Fricke, Klaus J.

[["dc.bibliographiccitation.artnumber","A11"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","579"],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Henkel, Cornelia"],["dc.date.accessioned","2018-11-07T09:54:58Z"],["dc.date.available","2018-11-07T09:54:58Z"],["dc.date.issued","2015"],["dc.description.abstract","We present a spectroscopic study of eight extremely low-metallicity candidate emission-line galaxies with oxygen abundances possibly below 12+logO/H = 7.35. These galaxies were selected from data release 10 of the Sloan Digital Sky Survey/Baryon Oscillation Spectroscopic Survey (SDSS/BOSS DR10). We will call these extremely metal-deficient (XMD) galaxies. The electron temperature-sensitive emission line [O III] lambda 4363 is detected in three galaxies and marginally detected in two galaxies, allowing for abundance determination by a \"direct\" method. Because of large uncertainties in the [O III]lambda 4363 angstrom line fluxes, we also calculated oxygen abundance in these galaxies together with the remaining three galaxies using a strong-line semi-empirical method. This method gives oxygen abundances higher than 7.35 for three galaxies with detected [O III]lambda 4363 angstrom line and lower than 7.35 for the remaining five objects of the sample. The newly-discovered galaxies represent excellent targets for follow-up spectroscopic observations with the largest telescopes to improve the oxygen abundance determination and to increase the number of these very rare low-metallicity objects. The extreme location of the most massive and luminous XMD galaxies and XMD candidates in the stellar mass-metallicity diagram implies that these galaxies may be genuine young objects. With stellar masses of up to similar to 10(7)-10(8) M-circle dot, the galaxies are not chemically enriched and strongly deviate to lower metallicity as compared to the relation obtained for a large sample of low-redshift, star-forming galaxies."],["dc.identifier.doi","10.1051/0004-6361/201525697"],["dc.identifier.isi","000358877100023"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/12444"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/36653"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","New candidates for extremely metal-poor emission-line galaxies in the SDSS/BOSS DR10"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","115"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","127"],["dc.bibliographiccitation.volume","429"],["dc.contributor.author","Noeske, K. G."],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Cairos, L. M."],["dc.contributor.author","Fricke, K. J."],["dc.date.accessioned","2018-11-07T08:34:49Z"],["dc.date.available","2018-11-07T08:34:49Z"],["dc.date.issued","2005"],["dc.description.abstract","This paper is part of a series of publications which present a systematic study of Blue Compact Dwarf (BCD) Galaxies in the near infrared (NIR). Compared to the visible light, NIR data allow a better separation of the starburst emission from the light distribution of the old stellar low-surface brightness (LSB) host galaxy. We analyze deep NIR broad band images of a sample of 11 BCDs, observed with the Calar Alto 3.6 m telescope. This work enlarges the samples presented in preceding papers of this study (Noeske et al. 2003, A A, 410, 481; Cairos et al. 2003, ApJ, 593, 312) by BCDs of the most common morphological type, displaying a regular elliptical LSB host galaxy. The data presented here allow the detection and quantitative study of the extended stellar LSB host galaxy in all sample BCDs. The NIR surface brightness profiles (SBPs) of the LSB host galaxies agree at large galactocentric radii with those from optical studies, showing also an exponential intensity decrease and compatible scale lengths. Similar to Noeske et al. ( 2003), we find centrally flattening exponential (type V) SBPs of the host galaxy for several BCDs. Such SBPs remain mostly undetected in optical bands, due to the comparatively stronger starburst emission at these wavelengths. We apply a modified exponential distribution to decompose and quantitatively analyze SBPs of LSB hosts with a type V intensity distribution. We present the results of the surface photometry and the decomposition of SBPs, and discuss individual objects with respect to morphological details of their star-forming regions."],["dc.identifier.doi","10.1051/0004-6361:20040221"],["dc.identifier.fs","38257"],["dc.identifier.isi","000225732700016"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9859"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/17913"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","E D P Sciences"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","New insights to the photometric structure of Blue Compact Dwarf Galaxies from deep near-infrared studies - II. The sample of northern BCDs"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","45"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","59"],["dc.bibliographiccitation.volume","457"],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Noeske, K. G."],["dc.contributor.author","Thuan, T. X."],["dc.contributor.author","Fricke, K. J."],["dc.date.accessioned","2019-07-09T11:54:53Z"],["dc.date.available","2019-07-09T11:54:53Z"],["dc.date.issued","2006-10-01"],["dc.description.abstract","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 3.6m 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."],["dc.identifier.doi","10.1051/0004-6361:20054458"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9875"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/60757"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.issn","1432-0746"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","New