On the radial abundance gradients in discs of irregular galaxies

Pilyugin, L. S.; Grebel, Eva K.; Zinchenko, I. A.

doi:10.1093/mnras/stv932

Cited by 42 publications

(54 citation statements)

References 65 publications

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“…We investigate the origin of such flat gradient comparing NGC 55 with its companion galaxy, NGC 300, similar in terms of mass and luminosity and located in the same group of galaxies. The most plausible hypothesis is related to the differences in their K-band surface density profile that, as suggested by Pilyugin et al (2015), which can provide higher mixing of the NGC55 gaseous component than in similar galaxies.…”

Section: Discussionmentioning

confidence: 99%

NGC 55: a disc galaxy with flat abundance gradients

Magrini

Gonçalves

Vajgel

2016

Mon. Not. R. Astron. Soc.

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We present new spectroscopic observations obtained with GMOS@Gemini-S of a sample of 25 H ii regions located in NGC 55, a late-type galaxy in the nearby Sculptor group. We derive physical conditions and chemical composition through the T e -method for 18 H ii regions, and strong-line abundances for 22 H ii regions. We provide abundances of He, O, N, Ne, S, Ar, finding a substantially homogenous composition in the ionised gas of the disc of NGC 55, with no trace of radial gradients. The oxygen abundances, both derived with T e -and strong-line methods, have similar mean values and similarly small dispersions: 12+log(O/H)=8.13±0.18 dex with the former and 12+log(O/H)=8.17±0.13 dex with the latter. The average metallicities and the flat gradients agree with previous studies of smaller samples of H ii regions and there is a qualitative agreement with the blue supergiant radial gradient as well. We investigate the origin of such flat gradients comparing NGC 55 with NGC 300, its companion galaxy, which is also twin of NGC 55 in terms of mass and luminosity. We suggest that the differences in the metal distributions in the two galaxies might be related to the differences in their K-band surface density profile. The flatter profile of NGC 55 probably causes in this galaxy higher infall/outflow rates than in similar galaxies. This likely provokes a strong mixing of gas and a re-distribution of metals.

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Section: Discussionmentioning

confidence: 99%

NGC 55: a disc galaxy with flat abundance gradients

Magrini

Gonçalves

Vajgel

2016

Mon. Not. R. Astron. Soc.

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“…Gas mass surface densities, H H2 I S + , are derived from the dust mass surface densities using Equation (4), after implementation of a metallicity-dependent gas-to-dust ratio (Equation (5)), using the metallicity gradient derived by Pilyugin et al (2015). Variations in the D/H ratio can be as large as a factor of ∼3 within galaxies (Roman-Duval et al 2014, which is larger than the systematic change from the metallicity gradient ( O H O H 0.15 D < ( ) ( ) ) across the central region; however, they are smaller than the dynamic range of our gas mass data.…”

Section: Spatially Resolved Dust and Gas Massesmentioning

confidence: 99%

“…d Central oxygen abundance and abundance gradient, respectively. The central oxygen abundance has an uncertainty of±0.01 (Pilyugin et al 2015).…”

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confidence: 99%

Spatially Resolved Dust, Gas, and Star Formation in the Dwarf Magellanic Irregular NGC 4449^*

Calzetti

Wilson

Draine

et al. 2018

ApJ

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We investigate the relation between gas and star formation in subgalactic regions, ∼360pc to ∼1.5kpc in size, within the nearby starburst dwarf NGC 4449, in order to separate the underlying relation from the effects of sampling at varying spatial scales. Dust and gas mass surface densities are derived by combining new observations at 1.1mm, obtained with the AzTEC instrument on the Large Millimeter Telescope, with archival infrared images in the range 8-500μm from the Spitzer Space Telescope and the Herschel Space Observatory. We extend the dynamic range of our millimeter (and dust) maps at the faint end, using a correlation between the far-infrared/ millimeter colors F(70)/F(1100) (and F(160)/F(1100)) and the mid-infrared color F(8)/F(24) that we establish for the first time for this and other galaxies. Supplementing our data with maps of the extinction-corrected star formation rate (SFR) surface density, we measure both the SFR-moleculargas and the SFR-totalgas relations in NGC 4449. We find that the SFR-moleculargas relation is described by a power law with an exponent that decreases from ∼1.5 to ∼1.2 for increasing region size, while the exponent of the SFR-totalgas relation remains constant with a value of ∼1.5 independent of region size. We attribute the molecular law behavior to the increasingly better sampling of the molecular cloud mass function at larger region sizes; conversely, the total gas law behavior likely results from the balance between the atomic and molecular gas phases achieved in regions of active star formation. Our results indicate a nonlinear relation between SFR and gas surface density in NGC 4449, similar to what is observed for galaxy samples.

