F. Cuisinier

Federal University of Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil

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Publications (52)61.15 Total impact

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    ABSTRACT: Through the application of the wavelet technique to a planetary nebulae image, we are able to identify different scale sizes structures present in its wavelet coefficient decompositions. In a multiscale vision model, an object is defined as a hierarchical set of these structures. We can then use this model to independently reconstruct the different objects that compose the nebulae. The result is the separation and identification of superposed objects, some of them with very low surface brightness, what makes them, in general, very difficult to be seen in the original images due to the presence of noise. This allows us to make a more detailed analysis of brightness distribution in these sources. In this project, we use this method to perform a detailed morphological study of some planetary nebulae and to investigate whether one of them indeed shows internal temperature fluctuations. We have also conducted a series of tests concerning the reliability of the method and the confidence level of the objects detected. The wavelet code used in this project is called OV_WAV and was developed by the UFRJ's Astronomy Departament team.
    No preview · Article · May 2009
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    ABSTRACT: Through the application of the wavelet technique to a planetary nebulae image, we are able to identify different scale sizes structures present in its wavelet coefficient decompositions. In a multiscale vision model, an object is defined as a hierarchical set of these structures. We can then use this model to independently reconstruct the different objects that compose the nebulae. The result is the separation and identification of superposed objects, some of them with very low surface brightness, what makes them, in general, very difficult to be seen in the original images due to the presence of noise. This allows us to make a more detailed analysis of brightness distribution in these sources. In this project, we use this method to perform a detailed morphological study of some planetary nebulae and to investigate whether one of them indeed shows internal temperature fluctuations. We have also conducted a series of tests concerning the reliability of the method and the confidence level of the objects detected. The wavelet code used in this project is called OV_WAV and was developed by the UFRJ's Astronomy Departament team.
    No preview · Conference Paper · Oct 2007
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    ABSTRACT: We present a detailed spectroscopic study of a sample of 34 star-forming dwarf galaxies, ranging from the blue to near-infrared (λ3700Å-1μm) (Kehrig et al. 2006). The metal enrichment in this kind of objects has been operating typically at low metallicity enviroments. The spectra were observed with the 1.52m telescope at La Silla/ESO. We derive fundamental parameters for HII regions and ionizing sources in our star-forming galaxies, as well as gaseous metal abundances. All the spectra include the nebular[SIII]λλ9069,9532Å lines, that are of crucial importance in the derivation of the S/H abundances, and relevant ionization diagnostics. We study the relative hardness of their ionizing sources using the η' parameter (Vílchez & Pagel 1988), and exploring the roles played by metallicity and age. The ionic and total O/H was also derived using direct determinations of the te[OIII]. The mean S/O ratio derived in this work is constant and slightly below the solar (S/O) value (see fig 1). The data presented here are consistent with the conclusion that S/O remains constant as O/H varies among the sample of HII galaxies. Variations in S/O along the whole O/H abundance range may be present, but the scatter in S/O (due mainly to observational errors) is still large to constrain them. The assumption that the S/O ratio remains constant for all abundances is still an open question and should be explored further (Pérez-Montero et al. 2006).
    Full-text · Article · Jul 2006 · Proceedings of the International Astronomical Union
