We develop a self-consistent model for the equilibrium gas temperature and size-dependent dust temperature in cold, dense pre-stellar cores, assuming an arbitrary power-law size distribution of dust grains. Compact analytical expressions applicable to a broad range of physical parameters are derived and compared with predictions of the commonly used standard model. It is suggested that combining the theoretical results with observations should allow us to constrain the degree of dust evolution and the cosmic-ray ionization rate in dense cores, and to help in discriminating between different regimes of cosmic-ray transport in molecular clouds. In particular, assuming a canonical MRN distribution of grain sizes, our theory demonstrates that the gas temperature measurements in the pre-stellar core L1544 are consistent with an ionization rate as high as $\sim 10^{-16}$ s$^{-1}$, an order of magnitude higher than previously thought.
Dust attenuation of an inclined galaxy can cause additional asymmetries in observations, even if the galaxy has a perfectly symmetric structure. {Taking advantage of the integral field spectroscopic data observed by the SDSS-IV MaNGA survey, we investigate the asymmetries of the emission-line and continuum maps of star-forming disk galaxies.} We define new parameters, $A_a$ and $A_b$, to estimate the asymmetries of a galaxy about its major and minor axes, respectively. Comparing $A_a$ and $A_b$ in different inclination bins, we attempt to detect the asymmetries caused by dust. For the continuu…
The origin of cosmic dust is a fundamental issue in planetary science. This paper revisits the origin of dust in galaxies, in particular, in the Milky Way, by using a chemical evolution model of a galaxy composed of stars, interstellar medium, metals (elements heavier than helium), and dust. We start from a review of time-evolutionary equations of the four components, and then, we present simple recipes for the stellar remnant mass and yields of metal and dust based on models of stellar nucleosynthesis and dust formation. After calibrating some model parameters with the data from the solar nei…
We have analysed the Herschel and SCUBA-2 dust continuum observations of the main filament in the Taurus L1495 star forming region, using the Bayesian fitting procedure PPMAP. (i) If we construct an average profile along the whole length of the filament, it has fwhm $\simeq 0.087\pm 0.003\,{\rm pc};\;$, but the closeness to previous estimates is coincidental. (ii) If we analyse small local sections of the filament, the column-density profile approximates well to the form predicted for hydrostatic equilibrium of an isothermal cylinder. (iii) The ability of PPMAP to distinguish dust emitting at …
We provide new ionization correction factors (ICFs) for carbon, nitrogen, neon, sulfur, chlorine, and argon in giant H II regions. The ICFs were computed using the most representative photoionization models from a large initial grid. The models were selected using an observational sample of 985 giant H II regions (GHR) in spiral galaxies and blue compact galaxies (BCG). The observational sample was also used to assign a weight to each model describing how well it agrees with observations in the [O III]/Hbeta versus [N II]/Halpha diagram. In addition to the ICFs we provide, for the first time, …
Stellar dust grains are predominantly composed of mineralic, anorganic material forming in the circumstellar envelopes of oxygen-rich AGB stars. However, the initial stage of the dust synthesis, or its nucleation, is not well understood. In particular, the chemical nature of the nucleating species, represented by molecular clusters, is uncertain. We investigated the vertical and adiabatic ionization energies of four different metal-oxide clusters by means of density functional theory. They included clusters of magnesia (MgO)$_n$, silicon monoxide (SiO)$_n$, alumina (Al$_2$O$_3$)$_n$, and titan…
We present numerical computations and analysis of atomic to molecular (HI-to-H$_2$) transitions in cool ($\sim$100 K) low-metallicity dust-free (primordial) gas, in which molecule formation occurs via cosmic-ray driven negative ion chemistry, and removal is by a combination of far-UV photodissociation and cosmic-ray ionization and dissociation. For any gas temperature, the behavior depends on the ratio of the Lyman-Werner (LW) band FUV intensity to gas density, $I_{\rm LW}/n$, and the ratio of the cosmic-ray ionization rate to the gas density, $ζ/n$. We present sets of HI-to-H$_2$ abundance pr…
Ionization-recombination balance in dense interstellar and circumstellar environments is a key factor for a variety of important physical processes, such as chemical reactions, dust charging and coagulation, coupling of the gas with magnetic field and development of instabilities in protoplanetary disks. We determine a critical gas density above which the recombination of electrons and ions on the grain surface dominates over the gas-phase recombination. For this regime, we present a self-consistent analytical model which allows us to exactly calculate abundances of charged species in dusty ga…
