, or red sequence. Results. We find that both the random forest and K-nearest neighbour algorithms accurately estimate the mass-weighted ages, u-band-weighted ages, and metallicities with low bias. The dispersion varies from 0.08–0.16 dex for age and 0.11–0.25 dex for metallicity, depending on the redshift and noise level. For dust attenuation, we find a similarly low bias and dispersion. For the sSFR, we find a very good constraining power for star-forming galaxies, log sSFR ≳ −11, where the bias is ∼0.01 dex and the dispersion is ∼0.10 dex. However, for more quiescent galaxies, with log sSFR ≲ −11, we find a higher bias, ranging from 0.61 to 0.86 dex, and a higher dispersion, ∼0.4 dex, depending on the noise level and redshift. In general, we find that the random forest algorithm outperforms the K-nearest neighbours. Finally, we find that the classification of galaxies as members of the green valley is successful across the different redshifts and S/Ns. Conclusions. We demonstrate that machine learning algorithms can accurately estimate the physical parameters of simulated galaxies for a WEAVE-StePS-like dataset, even at relatively low S/NI, obs = 10 per Å spectra with available ancillary photometric information. A more traditional approach, Bayesian inference, yields comparable results. The main advantage of using a machine learning algorithm is that, once trained, it requires considerably less time than other methods.

Ionized gas in quiescent galaxies: Temperature measurement and constraint on the ionization source

In non-star-forming, passively evolving galaxies, regions with emission lines dominated by low-ionization species are classified as low-ionization emission regions (LIERs). The ionization mechanism behind such regions has long been a mystery. Active galactic nuclei (AGNs), which were once believed to be the source, have been found not to be the dominant mechanism, especially in regions distant from the galaxy nuclei. The remaining candidates, photoionization by post-asymptotic giant branch (pAGB) stars and interstellar shocks can only be distinguished with in-depth analysis. As the temperature predictions of these two models differ, temperature measurements can provide strong constraints on this puzzle. We selected a sample of 2795 quiescent red-sequence galaxies from the Sloan Digital Sky Survey IV (SDSS-IV) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. We divided the sample spectra into three groups based on the flux ratio, and utilized stacking techniques to improve the signal-to-noise ratio of the observed spectra. We determined the temperature of and through their temperature-sensitive emission line ratios. Subsequently, we compared the measured temperatures with predictions from different models. The results demonstrate consistency with the interstellar shock model with pre-shock density n = 1 $ and solar metallicity, thus supporting shocks as the dominant ionization source of LIERs. Additionally, we also find that the interstellar dust extinction value measured through the Balmer decrement appears to be larger than that implied by the forbidden line ratios of low-ionization lines.

Growing a nuclear star cluster from star formation and cluster mergers: The JWST NIRSpec view of NGC 4654

We present a detailed study of the centre of NGC 4654, a Milky Way-like spiral galaxy in the Virgo cluster that has been reported to host a double stellar nucleus, thus promising a rare view of ongoing star cluster infall into a galaxy nucleus. Analysing JWST NIRSpec integral-field spectroscopic data in combination withHubbleSpace Telescope Wide Field Camera 3 imaging of the inner 330 × 330 pc, we find that the NGC 4645 nucleus is in fact more complex than previously thought, harbouring three massive star clusters within 32 pc of the centre. Maps of infrared emission lines in the NIRSpec spectra show different morphologies for the ionised and molecular gas components. The emission from molecular hydrogen gas is concentrated at the nuclear star cluster (NSC) location, while emission from hydrogen recombination lines is more extended beyond the central cluster. The velocity fields of both gas and stars indicate that the three clusters are part of a complicated dynamical system, with the NSC having an elevated velocity dispersion in line with its high stellar mass. To investigate the stellar populations of the three clusters in more detail, we used surface brightness modelling to measure their fluxes from UV to mid-infrared wavelengths. This information, together with spectroscopically derived extinction values, are then used to fit the spectral energy distributions (SEDs) of the clusters. Two of the clusters are UV-bright and well described by single stellar populations with young ages (∼3 and 5 Myr) and relatively low masses (M* ∼ 4 × 104 M⊙andM* ∼ 105 M⊙, respectively), whereas the central cluster is much more massive (M* = 3 × 107 M⊙), and cannot be fitted by a single stellar population. Instead, we find that the presence of a minor young population (∼1 Myr,M* ∼ 3 × 104 M⊙) embedded in a dominant old population (∼8 Gyr) is required to explain its SED. Given its complex composition and the close proximity of two young star clusters that are likely to merge with it within a few hundred million years, we consider the nucleus of NGC 4654 a unique laboratory to study NSC growth from both in situ star formation and the infall of star clusters.