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    ABSTRACT: A detailed spectroscopic study, from lambda 3700 A to 1 um, was performed for a sample of 34 HII galaxies in order to derive fundamental parameters for their HII regions and ionizing sources, as well as gaseous metal abundances. All the spectra included the nebular [SIII]9069,9532 A lines, given their importance in the derivation of the S/H abundance and relevant ionization diagnostics. A systematic method was followed to correct the near-IR [SIII] line fluxes for the effects of the atmospheric transmission.A comparative analysis of the predictions of the empirical abundance indicators R23 and S23 has been performed. The relative hardness of their ionizing sources was studied using the eta parameter, and exploring the role played by metallicity. For 22 galaxies of the sample a direct value of te[SIII] was derived, along with their ionic and total S/H abundances. Their ionic and total O/H abundances were derived using direct determinations of te[OIII].For the rest of the objects, the total S/H abundance was derived using S23. The abundance range covered by our sample goes from 1/20 solar up to solar metallicity. The mean S/O ratio derived is log (S/O)=-1.68+/-0.20 dex, 1 sigma below the solar S/O value. The S/O abundance ratio shows no significant trend with O/H over the range of abundance covered in this work, in agreement with previous findings.There is a trend for HII galaxies with lower gaseous metallicity to present harder ionizing spectra. We compared the distribution of the ionic ratios O+/O++ vs. S+/S++ derived for our sample with the predictions of a grid of photoionization models performed for different stellar effective temperatures. This analysis indicates that a large fraction of galaxies in our sample seem to be ionized by extremely hard spectra. Comment: 12 pages, 8 figures, accepted for publication in the A&A, minor gramatical corrections included
    Full-text · Article · Jun 2006 · Astronomy and Astrophysics
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    F. Cuisinier · P. Westera · E. Telles · R. Buser
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    ABSTRACT: In this paper, we investigate the behaviour of the number of Lyman continuum ionizing photons as compared to the actual number of hydrogen recombinations in HII galaxies. We evaluate the number of ionizing photons from the population synthesis of spectra observed in the visible, extrapolating the spectra to the extreme ultraviolet (EUV), beyond the Lyman limit. We check for possible systematic deviations of the predicted ionizing spectra in the EUV by comparing the ratio of the predicted number of ionizing photons to the number of recombinations, as measured in H$\beta$, ${\rm \Delta \log Q(H^0)}$, with the metallicity. We find that, as far as the number of ionizing photons is concerned, no systematic tendency can be detected. The ${\rm H\beta}$ equivalent width can be understood as a nebular age indicator, decreasing with age, although the observed ${\rm H\beta}$ equivalent width can also be affected by the contribution to the continuum by the accumulation of previous, non-ionizing stellar populations. We attribute the increase of ${\rm \Delta \log Q(H^0)}$ with the age of the burst to the fact that more and more ionizing photons escape the nebulae when the nebulae get older, because of their increasing, expansion-induced subfragmentation. Comment: 14 pages, accepted in A&A
    Full-text · Article · May 2006 · Astronomy and Astrophysics
  • P. Lagos · E. Telles · E. R. Carrasco · F. Cuisinier
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    ABSTRACT: In this work, we investigate the recycling properties of the interestellar medium in HII galaxies from the analysis of the spatial variation of Oxygen abundance. The spatial variation of the abundance of this element should reflect the physical mechanisms involved in their recycling processes. We present the preliminary results for the galaxy UM 408, observed at the Gemini south observatory using GMOS-IFU spectroscopy. UM 408 is a compact and low metallicity galaxy without WR signature in their spectra. Maps of emission lines, continuum, EW(Hbeta ), Log [OIII]/Hbeta and T_e are derived and compared with the spatial distribution of 12+Log(O/H). We do not observe a significant gradient in the oxygen abundance, suggesting that the new metals formed in the current star formation episode are possibly not observed and reside in a hot gas phase, whereas the metals from previous events are well mixed and homogeneously distributed through the whole extent of the galaxy. Under this supposition an underlying old stellar population would be expected.
    No preview · Article · Jan 2006
  • P. Westera · F. Cuisinier · E. Telles · C. Kehrig
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    ABSTRACT: We analyse the stellar content of a large number of HII galaxies from the continua and absorption features of their spectra using population synthesis methods, in order to gain information about the star formation histories of these objects. We find that all galaxies of our sample contain an old stellar population (>=1Gyr) that dominates the stellar mass, and in a majority of these we also found evidence for an intermediate-age population >=50Myr apart from the presently bursting, ionizing young generation
