We discovered a nebula in the low-metallicity (Z=0.1 ) nearby ( Mpc) dwarf galaxy NGC 4068, which reveals broad Hα line profile and unusual emission line fluxes in its spectrum. The object also shows significant nitrogen overabundance, not typical for metal-poor environment. We assumed that the nebula could be ionized by an evolved massive star with , Wolf-Rayet or Blue Supergiant, and built models of the nebula using Cloudy and CMFGEN codes. Our models successfully reproduce the optical emission spectrum of the object, including the peculiar [SII]/[NII] ratio and the presence of the HeII λ4686 line.

The depletion of CO molecules is observed in infrared dark clouds. However, only few exsamples are found in pc-scale. An NH3 emission is one of good counter parts of C18O because of similar effective critical density. Our NH3 observations of a molecular filament associated with CMa OB1 or KAG 71, which is a target of Kagoshima Galactic Object survey with Nobeyama 45-m telescope by Mapping in Ammonia lines (KAGONMA) project. Although NH3 data shows similarity in morphology with infrared data suggesting no depletion, C18O in the clumps 4 and 6 are weaker than expected based on NH3 data. After examining the dissipation of the high-density gas, photodissociation, and depletion, we concluded that CO is depleted at least in the clump 4. It is a new example of depletion in pc-scale.

The TYPHOON program is producing an atlas of spectroscopic data cubes of 44 large-angular-sized galaxies with complete spatial coverage from 3650–9000 Å. This survey provides an unparalleled opportunity to study variations in the interstellar medium (ISM) properties within individual H ii regions across the entire star-forming disks of nearby galaxies. This can provide key insights into the spatial distribution and resolved properties of the ISM to understand how efficiently metals are mixed and redistributed across spirals and dwarf galaxies. In this Proceeding, we present early science results from six nearby spiral galaxies as part of the TYPHOON program from Grasha et al. (2022). We use HIIPhot to identify the H ii regions within the galaxy based on the surface brightness of the Hα emisison line and measure variations of the H ii region oxygen abundance. In this initial work, we find that while the spiral pattern plays a role in organizing the ISM, it alone does not establish the relatively uniform azimuthal variations we observe across all the galaxies. Differences in the metal abundances are more likely driven by the strong correlations with the local physical conditions. We find a strong and positive correlation between the ionization parameter and the local abundances as measured by the relative metallicity offset Δ(O/H), indicating a tight relationship between local physical conditions and their localized enrichment of the ISM. These variations can be explained by a combination of localized, star formation-driven self-enrichment and large-scale mixing-driven dilution due to the passing of spiral density waves.

Understanding the nucleosynthetic origin of nitrogen and the evolution of the N/O ratio in the interstellar medium is crucial for a comprehensive picture of galaxy chemical evolution at high-redshift because most observational metallicity (O/H) estimates are implicitly dependent on the N/O ratio. The observed N/O at high-redshift shows an overall constancy with O/H, albeit with a large scatter. We show that these heretofore unexplained features can be explained by the pre-supernova wind yields from rotating massive stars (M≳10M⊙,ν/νcrit≳0.4). Our models naturally produce the observed N/O plateau, as well as the scatter at low O/H. We find the scatter to arise from varying star formation efficiency. However, the models that have supernovae dominated yields produce a poor fit to the observed N/O at low O/H. This peculiar abundance pattern at low O/H suggests that dwarf galaxies are most likely to be devoid of SNe yields and are primarily enriched by pre-supernova wind abundances.

We present a new tool for the analysis of the optical emission lines of the gas in the Narrow Line Region (NLR) around Active Galactic Nuclei (AGNs). This new tool can be used in large samples of objects in a consistent way using different sets of optical emission-lines taking into the account possible variations from the O/H - N/O relation. The code compares certain observed emission-line ratios with the predictions from a large grid of photoionization models calculated under the most usual conditions in the NLR of AGNs to calculate the total oxygen abundance, nitrogen-to-oxygen ratio and ionization parameter. We applied our method to a sample of Seyfert 2 galaxies with optical emission-line fluxes from the literature. Our results confirm the high metallicity of the objects of the sample and provide consistent values with the direct method. The usage of models to calculate precise ICFs is mandatory when only optical emission lines are available to derive chemical abundances using the direct method in NLRs of AGN.

We study the metallicity calibrations in high-redshift galaxies using a sample of local analogs of high-redshift galaxies selected from the SDSS survey. Located in the same region on the BPT diagram as star-forming galaxies at z ∼ 2, these high-redshift analogs share the same ionized ISM conditions as high-redshift galaxies. We establish empirical metallicity calibrations between the direct gas-phase oxygen abundances and varieties of metallicity indicators in our local analogs using direct Te method. These new metallicity calibrations are the best means to measure the metallicity in high-redshift galaxies. There exist significant offsets between these new high-redshift metallicity calibrations and local calibrations. Such offsets are mainly driven by the evolution of the ionized ISM conditions from high-z to low-z.

