Astrophysics and Astronomy Commons^™

Dielectronic Recombination And Stability Of Warm Gas In Active Galactic Nuclei, Susmita Chakravorty, Ajit K. Kembhavi, Martin Elvis, Gary J. Ferland, N. R. Badnell

Physics and Astronomy Faculty Publications

Understanding the thermal equilibrium (stability) curve may offer insights into the nature of the warm absorbers often found in active galactic nuclei. Its shape is determined by factors such as the spectrum of the ionizing continuum and the chemical composition of the gas. We find that the stability curves obtained under the same set of the above-mentioned physical factors, but using recently derived dielectronic recombination rates, give significantly different results, especially in the regions corresponding to warm absorbers, leading to different physical predictions. Using the current rates we find a larger probability of having a thermally stable warm absorber at …

Merged Ionization/Dissociation Fronts In Planetary Nebulae, William J. Henney, R. J. R. Williams, Gary J. Ferland, Gargi Shaw, C. R. O'Dell

Physics and Astronomy Faculty Publications

The hydrogen ionization and dissociation front around an ultraviolet radiation source should merge when the ratio of ionizing photon flux to gas density is sufficiently low and the spectrum is sufficiently hard. This regime is particularly relevant to the molecular knots that are commonly found in evolved planetary nebulae, such as the Helix Nebula, where traditional models of photodissociation regions have proved unable to explain the high observed luminosity in H₂ lines. In this paper we present results for the structure and steady state dynamics of such advection-dominated merged fronts, calculated using the Cloudy plasma/molecular physics code. We find …

Spitzer Irs Observations Of Seyfert 1.8 And 1.9 Galaxies: A Comparison With Seyfert 1 And Seyfert 2, R. P. Deo, D. M. Crenshaw, S. B. Kraemer, M. Dietrich, Moshe Elitzur, H. Teplitz, T. J. Turner

Physics and Astronomy Faculty Publications

We present Spitzer mid-infrared spectra of 12 Seyfert 1.8 and 1.9 galaxies over the 5-38 μm region. We compare the spectral characteristics of this sample to those of 58 Seyfert 1 and 2 galaxies from the Spitzer archives. An analysis of the spectral shapes, the silicate 10 μm feature and the emission-line fluxes have enabled us to characterize the mid-IR properties of Seyfert 1.8/1.9s. We find that the EWs of the 10 μm silicate feature are generally weak in all Seyfert galaxies, as previously reported by several studies. The few Seyfert galaxies in this sample that show …

The Agn-Obscuring Torus: The End Of The "Doughnut" Paradigm?, Moshe Elitzur, Isaac Shlosman

Physics and Astronomy Faculty Publications

Unified schemes of active galactic nuclei (AGNs) require an obscuring dusty torus around the central engine. The compact sizes (only a few parsecs) determined in recent high-resolution observations require that the obscuring matter be clumpy and located inside the region where the black hole gravity dominates over the galactic bulge. This location is in line with the scenario depicting the torus as the region of the clumpy wind coming off the accretion disk in which the clouds are dusty and optically thick. We study here the outflow scenario within the framework of hydromagnetic disk winds, incorporating the cloud properties determined …

Revisiting He-Like X-Ray Emission-Line Plasma Diagnostics, R. L. Porter, Gary J. Ferland

Physics and Astronomy Faculty Publications

A complete model of helium-like line and continuum emission has been incorporated into the plasma simulation code Cloudy. All elements between He and Zn are treated, any number of levels can be considered, and radiative and collisional processes are included. This includes photoionization from all levels, line transfer, including continuum pumping and destruction by background opacities, scattering, and collisional processes. The model is calculated self-consistently along with the ionization and thermal structure of the surrounding nebula. The result is a complete line and continuum spectrum of the plasma. Here we focus on the ions of the He I sequence and …

The Mid-Infrared Emission Of M87, Eric S. Perlman, R. E. Mason, Christopher Packham, N. A. Levenson, Moshe Elitzur, Justin J. Schaefer, Masatoshi Imanishi, William B. Sparks, James Radomski

