We aim to investigate the chemistry and gas phase abundance of HNCO and the variation of the HNCO/CS abundance ratio as a diagnostic of the physics and chemistry in regions of massive star formation. A numerical-chemical model has been developed which self-consistently follows the chemical evolution of a hot core. The model comprises of two distinct stages. An initial collapse phase is immediately followed by an increase in temperature which represents the switch on of a central massive star and the subsequent evolution of the chemistry in a hot, dense gas cloud (the hot core). During the collapse phase, gas species are allowed to accrete on to grain surfaces where they can participate in further reactions. During the hot core phase surface species thermally desorb back in to the ambient gas and further chemical evolution takes place. For comparison, the chemical network was also used to model a simple dark cloud and photodissociation regions. Our investigation reveals that HNCO is inefficiently formed when only gas-phase formation pathways are considered in the chemical network with reaction rates consistent with existing laboratory data. Using currently measured gas phase reaction rates, obtaining the observed HNCO abundances requires its formation on grain surfaces. However our model shows that the gas phase HNCO in hot cores is not a simple direct product of the evaporation of grain mantles. We also show that the HNCO/CS abundance ratio varies as a function of time in hot cores and can match the range of values observed. This ratio is not unambiguously related to the ambient UV field as been suggested - our results are inconsistent with the hypothesis of Martin et al (2008). In addition, our results show that this ratio is extremely sensitive to the initial sulphur abundance.
Using data from MALT90 (Millimetre Astronomy Legacy Team Survey at 90 GHz), we present molecular line study of a sample of ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) clumps. Twelve emission lines have been detected in all. We found that in most sources, emissions of HC$_3$N, HN$^{13}$C, CH$_3$CN, HNCO and SiO show more compact distributions than those of HCO$^+$, HNC, HCN and N$_2$H$^+$. By comparing with other molecular lines, we found that the abundance of HNCO ($χ$(HNCO)) correlates well with other species such as HC3N, HNC, C2H, H13CO+ and N2H+. Previous studies indicate the…
HOCN and HNCO abundance ratio in molecular gas can tell us the information of their formation mechanism. We performed high-sensitivity mapping observations of HOCN, HNCO, and HNC$^{18}$O lines around Sagittarius B2 (Sgr B2) with IRAM 30m telescope at 3-mm wavelength. HNCO 4$_{04}$-3$_{03}$ and HOCN 4$_{04}$-3$_{03}$ are used to obtain the abundance ratio of HNCO to HOCN. The ratio of HNCO 4$_{04}$-3$_{03}$ to HNC$^{18}$O 4$_{04}$-3$_{03}$ is used to calculate the optical depth of HNCO 4$_{04}$-3$_{03}$. The abundance ratio of HOCN and HNCO is observed to range from 0.4% to 0.7% toward most pos…
The isocyanic acid (HNCO) presents an extended distribution in the centers of the Milky Way and the spiral galaxy IC342. Based on the morphology of the emission and the HNCO abundance with respect to H2, several authors made the hypothesis that HNCO could be a good tracer of interstellar shocks. Here we test this hypothesis by observing a well-known Galactic source where the chemistry is dominated by shocks. We have observed several transitions of HNCO towards L1157-mm and two positions (B1 and B2) in the blue lobe of the molecular outflow. The HNCO line profiles exhibit the same characteristi…
Isocyanic acid (HNCO) is a simple molecule with a potential to form prebiotic and complex organic species. Using a spectral survey collected with the Atacama Pathfinder EXperiment (APEX), in this work we report the detection of 42 transitions of HNCO in the hot molecular core/outflow G331.512-0.103 (hereafter G331). The spectral lines were observed in the frequency interval $\sim$ 160 - 355 GHz. By means of Local Thermodynamic Equilibrium (LTE) analyses, applying the rotational diagram method, we studied the excitation conditions of HNCO. The excitation temperature and column density are estim…