Phytochemical characterization and nutritional value of vegetable oils from ripe berries of Schinus terebinthifolia raddi and Schinus molle L., through extraction methods

The aims of this study are the phytochemical exploration and food valorization of Schinus molle L. (S. molle) and Schinus terebinthifolia Raddi (S. terebinthifolia) from the Rabat, Morocco. Gas chromatography (GC) and high-performance liquid chromatography (HPLC) were used to analyze the chemical composition of the oils extracted from both species by soxhlet and maceration. Moreover, physicochemical characteristics such as lipid quality indexes such as thrombogenic index (TI), atherogenic index (AI), oxidation susceptibility (OS), and calculated oxidability (Cox) were determined. These characteristics included percentage acidity, peroxide, saponification, iodine, specific extinction values, chlorophyll, and carotenoid pigments. As results, the oil yields varied from 7% (S. molle) to 13% (S. terebinthifolia). In addition, unsaturated fatty acids represented the major fraction for S. terebinthifolia (79%) and S. molle (81%). However, S. terebinthifolia contains more saturated fatty acids (20%) than S. molle (16%) with a predominance of linoleic acid (59.53% and 55%, C18,2), oleic acid (19.29% and 21.69%, C18,1), and palmitic acid (12.56% and 15.48%, C16,0) in S. molle and S. terebinthifolia, respectively. Moreover, the main sterols are β-sitosterol followed by campesterol and then Δ-5-avenasterol, while β-sitosterol varies according to the species and the extraction method. Results revealed also that campesterol is influenced by the extraction results in a content of 179.66 mg/kg (soxhlet) and 63.48 mg/kg (maceration) for S. molle, while S. terebinthifolia yeilds concentrations of 170 mg/kg and 138 mg/kg, then Δ-5-avenasterol, which present with (117 mg/kg and 136 mg/kg), (34 mg/kg and 80 mg/kg) of the total amount of sterols for the oils extracted by soxhlet and maceration, respectively. In addition, there are favorable physicochemical properties for all oils, such as chlorophylls (0.4 to 0.8 mg/kg) and carotenoids (0.7 to 2 mg/kg). However, further investigations are needed to determine other chemical compounds of both extracts as well as to evaluate their biological and health benefits.

Computerized analysis of haptens for the ultrasensitive and specific detection of Pyriftalid

Pyriftalid (Pyr) is one of the most commonly used herbicides and due to its widespread and improper use, it has led to serious pollution of groundwater, soil and other ecosystems, threatening human health. A rapid method to detect Pyr was urgently needed. A high specific monoclonal antibody (mAb) against Pyr with IC50 values of 4.7 ng/mL was obtained by mAb screening technique and method with enhanced matrix effect. The study firstly proposed colloidal gold immunochromatographic test strips (CGIA) for Pyr, which enables rapid qualitative and quantitative determination of a large number of samples anytime and anywhere, so as to effectively monitor Pyr in environment and grain samples. Based on the properties of the desired Pyr antibody, the hapten Pyr-hapten-4 with high structural similarity to Pyr molecule, similar electrostatic potential distribution, and the ability to expose Pyr functional groups was screened out from five different Pyr haptens, which was consistent with mouse antiserum test. The CGIA quickly analyze the Pyr content in positive samples such as water samples, soil samples, paddy samples, brown rice samples within 10 min, the LOD for Pyr by CGIA as low as 1.84 ng/g, the v LOD value as low as 6 ng/g, and the extinction value as low as 25 ng/g. The content of positive samples detected by CGIA was consistent with the quantitative results of LC-MS/MS, the relative accuracy was within the range of 97–103 %. The recovery rate range for Pyr by CGIA was 92.0–99.7 %, and the coefficient of variation was between 1.30–8.56 %. It indicated Pyr-targeted CGIA test strip was an efficient and fast detection method to detect real environment and food samples.