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“…For example, on global scales they are one of the key parameters in the study of the luminosity-metallicity and massmetallicity relations of galaxies, their evolution with time, and their dependence on environment or star formation rate (e.g., Lequeux et al 1979;Grebel et al 2003;Tremonti et al 2004;Erb et al 2006;Panter et al 2008;Zahid et al 2012;Sánchez et al 2013;Peng & Maiolino 2014;Zahid et al 2014;Izotov et al 2015, to just name a few of the many studies). Local measurements within galaxies reveal the position-dependent metallicity of the chosen tracer population and may show abundance gradients, which in turn hold clues about galaxy evolution (e.g., Searle 1971;Janes 1979;Maciel & Quireza 1999;Harbeck et al 2001;Andrievsky et al 2002;Chen et al 2003;Mehlert et al 2003;Cioni 2009;Haschke et al 2012;Boeche et al 2013Boeche et al , 2014Pilyugin et al 2014Pilyugin et al , 2015.…”

Section: Introductionmentioning

confidence: 99%

New calibrations for abundance determinations in H ii regions

Pilyugin¹,

Grebel²

2016

Mon. Not. R. Astron. Soc.

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280

250

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Simple relations for deriving the oxygen abundance in H ii regions with intensities of the three strong emission lines R 2 , R 3 , and N 2 (R calibration) or S 2 , R 3 , and N 2 (S calibration) in their spectra are suggested. A sample of 313 reference H ii regions of the counterpart method (C method) is used as calibrating data points. Relations for the determination of nitrogen abundances, the R calibration, are also constructed. We find that the oxygen and nitrogen abundances in high-metallicity H ii regions can be estimated using the intensities of the two strong lines R 2 and N 2 (or S 2 and N 2 for oxygen) only. The corresponding two-dimensional relations are provided. There are considerable advantages of the suggested calibration relations as compared to the existing ones. First, the oxygen and nitrogen abundances estimated through the suggested calibrations agree with the T e -based abundances within ∼ 0.1 dex over the whole metallicity range, i.e., the relative accuracy of the calibration-based abundances is 0.1 dex. Although we constructed distinct relations for high-and low-metallicity objects, the separation between these two can be simply obtained from the intensity of the N 2 line. Moreover, the applicability ranges of the high-and low-metallicity relations overlap for adjacent metallicities, i.e., the transition zone disappears. Second, the oxygen abundances produced by the two suggested calibrations are in remarkable agreement with each other. In fact, the R-based and S -based oxygen abundances agree within ∼0.05 dex in the majority of cases for more than three thousand H ii region spectra.

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On the radial abundance gradients in discs of irregular galaxies

Cited by 42 publications

References 65 publications

NGC 55: a disc galaxy with flat abundance gradients

NGC 55: a disc galaxy with flat abundance gradients

Spatially Resolved Dust, Gas, and Star Formation in the Dwarf Magellanic Irregular NGC 4449^*

New calibrations for abundance determinations in H ii regions

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On the radial abundance gradients in discs of irregular galaxies

Cited by 42 publications

References 65 publications

NGC 55: a disc galaxy with flat abundance gradients

NGC 55: a disc galaxy with flat abundance gradients

Spatially Resolved Dust, Gas, and Star Formation in the Dwarf Magellanic Irregular NGC 4449*

New calibrations for abundance determinations in H ii regions

Contact Info

Product

Resources

About

Spatially Resolved Dust, Gas, and Star Formation in the Dwarf Magellanic Irregular NGC 4449^*