Isocyanic acid (HNCO), the most stable of the simplest molecules containing the four main elements essential for organic chemistry, has been observed in several astrophysical environments such as molecular clouds, star-forming regions, external galaxies and comets. In this work, we model HNCO spectral line profiles toward the low-mass solar type protostar IRAS 16293$-2$422 observed with the ALMA interferometer, the IRAM, JCMT and APEX single-dish radio telescopes, and the HIFI instrument on board the Herschel Space Observatory. In star-forming environments, the HNCO emission is not always in L…
OH231.8+4.2 is a well studied O-rich CSE around an intermediate-mass evolved star that displays bipolar molecular outflows accelerated up to 400 km/s. OH231 also presents an exceptional molecular richness probably due to shock-induced chemical processes. We report the first detection in this source of HNCO, HNCS, HC3N and NO, with the IRAM-30m telescope in a sensitive mm-wavelength survey towards this target. HNCO and HNCS are also first detections in CSEs. The observed line profiles show that the emission arises in the massive central component of the envelope and at the base of the fast lobe…
Little is known about the chemistry of isocyanates (compounds with the functional group R-N=C=O) in the interstellar medium, as only four of them have been detected so far: isocyanate radical (NCO), isocyanic acid (HNCO), N-protonated isocyanic acid (H$_2$NCO$^+$) and methyl isocyanate (CH$_3$NCO). The molecular cloud G+0.693-0.027, located in the Galactic Centre, represents an excellent candidate to search for new isocyanates since it exhibits high abundances of the simplest ones, HNCO and CH$_3$NCO. After CH$_3$NCO, the next complex isocyanates are ethyl isocyanate (C$_2$H$_5$NCO) and vinyl …
Pre-stellar cores are the basic unit for the formation of stars and stellar systems. The anatomy of the physical and chemical structures of pre-stellar cores is critical for understanding the star formation process. L1544 is a prototypical pre-stellar core, which shows significant chemical differentiation surrounding the dust peak. We aim to constrain the physical conditions at the different molecular emission peaks. This study allows us to compare the abundance profiles predicted from chemical models together with the classical density structure of Bonnor-Ebert (BE) sphere. We conducted multi…
Current gas phase models do not account for the abundances of HNCO isomers detected in various environments, suggesting a formation in icy grain mantles. We attempted to study a formation channel of HNCO and its possible isomers by vacuum-UV photoprocessing of interstellar ice analogues containing H$_2$O, NH$_3$, CO, HCN, CH$_3$OH, CH$_4$, and N$_2$ followed by warm-up, under astrophysically relevant conditions. Only the H$_2$O:NH$_3$:CO and H$_2$O:HCN ice mixtures led to the production of HNCO species. The possible isomerization of HNCO to its higher energy tautomers following irradiation or …
SiO(3-2) and HNCO(6-5) emission has been imaged in NGC 1068 with the Plateau de Bure Interferometer (PdBI). We perform an LTE and RADEX analysis to determine the column densities and physical characteristics of the gas emitting these two lines. We then use a chemical model to determine the origin of the emission. There is a strong SiO peak to the East of the AGN, with weak detections to the West. This distribution contrasts that of HNCO, which is detected more strongly to the West. The SiO emission peak in the East is similar to the peak of the molecular gas mass traced by CO. HNCO emission is…
We have obtained maps of the molecular emission within the central five arcminutes (12 pc) of the Galactic center (GC) in selected molecular tracers: SiO(2-1), HNCO(5_{0,5}-4_{0,4}), and the J=1-->0 transition of H^{13}CO+, HN^{13}C, and C^{18}O at an angular resolution of 30" (1.2 pc). The mapped region includes the circumnuclear disk (CND) and the two surrounding giant molecular clouds (GMCs) of the Sgr A complex, known as the 20 and 50 km s^{-1} molecular clouds.Additionally, we simultaneously observed the J=2-1 and 3-2 transitions of SiO toward selected positions to estimate the physical c…
L1157, a molecular dark cloud with an embedded Class 0 protostar possessing a bipolar outflow, is an excellent source for studying shock chemistry, including grain-surface chemistry prior to shocks, and post-shock, gas-phase processing. The L1157-B1 and B2 positions experienced shocks at an estimated ~2000 and 4000 years ago, respectively. Prior to these shock events, temperatures were too low for most complex organic molecules to undergo thermal desorption. Thus, the shocks should have liberated these molecules from the ice grain-surfaces en masse, evidenced by prior observations of SiO and m…