Extinction Values toward Embedded Planets in Protoplanetary Disks Estimated from Hydrodynamic Simulations

Upcoming new coronographs with deeper contrast limits, together with planned and current high-contrast imaging campaigns, will push the detectability limit of protoplanets. These planet-hunting campaigns present a new opportunity to characterize protoplanets and their surrounding environments. However, there are clear uncertainties as to what the extinction levels are at different regions of protoplanetary disks, which will impede our ability to characterize young planets. A correct understanding of the expected extinction, together with multiple photometric observations, will lead to constraints on the extinction levels, dust growth, disk evolution, and protoplanetary accretion rates. In this work, we used hydrodynamic simulations and protoplanetary disk observational constraints obtained from both dust and gas emission to explore the expected extinction maps for continuum filters associated with strong hydrogen lines as tracers of accretion and key broadband photometric filters. We provide a scaling relationship for the extinction as a function of planetary separation and disk mass for three different gas giant masses. We also report values for a subset of disks of interest targeted by multiple imaging campaigns. The described values will be useful for the optimal design of future planet-hunting surveys and for giving context to nondetections in protoplanetary disks and the observed fluxes of point sources along with the birth conditions of protoplanets.

Synergy between Short-Range Lidar and In Situ Instruments for Determining the Atmospheric Boundary Layer Lidar Ratio

Short-range elastic backscatter lidar (SR-EBL) systems are remote sensing instruments for studying low atmospheric boundary layer processes. This work presents a field campaign oriented to filling the gap between the near-surface aerosol processes regarding aerosol radiative properties and connecting them with the atmospheric boundary layer (ABL), centering attention on the residual layer and the ABL transition periods. A Colibri Aerosol Lidar (CAL) instrument, based on the short-range lidar with high spatio-temporal resolution, was used for the first time in the ACTRIS AGORA facility (Andalusian Global Observatory of the Atmosphere) in Granada (Spain). This study showed the possibility of combining lidar and in situ measurements in the lowermost 150 m. The results address, on the one hand, the characterization of the short-range lidar for developing a method to find the calibration constant of the system and to correct the incomplete overlap to further data exploitation. On the other hand, relevant radiative properties such as the temporal series of the aerosol lidar ratio and extinction coefficient were quantified. The campaign was divided in three different periods based on the vehicular emission peak in the early mornings, namely, before, during, and after the emission peak. For before and after the emission peak data classification, aerosol properties presented closer values; however, large variability was obtained after the emission peak reaching the maximum values of extinction and a lidar ratio up to 51.5 ± 11.9 (Mm)−1 and 36.0 ± 10.5 sr, respectively. During the emission peaks, the values reached for extinction and lidar ratio were up to 136.8 ± 26.5 (Mm)−1 and 119.0 ± 22.7 sr, respectively.

Photometric Re-calibration of VPHAS+ u-band photometry with the stellar colour regression method and gaia DR3