Physics and Astronomy Faculty Publications

We discuss Subaru and Spitzer Space Telescope imaging and spectroscopy of M87 in the mid-infrared (mid-IR) from 5 to 35 μm. These observations allow us to investigate mid-IR emission mechanisms in the core of M87 and to establish that the flaring, variable jet component HST-1 is not a major contributor to the mid-IR flux. The Spitzer data include a high signal-to-noise ratio 15-35 μm spectrum of the knot A/B complex in the jet, which is consistent with synchrotron emission. However, a synchrotron model cannot account for the observed nuclear spectrum, even when contributions from the jet, necessary due …

Optically Thick [O I] And [C Ii] Emission Toward Ngc 6334a, N. P. Abel, A. P. Sarma, Thomas H. Troland, Gary J. Ferland

Physics and Astronomy Faculty Publications

This work focuses on [O I] and [C II] emission toward NGC 6334A, an embedded H⁺ region/PDR only observable at infrared or longer wavelengths. A geometry in which nearly all the emission escapes out the side of the cloud facing the stars, such as Orion, is not applicable to this region. Instead, we find the geometry to be one in which the H⁺ region and associated PDR is embedded in the molecular cloud. Constant-density PDR calculations are presented which predict line intensities as a function of A_V [or N(H)], hydrogen density (n_H), and …

An Investigation Into The Effects Of Luminosity On The Mid-Infrared Spectral Energy Distributions Of Radio-Quiet Quasars, S. C. Gallagher, G. T. Richards, M. Lacy, D. C. Hines, Moshe Elitzur, L. J. Storrie-Lombardi

Physics and Astronomy Faculty Publications

We present an analysis of the effects of luminosity on the shape of the mid-infrared spectral energy distributions (SEDs) of 234 radio-quiet quasars originally presented by Richards et al. In quasars without evident dust extinction, the spectrally integrated optical and infrared luminosities are linearly correlated over nearly three decades in luminosity. We find a significant (≳99.99\% confidence) correlation between the 1.8-8.0 μm spectral index and infrared luminosity that indicates an enhancement of the mid-infrared continuum with increasing luminosity. Coupled with strong evidence for spectral curvature in more luminous quasars, we conclude that this trend is likely a manifestation of …

Gemini Mid-Ir Polarimetry Of Ngc 1068: Polarized Structures Around The Nucleus, C. Packham, S. Young, S. Fisher, K. Volk, R. Mason, J. H. Hough, P. F. Roche, Moshe Elitzur, J. Radomski, E. Perlman

Physics and Astronomy Faculty Publications

We present diffraction-limited, 10 μm imaging polarimetry data for the central regions of the archetypal Seyfert active galactic nucleus NGC 1068. The position angle of polarization is consistent with three dominant polarizing mechanisms. We identify three distinct regions of polarization: (1) north of the nucleus, arising from aligned dust in the narrow emission line region, (2) south, east, and west of the nucleus, consistent with dust being channeled toward the central engine, and (3) a central minimum of polarization consistent with a compact (≤22 pc) torus. These observations provide continuity between the geometrically and optically thick torus and the …

Determination Of The Physical Conditions Of The Knots In The Helix Nebula From Optical And Infrared Observations, C. R. O'Dell, W. J. Henney, Gary J. Ferland

Physics and Astronomy Faculty Publications

We use new Hubble Space Telescope and archived images to clarify the nature of the ubiquitous knots in the Helix Nebula, which are variously estimated to contain a significant to majority fraction of the material ejected by its central star. We employ published far-infrared spectrophotometry and existing 2.12 μm images to establish that the population distribution of the lowest rovibrational states of H2 is close to the distribution of a gas in local thermodynamic equilibrium at 988 ± 119 K. In addition, we present calculations that show that the weakness of the H₂ 0-0 S(7) line is not …

A Photon Dominated Region Code Comparison Study, M. Röllig, Nicholas Paul Abel, T. Bell, F. Bensch, J. Black, Gary J. Ferland, B. Jonkheid, I. Kamp, M. J. Kaufman, J. Le Bourlot, F. Le Petit, R. Meijerink, O. Morata, V. Ossenkopf, E. Roueff, Gargi Shaw, M. Spaans, A. Sternberg, J. Stutzki, W.-F. Thi, E. F. Van Dishoeck, P. A. M. Van Hoof, S. Viti, M. G. Wolfire

Physics and Astronomy Faculty Publications

Aims. We present a comparison between independent computer codes, modeling the physics and chemistry of interstellar photon dominated regions (PDRs). Our goal was to understand the mutual differences in the PDR codes and their effects on the physical and chemical structure of the model clouds, and to converge the output of different codes to a common solution.

