Spectroscopic and photometric studies of low-metallicity star-forming 
dwarf galaxies

Гусева, Н. Г.; Papaderos, P.; Izotov, Y. I.; Green, R. F.; Fricke, K. J.; Thuan, T. X.; Noeske, K. J.

doi:10.1051/0004-6361:20030806

Cited by 30 publications

(33 citation statements)

References 49 publications

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“…The sample of low-metallicity H  regions in blue compact dwarf galaxies observed by Izotov with colleagues (Fricke et al 2001;Guseva et al 2001Guseva et al , 2003aIzotov & Thuan 1998Izotov et al 1994Izotov et al , 1997Izotov et al , 2001Noeske et al 2000;Thuan et al 1995Thuan et al , 1999 Kennicutt et al (2003); Lee et al (2003); ; ; Peimbert (2003); Tsamis et al (2003); Vermeij et al (2002);Vílchez & Iglesias-Páramo (2003). The spectroscopic data so assembled form the basis of the present study.…”

Section: Observational Data: Line Fluxesmentioning

confidence: 76%

On the relationship between auroral and nebular oxygen line intensities in spectra of H II regions

Pilyugin¹

2005

A&A

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Abstract. We investigate relationships between observed auroral and nebular oxygen line fluxes in spectra of H  regions. We find a relation that is metallicity-dependent at low metallicities, but becomes independent of metallicity (within the uncertainties of the available data) above 12+logO/H ∼ 8.25, i.e. there is one-to-one correspondence (the ff-relation) between auroral and nebular oxygen line fluxes in spectra of high-metallicity H  regions. The ff-relation allows one to estimate the flux in the auroral line from strong oxygen line measurements only. This solves the problem of the electron temperature (and, consequently, abundance) determination in high-metallicity H  regions. The ff-relation confirms the basic idea of the "empirical" method, proposed by Pagel et al. (1979, MNRAS, 189, 95) a quarter of a century ago, that the oxygen abundance in H  region can be esimated from the strong oxygen lines measurements only.

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Section: Observational Data: Line Fluxesmentioning

confidence: 76%

On the relationship between auroral and nebular oxygen line intensities in spectra of H II regions

Pilyugin¹

2005

A&A

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“…They allow to infer the ratio dY/dZ of the mass fraction Y of helium released into the interstellar medium by stars relative to the mass fraction Z of heavy elements. This quantity determines the slope of the linear regression of 4 He against O and N and hence directly affects the extrapolation of those regression lines to zero metallicity to determine the primordial helium abundance (Peimpert & Torres-Peimpert 1974, 1976Pagel et al 1992;, and references therein).Fourth, recent work lends strong observational support to the idea that some among the most metal-deficient star-forming galaxies known in the local universe have formed most of their stellar mass within the last 1 Gyr, hence they qualify as young galaxy candidates (Papaderos et al 2002;Guseva et al 2003;Pustilnik et al 2004). Evidently, such systems are excellent nearby laboratories for studying at high spatial resolution the early chemical and dynamical evolution of galaxies and can yield fundamental insight into the process of galaxy formation in the distant universe.…”

