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Peering into the Milky Way by FAST: II Ionized gas in the inner Galactic disk revealed by the piggyback line observations of the FAST GPPS survey
Peering into the Milky Way by FAST: II Ionized gas in the inner Galactic disk revealed by the piggyback line observations of the FAST GPPS survey by L. G. Hou et al. on Wednesday 30 November
As one of the major components of the interstellar medium, the ionized gas in
our Milky Way, especially the low-density diffuse component, has not been
extensively observed in the radio band. The Galactic Plane Pulsar Snapshot
(GPPS) survey covers the sky area within the Galactic latitude of $\pm10^\circ$
around the Galactic plane visible by the Five-hundred-meter Aperture Spherical
radio Telescope (FAST), and the spectral line data are simultaneously recorded
during the pulsar survey observations. With an integration time of 5 minutes
for each beam, the GPPS survey project provides the most sensitive piggyback
spectra for tens of radio recombination lines (RRLs) in the band of 1000$-$1500
MHz for H$n\alpha$, He$n\alpha$, C$n\alpha$, as well as H$n\beta$ and
H$n\gamma$. We processed the spectral data of RRLs, and obtained a sensitive
averaged H$n\alpha$ RRL map of a sky area of 88 square degrees in the inner
Galaxy of 33$^\circ$ $\leqslant l \leqslant$ 55$^\circ$ and $|b| \leqslant$
2.0$^\circ$. The final spectral data of the H$n\alpha$ RRLs have a spatial
resolution of $\sim$3$^\prime$, a spectral resolution of 2.2 km s$^{-1}$, and a
typical spectral rms noise of 0.25 mJy beam$^{-1}$ or 6.3 mK in main-beam
brightness temperature. The new H$n\alpha$ RRL map shows complex structural
features dominated by a number of HII regions and large extended diffuse
ionized gas regions. We detect about 94% of the known HII regions and confirm
43 WISE HII regions in the observed sky area. Several large HII regions or
star-forming complexes in the distant outer Galaxy are resolved in the map of
H$n\alpha$ RRLs. Extended RRL features of the diffuse ionized gas are detected.
The RRL data products of the GPPS survey will be published and updated at
http://zmtt.bao.ac.cn/MilkyWayFAST/
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.11301v2
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By Corentin CadiouPeering into the Milky Way by FAST: II Ionized gas in the inner Galactic disk revealed by the piggyback line observations of the FAST GPPS survey by L. G. Hou et al. on Wednesday 30 November
As one of the major components of the interstellar medium, the ionized gas in
our Milky Way, especially the low-density diffuse component, has not been
extensively observed in the radio band. The Galactic Plane Pulsar Snapshot
(GPPS) survey covers the sky area within the Galactic latitude of $\pm10^\circ$
around the Galactic plane visible by the Five-hundred-meter Aperture Spherical
radio Telescope (FAST), and the spectral line data are simultaneously recorded
during the pulsar survey observations. With an integration time of 5 minutes
for each beam, the GPPS survey project provides the most sensitive piggyback
spectra for tens of radio recombination lines (RRLs) in the band of 1000$-$1500
MHz for H$n\alpha$, He$n\alpha$, C$n\alpha$, as well as H$n\beta$ and
H$n\gamma$. We processed the spectral data of RRLs, and obtained a sensitive
averaged H$n\alpha$ RRL map of a sky area of 88 square degrees in the inner
Galaxy of 33$^\circ$ $\leqslant l \leqslant$ 55$^\circ$ and $|b| \leqslant$
2.0$^\circ$. The final spectral data of the H$n\alpha$ RRLs have a spatial
resolution of $\sim$3$^\prime$, a spectral resolution of 2.2 km s$^{-1}$, and a
typical spectral rms noise of 0.25 mJy beam$^{-1}$ or 6.3 mK in main-beam
brightness temperature. The new H$n\alpha$ RRL map shows complex structural
features dominated by a number of HII regions and large extended diffuse
ionized gas regions. We detect about 94% of the known HII regions and confirm
43 WISE HII regions in the observed sky area. Several large HII regions or
star-forming complexes in the distant outer Galaxy are resolved in the map of
H$n\alpha$ RRLs. Extended RRL features of the diffuse ionized gas are detected.
The RRL data products of the GPPS survey will be published and updated at
http://zmtt.bao.ac.cn/MilkyWayFAST/
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.11301v2