Methods. A number of benchmark models have been created, covering low and high gas densities n = 10³,10^5.5 cm^-3 and far ultraviolet intensities χ = 10, 10⁵ in units of the Draine field (FUV: 6 < h_ν < 13.6 eV). The benchmark models were computed in two ways: one set assuming constant temperatures, thus testing the consistency of the chemical network and photo-processes, and a second set determining the temperature self consistently by solving the thermal balance, thus testing the modeling of the heating and cooling mechanisms accounting for the detailed energy balance throughout the clouds.

Results. …

Dust And Pah Emission In The Star-Forming Active Nucleus Of Ngc 1097, R. E. Mason, N. A. Levenson, C. Packham, Moshe Elitzur, J. Radomski, A. O. Petric, G. S. Wright

Physics and Astronomy Faculty Publications

The nucleus of the nearby galaxy NGC 1097 is known to host a young, compact (r < 9 pc) nuclear star cluster, as well as a low-luminosity active galactic nucleus (AGN). It has been suggested both that the nuclear stellar cluster is associated with a dusty torus and that low-luminosity AGNs like NGC 1097 do not have the torus predicted by the unified model of AGNs. To investigate these contradictory possibilities we have acquired Gemini/T-ReCS 11.7 and 18.3 μm images of the central few hundred parsecs of this galaxy at <45 pc angular resolution, in which the nucleus and spectacular, kiloparsec-scale star-forming ring are detected in both bands. The small-scale mid-IR luminosity implies thermal emission from warm dust close to the central engine. Fitting of torus models shows that the observed mid-IR emission cannot be accounted for by dust heated by the central engine. Rather, the principal source heating the dust in this object is the nuclear star cluster itself, suggesting that the detected dust is not the torus of AGN unified schemes (although it is also possible that the dusty starburst itself could provide the obscuration invoked by the unified model). Comparison of Spitzer IRS and Gemini GNIRS spectra shows that, although PAH bands are strong in the immediate circumnuclear region of the galaxy, PAH emission is weak or absent in the central 19 pc. The lack of PAH emission can probably be explained largely by destruction/ionization of PAH molecules by hard photons from the nuclear star cluster. If NGC 1097 is typical, PAH emission bands may not be a useful tool with which …

A Magnetically Supported Photodissociation Region In M17, E. W. Pellegrini, J. A. Baldwin, C. L. Brogan, M. M. Hanson, N. P. Abel, Gary J. Ferland, H. B. Nemala, G. Shaw, Thomas H. Troland

Physics and Astronomy Faculty Publications

The southwestern (SW) part of the Galactic H II region M17 contains an obscured ionization front that is most easily seen at infrared and radio wavelengths. It is nearly edge-on, thus offering an excellent opportunity to study the way in which the gas changes from fully ionized to molecular as radiation from the ionizing stars penetrates into the gas. M17 is also one of the very few H II regions for which the magnetic field strength can be measured in the photodissociation region ( PDR) that forms the interface between the ionized and molecular gas. Here we model an observed …

He I Emission In The Orion Nebula And Implications For Primordial Helium Abundance, R. L. Porter, Gary J. Ferland, K. B. Macadam

Physics and Astronomy Faculty Publications

We apply a recently developed theoretical model of helium emission to observations of both the Orion Nebula and a sample of extragalactic H II regions. In the Orion analysis, we eliminate some weak and blended lines and compare theory and observation for our reduced line list. With our best theoretical model we find an average difference between theoretical and observed intensities (I_pred/I_obs-1)=6.5%. We argue that both the red and blue ends of the spectrum may have been inadequately corrected for reddening. For the 22 highest quality lines, with 3499 Å≤λ≤6678 Å, our best model …

The Distribution Of Silicate Strength In Spitzer Spectra Of Agns And Ulirgs, Lei Hao, D. W. Weedman, H. Spoon, J. A. Marshall, N. A. Levenson, Moshe Elitzur, J. R. Houck

