The chemical composition of HII regions in blue compact dwarf galaxies

Holovatyy, V. V.; Melekh, B. Ya.

doi:10.1134/1.1515090

Cited by 6 publications

(15 citation statements)

References 14 publications

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“…[O iii]λ5007/Hβ line ratios (Holovatyy & Melekh 2002). Since the He iλ6678 was detected in every spaxel of the FLAMES field of view and with good S/N, for the purpose of this work, we determined y + = He + /H + from the He iλ6678/Hα line ratio using the expression y + = 2.58t 0.25 (2.87 He iλ6678/Hα)…”

Section: Nebular He II and Helium Abundancementioning

confidence: 99%

A study of the interplay between ionized gas and star clusters in the central region of NGC 5253 with 2D spectroscopy

Monreal-Ibero

Vı́lchez²,

Walsh

et al. 2010

A&A

111

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Context. Starbursts are one of the main contributors to the chemical enrichment of the interstellar medium. However, mechanisms governing the interaction between the recent star formation and the surrounding gas are not fully understood. Because of their a priori simplicity, the subgroup of H ii galaxies constitute an ideal sample to study these mechanisms.Aims. A detailed 2D study of the central region of NGC 5253 has been performed to characterize the stellar and ionized gas structure as well as the extinction distribution, physical properties and kinematics of the ionized gas in the central ∼210 pc × 130 pc. Methods. We utilized optical integral field spectroscopy (IFS) data obtained with FLAMES. Results. A detailed extinction map for the ionized gas in NGC 5253 shows that the largest extinction is associated with the prominent Giant H ii region. There is an offset of ∼0. 5 between the peak of the optical continuum and the extinction peak in agreement with findings in the infrared. We found that stars suffer less extinction than gas by a factor of ∼0.33. The [S ii]λ6717/[S ii]λ6731 map shows an electron density (N e ) gradient declining from the peak of emission in Hα (790 cm −3 ) outwards, while the argon line ratio traces areas with N e ∼ 4200−6200 cm −3 . The area polluted with extra nitrogen, as deduced from the excess [N ii]λ6584/Hα, extends up to distances of 3. 3 (∼60 pc) from the maximum pollution, which is offset by ∼1. 5 from the peak of continuum emission. Wolf-Rayet features are distributed in an irregular pattern over a larger area (∼100 pc × 100 pc) and associated with young stellar clusters. We measured He + abundances over most of the field of view and values of He ++ /H + < ∼ 0.0005 in localized areas which do not coincide, in general, with the areas presenting W-R emission or extra nitrogen. The line profiles are complex. Up to three emission components were needed to reproduce them. One of them, associated with the giant H ii region, presents supersonic widths and [N ii]λ6584 and [S ii]λλ6717,6731 emission lines shifted up to 40 km s −1 with respect to Hα. Similarly, one of the narrow components presents offsets in the [N ii]λ6584 line of < ∼ 20 km s −1 . This is the first time that maps with such velocity offsets for a starburst galaxy have been presented. The observables in the giant H ii region fit with a scenario where the two super stellar clusters (SSCs) produce an outflow that encounters the previously quiescent gas. The south-west part of the FLAMES IFU field is consistent with a more evolved stage where the star clusters have already cleared out their local environment.

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Section: Nebular He II and Helium Abundancementioning

confidence: 99%

A study of the interplay between ionized gas and star clusters in the central region of NGC 5253 with 2D spectroscopy

Monreal-Ibero

Vı́lchez²,

Walsh

et al. 2010

A&A

111

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“…All these parameters (except for EW abs (λ)) can be obtained from the OPhMs, including the volumeaveraged y + . Therefore, we do not need to use the χ 2 function from (5). For each HeI line, we can derive EW abs (λ) using (6):…”

Section: Optimized Photoionization Modelsmentioning

confidence: 99%

“…The initial equivalent widths of all HeI absorption lines are set equal to zero. The covering factor, slope of the power-law hydrogen-density distribution, and number of ionizing photons beyond 228Å (steps [3][4][5] are derived via a one-dimensional optimization of the corresponding PhM using the minimization method of Brent [16]. Thus, this algorithm yields correct Lyc spectra and best-fit values of the OPhM free parameters.…”

Section: Iterative Proceduresmentioning

confidence: 99%

“…Some empirical expressions for ICFs are based on the proximity of the ionization potentials of the corresponding ions, and do not take into account differences in their effective ionization cross sections. Other expressions for ICFs are obtained from calculations of photoionization-model (PhM) grids for HII regions [1][2][3][4][5]. However, such calculations are not oriented at reproducing the observed spectra of HII regions.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the helium mass fraction Y and heavy-element abundance decrement dY /dZ are assumed to be constant in most PhM-grid calculations. In our previous papers [4,5], we calculated a PhM grid for HII regions in blue compact dwarf (BCD) galaxies based on the ionizing spectra beyond 912Å (Lyc spectra) of three HII regions with a wide range of Lyc luminosities, which we selected from among the Lyc spectra of the cores of 37 HII regions. These PhM-grid calculations neglected differences in the shapes of the Lyc spectral energy distributions (SEDs).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

10.1007/s11444-008-3002-x

2010

CrossRef Listing of Deleted DOIs

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A new method for determining the physical parameters, ionizing Lyman continua (Lyc) and chemical compositions of HII regions in blue compact dwarf galaxies is developed. We propose our modified NLEHII method, which is independent on the initial mass function (IMF) for the determination of the Lyc spectra of the ionizing nuclei of HII regions. This method is based on the assumptions of ionization-recombination and thermal equilibria in the HII regions. It is used to calculate the Lyc spectra for optimization photoionization models (OPhMs) of HII regions in an iterative way, since the Lyc spectrum depends on parameters that can be found from photoionization modeling. We apply this method to determine the chemical composition of an HII region in the blue compact dwarf galaxy SBS 0940+544 and, in particular, the helium mass fraction Y .PACS numbers: 98.58.Hf, 98.56.Wm

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Astrophysics in 2003

Trimble

Aschwanden

2004

PUBL ASTRON SOC PAC

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Five coherent sections appear this year, addressing solar physics, cosmology (with WMAP highlights), gamma-ray bursters (and their association with Type Ia supernovae), extra-solar-system planets, and the formation and evolution of galaxies (from reionization to assemblage of Local Group galaxies). There are also eight incoherent sections that deal with other topics in stellar, galactic, and planetary astronomy and the people who study them. INTRODUCTIONSTriskaidekaphobics may prefer not to read this installment of ApXX, and their numbers may well be augmented even before the introduction is over. This is, in fact, the 13th overview of 365.24 days of the astronomy and astrophysics literature. The earlier ones are cited here as Ap91, Ap92, …, Ap02 and appear in volumes 104-115 of PASP. The authors have tried to read systematically the contents of about 30 journals and other periodicals. Only about 10% of what has been read gets cited, and being cited is not always an unqualified compliment.Section 2 was assembled using papers found on the Astrophysics Data Service, maintained with support from NASA and including Solar

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The chemical composition of HII regions in blue compact dwarf galaxies

Cited by 6 publications

References 14 publications

A study of the interplay between ionized gas and star clusters in the central region of NGC 5253 with 2D spectroscopy

A study of the interplay between ionized gas and star clusters in the central region of NGC 5253 with 2D spectroscopy

10.1007/s11444-008-3002-x

Astrophysics in 2003

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