Recent observations revealed that there is a difference in the spatial distribution of both nitrogen and oxygen bearing species towards massive star forming regions. These differences can be explained under different temperature regimes in hot cores. In this study, we attempt to model the chemistry of few nitrogen species; namely, vinyl cyanide (CH2CHCN), ethyl cyanide (CH3CH2CN), and formamide (NH2CHO), using gas-grain chemical models. A special attention is given to the role and efficiency of surface chemistry as it is suggested to play one of the main key roles in manufacturing these species.

The search for complex organic molecules in the interstellar medium (ISM) has revealed species of ever greater complexity. This search relies on the progress made in the laboratory to characterize their rotational spectra. Our understanding of the processes that lead to molecular complexity in the ISM builds on numerical simulations that use chemical networks fed by laboratory and theoretical studies. The advent of ALMA and NOEMA has opened a new door to explore molecular complexity in the ISM. Their high angular resolution reduces the spectral confusion of star-forming cores and their increased sensitivity allows the detection of low-abundance molecules that could not be probed before. The complexity of the recently-detected molecules manifests itself not only in terms of number of atoms but also in their molecular structure. We discuss these developments and report on ReMoCA, a new spectral line survey performed with ALMA toward the high-mass star-forming region Sgr B2(N).

The surfaces of interstellar and circumstellar dust grains are the sites of molecule formation, most of which, except H2, stick and form ice mantles. The study of ice evolution thus seems directly relevant for understanding our own origins, although the relation between interstellar and solar system ices remains a key question. The comparison of interstellar and solar system ices relies evidently on an accurate understanding of the composition and processes in both environments. With the accurate in situ measurements available for the comet 67P/Churyumov-Gerasimenko with the Rosetta mission, improving our understanding of interstellar ices is the more important. Here, I will address three specific questions. First, while laboratory experiments have made much progress in understanding complex organic molecule (COM) formation in the ices, the question remains, how does COM formation depend on environment and time? Second, what is the carrier of sulfur in the ices? And third, can ice absorption bands trace the processing history of the ices? Laboratory experiments, ranging from infrared spectroscopy to identify interstellar ice species, to surface experiments to determine reaction parameters in ice formation scenarios, to heating and irradiation experiments to simulate space environments, are essential to address these questions and analyze the flood of new observational data that will become available with new facilities in the next 2-10 years.

The mid-IR spectrum of the interstellar medium contains both aromatic and aliphatic hydrocarbon features. These are generally attributed to carbonaceous dust. The aliphatic component is of particular interest because it produces a significant 3.4 μm absorption feature. The optical depth of this feature is related to the number and type of aliphatic carbon C–H bonds in the line of sight. It is possible to estimate the column density of aliphatic carbon from quantitative analysis of the 3.4 μm interstellar feature, providing that the absorption coefficient of interstellar aliphatic hydrocarbon is known. We produced interstellar dust analogues with spectra closely matching astronomical observations. Using a combination of FTIR and 13C NMR spectroscopy, we determined an integrated absorption coefficient of the aliphatic component. The results thus obtained permit direct calibration of astronomical observations, providing rigorous estimates of the amount of aliphatic carbon in the ISM.

Complex organic molecules (COMs) have been detected in the gas-phase in cold and lightless molecular cores. Recent solid-state laboratory experiments have provided strong evidence that COMs can be formed on icy grains through ‘non-energetic’ processes. In this contribution, we show that propanal and 1-propanol can be formed in this way at the low temperature of 10 K. Propanal has already been detected in space. 1-propanol is an astrobiologically relevant molecule, as it is a primary alcohol, and has not been astronomically detected. Propanal is the major product formed in the C2H2 + CO + H experiment, and 1-propanol is detected in the subsequent propanal + H experiment. ALMA observations towards IRAS 16293-2422B are discussed and provide a 1-propanol:propanal upper limit of < 0.35–0.55, which are complemented by computationally-derived activation barriers in addition to the performed laboratory experiments.

Diffuse ionized gas (DIG) in galaxies can be found in early-type galaxies, in bulges of late-type galaxies, in the interarm regions of galaxy disks, and outside the plane of such disks. The emission-line spectrum of the DIG can be confused with that of a weakly active galactic nucleus. It can also bias the inference of chemical abundances and star formation rates in star forming galaxies. We discuss how one can detect and feasibly correct for the DIG contribution in galaxy spectra.

The stellar mass–star formation rate–metallicity relation provides clues on the chemical evolution of galaxies. We revisit this relation by measuring the gas-phase metallicity using the direct method. For metal-rich galaxies this is not straightforward, because auroral emission lines sensitive the electron temperature are lost in spectral noise. In order to increase the spectral signal-to-noise ratio and detect faint auroral lines, we stack the spectra of similar galaxies. This allows us to use the direct method to obtain consistent metallicity measurements.