Physics and Astronomy Faculty Publications

A sample of 196 AGNs and ULIRGs observed by the Infrared Spectrograph (IRS) on Spitzer is analyzed to study the distribution of the strength of the 9.7 μm silicate feature. Average spectra are derived for quasars, Seyfert 1 and Seyfert 2 AGNs, and ULIRGs. We find that quasars are characterized by silicate features in emission and Seyfert 1s equally by emission or weak absorption. Seyfert 2s are dominated by weak silicate absorption, and ULIRGs are characterized by strong silicate absorption (mean apparent optical depth about 1.5). Luminosity distributions show that luminosities at rest frame 5.5 μm are similar …

The Structure Of The Homunculus. Ii. Modeling The Physical Conditions In Η Carinae's Molecular Shell, Nathan Smith, Gary J. Ferland

Physics and Astronomy Faculty Publications

We present models that reproduce the observed double-shell structure of the Homunculus Nebula around η Carinae, including the stratification of infrared H₂ and [Fe II] emission seen in data obtained with the Phoenix spectrograph on Gemini South, as well as the corresponding stratified grain temperature seen in thermal-infrared data. Tuning the model to match the observed shell thickness allows us to determine the threshold density that permits survival of H₂. An average density of n_H~=(0.5-1)×10⁷ cm^-3 in the outer zone is required to allow H₂ to exist at all latitudes in the …

Thermal Properties Of Cubic Kta 1 X Nb X O 3 Crystals, X. P. Wang, J. Y. Wang, H. J. Zhang, Y. G. Yu, J. Wu, W. L. Gao, Robert I. Boughton

Physics and Astronomy Faculty Publications

Cubic potassium tantalite niobate KTa1−xNbxO3 KTN crystals of large size, good quality, and varying Nb concentration have been grown by the Czochralski method and their thermal properties have been systematically studied. The melting point, molar enthalpy of fusion, and molar entropy of fusion of the crystals were determined to be: 1536.9 K, 12 068.521 J mol−1, and 7.85 J K−1 mol−1 for KTa0.67Nb0.33O3; and 1520.61 K, 15 352.511 J mol−1, and 10.098 J K−1 mol−1 for KTa0.67Nb0.33O3, respectively. Based on the data, the Jackson factor was calculated to be 0.994f and 1.214f for KTa0.67Nb0.33O3 and KTa0.63Nb0.37O3, respectively. The thermal expansion …

Discovery Of Atomic And Molecular Mid-Infrared Emission Lines In Off-Nuclear Regions Of Ngc 1275 And Ngc 4696 With The Spitzer Space Telescope, R. M. Johnstone, N. A. Hatch, Gary J. Ferland, A. C. Fabian, C. S. Crawford, R. J. Wilman

Physics and Astronomy Faculty Publications

We present Spitzer high-resolution spectra of off-nuclear regions in the central cluster galaxies NGC 1275 and NGC 4696 in the Perseus and Centaurus clusters, respectively. Both objects are surrounded by extensive optical emission-line filamentary nebulae, bright outer parts of which are the targets of our observations. The 10–37 μm spectra show strong pure-rotational lines from molecular hydrogen revealing a molecular component to the filaments which has an excitation temperature of ∼300−400 K. The flux in the 0−0 S(1) molecular hydrogen line correlates well with the strength of the optical lines, having about 3 per cent of the Hα+[N II] emission. …

Mid-Infrared Galaxy Classification Based On Silicate Obscuration And Pah Equivalent Width, H. W. W. Spoon, J. A. Marshall, J. R. Houck, Moshe Elitzur, L. Hao, L. Armus, B. R. Brandl, V. Charmandaris

Physics and Astronomy Faculty Publications

We present a new diagnostic diagram for mid-infrared spectra of infrared galaxies based on the equivalent width of the 6.2 μm PAH emission feature and the strength of the 9.7 μm silicate feature. Based on the positions in this diagram, we classify galaxies into nine classes ranging from continuum-dominated AGN hot dust spectra and PAH-dominated starburst spectra to absorption-dominated spectra of deeply obscured galactic nuclei. We find that galaxies are systematically distributed along two distinct branches: one of AGN and starburst-dominated spectra and one of deeply obscured nuclei and starburst-dominated spectra. The separation into two branches likely reflects …

Deep Mid-Infrared Silicate Absorption As A Diagnostic Of Obscuring Geometry Toward Galactic Nuclei, N. A. Levenson, M. M. Sirocky, L. Hao, H. W. W. Spoon, J. A. Marshall, Moshe Elitzur, J. R. Houck

