Herschel★and JCMT observations of the early-type dwarf galaxy NGC 205 Academic Article uri icon

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abstract

  • We present Herschel dust continuum, James Clerk Maxwell Telescope CO(3-2) observations and a search for [CII] 158 micron and [OI] 63 micron spectral line emission for the brightest early-type dwarf satellite of Andromeda, NGC 205. While direct gas measurements (Mgas ~ 1.5e+6 Msun, HI + CO(1-0)) have proven to be inconsistent with theoretical predictions of the current gas reservoir in NGC 205 (> 1e+7 Msun), we revise the missing interstellar medium mass problem based on new gas mass estimates (CO(3-2), [CII], [OI]) and indirect measurements of the interstellar medium content through dust continuum emission. Based on Herschel observations, covering a wide wavelength range from 70 to 500 micron, we are able to probe the entire dust content in NGC 205 (Mdust ~ 1.1-1.8e+4 Msun at Tdust ~ 18-22 K) and rule out the presence of a massive cold dust component (Mdust ~ 5e+5 Msun, Tdust ~ 12 K), which was suggested based on millimeter observations from the inner 18.4 arcsec. Assuming a reasonable gas-to-dust ratio of ~ 400, the dust mass in NGC 205 translates into a gas mass Mgas ~ 4-7e+6 Msun. The non-detection of [OI] and the low L_[CII]-to-L_CO(1-0) line intensity ratio (~ 1850) imply that the molecular gas phase is well traced by CO molecules in NGC 205. We estimate an atomic gas mass of 1.5e+4 Msun associated with the [CII] emitting PDR regions in NGC 205. From the partial CO(3-2) map of the northern region in NGC 205, we derive a molecular gas mass of M_H2 ~ 1.3e+5 Msun. [abridged]

authors

  • De Looze, I
  • Baes, M
  • Parkin, TJ
  • Wilson, Christine D
  • Bendo, GJ
  • Boquien, M
  • Boselli, A
  • Cooray, A
  • Cormier, D
  • Fritz, J
  • Galliano, F
  • Gear, W
  • Gentile, G
  • Lebouteiller, V
  • Madden, SC
  • Roussel, H
  • Sauvage, M
  • Smith, MWL
  • Spinoglio, L
  • Verstappen, J
  • Young, L

publication date

  • July 1, 2012