We attempt to characterise the chemical properties of a sample of massive clumps of IRDCs through multi-molecular line observations. We also search for possible evolutionary trends among the derived chemical parameters. The clumps are studied using the MALT90 line survey data obtained with the Mopra telescope. The spectral-line data are used in concert with our previous LABOCA 870-$μ$m dust emission data. Most of the detected species (SiO, C$_2$H, HNCO, HCN, HCO$^+$, HNC, HC$_3$N, and N$_2$H$^+$) show spatially extended emission towards many of the sources. The fractional abundances of the mol…
The chemical inventory of planets is determined by the physical and chemical processes that govern the early phases of star formation. The aim is to investigate N-bearing complex organic molecules towards two Class 0 protostars (B1-c and S68N) at millimetre wavelengths with ALMA. Next, the results of the detected N-bearing species are compared with those of O-bearing species for the same and other sources. ALMA observations in Band 6 ($\sim$ 1 mm) and Band 5 ($\sim$ 2 mm) are studied at $\sim$ 0.5" resolution, complemented by Band 3 ($\sim$ 3 mm) data in a $\sim$ 2.5" beam. NH2CHO, C2H5CN, HNC…
We use direct method oxygen abundances in combination with strong optical emission lines, stellar masses ($M_{\star}$), and star formation rates (SFRs) to recalibrate the N2, O3N2, and N2O2 oxygen abundance diagnostics. We stack spectra of $\sim$200,000 star-forming galaxies from the Sloan Digital Sky Survey in bins of $M_{\star}$ and SFR offset from the star forming main sequence to measure the weak emission lines needed to apply the direct method. All three new calibrations are reliable to within $\pm 0.10$ dex from $\log(M_{\star}/M_{\odot}) \sim 7.5 - 10.5$ and up to at least $200~M_{\odot…
Peptide-like bond molecules, which can take part to the formation of proteins in a primitive Earth environment, have been detected up to now only towards a few sources. We present a study of HNCO, HC(O)NH$_{2}$, CH$_{3}$NCO, CH$_{3}$C(O)NH$_{2}$, CH$_{3}$NHCHO, CH$_{3}$CH$_{2}$NCO, NH$_{2}$C(O)NH$_{2}$, NH$_{2}$C(O)CN, and HOCH$_{2}$C(O)NH$_{2}$ towards the hot core G31.41+0.31. We have used the spectrum obtained from the ALMA 3mm spectral survey GUAPOS, with an angular resolution of 1.2"$\times$1.2" ($\sim$4500 au), to derive column densities of all the molecular species, together with other …
We present an analysis of Mg II $\lambda2798$ and Fe II UV emission lines for archival Sloan Digital Sky Survey (SDSS) quasars to explore diagnostics of the magnesium-to-iron abundance ratio in a broad-line region cloud. Our sample consists of 17,432 quasars selected from the SDSS Data Release 7 with a redshift range of $0.72 < z < 1.63$. A strong anticorrelation between Mg II equivalent width (EW) and the Eddington ratio is found, while only a weak positive correlation is found between Fe II EW and the Eddington ratio. To investigate the origin of these differing behaviors of Mg II and Fe II …
We present Jansky Very Large Array observations of 20 - 37 GHz absorption lines from nearby Galactic diffuse molecular gas seen against four cosmologically-distant compact radio continuum sources. The main new observational results are that \linearC3H\ and \methCN\ are ubiqitous in the local diffuse molecular interstellar medium at \AV\ $\la 1$ while HC$_3$N was seen only toward B0415 at \AV\ $>$ 4 mag. The linear/cyclic ratio is much larger in C$_3$H than in C$_3$\HH\ and the ratio \methCN/HCN is enhanced compared to TMC-1, although not as much as toward the Horsehead Nebula. More consequenti…
Aims. Our aim is to confirm the interstellar detection of cyanic acid, HOCN, in the Galactic center clouds. It has previously been tentatively detected only in Sgr B2(OH). Methods. We used a complete line survey of the hot cores Sgr B2(N) and (M) in the 3 mm range, complemented by additional observations carried out with the IRAM 30 m telescope at selected frequencies in the 2 mm band and towards four additional positions in the Sgr B2 cloud complex in the 2 and 3 mm bands. The spectral survey was analysed in the local thermodynamical equilibrium approximation (LTE) by modeling the emission of…
