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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
ALMA observations of cool dust in a low-metallicity starburst, SBS 0335-052
Astronomy and Astrophysics, Volume 561, Article A49, Year 2014
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Description
We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 0 Band 7 observations of an extremely metal-poor dwarf starburst galaxy in the Local Universe, SBS 0335-052 (12 + log (O/H) ~ 7.2). With these observations, dust is detected at 870 μm (ALMA Band 7), but 87% of the flux in this band is due to free-free emission from the starburst. We have compiled a spectral energy distribution (SED) of SBS 0335-052 that spans almost 6 orders of magnitude in wavelength and fit it with a spherical dust shell heated by a single-age stellar population; the best-fit model gives a dust mass of (3.8 ± 0.6) × 104 M. We have also constructed a SED including Herschel archival data for I Zw 18, another low-metallicity dwarf starburst (12 + log (O/H) ~ 7.17), and fit it with a similar model to obtain a dust mass of (3.4 ± 1.0) × 102 M. It appears that for such low-metallicity dwarf galaxies, the ratio of their stellar mass to their dust mass is within the range of values found for spirals and other star-forming galaxies. However, compared with their atomic gas mass, the dust mass of SBS 0335-052 far exceeds the prediction of a linear trend of dust-to-gas mass ratio with metallicity, while I Zw 18 falls far below. We use gas scaling relations to assess a putative missing gas component in both galaxies and find that the missing, possibly molecular, gas in SBS 0335-052 is a factor of 6 times higher than the value inferred from the observed Hi column density; in I Zw 18 the missing component is much smaller. Finally, we constrain the H2 surface density conversion factor αCO with our upper limit for CO J = 3-2 line in SBS 0335-052, and find that this is consistent with a linear or even super-linear trend of increasing αCO with decreasing metallicity. Ultimately, despite their similarly low metallicity, the differences in gas and dust column densities in SBS 0335-052 and I Zw 18 suggest that metal abundance does not uniquely define star-formation processes. At some level, self-shielding and the survival of molecules may depend just as much on gas and dust column density as on metallicity. The effects of low metallicity may at least be partially compensated for by large column densities in the interstellar medium. © 2013 ESO.
Authors & Co-Authors
Hunt, L. K.
Italy, Florence
Osservatorio Astrofisico Di Arcetri
Testi, Leonardo
Italy, Florence
Osservatorio Astrofisico Di Arcetri
Germany, Garching Bei Munchen
European Southern Observatory
Casasola, Viviana
Italy, Bologna
Inaf Istituto Di Astrofisica Spaziale e Fisica Cosmica, Bologna
García-Burillo, Santiago
Spain, Alcala de Henares
Observatorio Astronomico Nacional
Combes, Françoise
France, Paris
L'observatoire de Paris
Nikutta, R.
Chile, Santiago
Universidad Andrés Bello
Caselli, Paola
United Kingdom, Leeds
University of Leeds
Henkel, Christian
Germany, Bonn
Max Planck Institute for Radio Astronomy
Saudi Arabia, Jeddah
King Abdulaziz University
Maiolino, Roberto
United Kingdom, Cambridge
Department of Physics
Menten, Karlm M.
Germany, Bonn
Max Planck Institute for Radio Astronomy
Sauvage, Marc
France, Gif-sur-yvette
Institut de Recherche Sur Les Lois Fondamentales de L'univers
Weiss, Axel R.
Germany, Bonn
Max Planck Institute for Radio Astronomy
Statistics
Citations: 38
Authors: 12
Affiliations: 11
Identifiers
Doi:
10.1051/0004-6361/201322739
ISSN:
00046361
e-ISSN:
14320746
Research Areas
Environmental
Study Design
Cross Sectional Study