Nebular Spectroscopy: A Guide on H ii Regions and Planetary Nebulae

Peimbert, M.; Peimbert, Antonio; Delgado-Inglada, G.

doi:10.1088/1538-3873/aa72c3

Cited by 145 publications

(131 citation statements)

References 201 publications

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“…5. See the discussion by Peimbert et al 2017 In Table D.1 we present the beam-averaged total hydrogen column densities N H based on this nominal gas-phase carbon ratio (columns headed 'N'), which is taken to be the same for all galaxies unless otherwise noted. We present results for isotopologue ratios of 40 and 80, respectively, denoted by superscript.…”

Section: Appendix D: Hydrogen Amountmentioning

confidence: 99%

Central molecular zones in galaxies:¹²CO-to-¹³CO ratios, carbon budget, andXfactors

Israel¹

2020

A&A

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We present ground-based measurements of 126 nearby galaxy centers in 12 CO and 92 in 13 CO in various low-J transitions. More than 60 galaxies were measured in at least four lines. The average relative intensities of the first four 12 CO J transitions are 1.00 : 0.92 : 0.70 : 0.57. In the first three J transitions, the average 12 CO-to-13 CO intensity ratios are 13.0, 11.6, and 12.8, with individual values in any transition ranging from 5 to 25. The sizes of central CO concentrations are well defined in maps, but poorly determined by multi-aperture photometry. On average, the J=1-0 12 CO fluxes increase linearly with the size of the observing beam, but CO emission covers only a quarter of the HI galaxy disks. Using radiative transfer models (RADEX), we derived model gas parameters. The assumed carbon elemental abundances and carbon gas depletion onto dust are the main causes of uncertainty. The new CO data and published [CI] and [CII] data imply that CO, C • , and C + each represent about one-third of the gas-phase carbon in the molecular interstellar medium. The mean beam-averaged molecular hydrogen column density is N( H 2 ) = (1.5 ± 0.2) × 10 21 cm −2 . Galaxy center CO-to-H 2 conversion factors are typically ten times lower than the 'standard' Milky Way X • disk value, with a mean X(CO) = (1.9 ± 0.2) × 10 19 cm −2 / K km s −1 and a dispersion 1.7 × 10 19 cm −2 / K km s −1 . The corresponding [CI]-H 2 factor is five times higher than X(CO), with X[CI] = (9 ± 2) × 10 19 cm −2 / K km s −1 . No unique conversion factor can be determined for [CII]. The low molecular gas content of galaxy centers relative to their CO intensities is explained in roughly equal parts by high central gas-phase carbon abundances, elevated gas temperatures, and large gas velocity dispersions relative to the corresponding values in galaxy disks.

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Section: Appendix D: Hydrogen Amountmentioning

confidence: 99%

Central molecular zones in galaxies:¹²CO-to-¹³CO ratios, carbon budget, andXfactors

Israel¹

2020

A&A

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“…For a given gas cloud, the balance between gravity and thermal pressure is mediated by the temperature, density, and chemical composition of the gas itself (Evans 1999). Thus, understanding the mechanisms that drive and sustain star formation relies on our ability to measure the physical properties of the ISM (see recent reviews by Peimbert et al 2017;Maiolino & Mannucci 2018;Kewley et al 2019b;and references therein).…”

