Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution★

Esteban, C.; García‐Rojas, J.; Carigi, Leticia; Peimbert, M.; Bresolin, Fabio; López-Sánchez, Á. R.; Mesa‐Delgado, A.

doi:10.1093/mnras/stu1177

Cited by 96 publications

(135 citation statements)

References 93 publications

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“…This effect is seen in the detailed spectroscopic LBG study described by Steidel et al (2016), who find an offset between the nebular O/H abundance inferred from the [O III] "direct" method and that obtained through comprehensive modeling of the nebular and stellar spectra. Steidel et al find an offset consistent with that measured from CELs and RELs in local low-metallicity dwarf galaxies by Esteban et al (2014):…”

Section: [O Iii] Auroral Line and Gas Temperaturesupporting

confidence: 62%

“…Given that the results of Steidel et al (2016) appear to corraborate the Esteban et al (2014) offset at z ≈ 2−3, we apply a +0.24 dex correction to our "direct" abundance measurement described above in order to determine our final estimate of the nebular gas-phase metallicity:…”

Section: [O Iii] Auroral Line and Gas Temperaturementioning

confidence: 99%

“…where the uncertainty reflects both the statistical uncertainties from our bootstrap analysis and the statistical uncertainty in the Esteban et al (2014) calibration, but it does not include the systematic uncertainty in the application of the REL-CEL offset, nor those associated with the O II abundance discussed above. As described in Sec.…”

Section: [O Iii] Auroral Line and Gas Temperaturementioning

confidence: 99%

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THE REST-FRAME OPTICAL SPECTROSCOPIC PROPERTIES OF LYα-EMITTERS AT z ∼ 2.5: THE PHYSICAL ORIGINS OF STRONG LYα EMISSION*

Trainor

Strom²,

Steidel³

et al. 2016

ApJ

101

123

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We present the rest-frame optical spectroscopic properties of 60 faint (R AB ∼ 27; L ∼ 0.1L * ) Lyα-selected galaxies (LAEs) at z ≈ 2.56. These LAEs also have rest-UV spectra of their Lyα emission line morphologies, which trace the effects of interstellar and circumgalactic gas on the escape of Lyα photons. We find that the LAEs have diverse rest-optical spectra, but their average spectroscopic properties are broadly consistent with the extreme low-metallicity end of the populations of continuumselected galaxies selected at z ≈ 2 − 3. In particular, the LAEs have extremely high [O III] 4 K), low oxygen abundances (12 + log(O/H) ≈ 8.04, Z neb ≈ 0.22Z ), and high excitations with respect to their more luminous continuum-selected analogs. Several of our faintest LAEs have line ratios consistent with even lower metallicities, including six with 12 + log(O/H) ≈ 6.9−7.4 (Z neb ≈ 0.02 − 0.05Z ). We interpret these observations in light of new models of stellar evolution (including binary interactions) that have been shown to produce long-lived populations of hot, massive stars at low metallicities. We find that strong, hard ionizing continua are required to reproduce our observed line ratios, suggesting that faint galaxies are efficient producers of ionizing photons and important analogs of reionizationera galaxies. Furthermore, we investigate the physical trends accompanying Lyα emission across the largest current sample of combined Lyα and rest-optical galaxy spectroscopy, including both the 60 KBSS-Lyα LAEs and 368 more luminous galaxies at similar redshifts. We find that the net Lyα emissivity (parameterized by the Lyα equivalent width) is strongly correlated with nebular excitation and ionization properties and weakly correlated with dust attenuation, suggesting that metallicity plays a strong role in determining the observed properties of these galaxies by modulating their stellar spectra, nebular excitation, and dust content.

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Section: [O Iii] Auroral Line and Gas Temperaturesupporting

confidence: 62%

Section: [O Iii] Auroral Line and Gas Temperaturementioning

confidence: 99%

Section: [O Iii] Auroral Line and Gas Temperaturementioning

confidence: 99%

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THE REST-FRAME OPTICAL SPECTROSCOPIC PROPERTIES OF LYα-EMITTERS AT z ∼ 2.5: THE PHYSICAL ORIGINS OF STRONG LYα EMISSION*

Trainor

Strom²,

Steidel³

et al. 2016

ApJ

101

123

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“…We would be grateful for any feedback, query, or comment on the code and its accompanying documentation. PyNeb has already been used in a number of papers (García-Rojas et al 2012, 2014Esteban et al 2013Esteban et al , 2014Kameswara Rao et al 2013;Nicholls et al 2013Nicholls et al , 2014Marino et al 2013;Delgado-Inglada & Rodríguez 2014;Mesa-Delgado et al 2014;Sankrit et al 2014;Ho et al 2014;Pérez-Montero 2014). The scientific community is invited to keep using it for their projects.…”