southern blue compact dwarf galaxies in the 2dF Galaxy redshift survey"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A97"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","570"],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Kruegel, E."],["dc.contributor.author","Henkel, Cornelia"],["dc.date.accessioned","2018-11-07T09:34:03Z"],["dc.date.available","2018-11-07T09:34:03Z"],["dc.date.issued","2014"],["dc.description.abstract","We studied the global characteristics of dust emission in a large sample of emission-line star-forming galaxies. The sample consists of two subsamples. One subsample (SDSS sample) includes similar to 4000 compact star-forming galaxies from the Sloan Digital Sky Survey (SDSS), which were also detected in all four bands at 3.4 mu m, 4.6 mu m, 12 mu m, and 22 mu m of the WISE all-sky survey. The second subsample (Herschel sample) is a sample of 28 compact star-forming galaxies observed with Herschel in the FIR range. Data of the Herschel sample were supplemented by the photometric data from the Spitzer observations, GALaxy Evolution Explorer (GALEX) survey, SDSS, Wide-Field Infrared Survey Explorer (WISE), Two Micron All Sky Survey (2MASS), NRAO VLA Sky Survey (NVSS), and Faint Images of the Radio Sky at Twenty-cm (FIRST) survey, as well as optical and Spitzer spectra and data in submm and radio ranges. It is found that warm dust luminosities of galaxies from the SDSS sample and cold and warm dust luminosities of galaxies from the Herschel sample are strongly correlated with H beta luminosities, which implies that one of the main sources of dust heating in star-forming galaxies is ionising UV radiation of young stars. Likely, a significant fraction of dust is located inside H II and surrounding regions. We found tight correlations between masses of cold and warm dust, again implying the same source of dust heating. Using the relation between warm and cold dust masses for estimating the total dust mass in star-forming galaxies with an accuracy better than similar to 0.5 dex is proposed. On the other hand, it is shown for both samples that dust temperatures do not depend on the metallicities. The dust-to-neutral gas mass ratio strongly declines with decreasing metallicity, similar to that found in other studies of local emission-line galaxies, high-redshift gamma-ray burst hosts, and damped Ly-alpha absorbers. On the other hand, the dust-to-ionised gas mass ratio is about one hundred times as high implying that most of dust is located in the neutral gas. It is found that thermal free-free emission of ionised gas in compact star-forming galaxies is important in the submm and mm ranges, and it might be responsible for the submm emission excess. This effect is stronger in galaxies with lower metallicities and is also positively affected by an increased star-formation rate."],["dc.identifier.doi","10.1051/0004-6361/201423539"],["dc.identifier.fs","609693"],["dc.identifier.isi","000344158500023"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/11401"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/32097"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","1432-0746"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Dust emission in star-forming dwarf galaxies: General properties and the nature of the submm excess"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","75"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","90"],["dc.bibliographiccitation.volume","407"],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Green, R. F."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Thuan, T. X."],["dc.contributor.author","Noeske, K. G."],["dc.date.accessioned","2018-11-07T10:37:06Z"],["dc.date.available","2018-11-07T10:37:06Z"],["dc.date.issued","2003"],["dc.description.abstract","Spectroscopy and V, I CCD photometry of the dwarf irregular galaxy SBS 1129+576 are presented for the first time. The CCD images reveal a chain of compact H II regions within the elongated low-surface-brightness (LSB) component of the galaxy. Star formation takes place mainly in two high-surface-brightness H II regions. The mean (V-I) colour of the LSB component in the surface brightness interval mu(V) between 23 and 26 mag arcsec(-2) is relatively blue similar to0.56 +/- 0.03 mag, as compared to the (V-I) similar to 0.9-1.0 for the majority of known dwarf irregular and blue compact dwarf (BCD) galaxies. Spectroscopy shows that the galaxy is among the most metal-deficient galaxies with an oxygen abundance 12 + log (O/H) = 7.36 +/- 0.10 in the brightest H II region and 7.48 +/- 0.12 in the second brightest H II region, or 1/36 and 1/28 of the solar value(star), respectively. Hbeta and Halpha emission lines and Hdelta and Hgamma absorption lines are detected in a large part of the LSB component. We use two extinction-insensitive methods based on the equivalent widths of (1) emission and (2) absorption Balmer lines to put constraints on the age of the stellar populations in the galaxy. In addition, we use two extinction-dependent methods based on (3) the spectral energy distribution (SED) and (4) the (V-I) colour. Several scenarios of star formation were explored using all 4 methods. The observed properties of the LSB component can be reproduced by a stellar population forming continuously since 10 Gyr ago, provided that the star formation rate has increased during the last 100 Myr by a factor of 6 to 50 and no extinction is present. However, the observational properties of the LSB component in SBS 1129+576 can be reproduced equally well by continuous star formation which started not earlier than 100 Myr ago and stopped at 5 Myr, if some extinction is assumed. Hence, the ground-based spectroscopic and photometric