Section: Introductionmentioning

confidence: 99%

A Comparison of UV and Optical Metallicities in Star-forming Galaxies

Byler

Kewley

Rigby

et al. 2020

ApJ

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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 λ1640Å / C III] λ1906,1909Å vs. [O III] λ1666Å / C III] λ1906,9Å) is a reliable metallicity tracer, particularly at low metallicity (12 + log 10 (O/H) ≤ 8), where stellar contributions are minimal. We find that the Si3-O3C3 diagnostic ([Si III] λ1883Å / C III] λ1906Å vs. [O III] λ1666Å / C III] λ1906,9Å) is a reliable metallicity tracer, though with large scatter (0.2-0.3 dex), which we suggest is driven by variations in gas-phase abundances. We find that the C4-O3C3 diagnostic (C IV λ 1548,50Å / [O III] λ 1666Å vs. [O III] λ 1666Å / C III] λ 1906,9Å) correlates poorly with optically-derived metallicities. We discuss possible explanations for these discrepant metallicity determinations, including the hardness of the ionizing spectrum, contribution from stellar wind emission, and non-solar-scaled gas-phase abundances. Finally, we provide two new UV oxygen abundance diagnostics, calculated from polynomial fits to the model grid surface in the He2-O3C3 and Si3-O3C3 diagrams.

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“…Liu et al 2000;Liu 2006;Liu et al 2006;García-Rojas & Esteban 2007;Bohigas 2015). The abundance discrepancy is quantified in terms of the abundance discrepancy factor (ADF), which is defined as the ratio of the ionic abundance derived from ORLs to the abundance derived from CELs (Peimbert et al 2017):…”

Section: Introductionmentioning

confidence: 99%

Realistic models for filling and abundance discrepancy factors in photoionized nebulae

Bergerud

Spangler

Beauchamp

2019

Monthly Notices of the Royal Astronomical Society

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When comparing nebular electron densities derived from collisionally excited lines (CELs) to those estimated using the emission measure, significant discrepancies are common. The standard solution is to view nebulae as aggregates of dense regions of constant density in an otherwise empty void. This porosity is parametrized by a filling factor f < 1. Similarly, abundance and temperature discrepancies between optical recombination lines (ORLs) and CELs are often explained by invoking a dual delta distribution of a dense, cool, metal-rich component immersed in a diffuse, warm, metal-poor plasma. In this paper, we examine the possibility that the observational diagnostics that lead to such discrepancies can be produced by a realistic distribution of density and temperature fluctuations, such as might arise in plasma turbulence. We produce simulated nebulae with density and temperature fluctuations described by various probability distribution functions (pdfs). Standard astronomical diagnostics are applied to these simulated observations to derive estimates of nebular densities, temperatures, and abundances. Our results show that for plausible density pdfs the simulated observations lead to filling factors in the observed range. None of our simulations satisfactorily reproduce the abundance discrepancy factors (ADFs) in planetary nebulae, although there is possible consistency with H ii regions. Compared to the case of density-only and temperature-only fluctuations, a positive correlation between density and temperature reduces the filling factor and ADF (from optical CELs), whereas a negative correlation increases both, eventually causing the filling factor to exceed unity. This result suggests that real observations can provide constraints on the thermodynamics of small scale fluctuations.

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Nebular Spectroscopy: A Guide on H ii Regions and Planetary Nebulae

Cited by 145 publications

References 201 publications

Central molecular zones in galaxies:¹²CO-to-¹³CO ratios, carbon budget, andXfactors

Central molecular zones in galaxies:¹²CO-to-¹³CO ratios, carbon budget, andXfactors

A Comparison of UV and Optical Metallicities in Star-forming Galaxies

Realistic models for filling and abundance discrepancy factors in photoionized nebulae

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Nebular Spectroscopy: A Guide on H ii Regions and Planetary Nebulae

Cited by 145 publications

References 201 publications

Central molecular zones in galaxies:12CO-to-13CO ratios, carbon budget, andXfactors

Central molecular zones in galaxies:12CO-to-13CO ratios, carbon budget, andXfactors

A Comparison of UV and Optical Metallicities in Star-forming Galaxies

Realistic models for filling and abundance discrepancy factors in photoionized nebulae

Contact Info

Product

Resources

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Central molecular zones in galaxies:¹²CO-to-¹³CO ratios, carbon budget, andXfactors

Central molecular zones in galaxies:¹²CO-to-¹³CO ratios, carbon budget, andXfactors