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","A21"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","624"],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Henkel, C."],["dc.date.accessioned","2020-12-10T18:11:47Z"],["dc.date.available","2020-12-10T18:11:47Z"],["dc.date.issued","2019"],["dc.identifier.doi","10.1051/0004-6361/201834935"],["dc.identifier.eissn","1432-0746"],["dc.identifier.issn","0004-6361"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/74140"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Mg II  λ 2797, λ 2803 emission in a large sample of low-metallicity star-forming galaxies from SDSS DR14"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["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","A40"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","623"],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Henkel, C."],["dc.date.accessioned","2020-12-10T18:11:46Z"],["dc.date.available","2020-12-10T18:11:46Z"],["dc.date.issued","2019"],["dc.identifier.doi","10.1051/0004-6361/201834768"],["dc.identifier.eissn","1432-0746"],["dc.identifier.issn","0004-6361"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/74137"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Low-redshift lowest-metallicity star-forming galaxies in the SDSS DR14"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A65"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","599"],["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","2018-11-07T10:26:39Z"],["dc.date.available","2018-11-07T10:26:39Z"],["dc.date.issued","2017"],["dc.description.abstract","We present a spectroscopic study of metal-deficient dwarf galaxy candidates, selected from the SDSS DR12. The oxygen abundances were derived using the direct method in galaxies with the electron temperature-sensitive emission line [O III] lambda 4363 angstrom measured with an accuracy better than 30%. The oxygen abundances for the remaining galaxies with larger uncertainties of the [O III] angstrom 4363 line fluxes were calculated using a strong-line semi-empirical method by Izotov and Thuan. The resulting sample consists of 287 lowmetallicity candidates with oxygen abundances below 12 + log O/H = 7.65 including 23 extremely metal-deficient (XMD) candidates with 12 + log O/H less than or similar to 7.35. Ten out of sixteen XMDs known so far (or similar to 60%) have been discovered by our team using the direct method. Three XMDs were found in the present study. We study relations between global parameters of low-metallicity galaxies, including absolute optical magnitudes, H beta luminosities ( or equivalently star formation rates), stellar masses, mid-infrared colours, and oxygen abundances. Low-metallicity and XMD galaxies strongly deviate to lower metallicities in L-Z, L(H beta)- Z and M- - Z diagrams than in relations obtained for large samples of low-redshift, star-forming galaxies with non-restricted metallicities. These less chemically evolved galaxies with stellar masses approximate to 10(6)- 10(8) M-circle dot, H beta luminosities approximate to 10(38)- 10(41) erg s(-1), SFR approximate to 0.01-1.0 M-circle dot yr (-1), and sS FR similar to 50 Gyr (-1) have physical conditions which may be characteristic of high-redshift low-mass star-forming galaxies which are still awaiting discovery."],["dc.identifier.doi","10.1051/0004-6361/201629181"],["dc.identifier.isi","000395821900036"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/43086"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","1432-0746"],["dc.title","Searching for metal-deficient emission- line galaxy candidates: the final sample of the SDSS DR12 galaxies"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2251"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Monthly Notices of the Royal Astronomical Society"],["dc.bibliographiccitation.lastpage","2262"],["dc.bibliographiccitation.volume","451"],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Henkel, Cornelia"],["dc.date.accessioned","2018-11-07T09:53:19Z"],["dc.date.available","2018-11-07T09:53:19Z"],["dc.date.issued","2015"],["dc.description.abstract","We study relations between global characteristics of low-redshift (0 < z < 1) compact star-forming galaxies, including absolute optical magnitudes, H beta emission-line luminosities (or equivalently star formation rates), stellar masses, and oxygen abundances. The sample consists of 5182 galaxies with high-excitation H II regions selected from the SDSS DR7 and SDSS/BOSS DR10 surveys adopting a criterion [O III] lambda 4959/H beta >= 1. These data were combined with the corresponding data for high-redshift (2 less than or similar to z less than or similar to 3) star-forming galaxies. We find that in all diagrams low-z and high-z star-forming galaxies are closely related indicating a very weak dependence of metallicity on stellar mass, redshift, and star formation rate. This finding argues in favour of the universal character of the global relations for compact star-forming galaxies with high-excitation H II regions over redshifts 0 < z < 3."],["dc.identifier.doi","10.1093/mnras/stv1115"],["dc.identifier.isi","000360833700001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/36305"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Oxford Univ Press"],["dc.relation.issn","1365-2966"],["dc.relation.issn","0035-8711"],["dc.title","On the universality of luminosity-metallicity and mass-metallicity relations for compact star-forming galaxies at redshifts 0 < z < 3"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","4427"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Monthly Notices of the Royal Astronomical Society"],["dc.bibliographiccitation.lastpage","4434"],["dc.bibliographiccitation.volume","462"],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Henkel, Cornelia"],["dc.date.accessioned","2018-11-07T10:05:50Z"],["dc.date.available","2018-11-07T10:05:50Z"],["dc.date.issued","2016"],["dc.description.abstract","We study integrated characteristics of similar to 14 000 low-redshift (0 < z< 1) compact star-forming galaxies (SFGs) selected