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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

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Science China(Physics,Mechanics & Astronomy) 2022年第12期65卷 18-38页

作者： LiGang Hou JinLin Han Tao Hong XuYang Gao Chen Wang National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy University of Chinese Academy of SciencesBeijing 100049China

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 *** Galactic Plane Pulsar Snapshot(GPPS)survey covers the sky area within the Galactic latitude of±10°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 *** an integration time of 5 min 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 Hnα,Henα,Cnα,as well as Hnβand Hnγ.We processed the spectral data of RRLs,and obtained a sensitive averaged HnαRRL map of a sky area of 88 square degrees in the inner Galaxy of 33°≤l≤55°and∣b∣≤2°*** final spectral data of the HnαRRLs have a spatial resolution of∼3′,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 *** FAST GPPS HnαRRL observations are sensitive down to an emission measure of about 200 cm^(−6) pc if a 3σdetection limit is *** new HnαRRL map shows complex structural features dominated by a number of HII regions and large extended diffuse ionized gas *** detect about 94%of the known HII regions and confirm 43 WISE HII regions in the observed sky *** large HII regions or star-forming complexes in the distant outer Galaxy are resolved in the map of Hnα*** RRL features of the diffuse ionized gas are *** addition,the GPPS piggyback spectral-line data also provide sensitive detection for other kinds of RRLs,such as the Henα,Cnα,Hnβ,and Hnγ*** RRL data products of the GPPS survey will be published and updated at http://***/MilkyWayFAST/.

关键词： surveys ISM HII regions radio lines

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The ALMaQUEST Survey ⅩⅤ:The dependence of the molecular-to-atomic gas ratios on resolved optical diagnostics

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Science China(Physics,Mechanics & Astronomy) 2024年第9期67卷 174-196页

作者： Niankun Yu Zheng Zheng Chao-Wei Tsai Pei Zuo Sara L.Ellison David V.Stark Di Li Jingwen Wu Karen L.Masters Ting Xiao Yinghui Zheng Zongnan Li Kai Zhang Hongying Chen Shu Liu Sihan Jiao Fanyi Meng National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China Key Laboratory of radio Astronomy and Technology Chinese Academy of SciencesBeijing 100101China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Department of Physics&Astronomy University of VictoriaVictoriaV8P 1A1Canada Departments of Physics and Astronomy Haverford CollegeHaverford19041USA Space Telescope Science Institute San Martin Dr.Baltimore 21218USA Zhejiang Laboratory Hangzhou 311121China New Cornerstone Science Laboratory Shenzhen 518054China School of Physics Zhejiang UniversityHangzhou 310058China

The atomic-to-molecular gas conversion is a critical step in the baryon cycle of galaxies,which sets the initial conditions for subsequent star formation and influences the multi-phase interstellar *** compiled a sample of 94 nearby galaxies with observations of multi-phase gas contents by utilizing public H_(Ⅰ),CO,and optical IFU data from the Ma NGA survey together with new FAST H_(Ⅰ)*** agreement with previous results,our sample shows that the global molecular-to-atomic gas ratio(R_(mol)≡log M_(H2)/M_(H_(Ⅰ)))is correlated with the global stellar mass surface densityμ_*with a Kendall'sτcoefficient of 0.25 and p<10^(-3),less tightly but still correlated with stellar mass and NUV-r color,and not related to the specific star formation rate(sSFR).The cold gas distribution and kinematics inferred from the H_(Ⅰ)and CO global profile asymmetry and shape do not significantly rely on R_(mol).Thanks to the availability of kpc-scale observations of MaNGA,we decompose galaxies into H_(Ⅱ),composite,and AGN-dominated regions by using the BPT *** increasing R_(mol),the fraction of H_(Ⅱ)regions within 1.5 effective radius decreases slightly;the density distribution in the spatially resolved BPT diagram also changes significantly,suggesting changes in metallicity and ionization *** with high R_(mol)tend to have high oxygen abundance,both at one effective radius with a Kendall'sτcoefficient of 0.37(p<10^(-3))and their central *** all parameters investigated here,the oxygen abundance at one effective radius has the strongest relation with global R_(mol).The dependence of gas conversion on gas distribution and galaxy ionization states is *** contrast,the observed positive relation between oxygen abundance(μ_(*))and R_(mol)indicates that the gas conversion is efficient in regions of high metallicity(density).