Abstract The u band magnitude is vital for determining stellar parameters and investigating specific astronomical objects. However, flux calibration in the u band for stars in the Galactic disk presents significant challenges. In this study, we introduce a comprehensive re-calibration of u-band photometric magnitudes of the VPHAS+ Data Release 4 (DR4), employing the Stellar Colour Regression (SCR) technique. By leveraging the expansive set of XP spectra and GBP photometry from Gaia Data Release 3 (DR3), as well as the individual stellar extinction values provided by the literature, we have obtained precise model magnitudes of nearly 3 million stars. Our analysis identifies systematic magnitude offsets that exhibit a standard deviation of 0.063 mag across different observational visits, 0.022 mag between various CCDs, and 0.009 mag within pixel bins. We have implemented precise corrections for these observational visits, CCD chips, and pixel bins-dependent magnitude offsets. These corrections have led to a reduction in the standard deviation between the observed magnitudes and the model magnitudes from 0.088 mag to 0.065 mag, ensuring that the calibrated magnitudes are independent of stellar magnitude, colour, and extinction. The enhanced precision of these magnitudes substantially improves the quality of astrophysical research and offers substantial potential for furthering our understanding of stellar astrophysics.

Typical solar extinction year at Plataforma Solar de Almería (Spain). Application to thermoelectric solar tower plants

The atmospheric extinction of solar radiation reflected by heliostats are recognized as an important factor of radiative losses in Concentrating Solar Power technologies in general and especially in thermoelectric solar tower plants. These types of plants are getting larger (≥100 MWe), and consequently the distances between the heliostats and the receiver very often exceed 1 km and radiative losses due to solar extinction on this path can represent a high percentage. The aerosols and water vapor along this route scatter and absorb solar radiation, preventing a percentage of it from reaching the solar receiver. For this reason, in the process of choosing a location for the design and construction of these plants, the radiative losses due to extinction in that place should be known in advance. Until now, Typical Meteorological Years have been available for the location chosen in the plant design stage, mainly considering Direct Normal Irradiance but not solar extinction. Unfortunately, ground-based measurement of solar extinction has never been properly considered because it was not known how to measure or estimate it adequately. The Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT, Spain) has developed a reliable solar extinction measurement system which has been recording accurate horizontal extinction values at Plataforma Solar de Almería (PSA) since 2017. Based on this unique in the world solar extinction database of more than five years, a Typical Solar Extinction Year has been obtained for the first time to rigorously validate extinction models that then allow knowing the extinction in any area of interest in the world for solar tower power plants and to choose the most convenient one. It has been found that the annual average extinction at PSA for the measurement distance (742 m) is 6 %, with a standard deviation of 2 % and a median of 6 %. This average annual extinction value corresponds to a horizontal extinction coefficient of (0.083 ± 0.029) km−1 and a Visual Range of 47 km (-12 km, +23 km). Frequent haze events have been observed at PSA mainly caused by Saharan dust, which can be considered one more symptom of the current increased desertification and climate change.

Illuminating the Dark Side of Cosmic Star Formation. III. Building the Largest Homogeneous Sample of Radio-selected Dusty Star-forming Galaxies in COSMOS with PhoEBO

In the last decades, an increasing scientific interest has been growing in the elusive population of dark (i.e., lacking an optical/near-IR, hereafter NIR, counterpart) dusty star-forming galaxies (DSFGs). Although extremely promising for their likely contribution to the cosmic star formation rate density (SFRD) and for their possible role in the evolution of the first massive and passive galaxies around z ∼ 3, the difficulty in selecting statistically significant samples of dark DSFGs is limiting their scientific potentialities. This work presents the first panchromatic study of a sample of 263 radio-selected NIR-dark (RS-NIRdark) galaxies discovered in the COSMOS field following the procedure by Talia et al. These sources are selected as radio-bright galaxies (S 3 GHz > 12.65 μJy) with no counterpart in the NIR-selected COSMOS2020 catalog (Ks ≳ 25.5 mag). For these sources, we build a new photometric catalog including accurate photometry from the optical to the radio obtained with a new deblending pipeline (Photometry Extractor for Blended Objects, or PhoEBO). We employ this catalog to estimate the photo-zs and the physical properties of the galaxies through an spectral energy distribution-fitting procedure performed with two different codes (Magphys and Cigale). Finally, we estimate the active galactic nucleus contamination in our sample by performing a series of complementary tests. The high values of the median extinction (A v ∼ 4) and star formation rate (SFR ∼ 500 M ⊙ yr−1) confirm the likely DSFG nature of the RS-NIRdark galaxies. The median photo-z (z ∼ 3) and the presence of a significant tail of high-z candidates (z > 4.5) suggest that these sources are important contributors to the cosmic SFRD and the evolutionary path of galaxies at high redshifts.