Section: Concluding Remarks: the Present And Future Of Pynebmentioning

confidence: 99%

PyNeb: a new tool for analyzing emission lines

Luridiana

Morisset

Shaw

2014

A&A

478

409

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Analysis of emission lines in gaseous nebulae yields direct measures of physical conditions and chemical abundances and is the cornerstone of nebular astrophysics. Although the physical problem is conceptually simple, its practical complexity can be overwhelming since the amount of data to be analyzed steadily increases; furthermore, results depend crucially on the input atomic data, whose determination also improves each year. To address these challenges we created PyNeb, an innovative code for analyzing emission lines. PyNeb computes physical conditions and ionic and elemental abundances and produces both theoretical and observational diagnostic plots. It is designed to be portable, modular, and largely customizable in aspects such as the atomic data used, the format of the observational data to be analyzed, and the graphical output. It gives full access to the intermediate quantities of the calculation, making it possible to write scripts tailored to the specific type of analysis one wants to carry out. In the case of collisionally excited lines, PyNeb works by solving the equilibrium equations for an n-level atom; in the case of recombination lines, it works by interpolation in emissivity tables. The code offers a choice of extinction laws and ionization correction factors, which can be complemented by user-provided recipes. It is entirely written in the python programming language and uses standard python libraries. It is fully vectorized, making it apt for analyzing huge amounts of data. The code is stable and has been benchmarked against IRAF/NEBULAR. It is public, fully documented, and has already been satisfactorily used in a number of published papers.

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“…However, thanks to the new large aperture telescopes is possible to determine C abundances using the faint optical recombination lines (hereafter RLs) in bright nebulae. Some authors (e.g., Peimbert et al 1992;Esteban et al 2002Esteban et al , 2009Esteban et al , 2014a; López- Sánchez et al 2007) measured the C ii 4267Å RL in Galactic and extragalactic H ii regions. Besides they could also measure the faint RLs of the multiplet 1 of O ii at about 4650Å.…”

Section: Introductionmentioning

confidence: 99%

Carbon and oxygen abundance gradients in NGC 300 and M33 from optical recombination lines

Cipriano¹,

García‐Rojas²,

Esteban³

et al. 2016

Mon. Not. R. Astron. Soc.

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We present deep spectrophotometry of several H ii regions in the nearby low-mass spiral galaxies NGC 300 and M 33. The data have been taken with UVES and OSIRIS spectrographs attached to the 8 m VLT and 10.4 m GTC telescopes, respectively. We have derived precise values of the physical conditions for each object making use of several emission line-intensity ratios. In particular, we have obtained direct determinations of the electron temperature in all the observed objects. We detect pure recombination lines (RLs) of C ii and O ii in several of the H ii regions, permitting to derive their C/H and C/O ratios. We have derived the radial abundance gradient of O for each galaxy making use of collisionally excited lines (CELs) and RLs, as well as the C and N gradients using RLs and CELs, respectively. We obtain the first determination of the C/H gradient of NGC 300 and improve its determination in the case of M 33. In both galaxies, the C/H gradients are steeper that those of O/H, leading to negative C/O gradients. Comparing with similar results for other spiral galaxies, we find a strong correlation between the slope of the C/H gradient and M V . We find that some H ii regions located close to the isophotal radius (R 25 ) of NGC 300 and M 33 show C/O ratios more similar to those typical of dwarf galaxies than those of H ii regions in the discs of more massive spirals. This may be related to the absence of flattening of the gradients in the external parts of NGC 300 and M 33. Finally, we find very similar N/H gradients in both galaxies and a fair correlation between the slope of the N/H gradient and M V comparing with similar data for a sample of spiral galaxies.

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Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution★

Cited by 96 publications

References 93 publications

THE REST-FRAME OPTICAL SPECTROSCOPIC PROPERTIES OF LYα-EMITTERS AT z ∼ 2.5: THE PHYSICAL ORIGINS OF STRONG LYα EMISSION*

THE REST-FRAME OPTICAL SPECTROSCOPIC PROPERTIES OF LYα-EMITTERS AT z ∼ 2.5: THE PHYSICAL ORIGINS OF STRONG LYα EMISSION*

PyNeb: a new tool for analyzing emission lines

Carbon and oxygen abundance gradients in NGC 300 and M33 from optical recombination lines

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