关键词： Galaxies baryon cycle radio lines H_(Ⅰ)21 cm atomic-to-molecular gas conversion

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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

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Science China(Physics,Mechanics & Astronomy) 2022年第12期65卷 3-17页

作者： Tao Hong JinLin Han LiGang Hou XuYang Gao Chen Wang Tao Wang National Astronomical Observatories Chinese Academy of SciencesBeijing100101China School of Astronomy University of Chinese Academy of SciencesBeijing100049China

Neutral hydrogen(Hi)is the fundamental component of the interstellar *** 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|≤10°.The survey observations are conducted with the L-band 19-beam receivers in the frequency range of 1.0-1.5 GHz,and each pointing has an integration time of 5 *** piggyback spectral data simultaneously recorded during the FAST GPPS survey are great resources for studies on the Galactic Hi distribution and ionized *** process the piggyback Hi data of the FAST GPPS survey in the region of 33°≤l≤55°and|b|≤2°.The rms of the data cube is found to be approximately 40 m K at a velocity resolution of 0.1 km s^(-1),placing it the most sensitive observations of the Galactic Hi by *** high velocity resolution and high sensitivity of the FAST GPPS Hi data enable us to detect weak exquisite Hi structures in the interstellar *** absorption line with great details can be obtained against bright continuum *** FAST GPPS survey piggyback Hi data cube will be released and updated on the web:http://***/Milky Way FAST/.

关键词： interstellar medium atoms radio lines surveys

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The FAST all sky HI survey(FASHI):The first release of catalog

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Science China(Physics,Mechanics & Astronomy) 2024年第1期67卷 112-133页

作者： Chuan-Peng Zhang Ming Zhu Peng Jiang Cheng Cheng Jing Wang Jie Wang Jin-Long Xu Xiao-Lan Liu Nai-Ping Yu Lei Qian Haiyang Yu Mei Ai Yingjie Jing Chen Xu Ziming Liu Xin Guan Chun Sun Qingliang Yang Menglin Huang Qiaoli Hao FAST Collaboration Guizhou radio Astronomical Observatory Guizhou UniversityGuiyang 550000China National Astronomical Observatories Chinese Academy of Sciences(CAS)Beijing 100101China Chinese Academy of Sciences South America Center for Astronomy National Astronomical ObservatoriesCASBeijing 100101China Kavli Institute for Astronomy and Astrophysics Peking UniversityBeijing 100871China

The FAST All Sky HI survey(FASHI)was designed to cover the entire sky observable by the Five-hundred-meter Aperture Spherical radio Telescope(FAST),spanning approximately 22000 square degrees of declination between-14°and+66°,and in the frequency range of 1050-1450 MHz,with the expectation of eventually detecting more than 100000 HI *** August 2020 and June 2023,FASHI had covered more than 7600 square degrees,which is approximately 35%of the total sky observable by *** has a median detection sensitivity of around 0.76 m Jy beam-1and a spectral line velocity resolution of~6.4 km s-1at a frequency of~1.4 *** of now,a total of 41741 extragalactic HI sources have been detected in the frequency range 1305.5-1419.5 MHz,corresponding to a redshift limit of z■*** cross-matching FASHI sources with the Siena Galaxy Atlas(SGA)and the Sloan Digital Sky Survey(SDSS)catalogs,we found that 16972(40.7%)sources have spectroscopic redshifts and 10975(26.3%)sources have only photometric *** of the remaining 13794(33.0%)HI sources are located in the direction of the Galactic plane,making their optical counterparts difficult to identify due to high extinction or high contamination of Galactic stellar *** on current survey results,the FASHI survey is an unprecedented blind extragalactic H I *** has higher spectral and spatial resolution and broader coverage than the Arecibo Legacy Fast ALFA Survey(ALFALFA).When completed,FASHI will provide the largest extragalactic HI catalog and an objective view of HI content and large-scale structure in the local universe.