    No preview · Article · Aug 2005
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    ABSTRACT: We present an analysis of narrowband images of planetary nebulae, obtained from the HST archive, by wavelet transform. This technique allows us to identify new substructures, present in all planetary nebulae of our sample at some level. In the case of one planetary nebula Hubble 4, we were even able to identify a new secondary pair of low ionization structures. We repport as well on the extension of our work to ground based photometry, through an analysis of images from the ``IAC catalogue of Galactic Planetary Nebulae'' (Manchado et al. 1996).
    No preview · Conference Paper · Jun 2005
  • C. Kehrig · J. M. Vílchez · E. Pérez · E. Telles · F. Cuisinier
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    ABSTRACT: We have analysed long-slit spectrophotometric observations of a sample of 35 H II galaxies in the red (between 6000Å and 1 μm), including the nebular [S III] λλ9069,9532Å lines. For 6 of the 35 objects observed it has been possible to measure the auroral [S III] line at 6312Å. All of these galaxies were observed previously in the blue, and it has therefore been possible to derive two line temperatures directly: t([O III]) from the [O III] λ4363Å line and t([S III]) from the [S III] λ6312Å line. Both spectra, red and blue, were obtained on the 1.52m telescope with the Boller & Chivens spectrograph at La Silla, ESO. In this work, we present the physical conditions and chemical abundances of these 6 galaxies derived from the measured [S III]λ6312Å line, with particular emphasis on the S/H abundance. Despite the observed dispersion in the temperatures, the final result for the abundances is in accordance with the expected values for H II galaxies. In addition, we have added our observed H II galaxies to the empirical calibration of the metallicity parameter, S23 = ([S II]+[S III])/Hα (Pérez-Montero & Díaz 2003). This calibration presents two important advantages with respect to the R23 parameter, which is based on the optical oxygen lines: it remains single-valued up to abundances close to solar and is almost independent of the ionization parameters of the nebula.
    No preview · Article · Apr 2005
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    ABSTRACT: We have analysed long-slit spectrophotometric observations of a sample of 35 HII galaxies in the red (6000 Å -1µm), including the nebular [SIII] lines λλ9069, 9532Å. Given the uncertainties associated with the [SIII]λ6312Å line and the importance of S ++ (the dominant ion) in determining the S/H, it is clear that the observations of the strong near-IR [SIII] lines were needed. All these galaxies were observed previously in the blue wavelength range from which we could derive the O/H abundance using the T e [OIII] temperature.
    Full-text · Article · Jan 2005
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    Pieter Westera · F. Cuisinier · E. Telles · C. Kehrig
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    ABSTRACT: We analyse the stellar content of a large number of HII galaxies from the continua and absorption features of their spectra using population synthesis methods, in order to gain information about the star formation histories of these objects. We find that all galaxies of our sample contain an old stellar population (>= 1 Gyr) that dominates the stellar mass, and in a majority of these we also found evidence for an intermediate-age population >= 50 Myr apart from the presently bursting, ionizing young generation <= 10^7 yrs Comment: 23 pages, 14 Encapsulated Postscript figures, accepted for publication in A&A
    Full-text · Article · May 2004 · Proceedings of the International Astronomical Union
  • C. Kehrig · E. Telles · F. Cuisinier
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    ABSTRACT: Galáxias HII são galáxias anãs de baixa luminosidade que apresentam alta taxa de formação estelar. Seus espectros são dominados por intensas linhas de emissão devido à fotoionização pela presença de um grande número de estrelas do tipo O e B. Nós apresentamos um catálogo espectrofotométrico de 111 galáxias HII observadas no telescópio 1.52m do ESO com o espectrógrafo Boller & Chivens. Determinamos propriedades estatísticas da amostra e derivamos condições físicas (temperatura eletrônica, densidade eletrônica) e abundâncias químicas. Para algumas galáxias, fomos também capazes de resolver espacialmente regiões de formação estelar individuais e determinar propriedades espectroscópicas para estas regiões separadamente, o que nos permitiu avaliar as flutuações das condições físico-químicas dentro das galáxias HII. Em particular, vimos que apesar das galáxias HII apresentarem formação estelar espalhada