Feasible Application of PCLake Model to Predict Water Quality in Tropical Reservoirs

The PCLake model has not previously been used for tropical reservoirs. This study attempted to apply the PCLake model to predict the chlorophyll a concentrations (Chl-a) in a tropical reservoir in Thailand. Sensitivity analyses were performed for the constants affecting the prediction of Chl-a in the phytoplankton module. The model calibration was performed by using the adjusted value of the most sensitive constant with the observed data from July to December 2020. The effects of the initial trophic state of the reservoir on the simulated Chl-a were evaluated. The results showed that Chl-a were sensitive to six constants. Among these constants, the value of the specific extinction of detritus (cExtSpDet) was adjusted using the calculated values from the typical limnological parameters of the studied reservoir. Statistical analyses of the results of calibration and the subsequent validation with the observed data from February to September 2022 were listed as follows: NSE=0.55 and 0.37, RSR=0.67 and 0.79, and PBIAS=27% and 9%, respectively. The initial trophic state of the reservoir had no influence on the long-term prediction of Chl-a. This preliminary effort indicates that the PCLake model can be used to predict Chl-a, which is representative of algal biomass in tropical reservoirs and is essential to water quality models, without complex modifications.

Date seeds (Phoenix Dactylifera L.) valorization: chemical composition of lipid fraction.

This research was aimed to study the lipid fraction of date seeds. Seventeen seeds of date palm varieties and clones were evaluated and assessed for their chemical components and for the properties of the date pits oil. Gas liquid chromatography showed that the main unsaturated fatty acid was oleic acid (46.00 - 50.87%), while the main saturated fatty acid was lauric acid (10.11 - 19.03%) for the cultivars Mentouj Tissgharine (MTN) and Bheir Ingli (KBN) respectively; other fatty acids were also identified. The physicochemical characterization showed an acid value ranging from 0.068 to 1.188%, a specific extinction value equal to (K232: 1.350-2.225; K270: 0.318- 0.521), a peroxide value in the interval (1.059-5.618 meq O2/kg) and an iodine value (41.861-59.980 g Iodine/100 g). The pheophytin content of date seed oils was found within the range from 21.855 to 75.685%. The chemical analysis showed that date seed oil can be useful in cosmetic and food products processing.

An HST Study of the Substellar Population of NGC 2024

We performed an HST/WFC3-IR imaging survey of the young stellar cluster NGC 2024 in three filters probing the 1.4 μm H2O absorption feature, characteristic of the population of low-mass and substellar-mass objects down to a few Jupiter masses. We detect 812 point sources, 550 of them in all three filters with signal-to-noise ratio greater than 5. Using a distance-independent two-color diagram, we determine extinction values as high as A V ≃ 40. We also find that the change of effective wavelengths in our filters results in higher A V values as the reddening increases. Reconstructing a dereddened color–magnitude diagram, we derive a luminosity histogram both for the full sample of candidate cluster members and for an extinction-limited subsample containing the 50% of sources with A V ≲ 15. Assuming a standard extinction law like Cardelli et al. with a nominal R V = 3.1, we produce a luminosity function in good agreement with the one resulting from a Salpeter-like initial mass function for a 1 Myr isochrone. There is some evidence of an excess of luminous stars in the most embedded region. We posit that the correlation may be due to those sources being younger, and therefore overluminous, than the more evolved and less extincted cluster's stars. We compare our classification scheme based on the depth of the 1.4 μm photometric feature with the results from the spectroscopic survey of Levine et al., and we report a few peculiar sources and morphological features typical of the rich phenomenology commonly encountered in young star-forming regions.