observations are not sufficient for distinguishing between a young and an old age for SBS 1129+576."],["dc.identifier.doi","10.1051/0004-6361:20030806"],["dc.identifier.isi","000184435000013"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9799"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/45481"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","1432-0746"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies - I. SBS 1129+576"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","885"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","893"],["dc.bibliographiccitation.volume","464"],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Fricke, K. J."],["dc.date.accessioned","2019-07-09T11:54:59Z"],["dc.date.available","2019-07-09T11:54:59Z"],["dc.date.issued","2007-03-04"],["dc.description.abstract","Aims.Continuing the systematic determination of the electron temperature of H II regions using the Balmer and/or Paschen discontinuities by Guseva et al. (2006, ApJ, 644, 890) we focus here on 3.6 m ESO telescope observations of a large new sample of 69 H II regions in 45 blue compact dwarf (BCD) galaxies. This data set spans a wide range in metallicity ( $Z_{\\odot}/60 \\la Z \\la Z_{\\odot}/3$) and, combined with the sample of 47 H II regions from Guseva et al. (2006), yields the largest spectroscopic data set ever used to derive the electron temperature in the H+ zone. Methods.In the same way as in Guseva et al. (2006) we have used a Monte Carlo technique to vary free parameters and to calculate a series of model spectral energy distributions (SEDs) for each H II region. The electron temperature in the H+ zones was derived from the best fitting synthetic and observed SEDs in the wavelength range ~3200-5100 Å, which includes the Balmer jump. Results.On the base of the present large spectroscopic sample we find that in hot ($T_{\\rm e}$(H+) $\\ga$ 11 000 K) H II regions the temperature of the O2+ zone, determined from doubly ionised oxygen forbidden lines, does not differ statistically from the temperature of the H+ zone. Thus, we confirm and strengthen the finding by Guseva et al. (2006). We emphasize that due to a number of modelling assumptions and the observational uncertainties for individual objects, only a large, homogeneous sample, as the one used here, can enable a conclusive study of the relation between $T_{\\rm e}$(H+) and $T_{\\rm e}$(O III)."],["dc.identifier.doi","10.1051/0004-6361:20066067"],["dc.identifier.fs","297790"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9939"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/60774"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.issn","1432-0746"],["dc.relation.orgunit","Fakultät für Physik"],["dc.rights","Goescholar"],["dc.rights.access","openAccess"],["dc.rights.uri","https://goedoc.uni-goettingen.de/licenses"],["dc.title","Balmer jump temperature determination in a large sample of low-metallicity HII regions"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","19"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics Supplement Series"],["dc.bibliographiccitation.lastpage","30"],["dc.bibliographiccitation.volume","138"],["dc.contributor.author","Kurth, O. M."],["dc.contributor.author","Alvensleben, U. Fritze - v."],["dc.contributor.author","Fricke, K. J."],["dc.date.accessioned","2019-07-09T11:54:51Z"],["dc.date.available","2019-07-09T11:54:51Z"],["dc.date.issued","1999"],["dc.description.abstract","We construct evolutionary synthesis models for simple stellar populations using the evolutionary tracks from the Padova group (1993, 1994), theoretical colour calibrations from [Lejeune et al. (1997, 1998)] and fit functions for stellar atmospheric indices from [Worthey et al. (1994)]. A Monte-Carlo technique allows us to obtain a smooth time evolution of both broad band colours in UBVRIK and a series of stellar absorption features for Single Burst Stellar Populations (SSPs). We present colours and indices for SSPs with ages from \\ 10^9$ yrs to .6 \\ 10^{10}$ yrs and metallicities [M/H]=-2.3, -1.7, -0.7, -0.4, 0.0 and 0.4. Model colours and indices at an age of about a Hubble time are in good agreement with observed colours and indices of the Galactic and M 31 GCs."],["dc.identifier.doi","10.1051/aas:1999499"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9761"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/60747"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.issn","1286-4846"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Evolutionary synthesis of simple stellar populations"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","91"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","104"],["dc.bibliographiccitation.volume","407"],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Green, R. F."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Thuan, T. X."],["dc.contributor.author","Noeske, K. G."],["dc.date.accessioned","2018-11-07T10:37:06Z"],["dc.date.available","2018-11-07T10:37:06Z"],["dc.date.issued","2003"],["dc.description.abstract","We present broad-band V and I imaging and long-slit spectroscopy in the optical range lambdalambda3600-7500 Angstrom of the dwarf irregular galaxy HS 1442+4250. The oxygen abundance 12 + log (O/H) = 7.63 +/- 0.02 (Z = Z(circle dot)19)(star) in the brightest H II region of HS 1442+4250 places the galaxy among the most metal-deficient emission-line galaxies. The low metallicity and blue colour (V-I) similar to0.4 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 Halpha and Hbeta emission lines, and of hydrogen Hgamma and Hdelta 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 greater than or equal to 2 Gyr. While a faint old stellar population in HS 1442+4250 with an age greater than or equal to2 Gyr is not excluded, we find no evidence for such a population from the present data."],["dc.identifier.doi","10.1051/0004-6361:20030807"],["dc.identifier.isi","000184435000014"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9800"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/45483"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","1432-0746"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies - II. HS 1442+4250"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A149"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","529"],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Stasinska, G."