ao longo do corpo da galáxia, são objetos quimicamente homogêneos. A fim de estudar a evolução temporal dos objetos durante o tempo de vida das estrelas ionizantes construimos também alguns diagramas relacionando razões de linhas de emissão com a largura equivalente de Hb (EW(Hb)). Para interpretar tais diagramas utilizamos modelos de fotoionização para populações estelares integradas. Concluímos que as galáxias HII não correspondem a simples idéia de um burst instantâneo envolvido por um gás opaco aos fótons ionizantes e com densidade constante. As relações observadas entre razões de linhas e EW(Hb) podem ser melhor compreendidas se as galáxias HII apresentarem populações estelares mais velhas, que contribuem para o contínuo óptico observado.
    No preview · Article · Aug 2003
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    ABSTRACT: Hubble 4 is a well studied bipolar planetary nebula (PN). It is known to present off-axis spouts, known as FLIERs (Fast Low-Ionization Emission Regions), which are inclined by 62 degrees with respect to the main bipolar structure, oriented roughly NS. Only few such objects are known; most FLIERs being aligned with the longest elongation axis of their PN. We retreived WFPC2 frames of Hubble 4 available in the F656N (Ha) and F658N ([NII]) narrow bandpass filters from the HST archive. An "à trous" ("with holes") wavelet decomposition of the combined filters was obtained. Using a multiscale vision model similar to the one introduced by Bijaoui and Rué (1995, Signal Processing, 46, 345) we were able to identify and reconstruct many complex and sometimes faint structures present in the nebula. We first show that Hubble 4 also presents an extended outer shell, a faint secondary bipolar structure aligned with the main FLIERs, and secondary FLIERs. We were also able to evidence a bright internal rim, which we identify with the interaction of the fast wind from the central star with the surrounding nebula. We finally detect a faint extended halo, from which we derive a mass. We discuss the implication of the existence of this halo on the distance of this nebula.
    No preview · Article · Aug 2003
  • M. Ferraresi Jr · F. Cuisinier · E. Telles
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    ABSTRACT: Galáxias HII anãs são galáxias de baixa massa, com alto conteúdo de gás, e se encontram em uma fase intensa de formação estelar. A taxa de formação estelar está tão alta nestas galáxias que não pode ter se mantido durante sua vida inteira. O tempo máximo de duração do episódio atual de formação estelar deve ser no máximo de algumas dezenas de milhões de anos, bem inferior à idade destas galáxias. Isto leva naturalmente a idéia de que já aconteceram surtos anteriores. Abundâncias químicas oferecem uma ferramenta poderosa para investigar a história evolutiva destas galáxias, porque aumentam de geração em geração estelar. O hidrogênio, o oxigênio, o nitrogênio produzem algumas das linhas mais importantes em um gás foto-ionizado, permitindo a determinação das abundâncias destes elementos facilmente. A dispersão das abundâncias em oxigênio e nitrogênio é significativa, sendo maior que os erros observacionais. O oxigênio é produzido em estrelas massivas, que explodem quase instâneamente, enquanto o nitrogênio é produzido em estrelas de massa intermediária, que só o liberam depois de um atraso de @ 500 mihões de anos. Construímos um modelo de evolução química semi-analítico, utilizando rendimentos empíricos baseados nas abundâncias observadas destes dois elementos. Conseguimos através deste modelo rudimentar explicar nas galáxias de mais baixas metalicidades as abundâncias de oxigênio e de nitrogênio, assim como a dispersão dos dados observacionais devida a formação estelar descontínua, e isto com um número baixo de surtos (1 ou 2, no máximo 3).
    No preview · Article · Aug 2003
  • P. Westera · F. Cuisinier · E. Telles · C. Kehrig
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    ABSTRACT: Analisamos o conteúdo estelar de 74 galáxias HII a partir do contínuo observado nos espectros ópticos dessas galáxias, utilizando métodos de síntese de população estelar. Descobrimos que todas as galáxias para as quais encontramos soluções contêm uma população estelar velha que domina a massa estelar, e numa maioria dessas também encontramos evidência de uma população de idade intermediaria além da geração jovem que está se formando agora. Concluímos que a formação estelar dessas galáxias se realiza em surtos individuais, Esses surtos são interrompidos por longos períodos de inatividade, com os primeiros consumindo a maior parte do gás. Sugerimos, portanto, que as galáxias HII sejam galáxias anãs normais flagradas em um período de surto.
    No preview · Article · Aug 2003
  • F. Cuisinier · E. Telles · C. Kehrig