The Preexplosion Environments and the Progenitor of SN 2023ixf from the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX)

Supernova (SN) 2023ixf was discovered on 2023 May 19. The host galaxy, M101, was observed by the Hobby–Eberly Telescope Dark Energy Experiment collaboration over the period 2020 April 30–2020 July 10, using the Visible Integral-field Replicable Unit Spectrograph (3470 ≲ λ ≲ 5540 Å) on the 10 m Hobby–Eberly Telescope. The fiber filling factor within ±30″ of SN 2023ixf is 80% with a spatial resolution of 1″. The r < 5.″5 surroundings are 100% covered. This allows us to analyze the spatially resolved preexplosion local environments of SN 2023ixf with nebular emission lines. The two-dimensional maps of the extinction and the star formation rate (SFR) surface density (ΣSFR) show weak increasing trends in the radial distributions within the r < 5.″5 regions, suggesting lower values of extinction and SFR in the vicinity of the progenitor of SN 2023ixf. The median extinction and that of the surface density of SFR within r < 3″ are E(B − V) = 0.06 ± 0.14, and There is no significant change in extinction before and after the explosion. The gas metallicity does not change significantly with the separation from SN 2023ixf. The metal-rich branch of the R 23 calculations indicates that the gas metallicity around SN 2023ixf is similar to the solar metallicity (∼Z ☉). The archival deep images from the Canada–France–Hawaii Telescope Legacy Survey (CFHTLS) show a clear detection of the progenitor of SN 2023ixf in the z band at 22.778 ± 0.063 mag, but nondetections in the remaining four bands of CFHTLS (u, g, r, i). The results suggest a massive progenitor of ≈22 M ☉.

Dynamical analysis of a stochastic epidemic HBV model with log-normal Ornstein–Uhlenbeck process and vertical transmission term

Considering the transmission rate perturbed by log-normal Ornstein–Uhlenbeck process, we develop a stochastic HBV model with vertical transmission term. For higher-dimensional deterministic system, the local asymptotic stability of the endemic equilibrium is given by proving the global stability of the corresponding linearized system. For stochastic system, the existence of stationary distribution is obtained by constructing several suitable Lyapunov functions and using the ergodicity of the Ornstein–Uhlenbeck process and the critical value corresponding to the basic reproduction number for determined system is derived, which means the persistence of the disease. And sufficient conditions for disease extinction are given. Furthermore, by solving five-dimensional Fokker–Planck equation, the exact expression of the probability density function near the quasi-equilibrium is provided to reveal the statistical properties. In the end, numerical simulations illustrate our theoretical results and exhibit the trends of the critical values for persistence and extinction of diseases along with the change of noise intensity and reversion speed.

Parameterization of stars and determination of interstellar extinction from multicolor photometry

We have developed a method for the determination of stellar parameters and interstellar extinction values from multicolor photometry. The application of this method to a set of stars in a small area in the sky allows us to determine an increase of interstellar extinction with distance in that direction and, consequently, to construct a 3D extinction map of the Milky Way Galaxy.

Long-period maser-bearing Miras in the Galactic center

We establish a sample of 370 Mira variables that are likely near the Galactic center (GC). The sources have been selected from the OGLE and BAaDE surveys based on their sky coordinates, OGLE classifications, and BAaDE maser-derived line-of-sight velocities. As the distance to the GC is known to a high accuracy, this sample is a test bed for reddening and extinction studies toward the GC and in Mira envelopes. We calculated separate interstellar- and circumstellar-extinction values for individual sources, showing that there is a wide range of circumstellar extinction values (up to four magnitudes in the Ks band) in the sample, and that circumstellar reddening is statistically different from interstellar reddening laws. Further, the reddening laws in the circumstellar environments of our sample and the circumstellar environments of Large Magellanic Cloud (LMC) Miras are strikingly similar despite the different metallicities of the samples. Period-magnitude relations for the mid-infrared (MIR) WISE and MSX bands are also explored, and in the WISE bands we compare these to period-magnitude relationships derived from Miras in the LMC as it is important to compare these LMC relations to those in a higher metallicity environment. Emission from the envelope itself may contaminate MIR magnitudes altering the relations, especially for sources with thick envelopes.