Fricke, Klaus J.

[["dc.bibliographiccitation.firstpage","222"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","The Astrophysical Journal"],["dc.bibliographiccitation.lastpage","235"],["dc.bibliographiccitation.volume","560"],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Chaffee, F. H."],["dc.contributor.author","Foltz, C. B."],["dc.contributor.author","Thuan, T. X."],["dc.contributor.author","Green, R. F."],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Guseva, N. G."],["dc.date.accessioned","2018-11-07T08:32:43Z"],["dc.date.available","2018-11-07T08:32:43Z"],["dc.date.issued","2001"],["dc.description.abstract","Long-slit Keck II,(1) 4 m Kitt Peak,(2) and 4.5 m MMT3 spectrophotometric data are used to investigate the stellar population and the evolutionary status of I Zw 18C, the faint C component of the nearby blue compact dwarf galaxy I Zw 18. Hydrogen H alpha and H beta emission lines are detected in the spectra of I Zw 18C, which implies that ionizing massive stars are present. High signal-to-noise Keck II spectra of different regions in I Zw 18C reveal H gamma, H delta, and higher order hydrogen lines in absorption. Several techniques are used to constrain the age of the stellar population in I Zw 18C. Ages derived from two different methods, one based on the equivalent widths of the H alpha, H beta emission lines and the other on H gamma, H delta absorption lines are consistent with a 15 Myr instantaneous burst model. We find that a small extinction in the range A(V) = 0.20-0.65 mag is needed to fit the observed spectral energy distribution of I Zw 18C with that model. In the case of constant star formation, all observed properties are consistent with stars forming continuously between similar to 10 and less than or similar to 100 Myr ago. We use all available observational constraints for I Zw 18C, including those obtained from Hubble Space Telescope color-magnitude diagrams, to argue that the distance to I Zw 18 should be as high as similar to 15 Mpc. The deep spectra also reveal extended ionized gas emission around I Zw 18. H alpha emission is detected as far as 30\" from it. To a B surface brightness limit of similar to 27 mag arcsec(-2), we find no observational evidence for extended stellar emission in the outermost regions at distances less than or similar to 15\" from I Zw 18."],["dc.identifier.doi","10.1086/322494"],["dc.identifier.isi","000171587300023"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/17405"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Univ Chicago Press"],["dc.relation.issn","0004-637X"],["dc.title","A spectroscopic study of component C and the extended emission around I Zw 18"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["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.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","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.firstpage","169"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","The Astronomical Journal"],["dc.bibliographiccitation.lastpage","181"],["dc.bibliographiccitation.volume","121"],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Thuan, T. X."],["dc.date.accessioned","2018-11-07T09:29:17Z"],["dc.date.available","2018-11-07T09:29:17Z"],["dc.date.issued","2001"],["dc.description.abstract","We present a spectrophotometric study based on VLT/FORS I observations of one of the most metal-deficient blue compact dwarf (BCD) galaxies known, Tol 1214-277 (Z similar to Z(.)/25). The data show that roughly half of the total luminosity of the BCD originates from a bright and compact starburst region located at the northeastern tip of a faint dwarf galaxy with cometary appearance. The starburst has ignited less than 4 Myr ago and its emission is powered by several thousand O7V stars and similar to 170 late-type nitrogen Wolf-Rayet stars located within a compact region with less than or similar to 500 pc in diameter. For the first time in a BCD, a relatively strong [Fe V] lambda 4227 emission line is seen which together with intense He II lambda 4686 emission indicates the presence of a very hard radiation field in Tol 1214-277. We argue that this extraordinarily hard radiation originates from both Wolf-Rayet stars and radiative shocks in the starburst region. The structural properties of the low surface brightness (LSB) component underlying the starburst have been investigated by means of surface photometry down to 28 B mag arcsec(-2). We find that, for a surface brightness level fainter than similar to 24.5 B mag arcsec(-2), an exponential fitting law provides an adequate approximation to its radial intensity distribution. The broadband colors in the outskirts of the LSB component of Tol 1214-277 are nearly constant and are consistent with an age below one Gyr. This conclusion is supported by the comparison of the observed spectral energy distribution (SED) of the LSB host with theoretical SEDs."],["dc.identifier.doi","10.1086/318016"],["dc.identifier.isi","000166173300013"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/30987"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Univ Chicago Press"],["dc.relation.issn","0004-6256"],["dc.title","An imaging and spectroscopic study of the very metal-deficient blue compact dwarf galaxy Tol 1214-277"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","A138"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","646"],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Henkel, C."],["dc.contributor.author","Schaerer, D."],["dc.contributor.author","Thuan, T. X."],["dc.date.accessioned","2021-04-14T08:28:32Z"],["dc.date.available","2021-04-14T08:28:32Z"],["dc.date.issued","2021"],["dc.identifier.doi","10.1051/0004-6361/202039772"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/82638"],["dc.notes.intern","DOI Import GROB-399"],["dc.relation.eissn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.title","Low-redshift compact star-forming galaxies as analogues of high-redshift star-forming galaxies"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","756"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","776"],["dc.bibliographiccitation.volume","378"],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Chaffee, F. H."],["dc.contributor.author","Foltz, C. B."],["dc.contributor.author","Green, R. F."],["dc.contributor.author","Thuan, T. X."