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Henkel, Cornelia"],["dc.contributor.author","Papaderos, P."],["dc.date.accessioned","2018-11-07T08:56:17Z"],["dc.date.available","2018-11-07T08:56:17Z"],["dc.date.issued","2011"],["dc.description.abstract","Context. We present deep spectroscopy of a large sample of low-metallicity emission-line galaxies. Aims. The main goal of this study is to derive element abundances in these low-metallicity galaxies. Methods. We analyze 121 VLT spectra of H II regions in 46 low-metallicity emission-line galaxies. Of these spectra 83 are archival VLT/FORS1 + UVES spectra of H II regions in 31 low-metallicity emission-line galaxies that are studied for the first time with standard direct methods to determine the electron temperatures, the electron number densities, and the chemical abundances. Results. The oxygen abundance of the sample lies in the range 12 + log O/H = 7.2-8.4. We confirm previous findings that Ne/O increases with increasing oxygen abundance, likely because of a higher depletion of oxygen in higher-metallicity galaxies. The Fe/O ratio decreases from roughly solar at the lowest metallicities to about one tenth of solar, indicating that the degree of depletion of iron into dust grains depends on metallicity. The N/O ratio in extremely low-metallicity galaxies with 12 + log O/H < 7.5 shows a slight increase with decreasing oxygen abundance, which could be the signature of enhanced production of primary nitrogen by rapidly rotating stars at low metallicity. We present the first empirical relation between the electron temperature derived from [S III]lambda 6312/lambda 9069 or [N II]lambda 5755/lambda 6583 and the one derived from [O III]lambda 4363/lambda(4959 + 5007) in low-metallicity galaxies. We also present an empirical relation between t(e) derived from [O II]lambda 3727/(lambda 7320 + lambda 7330) or [S II]lambda 4068/(lambda 6717 + lambda 6730) and [O III]lambda 4363/lambda(4959 + 5007). The electron number densities N-e(Cl III) and N-e(Ar IV) were derived in a number of objects and are found to be higher than N-e(O II) and N-e(S II). This has potential implications for the derivation of the pregalactic helium abundance. In a number of objects, the abundances of C++ and O++ could be derived from recombination lines. Our study confirms the discrepancy between abundances found from recombination lines (RLs) and collisionally excited lines (CELs) and that C/O increases with O/H."],["dc.identifier.doi","10.1051/0004-6361/201016291"],["dc.identifier.fs","590499"],["dc.identifier.isi","000294240700024"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/8604"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/23104"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","VLT spectroscopy of low-metallicity emission-line galaxies: abundance patterns and abundance discrepancies"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","519"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","528"],["dc.bibliographiccitation.volume","421"],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Noeske, K. G."],["dc.contributor.author","Fricke, K. J."],["dc.date.accessioned","2018-11-07T10:47:20Z"],["dc.date.available","2018-11-07T10:47:20Z"],["dc.date.issued","2004"],["dc.description.abstract","We present a ground-based optical spectroscopic and HST U, V, I photometric study of the blue compact dwarf (BCD) galaxy Pox 186. It is found that the emission of the low-surface brightness (LSB) component in Pox 186 at radii less than or similar to3\" (5270 pc in linear scale) is mainly gaseous in origin. We detect Ha emission out to radii as large as 6\". At radii greater than or similar to3\" the light of the LSB component is contaminated by the emission of background galaxies complicating the study of the outermost regions. The surface brightness distribution in the LSB component can be approximated by an exponential law with a scale length alpha less than or similar to 120 pc. This places Pox 186 among the most compact dwarf galaxies known. The derived a is likely to be an upper limit to the scale length of the LSB component because of the strong contribution of the gaseous emission. The oxygen abundance in the bright H II region derived from the 4.5 m Multiple Mirror Telescope (MMT) and 3.6 m ESO telescope spectra are 12 + log (O/H) = 7.76 +/- 0.02 and 7.74 +/- 0.01 (-Z(circle dot)/15) , respectively, in accordance with previous determinations. The helium mass fractions found in this region are Y = 0.248 +/- 0.009 (MMT) and Y = 0.248 +/- 0.004 (3.6 m) suggesting a high primordial helium abundance."],["dc.identifier.doi","10.1051/0004-6361:20035949"],["dc.identifier.fs","21429"],["dc.identifier.isi","000222897700017"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9820"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/47940"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","E D P Sciences"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Pox 186: An ultracompact galaxy with dominant ionized gas emission"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]