We present interferometric observations of CO lines (12CO(1-0, 2-1) and 13CO(1-0, 2-1)) and dense gas tracers (HCN(1-0), HCO+(1-0), HNC(1-0) and HNCO(4-3)) in two nearby edge-on barred lenticular galaxies, NGC 4710 and NGC 5866, with most of the gas concentrated in a nuclear disc and an inner ring in each galaxy. We probe the physical conditions of a two-component molecular interstellar medium in each galaxy and each kinematic component by using molecular line ratio diagnostics in three complementary ways. First, we measure the ratios of the position-velocity diagrams of different lines, secon…
The depletion of elements onto dust grains is characterized using a generalized depletion strength $F_*$ for any sightline, and trend-line parameters $A_X, B_X$ and $z_X$. The parameters $A_X, B_X$ and $z_X$ define the relative depletion pattern, for which values are published in previous works. The present study uses these parameters to calculate post-depleted gas-phase abundances of 15 different elements while varying $F_*$ from 0 to 1. An analysis of emergent strong spectral line intensities, obtained by inputting the calculated abundances into a cloudy model, shows that the depletion stren…
We present the first direct calibration of strong-line metallicity diagnostics at significant cosmological distances using a sample at z=0.8 drawn from the DEEP2 Galaxy Redshift Survey. Oxygen and neon abundances are derived from measurements of electron temperature and density. We directly compare various commonly used relations between gas-phase metallicity and strong line ratios of O, Ne, and H at z=0.8 and z=0. There is no evolution with redshift at high precision ($Δ\log{\mathrm{O/H}} = -0.01\pm0.03$, $Δ\log{\mathrm{Ne/O}} = 0.01 \pm 0.01$). O, Ne, and H line ratios follow the same locus …
We report the first detection of a hot molecular core outside our Galaxy based on radio observations with ALMA toward a high-mass young stellar object (YSO) in a nearby low metallicity galaxy, the Large Magellanic Cloud (LMC). Molecular emission lines of CO, C17O, HCO+, H13CO+, H2CO, NO, SiO, H2CS, 33SO, 32SO2, 34SO2, and 33SO2 are detected from a compact region (0.1 pc) associated with a high-mass YSO, ST11. The temperature of molecular gas is estimated to be higher than 100 K based on rotation diagram analysis of SO2 and 34SO2 lines. The compact source size, warm gas temperature, high densit…
The Nitrogen-to-Oxygen (N/O) abundance ratio is an important diagnostic of galaxy evolution since the ratio is closely tied to the growth of metallicity and the star formation history in galaxies. Estimates for the N/O ratio are traditionally accomplished with optical lines that could suffer from extinction and excitation effects, so the N/O ratio is arguably measured better through far-infrared (far-IR) fine-structure lines. Here we show that the [N III]57$μ$m/[O III]52$μ$m line ratio, denoted $N3O3$, is a physically robust probe of N/O. This parameter is insensitive to gas temperature and on…
We present results from integral field spectroscopy with PMAS. The observed field contains: five protoplanetary discs (also known as proplyds), the high-velocity jet HH 514 and a bowshock. Spatial distribution maps are obtained for different emission line fluxes, the c(Hβ) coefficient, electron densities and temperatures, ionic abundances of different ions from collisionally excited lines (CELs), C2+ and O2+ abundances from recombination lines (RLs) and the abundance discrepancy factor of O2+, ADF(O2+). We find that collisional de-excitation has a major influence on the line fluxes in the prop…
This Letter presents a new, remarkably simple diagnostic specifically designed to derive chemical abundances for high redshift galaxies. It uses only the H α, [N II] and [S II] emission lines, which can usually be observed in a single gating stetting, and is almost linear up to an abundance of 12+log (O/H) = 9.05. It can be used over the full abundance range encountered in high redshift galaxies. By its use of emission lines located close together in wavelength, it is also independent of reddening. Our diagnostic depends critically on the calibration of the N/O ratio. However, by using realist…
The First Empirical Calibration of the MIR Abundance Diagnostic Ne$_{23}$ with JWST