We present sub-arcsecond 7.5$-$13 $μ$m imaging- and spectro-polarimetric observations of NGC 1068 using CanariCam on the 10.4-m Gran Telescopio CANARIAS. At all wavelengths, we find: (1) A 90 $\times$ 60 pc extended polarized feature in the northern ionization cone, with a uniform $\sim$44$^{\circ}$ polarization angle. Its polarization arises from dust and gas emission in the ionization cone, heated by the active nucleus and jet, and further extinguished by aligned dust grains in the host galaxy. The polarization spectrum of the jet-molecular cloud interaction at $\sim$24 pc from the core is h…
Using a sample of 28 HII regions from the literature with measured temperature inhomogeneity parameter, t^2, we present a statistical correction to the chemical abundances determined with the Te(4363/5007) method. We used the t^2 values to correct the oxygen gaseous abundances and consider the oxygen depletion into dust to calculate the total abundances for these objects. This correction is used to obtain a new calibration of Pagel's strong-line method, R_{23}, to determine oxygen abundances in HII regions. Our new calibration simultaneously considers the temperature structure, the ionization …
We present a new dust extension to the Monte Carlo radiative transfer code crash, which enables it to simulate the propagation of ionizing radiation through mixtures of gas and dust. The new code is applied to study the impact of dust absorption on idealized galactic H II regions and on small scale reionization. We find that H II regions are reduced in size by the presence of dust, while their inner temperature and ionization structure remain largely unaffected. In the small scale reionization simulation, dust hardens ionization fronts and delays the overlap of ionized bubbles. This effect is …
We present new high resolution and dynamic range dust column density and temperature maps of the California Molecular Cloud derived from a combination of Planck and Herschel dust-emission maps, and 2MASS NIR dust-extinction maps. We used these data to determine the ratio of the 2.2 micron extinction coefficient to the 850 micron opacity and found the value to be close to that found in similar studies of the Orion B and Perseus clouds but higher than that characterizing the Orion A cloud, indicating that variations in the fundamental optical properties of dust may exist between local clouds. We…
The aim of this study is to investigate systematic chemical differentiation of molecules in regions of high mass star formation. We observed five prominent sites of high mass star formation in HCN, HNC, HCO+, their isotopes, C18O, C34S and some other molecular lines, for some sources both at 3 and 1.3 mm and in continuum at 1.3 mm. Taking into account earlier obtained data for N2H+ we derive molecular abundances and physical parameters of the sources (mass, density, ionization fraction, etc.). The kinetic temperature is estimated from CH3C2H observations. Then we analyze correlations between m…
The problem of impulsive heating of dust grains in cold, dense interstellar clouds is revisited theoretically, with the aim to better understand leading mechanisms of the explosive desorption of icy mantles. It is rigorously shown that if the heating of a reactive medium occurs within a sufficiently localized spot (e.g., heating of mantles by cosmic rays), then the subsequent thermal evolution is characterized by a single dimensionless number $λ$. This number identifies a bifurcation between two distinct regimes: When $λ$ exceeds a critical value (threshold), the heat equation exhibits the exp…
We revisit the cold gas contents of galaxies in a protocluster at z=2.49 using the lowest neutral atomic carbon transition [CI]$^3$P$_1$-$^3$P$_0$ from Atacama Large Millimeter/submillimeter Array observations. We aim to test if the same gas mass calibration applied in field galaxies can be applied to protocluster galaxies. Five galaxies out of sixteen targeted galaxies are detected in the [CI] line, and these are all previously detected in CO(3-2) and CO(4-3) and three in 1.1 mm dust continuum. We investigate the line luminosity relations between CO and [CI] in the protocluster and compare th…
Ionization Structure and Metal Enrichment of the Galactic Center Minispiral Observed with JWST
McGill University（麦吉尔大学）；Trottier Space Institute（特罗蒂尔太空研究所）；Canadian Institute for Theoretical Astrophysics, University of Toronto（多伦多大学加拿大理论天体物理研究所）；Max Planck Insitute for Radioastronomy（马克斯·普朗克射电天文研究所）；Center for Astrophysics — Harvard & Smithsonian（哈佛-史密森尼天体物理中心）；Institute of Astrophysics, Central China Normal University（华中师范大学天体物理研究所）；Villanova University（维拉诺瓦大学）
A majority of early-type galaxies contain interstellar dust, yet the origin of this dust, and why the dust sometimes exhibits unusual polycyclic aromatic hydrocarbon (PAH) ratios, remains a mystery. If the dust is internally produced, it likely originates from the large number of AGB stars associated with the old stellar population. We present GALEX and WISE elliptical aperture photometry of $\sim310$ early-type galaxies with Spitzer mid-infrared spectroscopy and/or ancillary data from ATLAS3D, to characterize their circumstellar dust and the shape of the radiation field that illuminates the i…
