Peering into the Milky Way by FAST: I. Exquisite HI structures in the inner Galactic disk from the piggyback line observations of the FAST GPPS survey

Abstract

Neutral hydrogen (HI) is the fundamental component of the interstellar medium. The Galactic Plane Pulsar Snapshot (GPPS) survey is designed for hunting pulsars by using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) from the visible Galactic plane within $|b|\le 10^{\circ }$. The survey observations are conducted with the L-band 19-beam receiver in the frequency range of 1.0 $-$ 1.5 GHz, and each pointing has an integration time of 5 minutes. The piggyback spectral data simultaneously recorded during the FAST GPPS survey are great resources for studies on the Galactic HI distribution and ionized gas. We process the piggyback HI data of the FAST GPPS survey in the region of $33^{\circ }\le l\le 55^{\circ }$ and $|b|\le 2^{\circ }$. The rms of the data cube is found to be approximately 40 mK at a velocity resolution of $0.1$ km s${}^{-1}$, placing it the most sensitive observations of the Galactic HI by far. The high velocity resolution and high sensitivity of the FAST GPPS HI data enable us to detect weak exquisite HI structures in the interstellar medium. HI absorption line with great details can be obtained against bright continuum sources. The FAST GPPS survey piggyback HI data cube will be released and updated on the web: http://zmtt.bao.ac.cn/MilkyWayFAST/.

Published by ScienceChinaPMA on the special topic "Peering into the Milky Way by FAST" https://www.sciengine.com/SCPMA/issue/65/12 . See News & Views by Prof. John M. Dickey https://link.springer.com/content/pdf/10.1007/s11433-022-2030-x.pdf

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Cited by in corpus (7)

• The FAST Galactic Plane Pulsar Snapshot survey: VI. The discovery of 473 new pulsars
• 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: IV. Identification of two new Galactic supernova remnants G203.1+6.6 and G206.7+5.9
• Peering into the Milky Way by FAST: III. Magnetic fields in the Galactic halo and farther spiral arms revealed by the Faraday effect of faint pulsars
• Accurate polarization calibration of FAST spectral data for measurements of Zeeman splittings of OH megamasers in IRAS 02524+2046
• Constraints on the properties of warm ionized gas from low-frequency hydrogen radio recombination lines
• Insights into the structure and kinematics of a Milky Way-like galaxy