Northwestern University（西北大学）；University of Minnesota（明尼苏达大学）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）；University of Edinburgh（爱丁堡大学）；The Ohio State University（俄亥俄州立大学）；Space Telescope Science Institute（太空望远镜科学研究所）；NASA Headquarters（美国国家航空航天局总部）；INAF—Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切尔蒂天文台）
Our ability to study the properties of the interstellar medium (ISM) in the earliest galaxies will rely on emission line diagnostics at rest-frame ultraviolet (UV) wavelengths. In this work, we identify metallicity-sensitive diagnostics using UV emission lines. We compare UV-derived metallicities with standard, well-established optical metallicities using a sample of galaxies with rest-frame UV and optical spectroscopy. We find that the He2-O3C3 diagnostic (He II 1640 / C III 1906,1909 vs. O III 1666 / C III 1906,1909) is a reliable metallicity tracer, particularly at low metallicity (12+log(O…
We present spatially resolved ($\sim$50 pc) imaging of molecular gas species in the central kiloparsec of the nearby starburst galaxy NGC 253, based on observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA). A total of 50 molecular lines are detected over a 13 GHz bandwidth imaged in the 3 mm band. Unambiguous identifications are assigned for 27 lines. Based on the measured high CO/C$^{17}$O isotopic line ratio ($\gtrsim$350), we show that $^{12}$CO(1-0) has moderate optical depths. A comparison of the HCN and HCO$^{+}$ with their $^{13}$C-substituted isotopologues sho…
We present a new method for inferring the metallicity (Z) and ionization parameter (q) of HII regions and star-forming galaxies using strong nebular emission lines (SEL). We use Bayesian inference to derive the joint and marginalized posterior probability density functions for Z and q given a set of observed line fluxes and an input photo-ionization model. Our approach allows the use of arbitrary sets of SELs and the inclusion of flux upper limits. The method provides a self-consistent way of determining the physical conditions of ionized nebulae that is not tied to the arbitrary choice of a p…
Context. The Galactic chemical evolution of sulphur is still under debate. At low metallicities some studies find no correlation between [S/Fe] and [Fe/H], others find [S/Fe] increasing towards lower metallicities, and still others find a combination of the two. Each scenario has different implications for the Galactic chemical evolution of sulphur. Aims. To contribute to the discussion on the Galactic chemical evolution of sulphur by deriving sulphur abundances from non-LTE insensitive spectral diagnostics in Disk and Halo stars with homogeneously determined stellar parameters. Methods. We de…
Aims: To reveal the morphology, chemical composition, kinematics and to establish the main processes prevalent in the gas at the foot points of the giant molecular loops (GMLs) in the Galactic center region Methods: Using the 22-m Mopra telescope, we mapped the M$-3.8+0.9$ molecular cloud, placed at the foot points of a giant molecular loop, in 3-mm range molecular lines. To derive the molecular hydrogen column density, we also observed the $^{13}$CO $(2-1)$ line at 1 mm using the 12-m APEX telescope. From the 3 mm observations 12 molecular species were detected, namely HCO$^+$, HCN, H$^{13}$C…
It is currently assumed that infrared dark clouds (IRDCs) represent the earliest evolutionary stages of high-mass stars ($>$ 8 M$_{\odot}$). Submillimeter and millimeter-wave studies performed over the past 15 years show that IRDCs possess a broad variety of properties, and hence a wide range of problems and questions that can be tackled. In this paper, we report an investigation of the molecular composition and chemical processes in two groups of IRDCs. Using the Mopra, APEX, and IRAM radio telescopes over the last four years, we have collected molecular line data for CO, H$_2$CO, HNCO, CH$_3…
We present a spectrum of the planetary nebula M 2-36 obtained using the Ultra Violet and Visual Echelle Spectrograph (UVES) at the Very Large Telescope (VLT). 446 emission lines are detected. We perform an analysis of the chemical composition using multiple electron temperature ($T_{e}$) and density ($n_{e}$) diagnostics. $T_{e}$ and $n_{e}$ are computed using a variety of methods, including collisionally excited line (CEL) ratios, O$^{++}$ optical recombination lines (ORLs), and measuring the intensity of the Balmer jump. Besides the classical CEL abundances, we also present robust ionic abun…