Nowadays, there are several observational studies about the 13CO/C18O abundance ratio ( $X^{13/18}$ ) towards nearby molecular clouds. These works give observational support to the C18O selective photodissociation due to the interaction between the far ultraviolet (FUV) radiation and the molecular gas. It is necessary to increase the sample of molecular clouds located at different distances and affected in different ways by nearby or embedded H ii regions and OB associations to study the selective photodissociation. Using 12CO, 13CO, and C18O J = 1–0 data obtained from the FOREST unbiased Galactic plane imaging survey performed with the Nobeyama 45-m telescope, we analyse the filamentary infrared dark cloud IRDC $34.43+0.24$ located at the distance of about 3.9 kpc. This infrared dark cloud (IRDC) is related to several H ii regions and young stellar objects. Assuming local thermodynamic equilibrium, we obtain: $0.8 \times 10^{16} <$ N(13CO) $<4 \times 10^{17}$ cm–2 (average value $= 4.2 \times 10^{16}$ cm–2), $0.6 \times 10^{15} <$ N(C18O) $<4.4 \times 10^{16}$ cm–2 (average value $= 5.0 \times 10^{15}$ cm–2), and 3 $<$ $X^{13/18}$ $<$ 30 (average $= 8$ ) across the whole IRDC. Larger values of $X^{13/18}$ were found towards portions of the cloud related to the H ii regions associated with the N61 and N62 bubbles and with the photodissociation regions, precisely the regions in which FUV photons are strongly interacting with the molecular gas. Our result represents an observational support to the C18O selectively photodissociation phenomenon occurring in a quite distant filamentary IRDC. Additionally, based on IR data from the Hi-GAL survey, the FUV radiation field was estimated in Habing units, and the dust temperature (T $_{dust}$ ) and H2 column density (N(H2)) distribution were studied. Using the average of N(H2), values in close agreement with the ‘canonical’ abundance ratios [H2]/[13CO] and [H2]/[C18O] were derived. However, the obtained ranges in the abundance ratios show that if an accurate analysis of the molecular gas is required, the use of the ‘canonical’ values may introduce some bias. Thus, it is important to consider how the gas is irradiated by the FUV photons across the molecular cloud. The analysis of $X^{13/18}$ is a good tool to perform that. Effects of beam dilution and clumpiness were studied.

There is a growing evidence that our Sun was born in a rich cluster that also contained massive stars. Therefore, the study of high-mass star-forming regions is key to understand our chemical heritage. In fact, molecules found in comets, in other pristine Solar System bodies and in protoplanetary disks, are enriched in 15N, because they show a lower 14N/15N ratio (100-150) with respect to the value representative of the Proto-Solar Nebula (PSN, 441 ± 6), but the reasons of this enrichment cannot be explained by current chemical models. Moreover, the 14N/15N ratio is important because from it we can learn more about the stellar nucleosynthesis processes that produces both the elements. In this sense observations of star-forming regions are useful to constrain Galactic chemical evolution (GCE) models.

Radial metallicity gradients measured today in the interstellar medium (ISM) and stellar components of disk galaxies are the result of chemo-dynamical evolution since the beginning of disk formation. This makes it difficult to infer the disk past without knowledge of the ISM metallicity gradient evolution with cosmic time. We show that abundance gradients are meaningful only if stellar age information is available. The observed gradient inversion with distance from the disk mid-plane seen in the Milky Way can be explained as the effect of inside-out disk formation and disk flaring of mono-age populations. A novel recent method is presented for constraining the evolution of the Galactic ISM metallicity with radius and time directly from the observations, while at the same time recovering the birth radii of any stellar sample with precise metallicity and age measurements.

Physical conditions and chemical abundances of two H II regions and a planetary nebula in the dIrr galaxy Leo A are presented. These determinations were performed using the direct method (Te measured) and the ONS method. We also constructed photoionization models for the three nebulae to determine the abundances and to analyse the ionizing stars. The O abundance was determined to be 12+log(O/H) = 7.4±0.2 in all cases.

We investigate, in the light of new diagnostic diagrams, the role of shocks in the ionization profile of type-I planetary nebulae, and their relation to the empirical derivation of chemical abundances. We apply our technique to two well-known type-I objects: NGC 2440 and NGC 6302. Our results indicate that shocks play a very important role in the spectra of both nebulae and, since the presence of shocks reinforces the flux of low ionization lines, this artificial reinforcement can lead to incorrect chemical abundances, when they are derived through Ionization Correction Factors, at least for type-I PNe.

Hii regions in galaxy disks can be used as a powerful tool to trace the radial distribution of several of their properties and shed some light on the different relevant processes on galaxy formation and evolution. Among the properties that can be extracted from the study of the ionized gas are the metallicity, the excitation and the hardness of the ionizing field of radiation. In this contribution we focus on the determination of both the ionization parameter (U) and the effective temperature of the ionizing clusters (T) by means of a bayesian-like comparison between the observed relative fluxes of several emission-lines with the predictions from a set of photoionization models. We also show the implications that the use of our method has for the study of the radial variation of both U and T in some very well-studied disk galaxies of the Local Universe.