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Noeske, K. G."],["dc.date.accessioned","2018-11-07T11:25:54Z"],["dc.date.available","2018-11-07T11:25:54Z"],["dc.date.issued","2001"],["dc.description.abstract","We present the results of spectrophotometry and V, R, I, H alpha CCD photometry of the blue compact dwarf (BCD) galaxy SBS 0940+544. Broad-band images taken with the 2.1 m KPNO and 1.23 m Calar Alto telescopes reveal a compact high-surface-brightness H II region with ongoing star formation, located at the northwestern tip of the elongated low surface brightness (LSB) main body of the BCD. Very faint, patchy emission along the main body is seen in the H alpha image. High signal-to-noise 4.5 m Multiple Mirror Telescope (MMT) and 10 m Keck II telescope dagger long-slit spectroscopy of SBS 0940+544 is used to derive element abundances of the ionized gas in the brightest H II region and to study the stellar population in the host galaxy. The oxygen abundance in the brightest region with strong emission lines is 12 + log(O/H) = 7.46-7.50, or 1/29-1/26 solar, in agreement with earlier determinations and among the lowest for BCDs. H beta and H alpha emission lines and H delta and H gamma absorption lines are detected in a large part of the main body. Three methods are used to put constraints on the age of the stellar population at different positions along the major axis. They are based on (a) the equivalent widths of the emission lines, (b) the equivalent widths of the absorption lines and (c) the spectral energy distributions (SED). Several scenarios of star formation have been considered. We find that models with single instantaneous bursts cannot reproduce the observed SEDs, implying that star formation in the main body of SBS 0940+544 was continuous. The observed properties in the main body can be reproduced by a continuous star formation process which started not earlier than 100 Myr ago, if a small extinction is assumed. However, the observations can be reproduced equally well by a stellar population forming continuously since 10 Gyr, if the star formation rate has increased during last 100 Myr in the main body of SBS 0940+544 by at least a factor of five. We also investigate the age of the reddest southern region of the main body, where no absorption and emission lines are detected. On the assumption of zero extinction in this faint region, the observed spectrum can be fitted by a theoretical SED of a stellar population continuously formed with a constant star formation rate between 100 Myr and 10 Gyr ago. If, however, a small extinction of C(H beta) similar to 0.1 is present in this region then the observed spectrum can be fitted by a theoretical SED of a stellar population continuously formed between 100 Myr and 1 Gyr ago with a constant star formation rate. However, the poor signal-to-noise ratio of the spectrum and large photometric errors preclude reliable determination of the age of the southern region. In summary, we find no compelling evidence which favors either a young or an old age of SBS 0940+544."],["dc.identifier.doi","10.1051/0004-6361:20011195"],["dc.identifier.isi","000171897200007"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9715"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/56731"],["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","The evolutionary status of the low-metallicity blue compact dwarf galaxy SBS 0940+544"],["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","461"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","483"],["dc.bibliographiccitation.volume","393"],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Thuan, T. X."],["dc.contributor.author","Noeske, K. G."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Green, R. F."],["dc.date.accessioned","2018-11-07T09:57:26Z"],["dc.date.available","2018-11-07T09:57:26Z"],["dc.date.issued","2002"],["dc.description.abstract","Using HST and ground-based optical and NIR imaging data , we investigate whether the blue compact dwarf (BCD) galaxy I Zw 18 possesses an extended low-surface-brightness (LSB) old stellar population underlying its star-forming regions, as is the case in the majority of BCDs. This question is central to the long-standing debate on the evolutionary state of I Zw 18. We show that the exponential intensity decrease observed in the filamentary LSB envelope of the BCD out to greater than or similar to18\" (greater than or similar to1.3 kpc assuming a distance of 15 Mpc) is not due to an evolved stellar disc underlying its star-forming regions, but rather, due to extended ionized gas emission. Ionized gas accounts for more than 80% of the line-of-sight emission at a galactocentric distance of similar to0.65 kpc (similar to3 effective radii), and for greater than or similar to30% to 50% of the R light of the main body of I Zw 18. Broad-band images reveal, after subtraction of nebular line emission, a relatively smooth stellar host extending slightly beyond the star-forming regions. This unresolved stellar component, though very compact, is not exceptional for intrinsically faint dwarfs with respect to its structural properties. However, being blue over a radius range of 5 exponential scale lengths and showing little colour contrast to the star-forming regions, it differs strikingly