Physics and Astronomy Faculty Publications

The silicate cross section peak near 10 μm produces emission and absorption features in the spectra of dusty galactic nuclei observed with the Spitzer Space Telescope. Especially in ultraluminous infrared galaxies, the observed absorption feature can be extremely deep, as IRAS 08572+3915 illustrates. A foreground screen of obscuration cannot reproduce this observed feature, even at a large optical depth. Instead, the deep absorption requires a nuclear source to be deeply embedded in a smooth distribution of material that is both geometrically and optically thick. In contrast, a clumpy medium can produce only shallow absorption or emission, which are …

Detection Of A Far-Infrared Bow Shock Nebula Around R Hya: The First Miriad Results, T. Ueta, A. K. Speck, R. E. Stencel, F. Herwig, R. D. Gehrz, R. Szczerba, H. Izumiura, A. A. Zijlstra, W. B. Latter, M. Matsuura, M. Meixner, M. Steffen, Moshe Elitzur

Physics and Astronomy Faculty Publications

We present the first results of the MIRIAD (MIPS InfraRed Imaging of AGB Dust shells) project using the Spitzer Space Telescope. The primary aim of the project is to probe the material distribution in the extended circumstellar envelopes (CSEs) of evolved stars and recover the fossil record of their mass-loss history. Hence, we must map the whole of the CSEs plus the surrounding sky for background subtraction while avoiding the central star that is brighter than the detector saturation limit. With our unique mapping strategy, we have achieved better than 1 MJy sr^-1 sensitivity in 3 hr of …

Energy Levels And Transition Probabilities For Boron-Like Fe Xxii, V. Jonauskas, P. Bogdanovich, F. P. Keenan, R. Kisielius, M. E. Foord, R. F. Heeter, S. J. Rose, Gary J. Ferland, P. H. Norrington

Physics and Astronomy Faculty Publications

The Multiconfiguration Dirac-Fock method is used to calculate the energies of the 407 lowest levels in FeXXII. These results are cross-checked using a suite of codes which employ the configuration interaction method on the basis set of transformed radial orbitals with variable parameters, and takes into account relativistic corrections in the Breit-Pauli approximation. Transition probabilities, oscillator and line strengths are presented for electric dipole (E1), electric quadrupole (E2) and magnetic dipole (M1) transitions among these levels. The total radiative transition probabilities, as well as the five largest values from each level be it of E1, M1, E2, M2, or E3 …

Determining The H+ Region / Pdr Equation Of State In Star-Forming Regions, N. P. Abel, Gary J. Ferland

Physics and Astronomy Faculty Publications

The emission-line regions of starburst galaxies and active nuclei reveal a wealth of spectroscopic information. A unified picture of the relationship among ionized, atomic, and molecular gas makes it possible to better understand these observations. We performed a series of calculations designed to determine the equation of state-the relationship among density, temperature, and pressure-through emission-line diagnostic ratios that form in the H⁺ region and the photodissociation region (PDR). We consider a wide range of physical conditions in the H⁺ region. We connect the H⁺ region to the PDR by considering two constant pressure cases: one with no …

Physical Conditions In Orion's Veil. Ii. A Multicomponent Study Of The Line Of Sight Toward The Trapezium, N. P. Abel, Gary J. Ferland, C. R. O'Dell, G. Shaw, Thomas H. Troland

Physics and Astronomy Faculty Publications

Orion's Veil is an absorbing screen that lies along the line of sight to the Orion H II region. It consists of two or more layers of gas that must lie within a few parsecs of the Trapezium cluster. Our previous work considered the Veil as a whole and found that the magnetic field dominates the energetics of the gas in at least one component. Here we use high-resolution STIS UV spectra that resolve the two velocity components in absorption and determine the conditions in each. We derive a volume hydrogen density, 21 cm spin temperature, turbulent velocity, and kinetic …

The Eclipsing Binary V1061 Cygni: Confronting Stellar Evolution Models For Active And Inactive Solar-Type Stars, Guillermo Torres, Claud H. Sandberg Lacy, Laurence A. Marschall, Holly A. Sheets, Jeff A. Mader