    No preview · Article · Jan 2003

  • No preview · Article · Jan 2003 · Proceedings of the International Astronomical Union
  • F. Cuisinier · A. Acker · W. J. Maciel
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    ABSTRACT: We compare abundance patterns in the Galactic bulge for elements observed in stars and in planetary nebulae. Some # elements, like Mg and Ti, are overabundant in respect to Fe, and others, like He, O, Si, S, Ar, and Ca, are not. The first ones favor a quick evolution of the Galactic bulge, and the seconds a much slower one.
    No preview · Article · Mar 2002
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    A. Acker · F. Cuisinier · J. Köppen · W. J. Maciel
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    ABSTRACT: We compare abundance patterns in the Galactic bulge for elements observed in stars and in planetary nebulae. Some elements, like Mg and Ti, are overabundant in respect to Fe, and others, like He, O, Si, S, Ar, and Ca, are not. The rst ones favor a quick evolution of the Galactic bulge, and the seconds a much slower one.
    Preview · Article · Jan 2002
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    ABSTRACT: We present a sample of 9 nearby F-type stars with detailed spectroscopic analyses to investigate the Basel Stellar Library (BaSeL) in two photometric systems simultaneously, Johnson UBV and Strömgren uvby. The sample corresponds to potential targets of the central seismology programme of the COROT (COnvection & ROtation) space experiment, which have been recently observed at Observatoire de Haute-Provence (OHP, France). The atmospheric parameters Teff, [Fe/H], and log g obtained from the BaSeL models are compared with spectroscopic determinations as well as with results of other photometric calibrations (the TEMPLOGG method and the catalogue of Marsakov & Shevelev, 1995). Moreover, new rotational velocity determinations are also derived from the spectroscopic analysis and compared with previous results compiled in the SIMBAD database. For a careful interpretation of the BaSeL solutions, we computed confidence regions around the best χ2-estimates and projected them on Teff-[Fe/H], Teff-log g, and log g-[Fe/H] diagrams. In order to simultaneously and accurately determine the stellar parameters Teff, [Fe/H] and log g, we suggest to use the combination of the synthetic BaSeL indices B-V, U-B and b-y (rather than the full photometric information available for these stars: B-V, U-B, b-y, m1 and c1) and we present complete results in 3 different diagrams, along with the results of other methods (photometric and spectroscopic). All the methods presented give consistent solutions, and the agreement between TEMPLOGG and BaSeL for the hottest stars of the sample could be especially useful in view of the well-known difficulty of spectroscopic determinations for fast rotating stars. Finally, we present current and future developments of the BaSeL models for a systematic application to all the COROT targets.
    No preview · Article · Nov 2001

Publication Stats

1k Citations
61.15 Total Impact Points

Institutions

  • 2006
    • Federal University of Rio de Janeiro
      • Departamento de Anatomia
      Rio de Janeiro, Rio de Janeiro, Brazil
  • 1999
    • Christian-Albrechts-Universität zu Kiel
      • Institute for Theoretical Physics and Astrophysics (ITAP)
      Kiel, Schleswig-Holstein, Germany
  • 1997
    • Universität Basel
      Bâle, Basel-City, Switzerland
  • 1996
    • IHU de Strasbourg
      Strasburg, Alsace, France