We explore the gas morphology and excitation mechanisms of the ionization cones of the Type II Seyfert galaxy NGC 5728. Near-IR and optical data from the SINFONI and MUSE IFUs on the VLT are combined with $HST$ optical images, $Chandra$ X-ray data and VLA radio observations. The complex nuclear structure has a star-forming (SF) ring with a diameter of 2 kpc. A radio jet impacts on the ISM at about 200 pc from the nucleus, with the SN remnants in the SF ring also present. Emission-line ratios of [Fe II] and H II show heavy extinction towards the nucleus, moderate extinction in the SF ring and r…
We study the ionization and kinematics of the ionized gas in the nuclear region of the barred Seyfert 2 galaxy NGC~5643 using MUSE integral field observations in the framework of the MAGNUM (Measuring Active Galactic Nuclei Under MUSE Microscope) survey. The data were used to identify regions with different ionization conditions and to map the gas density and the dust extinction. We find evidence for a double sided ionization cone, possibly collimated by a dusty structure surrounding the nucleus. At the center of the ionization cone, outflowing ionized gas is revealed as a blueshifted, asymmet…
In this paper, we report a detailed study with a variety of data from optical, near-infrared, X-ray, and radio telescopes of the nuclear region of the galaxy NGC 613 with the aim of understanding its complexity. We detected an extended stellar emission in the nucleus that, at first, appears to be, in the optical band, two stellar nuclei separated by a stream of dust. The active galactic nucleus (AGN) is identified as a variable point-like source between these two stellar components. There is a central hard X-ray emission and an extended soft X-ray emission that closely coincides with the ioniz…
Predicting HCN, HCO$^+$, multi-transition CO, and dust emission of star-forming galaxies -- Extension to luminous infrared galaxies and the role of cosmic ray ionization
We present measurements of the singly ionized helium to hydrogen ratio ($n_{He^+}/n_{H^+}$) toward diffuse gas surrounding three Ultra-Compact HII (UCHII ) regions: G10.15-0.34, G23.46-0.20 \& G29.96-0.02. We observe radio recombination lines (RRLs) of hydrogen and helium near 5 GHz using the GBT to measure the $n_{He^+}/n_{H^+}$ ratio. The measurements are motivated by the low helium ionization observed in the warm ionized medium (WIM) and in the inner Galaxy diffuse ionized regions (DIR). Our data indicate that the helium is not uniformly ionized in the three observed sources. Helium lines a…
We present our new ALMA observations targeting [OIII]88um, [CII]158um, [NII]122um, and dust continuum emission for three Lyman break galaxies at z=6.0293-6.2037 identified in the Subaru/Hyper Suprime-Cam survey. We clearly detect [OIII] and [CII] lines from all of the galaxies at 4.3-11.8sigma levels, and identify multi-band dust continuum emission in two of the three galaxies, allowing us to estimate infrared luminosities and dust temperatures simultaneously. In conjunction with previous ALMA observations for six galaxies at z>6, we confirm that all the nine z=6-9 galaxies have high [OIII]/[C…
Silicon carbide (SiC) is one of the major cosmic dust components in carbon-rich environments. However, the formation of SiC dust is not well understood. In particular, the initial stages of the SiC condensation (i.e. the SiC nucleation) remain unclear, as the basic building blocks (i.e. molecular clusters) exhibit atomic segregation at the (sub-)nanoscale. We report vertical and adiabatic ionization energies of small silicon carbide clusters, (SiC)$_n$ , n=2-12, ranging from 6.6-10.0 eV, which are lower than for the SiC molecule ($\sim$ 10.6 eV). The most favorable structures of the singly ion…
As the number of complex organic molecules (COMs) detected in the interstellar medium increases, it becomes important to place meaningful constraints on the formation pathways of these species. The molecular cloud SgrB2(N) is host to several hot molecular cores in the early stage of star formation, where a great variety of COMs are detected in the gas phase. Because of its exposure to the extreme conditions of the the Galactic center region, SgrB2(N) is one of the best targets to study the impact of environmental conditions on the production of COMs. Our main goal is to characterize the physic…
The high-velocity clouds (HVCs) in the outer Milky Way at $20^{\circ} < l < 190^{\circ}$ have similar spatial locations, metallicities, and kinematics. Moreover, their locations and kinematics are coincident with several extraplanar stellar streams. The HVC origins may be connected to the stellar streams, either stripped directly from them or precipitated by the aggregate dynamical roiling of the region by the stream progenitors. This paper suggests that these HVCs are "misty" precipitation in the stream wakes based on the following observations. New high-resolution (2.6 km/s) ultraviolet spec…