from the red LSB host of standard BCDs. This fact, together with the comparably blue colours of the faint C component, similar to1.6 kpc away from the main body of I Zw 18, suggests that the formation of I Zw 18 as a whole has occurred within the last 0.5 Gyr, making it a young BCD candidate. Furthermore, we show that the ionized envelope of I Zw 18 is not exceptional among star-forming dwarf galaxies, neither by its exponential intensity fall-off nor by its scale length. However, contrary to evolved BCDs, the stellar LSB component of I Zw 18 is much more compact than the ionized gas envelope. In the absence of an appreciable underlying stellar population, extended ionized gas emission dominates in the outer parts of I Zw 18, mimicking an exponential stellar disc on optical surface brightness profiles."],["dc.identifier.doi","10.1051/0004-6361:20021023"],["dc.identifier.isi","000178247400013"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9780"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/37154"],["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","The blue compact dwarf galaxy I Zw 18: A comparative study of its low-surface-brightness component"],["dc.type","review"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","539"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","554"],["dc.bibliographiccitation.volume","421"],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Thuan, T. X."],["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 VLT spectroscopic observations with different spectral resolutions and different slit orientations of the two metal-deficient blue compact dwarf (BCD) galaxies Tot 1214-277 and Tot 65. The oxygen abundances in the brightest H II regions of Tot 1214-277 and Tol 65 are found to be 12 + log O/H = 7.55 +/- 0.01 and 7.54 +/- 0.01, or Z(circle dot)/24 . The nitrogen-to-oxygen abundance ratios in the two galaxies are log N/O =-1.64 +/- 0.03 and -1.60 +/- 0.02 and lie in the narrow range found for other most metal-deficient BCDs. The helium mass fraction derived in several H II regions in both galaxies is consistent with a high primordial helium mass fraction, Y-p similar to 0.244. We confirm the detection of the high-ionization forbidden emission line [Fe V] lambda4227 in the spectrum of Tol 1214-277. Additionally, weak [Ne IV] lambda4725, [Fe VI] lambda5146, lambda5177, and [Fe VII] lambda5721, lambda6087 emission lines are detected in the high-resolution spectrum of Tol 1214-277. The detection of these lines implies the presence of hard radiation with photon energy in the range similar to4-8 Ryd. Emission lines are detected in the spectra of eight galaxies in the fields of Tol 1214-277 and Tot 65. Seven of these galaxies are background objects, while one galaxy has a redshift close to that of Tol 1214-277. Situated at a projected distance of similar to14.5 kpc from Tol 1214-277, this galaxy is probably a companion of the BCD."],["dc.identifier.doi","10.1051/0004-6361:20035847"],["dc.identifier.fs","21416"],["dc.identifier.isi","000222897700019"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9826"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/47942"],["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","Deep VLT spectroscopy of the blue compact dwarf galaxies Tol 1214-277 and Tol 65"],["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","105"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","120"],["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 a detailed optical spectroscopic and B, V, I, Halpha photometric study of the metal-deficient cometary blue compact dwarf (BCD) galaxy SBS 1415+437. We derive an oxygen abundance 12 + log (O/H) = 7.61 +/- 0.01 and 7.62 +/- 0.03 (Z = Z(/circle dot)20)(star) in the two brightest H II regions, among the lowest in BCDs. The helium mass fractions in these regions are Y = 0.246 +/- 0.003 and 0.243 +/- 0.010. Four techniques based on the equivalent widths of the hydrogen emission and absorption lines, the spectral energy distribution and the colours of the galaxy are used to put constraints on the age of the stellar population in the low-surface-brightness (LSB) component of the galaxy, assuming two limiting cases of star formation ( SF), the case of an instantaneous burst and that of a continuous SF with a constant or a variable star formation rate (SFR). The spectroscopic and photometric data for different regions of the LSB component are well reproduced by a young stellar population with an age t less than or equal to 250 Myr, assuming a small extinction in the range A(V) = 0-0.6 mag. Assuming no extinction, we find that the upper limit for the mass of the old stellar population, formed between 2.5 Gyr and 10 Gyr, is not greater than similar to(1/20-1) of that of the stellar population formed during the last similar to250 Myr. Depending on the region considered, this also implies that the SFR in the most recent SF period must be 20 to 1000 times greater than the SFR at ages greater than or similar to2.5 Gyr. We compare the photometric and spectroscopic properties of SBS 1415+437 with those of a sample of 26 low-metallicity dwarf irregular and BCD galaxies. We show that there is a clear trend for the stellar LSB component of lower-metallicity galaxies to be bluer. This trend cannot be explained only by metallicity effects. There must be also a change in the age of the stellar populations. The most metal-deficient galaxies have also smaller luminosity-weighted ages."],["dc.identifier.doi","10.1051/0004-6361:20030808"],["dc.identifier.isi","000184435000015"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9801"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/45484"],["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 - III. SBS 1415+437"],["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"]]