We present spectra of 14 A-type supergiants in the metal-rich spiral galaxy M83. We derive stellar parameters and metallicities, and measure a spectroscopic distance modulus m-M = 28.47 +\- 0.10 (4.9 +\- 0.2 Mpc), in agreement with other methods. We use the stellar characteristic metallicity of M83 and other systems to discuss a version of the galaxy mass-metallicity relation that is independent of the analysis of nebular emission lines and the associated systematic uncertainties. We reproduce the radial metallicity gradient of M83, which flattens at large radii, with a chemical evolution mode…
We used FIR and submillimeter continuum data from Herschel and the Atacama Pathfinder EXperiment (APEX) to fit pixel-by-pixel modified Planck SEDs to prestellar and protostellar clumps in the Census of High- and Medium-mass Protostars (CHaMP) ($280^{\circ}<\ell<300^{\circ}$, $-4^{\circ}<b<+2^{\circ}$). We present maps of dust temperature ($T_{\text{d}}$) and H$_2$ column density (\ncol) for molecular clumps in the Carina Nebula complex (Regions 9 through 11), and surrounding RCW 64 (Region 26). We compare the column densities of CO and H$_2$ to chart regional variations in their correspondence…
We present a survey of 3 mm molecular lines in IRAS 04296+2923, one of the brightest known molecular-line emitting galaxies, and one of the closest LIRGs. Data are from the Owens Valley and CARMA millimeter interferometers. Species detected at ~<4" resolution include C^18O, HCN, HCO+, HNC, CN, CH_3OH and, tentatively, HNCO. Along with existing CO, ^13CO and radio continuum data, these lines constrain the chemical properties of the inner disk. Dense molecular gas in the nucleus fuels a star formation rate ~>10 M_sun/yr and is traced by lines of HCN, HCO+, HNC, and CN. A correlation between HCN …
There are two accepted mechanisms to explain the origin of runaway OB-type stars: the Binary Supernova Scenario (BSS), and the Cluster Ejection Scenario (CES). In the former, a supernova explosion within a close binary ejects the secondary star, while in the latter close multi-body interactions in a dense cluster cause one or more of the stars to be ejected from the region at high velocity. Both mechanisms have the potential to affect the surface composition of the runaway star. TLUSTY non-LTE model atmosphere calculations have been used to determine atmospheric parameters and carbon, nitrogen…
Aims: The physical structure of a shock wave may take a form unique to its shock type, implying that the chemistry of each shock type is unique as well. We aim to investigate the different chemistries of J-type and C-type shocks in order to identify unique molecular tracers of both shock types. We apply these diagnostics to the protostellar outflow L1157 to establish whether the B2 clump could host shocks exhibiting type-specific behaviour. Of particular interest is the L1157-B2 clump, which has been shown to exhibit bright emission in S-bearing species and HNCO. Methods: We simulate, using a …
Massive stars are the main objects that illuminate H II regions and they evolve quickly to end their lives in core-collapse supernovae (CCSNe). Thus it is important to investigate the association between CCSNe and H II regions. In this paper, we present emission line diagnostics of the stellar populations around nearby CCSNe, that include their host H II regions, from the PMAS/PPAK Integral-field Supernova hosts COmpilation (PISCO). We then use BPASS stellar population models to determine the age, metallicity and gas parameters for H II regions associated with CCSNe, contrasting models that co…
Unveiling the Chemical Complexity and C/O Ratio of the HD 163296 Protoplanetary Disk: Constraints from Multi-line ALMA Observations of Organics, Nitriles, Sulfur-bearing, and Deuterated Molecules
(Abridged) The aim of this study is to investigate the chemical evolution from the prestellar phase to the formation of the disk, and to determine the impact that the chemical composition of the cold and dense core has on the final composition of the disk. We performed 3D nonideal magneto-hydrodynamic (MHD) simulations of a dense core collapse using the adaptive-mesh-refinement RAMSES code. For each particle ending in the young rotationally supported disk, we ran chemical simulations with the three-phase gas-grain chemistry code Nautilus. Two different sets of initial abundances, which are cha…