关键词： surveys redshifts galaxies telescope radio lines HI line

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Revisiting the Velocity Dispersion-Size Relation in Molecular Cloud Structures

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Research in Astronomy and Astrophysics 2024年第11期24卷 192-210页

作者： Haoran Feng Zhiwei Chen Zhibo Jiang Yuehui Ma Yang Yang Shuling Yu Dongqing Ge Wei Zhou Fujun Du Chen Wang Shiyu Zhang Yang Su Ji Yang Purple Mountain Observatory Chinese Academy of SciencesNanjing 210023China University of Science and Technology of China Chinese Academy of SciencesHefei 230026China Center for Astronomy and Space Sciences China Three Gorges UniversityYichang 443000China Center for Astrophysics Guangzhou UniversityGuangzhou 510006China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China

Structures in molecular ISM are observed to follow a power-law relation between the velocity dispersion and spatial size,known as Larson’s first relation,which is often attributed to the turbulent nature of molecular ISM and imprints the dynamics of molecular cloud *** the^(13)CO(J=1-0)data from the Milky Way Imaging Scroll Painting survey,we built a sample with 360 structures having relatively accurate distances obtained from either the reddened background stars with Gaia parallaxes or associated maser parallaxes,spanning from 0.4 to~15 *** this sample and about 0.3 million pixels,we analyzed the correlations between velocity dispersion,surface/column density,and spatial *** structure-wise results show power-law indices smaller than 0.5 in both theσ_(v)-R_(eff)andσ_(v)-R_(eff)·Σ*** the pixel-wise results,the v spix is statistically scaling with the beam physical size(R_(s)≡ΘD/2)in form ofσ_(v)^(pix)■R_(s)^(0.43±0.03).Meanwhile,σ_(v)_(pix)in the inner Galaxy is statistically larger than the outer *** also analyzed correlations betweenσ_(v)_(pix)and the H_(2)column density N(H_(2)),finding thatσ_(v)_(pix)stops increasing with N(H_(2))after>10^(22)cm^(-2).The structures with and without high-column-density(>10^(22)cm^(-2))pixels show differentσ_(v)_(pix)■N(H_(2))^(ξ)relations,where the mean(std)ξvalues are 0.38(0.14)and 0.62(0.27),respectively.

关键词： ISM structure ISM kinematics and dynamics radio lines ISM

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E ect of Optical Depth on Study of Chemical Properties of Massive Star Forming Clumps

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Chinese Journal of Chemical Physics 2020年第1期33卷 114-118页

作者： Jian-jun Zhou Run-xia Li Donghui Quan Jarken Esimbek Yu-xin He Da-lei Li Xin-di Tang Gang Wu Wei-guang Ji Zheng-xue Chang Xia Zhang Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China University of the Chinese Academy of Sciences Beijing 100080China Key Laboratory of radio Astronomy Chinese Academy of SciencesUrumqi 830011China Department of Chemistry Eastern Kentucky UniversityRichmond KY 40475USA

Here we present the study on chemical properties of massive star forming clumps using N2H^+(1-0),H^13CO+(1-0),HCN(1-0)and HN^13C(1-0)data from the literature[***.563,A97(2014)].We found that abundances of H^13CO+ and HN^13C are a ected by H2 column *** the median values of these two abundances increase by nearly 10 times from stages A to B,H^13CO+and HN^13C are suitable for tracing the evolution of massive star forming *** order of rapidity in growth of abundances of all the four studied molecules from stages A to B,is H^13CO^+,HCN,HN^13C,and N2H^+,from the highest to the *** results suggest that the observing optically thin molecular lines with high angular resolution are necessary to study the chemical evolution of massive star forming clumps.

关键词： Stars formation Clumps Molecules radio lines

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