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confidence: 92%

New southern blue compact dwarf galaxies in the 2dF Galaxy redshift survey

Papaderos¹,

Гусева

Izotov

et al. 2006

A&A

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Aims. Aiming to find new extremely metal-deficient star-forming galaxies we extracted from the Two-Degree Field Galaxy Redshift Survey (2dFGRS) 100 K Data Release 14 emission-line galaxies with relatively strong [O iii] λ4363 emission.Methods. Spectroscopic and photometric studies of this sample and, in addition, of 7 Tololo and 2 UM galaxies were performed on the basis of observations with the ESO 3.6 m telescope. Results. All sample galaxies qualify with respect to their photometric and spectroscopic properties as blue compact dwarf (BCD) galaxies. Additionally, they show a good overlap with a comparison sample of ∼100 well-studied emission-line galaxies on the 12 + log (O/H) vs. log(Ne/O), log(Ar/O) and log(Fe/O) planes. From the analysis of the 2dFGRS subsample we report the discovery of two new extremely metal-deficient BCDs with an oxygen abundance 12 + log (O/H) ≤ 7.6 and of another seven galaxies with 12 + log (O/H) < ∼ 7.8. Furthermore, we confirm previous oxygen abundance determinations for the BCDs Tol 1304−353, Tol 2146−391, UM 559 and UM 570 to be 12 + log (O/H) ≤ 7.8. Key words. galaxies: starburst -galaxies: abundances -galaxies: fundamental parameters -galaxies: structure IntroductionThe identification of chemically unevolved star-forming galaxies in the local universe, with a nearly pristine chemical composition, is a fundamental quest of contemporary observational cosmology. This is because of several reasons.First, studies of abundance ratios and abundance gradients in these systems are crucial for our understanding of the early chemical evolution of galaxies and for constraining models of stellar nucleosynthesis and the properties of massive stars in the early universe.Second, if we wish to understand the spectra of primeval galaxies, it is highly important to understand how the UV radiation field of these systems changes as metallicity decreases. It is well established that the lower the metallicity, the harder is the radiation from massive stars (Campbell et al. 1986). As a consequence, strong high-ionization lines are expected in the spectra of metal-deficient star-forming galaxies. Indeed, deep spectroscopy has led recently to the discovery of high-ionization emission lines, such as [Fe v] λ4227 and [Ne v] λ3346, 3426, in addition to strong He ii λ4686 emission, in a few of the most metal-poor star-forming galaxies known in the local universe (Fricke et al. 2001;Izotov et al. 2001.Third, systematic studies of star-forming galaxies all the way down to a strongly subsolar metallicity are indispensable for Based on observations collected at the European Southern Observatory, Chile, ESO program 71.B-0032.Tables 3-5 are only available in electronic form at http://www.edpsciences.org putting tight observational constraints to the primordial helium abundance, which constitutes one of the key tests of Standard Big Bang Nucleosynthesis. They allow to infer the ratio dY/dZ of the mass fraction Y of helium released into the interstellar medium by stars relative to the mass fraction Z of heav...

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“…The surface brightness profile of this source can be fitted by a Sérsic profile (Sérsic 1968) with a V central surface brightness of ≈21.9 mag arcsec −2 and an exponent η of ∼ 0.7 (see Eq. (1) in Guseva et al 2003). Most likely, this source as well as those labeled 1-4 in Fig.…”

Section: Morphologymentioning

confidence: 82%

“…4a were obtained using one of the methods (method iii) described in Papaderos et al (1996a) and Guseva et al (2003) after the red compact sources 1 through 5 in Fig. 2a have been fitted and subtracted from the combined V and I images.…”

Section: Surface Brightness and Colour Distributionmentioning

confidence: 99%

“…(22); see also Guseva et al 2003 for a detailed explanation). Near the center, such an intensity distribution depends on the relative central intensity depression q = ∆I/I 0 , where I 0 is the central intensity obtained by extrapolation of the outer exponential slope to R * = 0, and on the cutoff-radius bα inside of which the central flattening occurs.…”

Section: Surface Brightness and Colour Distributionmentioning

confidence: 99%

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Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies

Гусева

Papaderos

Izotov

et al. 2003

A&A

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Abstract. We present broad-band V and I imaging and long-slit spectroscopy in the optical range λλ3600-7500 Å of the dwarf irregular galaxy HS 1442+4250. The oxygen abundance 12 + log (O/H) = 7.63 ± 0.02 (Z = Z /19) in the brightest H  region of HS 1442+4250 places the galaxy among the most metal-deficient emission-line galaxies. The low metallicity and blue colour (V − I) ∼ 0.4 mag of the low-surface-brightness (LSB) component make HS 1442+4250 a likely rare young dwarf galaxy candidate. We use four methods to estimate the stellar population age in the LSB component of HS 1442+4250. Different star formation histories are considered. The equivalent widths of hydrogen Hα and Hβ emission lines, and of hydrogen Hγ and Hδ absorption lines, the spectral energy distribution and the observed (V − I) colours of the LSB regions are reproduced quite well by models with only young and intermediate-age stellar populations. By contrast, the observational data cannot be reproduced by a stellar population formed continuously with a constant star formation rate in the age range from 0 to > ∼ 2 Gyr. While a faint old stellar population in HS 1442+4250 with an age > ∼ 2 Gyr is not excluded, we find no evidence for such a population from the present data.

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Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies

Cited by 30 publications

References 49 publications

On the relationship between auroral and nebular oxygen line intensities in spectra of H II regions

On the relationship between auroral and nebular oxygen line intensities in spectra of H II regions

New southern blue compact dwarf galaxies in the 2dF Galaxy redshift survey

Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies

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