It is still debated whether or not the Galactic chemical evolution of sulphur in the halo followed the constant or flat trend with [Fe/H], ascribed to the result of explosive nucleosynthesis in type II SNe. The aim of this study is to try to clarify this situation by measuring the sulphur abundance in a sample of halo giants using two diagnostics; the S I triplet around 1045 nm and the [S I] line at 1082 nm. The latter of the two is not believed to be sensitive to non-LTE effects. We can thereby minimize the uncertainties in the diagnostic used and estimate the usefulness of the triplet in sul…
Molecular diagnostics for the mid-infrared emission of planet-forming disks. Carbon and oxygen elemental abundances
Kapteyn Astronomical Institute, Rijksuniversiteit Groningen（格罗宁根大学卡普坦天文研究所）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；Max-Planck Institut für Extraterrestrische Physik (MPE)（马克斯·普朗克地外物理研究所）；Space Research Institute, Austrian Academy of Sciences（奥地利科学院空间研究所）；University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München（慕尼黑大学物理学院大学天文台）；Department of Physics and Astronomy, University of Exeter（埃克塞特大学物理与天文学系）；Department of Astronomy, University of Michigan（密歇根大学天文学系）；Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale（巴黎萨克雷大学、法国国家科学研究中心、空间天体物理学研究所）
We present ALMA data on the 3mm continuum emission, CO isotopologues (12CO, 13CO, C18O), and high-density molecular tracers (HCN, HCO+, HNC, HNCO, CS, CN, and CH3OH) in NGC4526. These data enable a detailed study of the physical properties of the molecular gas in a longtime resident of the Virgo Cluster; comparisons to more commonly-studied spiral galaxies offer intriguing hints into the processing of molecular gas in the cluster environment. Many molecular line ratios in NGC4526, along with our inferred abundances and CO/H2 conversion factors, are similar to those found in nearby spirals. One…
The Large Magellanic Cloud (LMC) is the nearest laboratory for detailed studies on the formation and survival of complex organic molecules (COMs), including biologically important ones, in low-metallicity environments--typical for earlier cosmological epochs. We report the results of 1.2 mm continuum and molecular line observations of three fields in the star-forming region N105 with the Atacama Large Millimeter/submillimeter Array (ALMA). N105 lies at the western edge of the LMC bar with on-going star formation traced by H$_2$O, OH, and CH$_3$OH masers, ultracompact H II regions, and young st…
Spectral modelling of SNII atmospheres indicates a clear dependence of metal line strengths on progenitor metallicity. This motivates further work to evaluate the accuracy with which these SNe can be used as metallicity indicators. To assess this accuracy we present a sample of SNII HII-region spectroscopy, from which environment abundances are derived. These environment abundances are compared to the observed strength of metal lines in SN spectra. Combining our sample with measurements from the literature, we present oxygen abundances of 119 host HII regions, by extracting emission line fluxe…
Aims. We present new IRAM Plateau de Bure Interferometer observations of Arp 220 in HCN, HCO$^{+}$, HN$^{13}$C J=1-0, C$_{2}$H N=1-0, SiO J = 2-1, HNCO J$_{k,k'}$ = 5$_{0,4}$ - 4$_{0,4}$, CH$_{3}$CN(6-5), CS J=2-1 and 5-4 and $^{13}$CO J=1-0 and 2-1 and of NGC 6240 in HCN, HCO$^{+}$ J = 1-0 and C$_{2}$H N = 1-0. In addition, we present Atacama Large Millimeter/submillmeter Array science verification observations of Arp 220 in CS J = 4-3 and CH$_{3}$CN(10-9). Various lines are used to analyse the physical conditions of the molecular gas including the [$^{12}$CO]/[$^{13}$CO] and [$^{12}$CO]/[C$^…
The Sloan Digital Sky Survey (SDSS) has proved to be a powerful resource for understanding the physical properties and chemical composition of star-forming galaxies in the local universe. The SDSS population of active galactic nuclei (AGN) remains as of yet less explored in this capacity. To extend the rigorous study of \ion{H}{ii} regions in the SDSS to AGN, we adapt methods for computing direct-method chemical abundances for application to the narrow-line regions (NLR) of AGN. By accounting for triply-ionized oxygen, we are able to more completely estimate the total oxygen abundance. We find…
