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No Diffuse H2 in the Metal-deficient Galaxy I Zw 18

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Published 17 July 2000 • © 2000. The American Astronomical Society. All rights reserved. Printed in U.S.A.
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1 Institut d'Astrophysique de Paris, CNRS, 98 bis Boulevard Arago, F-75014 Paris, France

2 Département de Matière Interstellaire et Radioastronomie Millimétrique, Observatoire de Paris, 61 avenue de l'Observatoire, F-75014 Paris, France

3 Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218

4 Département d'Astrophysique Relativiste et de Cosmologie, UMR-8629 CNRS, Observatoire de Paris-Meudon, Place Jules Janssen, F-92195 Meudon, France

5 Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Code 680, Greenbelt, MD 20771

6 Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637

Dates

Received 23 March 2000
Accepted 13 June 2000
Published

Citation

A. Vidal-Madjar et al 2000 ApJ 538 L77

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DOI

https://doi.org/10.1086/312797

Keywords

galaxies: abundances; galaxies: dwarf; galaxies: individual (I Zw 18) ; galaxies: ISM; ISM: molecules; ultraviolet: galaxies

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1538-4357/538/1/L77

Abstract

The metal-deficient starburst galaxy I Zw 18 has been observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) in a search for H2 molecules. The spectrum obtained with an aperture covering the full galaxy shows no absorption lines of diffuse H2 at the radial velocity of the galaxy. The upper limit for the diffuse H2 column density is found to be very low, N(H2) lesssim 1015 cm-2 (10 σ), unlike our Galaxy where H2 is generally present for even low H I column densities. Although the H I column density here is as high as N(H I) ≈ 2 × 1021 cm-2, we observe 2N(H2)/N(H I) Lt 10-6. We cannot exclude the possibility that some H2 could be in very dense, small, and discrete clumps that cannot be detected with the present observation. However, the remarkable absence of diffuse H2 in this metal-poor galaxy can be explained by the low abundance of dust grains (needed to form this molecule from H atoms), the high ultraviolet flux, and the low density of the H I cloud surrounding the star-forming regions. Thus, having eliminated diffuse H2 as a significant contributor to the total mass, it appears that the gas of the galaxy is dominated by H I and that the high dynamical mass is not composed of cold and diffuse baryonic dark matter.

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References

  • Arnault, P., Kunth, D., Casoli, F., & Combes, F. 1988, A&A, 205, 41

    ADS

  • Black, J. H., Chaffee, F. H., & Foltz, C. B. 1987, ApJ, 317, 442

    CrossrefADS

  • Combes, F. 1986, in Star-forming Dwarf Galaxies and Related Objects, ed. D. Kunth, T. X. Thuan, & J. Tran Thanh Van (Gif-sur-Yvette: Éditions Frontières), 307
  • Dixon, W. V. D., Hurwitz, M., & Bowyer, S. 1998, ApJ, 492, 569

    IOPscienceADS

  • Draine, B. T., & Lee, H. M. 1984, ApJ, 285, 89

    CrossrefADS

  • Dufour, R. J., Garnett, D. R., Skillman, E. D., & Shields, G. A. 1996, in Science with the Hubble Space Telescope-II, ed. P. Benvenuti, F. D. Macchetto, E. J. Schreier, & H. Payne (Paris: ESA), 348
  • Friedman, S., et al. 2000, ApJ, 538, L39

    IOPscience

  • Garnett, D. R., Skillman, E. D., Dufour, R. J., & Shields, G. A. 1997, ApJ, 481, 174

    IOPscienceADS

  • Gondhalekar, P. M., Johansson, L. E. B., Brosch, N., Glass, I. S., & Brinks, E. 1998, A&A, 335, 152

    ADS

  • Hollenbach, D. J., & Salpeter, E. E. 1971, ApJ, 163, 155

    CrossrefADS

  • Israël, F. P., Tacconi, L. J., & Baas, F. 1995, A&A, 295, 599

    ADS

  • Jenkins, E. B., & Peimbert, A. 1997, ApJ, 477, 265

    IOPscienceADS

  • Jura, M. 1974, ApJ, 191, 375

    CrossrefADS

  • Kunth, D., Lequeux, J., Sargent, W. L. W., & Viallefond, F. 1994, A&A, 282, 709

    ADS

  • Lequeux, J., & Viallefond, F. 1980, A&A, 91, 269

    ADS

  • Martin, C. 1996, ApJ, 465, 680

    CrossrefADS

  • Moos, H. W., et al. 2000, ApJ, 538, L1

    IOPscience

  • Petrosian, A. R., Boulesteix, J., Comte, G., Kunth, D., & LeCoarer, E. 1997, A&A, 318, 390

    ADS

  • Pfenniger, D., Combes, F., & Martinet, L. 1994, A&A, 285, 79

    ADS

  • Sage, L. J., Salzer, J. J., Loose, H.-H., & Henkel, C. 1992, A&A, 265, 19

    ADS

  • Shull, M., et al. 2000, ApJ, 538, L73

    IOPscience

  • Viallefond, F., Lequeux, J., & Comte, G. 1987, in Starbursts and Galaxy Evolution, ed. T. X. Thuan, T. Montmerle, J. Tran Thanh Van (Gif-sur-Yvette: Éditions Frontières), 139
  • Young, J. S., Kenney, J. D., Tacconi, L., Claussen, M. J., Huang, Y.-L., Tacconi-Garman, L., Xie, S., & Schloerb, F. P. 1986, ApJ, 311, L17

    CrossrefADS

  • van Zee, L., Westpfahl, D., & Haynes, M. P. 1998, AJ, 115, 1000

    IOPscienceADS

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