from the Data Release 12 of the Sloan Digital Sky Survey. It is found that emission of these galaxies is dominated by strong young bursts of star formation, implying that their luminosities experience rapid variations on a time-scale of a few Myr. Reducing integrated characteristics of these galaxies to zero burst age would result in a considerably tighter and almost linear relation between stellar mass and star formation rate (SFR). The same correction implies that the specific star formation rate (the ratio of SFR and stellar mass) is not dependent on the galaxy stellar mass. We conclude that the correction for rapid luminosity evolution must be taken into account in a similar way when comparing different samples of low-and high-redshift SFGs. If the bursting nature of star formation and young burst ages are characteristics of the galaxies selected at high redshifts, the age correction of observed SFRs derived from the H beta emission line or UV continua would modify the derived SFR densities in the early universe."],["dc.identifier.doi","10.1093/mnras/stw1973"],["dc.identifier.isi","000385231600069"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/38976"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Oxford Univ Press"],["dc.relation.issn","1365-2966"],["dc.relation.issn","0035-8711"],["dc.title","The bursting nature of star formation in compact star-forming galaxies from the Sloan Digital Sky Survey"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","L27"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","L30"],["dc.bibliographiccitation.volume","415"],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Noeske, K. G."],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Thuan, T. X."],["dc.contributor.author","Fricke, K. J."],["dc.date.accessioned","2018-11-07T10:51:16Z"],["dc.date.available","2018-11-07T10:51:16Z"],["dc.date.issued","2004"],["dc.description.abstract","The discovery of the high-ionization [Ne V] lambda3426 Angstrom emission line in the spectrum of the blue compact dwarf (BCD) galaxy Tol 1214-277 is reported. The detection of this line implies the presence of intense ionizing X-ray emission with a luminosity L-x in the range 10(39)-10(40) erg s(-1), Such a high X-ray luminosity cannot be reproduced by models of massive stellar populations. Other mechanisms, such as fast shocks or accretion of gas in high-mass X-ray binaries need to be invoked to account for the high intensity of the [Ne V] lambda3426 Angstrom emission line."],["dc.identifier.doi","10.1051/0004-6361:20040006"],["dc.identifier.isi","000188936100005"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/48851"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","E D P Sciences"],["dc.relation.issn","0004-6361"],["dc.title","Discovery of the high-ionization emission line [Ne V] lambda 3426 in the 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","33"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","52"],["dc.bibliographiccitation.volume","361"],["dc.contributor.author","Noeske, K. G."],["dc.contributor.author","Guseva, N. G."],["dc.contributor.author","Fricke, K. J."],["dc.contributor.author","Izotov, Y. I."],["dc.contributor.author","Papaderos, P."],["dc.contributor.author","Thuan, T. X."],["dc.date.accessioned","2018-11-07T10:26:08Z"],["dc.date.available","2018-11-07T10:26:08Z"],["dc.date.issued","2000"],["dc.description.abstract","\"Cometary\" Blue Compact Dwarf Galaxies (iI,C BCDs) are characterized by an off-center starburst close to the end of their elongated stellar bodies. This rare phenomenon may carry some clues on how collective star formation ignites and propagates in gas-rich low-mass stellar systems. This off-center burst may be a fortuitous enhancement of the otherwise moderate star-forming activity of a dwarf irregular (dI), or may be caused by a set of special properties of such systems or their environment. We attempt here a first investigation of this issue by analysing two prototypical examples of cometary dwarf galaxies, the nearby II,C BCDs Markarian 59 and Markarian 71, both containing an extraordinarily luminous HII region in the outskirts of a dI-like host. Using deep ground-based spectrophotometric data(1,2) and HST images(3), we study the physical state of the starburst regions and the structural properties of the underlying irregular galaxies. We find that the average metallicities show small scatter in the vicinity of the star-forming regions and along the major axis of Mkn 59 which suggests that mixing of heavy elements must have been efficient on scales of several kpc. The azimuthally averaged radial intensity distributions of the underlying host galaxies in either iI,C BCD can be approximated by an exponential law with a central surface brightness and scale length that is intermediate between typical iE/nE BCDs and dwarf irregulars. Spectral population synthesis models in combination with colour magnitude diagrams and colour profiles yield a most probable formation age of similar to 2 Gyr for the low surface brightness (LSB) host galaxies in both LI,C BCDs, with upper age limits of similar to 4 Gyr for Mkn 59 and similar to 3 Gyr for Mkn 71, i.e. significantly lower than the typical age of several Gyr derived for the LSB component of iE/nE BCDs. These findings raise the question whether iI,C systems form a distinct physical class within BCDs with respect to the age and structural properties of their hosts, or whether they represent an evolutionary stage connecting young i0 BCDs and \"classical\" iE/nE BCDs. In spite of the scarcity of available data, a review of the properties of analogous objects studied in the local universe and at medium redshifts provides some support for this evolutionary hypothesis."],["dc.identifier.isi","000089510600010"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/42976"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","0004-6361"],["dc.title","The cometary blue compact dwarf galaxies Mkn 59 and Mkn 71 - A clue to dwarf galaxy evolution?"],["dc.type","review"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]