Physics and Astronomy Faculty Publications

We present spectroscopic and photometric observations of the chromospherically active (X-ray strong) eclipsing binary V1061 Cyg (P = 2.35 days) showing that it is in reality a hierarchical triple system. We combine these observations with Hipparcos intermediate data (abscissa residuals) to derive the outer orbit with a period of 15.8 yr. We determine accurate values for the masses, radii, and effective temperatures of the eclipsing binary components, as well as for the mass and temperature of the third star. For the primary we obtain M = 1.282 ± 0.015 M⊙, R = 1.615 ± 0.017 R⊙, Teff = 6180 ± …

Spatially Resolved Mid-Infrared Spectroscopy Of Ngc 1068: The Nature And Distribution Of The Nuclear Material, R. E. Mason, T. R. Geballe, C. Packham, N. A. Levenson, Moshe Elitzur, R. S. Fisher, E. Perlman

Physics and Astronomy Faculty Publications

We present spatially resolved, near-diffraction-limited 10 μm spectra of the nucleus of the Seyfert 2 galaxy NGC 1068, obtained with Michelle, the mid-IR imager and spectrometer on the 8.1 m Gemini North Telescope. The spectra cover the nucleus and the central 6.0” × 0.4” of the ionization cones at a spatial resolution of approximately 0.4” (≈30 pc). The spectra extracted in 0.4” steps along the slit reveal striking variations in continuum slope, silicate feature profile and depth, and fine-structure line fluxes on subarcsecond scales, illustrating in unprecedented detail the complexity of the circumnuclear regions of NGC 1068 at mid-IR …

Physical Conditions In The Interstellar Medium Toward Hd 185418, Gargi Shaw, Gary J. Ferland, R. Srianand, N. P. Abel

Physics and Astronomy Faculty Publications

We have developed a complete model of the hydrogen molecule as part of the spectral simulation code Cloudy. Our goal is to apply this to spectra of high-redshift star-forming regions where H₂ absorption is seen, but where few other details are known, to understand its implication for star formation. The microphysics of H₂ is intricate, and it is important to validate these numerical simulations in better understood environments. This paper studies a well-defined line of sight through the Galactic interstellar medium (ISM) as a test of the microphysics and methods we use. We present a self-consistent calculation of …

Near-Infrared And The Inner Regions Of Protoplanetary Disks, Dejan Vinković, Željko Ivezić, Tomislav Jurkić, Moshe Elitzur

Physics and Astronomy Faculty Publications

We examine the “puffed-up inner disk” model proposed by Dullemond, Dominik, & Natta for explaining the near-IR excess radiation from Herbig Ae/Be stars. Detailed model computations show that the observed near-IR excess requires more hot dust than is contained in the puffed-up disk rim. The rim can produce the observed near-IR excess only if its dust has perfectly gray opacity, but such dust is in conflict with the observed 10 μm spectral feature. We find that a compact (~10 AU), tenuous (τ_V ≲ 0.4), dusty halo around the disk inner regions contains enough dust to readily explain …

Growth And Thermal Properties Of Sr W O 4 Single Crystal, J. D. Fan, H. J. Wang, M. H. Jiang, Robert I. Boughton, D. G. Ran, S. Q. Sun, H. R. Xia

Physics and Astronomy Faculty Publications

A strontium tungstate SrWO4 single crystal with dimensions of 25 40 mm2 has been grown by the Czochralski method using an iridium crucible. X-ray powder diffraction results show that as grown the SrWO4 crystal belongs to the tetragonal system in the scheelite structure. The effective segregation coefficients of elemental W and Sr in the crystal growth are measured by x-ray fluorescence, and the respective values are close to 1. The thermal properties of the SrWO4 crystal were systemically studied by measuring the thermal expansion, specific heat, and thermal diffusion coefficient. These results show that the crystal possesses a large anisotropic …

The H Ii Region/Pdr Connection: Self-Consistent Calculations Of Physical Conditions In Star-Forming Regions, Nicholas Paul Abel, Gary J. Ferland, G. Shaw, Peter A. M. Van Hoof

Physics and Astronomy Faculty Publications

We have performed a series of calculations designed to reproduce infrared diagnostics used to determine physical conditions in star-forming regions. We self-consistently calculate the thermal and chemical structure of an H II region and photodissociation region (PDR) that are in pressure equilibrium. This differs from previous work, which used separate calculations for each gas phase. Our calculations span a wide range of stellar temperatures, gas densities, and ionization parameters. We describe improvements made to the spectral synthesis code Cloudy that made these calculations possible. These include the addition of a molecular network with ~1000 reactions involving 68 molecular species and …