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Hydrogen Radio Recombination Line Emission from M51 and NGC628
Ist Teil von
Publications of the Astronomical Society of the Pacific, 2018-08, Vol.130 (990), p.1-7
Ort / Verlag
IOP Publishing Limited
Erscheinungsjahr
2018
Link zum Volltext
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
We report the discovery of hydrogen radio recombination line (RRL) emission from two galaxies with star formation rates (SFRs) similar to that of the Milky Way: M51 and NGC 628. We use the Green Bank Telescope (GBT) to measure ∼15 Hnα recombination transitions simultaneously and average these data to improve our spectral signal-to-noise ratio. We show that our data can be used to estimate the total ionizing photon flux of these two sources, and we derive their SFRs within the GBT beam: ΨOB = 3.46 M
⊙ yr−1 for M51 and ΨOB = 0.56 M
⊙ yr−1 for NGC 628. Here, we demonstrate that it is possible to detect RRLs from normal galaxies that are not undergoing a starburst with current instrumentation and reasonable integration times (∼12 hr for each source). We also show that we can characterize the overall star-forming properties of M51 and NGC 628, although the GBT beam cannot resolve individual H II region complexes. Our results suggest that future instruments, such as the Square Kilometre Array and the Next Generation Very Large Array, will be able to detect RRL emission from a multitude of Milky Way-like galaxies, making it possible to determine SFRs of normal galaxies unaffected by extinction and to measure global star formation properties in the local universe.