科研之友
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摘要
We use the Atacama Large Millimeter Array ( ALMA) to detect and image CO (1-0) emission from Minkowski's Object, a dwarf galaxy in the cluster Abell 194 that is interacting with a radio jet from a nearby elliptical galaxy. The ALMA observations, which are the first to detect molecular gas in Minkowski's Object, also image the highfrequency continuum emission from the radio jet, allowing us to study the interaction in detail. We estimate the range in the mass of molecular gas in Minkowski's Object assuming two different values of the ratio of the molecular gas mass to the CO luminosity, alpha CO. For the Milky Way value of alpha CO =4.6M(circle dot)(K km s(-1) pc(2))(-1)we obtain a molecular gas mass of MH2= 3.0x 10(7)M(circle dot),of the HI gas mass. We also use the prescription of Narayanan et al. ( 2012) to estimate an alpha CO= 27 M-circle dot(K km s(-1) pc(2))(-1) in which case we obtainMH(2)= 1.8 x 10(8)M(circle dot) ,36% of the H I mass. The observations are consistent with previous claims of star formation being induced in Minkowski's Object via the passage of the radio jet, and it therefore being a rare local example of positive feedback from an active galactic nucleus. In particular, we find highly efficient star formation, with gas depletion timescales similar to 5 x 10(7)- 3 x 10(8)year ( for assumed values of alpha CO = 4.6 and 27 M-circle dot (K km s(-1)pc(2))(-1), respectively) in the upstream regions of Minkowski's Object that were struck first by the jet, and less efficient star formation downstream. We discuss the implications of this observation for models of jet- induced star formation and radio-mode feedback in massive galaxies.
- 出版日期2017-4-1