We present maps for the electron temperature in the inner kpc of three luminous Seyfert galaxies: Mrk 79, Mrk 348, and Mrk 607 obtained from Gemini GMOS-IFU observations at spatial resolutions of 110-280 pc. We study the distributions of electron temperature in active galaxies and find temperatures varying in the range from 8000 to >30000 K. Shocks due to gas outflows play an important role in the observed temperature distributions of Mrk 79 and Mrk 348, while standard photoionization models reproduce the derived temperature values for Mrk 607. In Mrk 79 and Mrk 348, we find direct evidence fo…
We modelled recent observations of UV absorption of HD and \HH\ in the Milky Way and toward damped/sub-damped Lyman alpha systems at z=0.18 and z $>$ 1.7. N(HD)/N(\HH) ratios reflect the separate self-shieldings of HD and \HH\ and the coupling introduced by deuteration chemistry. Locally, observations are explained by diffuse molecular gas with $ 16 \pccc \la$ n(H) $\la 128 \pccc $ if the cosmic-ray ionization rate per H-nucleus \zetaH $= 2\times 10^{-16}\ps$ as inferred from \H3\p\ and OH\p. The dominant influence on N(HD)/N(\HH) is the cosmic-ray ionization rate with a much weaker downward d…
The ionization parameter U is potentially useful for measuring radiation pressure feedback from massive star clusters, as it reflects the radiation-to-gas-pressure ratio and is readily derived from mid-infrared line ratios. We consider several effects which determine the apparent value of U in HII regions and galaxies. An upper limit is set by the compression of gas by radiation pressure. The pressure from stellar winds and the presence of neutral clumps both reduce U for a given radiation intensity. The most intensely irradiated regions are selectively dimmed by internal dust absorption of io…
Early B-type stars are invaluable indicators for elemental abundances of their birth environments. In contrast to the surrounding neutral interstellar matter (ISM) and HII regions their chemical composition is unaffected by depletion onto dust grains and by the derivation of different abundances from recombination and collisional lines. In combination with ISM or nebular gas-phase abundances they facilitate the dust-phase composition to be constrained. Precise abundances of C, N, Mg, Ne, Fe in early B-type stars in the Orion star-forming region are determined in order to: a) review previous de…
Dust grains influence many aspects of star formation, including planet formation, opacities for radiative transfer, chemistry, and the magnetic field via Ohmic, Hall, and ambipolar diffusion. The size distribution of the dust grains is the primary characteristic influencing all these aspects. Grain size increases by coagulation throughout the star formation process. We describe here numerical simulations of protostellar collapse using methods described in earlier papers of this series. We compute the evolution of the grain size distribution from coagulation and the non-ideal magnetohydrodynami…
The planetary nebula (PN) PB 8 around a [WN/WC]-hybrid central star is one of PNe with moderate abundance discrepancy factors (ADFs ~ 2-3), which could be an indication of a tiny fraction of metal-rich inclusions embedded in the nebula (bi-abundance). In this work, we have constructed photoionization models to reproduce the optical and infrared observations of the PN PB 8 using a non-LTE stellar model atmosphere ionizing source. A chemically homogeneous model initially used cannot predict the optical recombination lines (ORLs). However, a bi-abundance model provides a better fit to most of the…
The X-ray luminosities of T Tauri stars are about two to four orders of magnitude higher than the luminosity of the contemporary Sun. As these stars are born in clusters, their disks are not only irradiated by their parent star but also by an X-ray background field produced by the cluster members. We aim to quantify the impact of X-ray background fields produced by young embedded clusters on the chemical structure of disks. Further, we want to investigate the importance of the dust for X-ray radiative transfer in disks. We present a new X-ray radiative transfer module for the radiation thermo-…
We simulate a self-gravitating, turbulent cloud of 1000 Msol with photoionization and radiation pressure feedback from a 34 Msol star. We use a detailed Monte Carlo radiative transfer scheme alongside the hydrodynamics to compute photoionization and thermal equilibrium with dust grains and multiple atomic species. Using these gas temperatures, dust temperatures, and ionization fractions, we produce self-consistent synthetic observations of line and continuum emission. We find that all material is dispersed from the (15.5 pc)$^3$ grid within 1.6 Myr or 0.74 free-fall times. Mass exits with a pe…
In dense parts of interstellar clouds (> 10^5 cm^-3), dust & gas are expected to be in thermal equilibrium, being coupled via collisions. However, previous studies have shown that the temperatures of the dust & gas may remain decoupled even at higher densities. We study in detail the temperatures of dust & gas in the photon-dominated region S 140, especially around the deeply embedded infrared sources IRS 1-3 and at the ionization front. We derive the dust temperature and column density by combining Herschel PACS continuum observations with SOFIA observations at 37 $μ$m and SCUBA at 450 $μ$m. …
