We present the first search for pulsed CH maser emission potentially stimulated by PSR J1644-4559,conducted using the ultra-wide-bandwidth low-frequency receiver on Murriyang,CSIRO's Parkes Radio Telescope.Observa...We present the first search for pulsed CH maser emission potentially stimulated by PSR J1644-4559,conducted using the ultra-wide-bandwidth low-frequency receiver on Murriyang,CSIRO's Parkes Radio Telescope.Observations targeted three CHΛ-doublet transitions at 3264,3335,and 3349 MHz,with a variability timescale of78 ms.We detected ten CH emission features at 3335 and 3349 MHz,and seven features at 3264 MHz,during both pulsar-ON and pulsar-OFF phases.The observed velocities align with the OH emission and absorption reported by a previous study,suggesting a close spatial association between CH and OH molecules.The derived column densities for CH clouds within the Parkes beam range from 0.05 to 9.8×10^(13)cm^(-2),indicating that these clouds are likely in diffuse and translucent states.Upper limits for CH column densities within the pulsar beam ranged from 0.3 to 9.8×10^(13)cm^(-2).Comparison of these column densities suggests that CH clouds may exhibit clumpiness and substructure.No significant stimulated emission feature was detected in the optical depth spectra.Additionally,as part of our search for pulsed stimulated emission,we investigated the potential CH absorption of the pulsar signal and found none,in agreement with astrophysical expectations.The upper limits for the potential maser amplification factors towards PSR J1644-4559 at 3264,3335,and 3349 MHz are 1.014,1.009,and 1.009,respectively.This study demonstrates the feasibility of detecting pulsed CH maser emission in the interstellar medium stimulated by pulsar photons.展开更多
The distribution of ultraviolet(UV)radiation field provides critical constraints on the physical environments of molecular clouds.Within 1 kpc of our solar system and fostering protostars of different masses,the giant...The distribution of ultraviolet(UV)radiation field provides critical constraints on the physical environments of molecular clouds.Within 1 kpc of our solar system and fostering protostars of different masses,the giant molecular clouds in the Gould Belt present an excellent opportunity to resolve the UV field structure in star-forming regions.We performed spectral energy distribution(SED)fitting of the archival data from the Herschel Gould Belt Survey(HGBS).Dust radiative transfer analysis with the DUSTY code was applied to 23 regions in 14 molecular complexes of the Gould Belt,resulting in the spatial distribution of the radiation field in these regions.For 10 of 15 regions with independent measurements of star formation rate,their star formation rate and UV radiation intensity largely conform to a linear correlation found in previous studies.展开更多
Accurate flux density calibration is essential for precise analysis and interpretation of observations across different observation modes and instruments.In this research,we first introduce the flux calibration model ...Accurate flux density calibration is essential for precise analysis and interpretation of observations across different observation modes and instruments.In this research,we first introduce the flux calibration model that incorporated in Hi FAST pipeline,and designed for processing HⅠ21 cm spectra.Furthermore,we investigate different calibration techniques and assess the dependence of the gain parameter on the time and environmental factors.A comparison is carried out in various observation modes(e.g.,tracking and scanning modes)to determine the flux density gain(G),revealing insignificant discrepancies in G among different methods.Long-term monitoring data shows a linear correlation between G and atmospheric temperature.After subtracting the G-Temperature dependence,the dispersion of G is reduced to<3%over a one-year timescale.The stability of the receiver response of Five-hundred-meter Aperture Spherical radio Telescope(FAST)is considered sufficient to facilitate HⅠobservations that can accommodate a moderate error in flux calibration(e.g.,>~5%)when utilizing a constant G for calibration purposes.Our study will serve as a useful addition to the results provided by Jiang et al.Detailed measurement of G for the 19 beams of FAST,covering the frequency range 1000-1500 MHz,can be found on the Hi FAST homepage:https://hifast.readthedocs.io/fluxgain.展开更多
We report a constraint on the cosmological variation of the proton g-factor,g p.By comparing the measured redshifts between mboxH[131612871054103210261171106210321026817374340333324]21 cm and OH 18 cm lines observed w...We report a constraint on the cosmological variation of the proton g-factor,g p.By comparing the measured redshifts between mboxH[131612871054103210261171106210321026817374340333324]21 cm and OH 18 cm lines observed with the newly commissioned Five-hundred-meter Aperture Spherical radio Telescope(FAST)toward PKS 1413+135 at z=0.24671,we obtain Δg _(p)/g_(p)=(−4.3±2.5)×10^(−5),which is more than two orders of magnitude more sensitive than previous constraints.In addition,we obtain sensitive constraints ofΔ(μα^(2))/(μα^(2))=(2.0±1.2)×10^(−5) and Δ(μα^(2)g_(p)^(0.64))/(μα^(2)g_(p)^(0.64))=(−4.7±1.9)×10^(−6).展开更多
The Five-hundred-meter Aperture Spherical radio Telescope(FAST)was completed with its main structure installed on September 25,2016,after which it entered the commissioning phase.This paper aims to introduce the commi...The Five-hundred-meter Aperture Spherical radio Telescope(FAST)was completed with its main structure installed on September 25,2016,after which it entered the commissioning phase.This paper aims to introduce the commissioning progress of the FAST over the past two years.To improve its operational reliability and ensure effective observation time,FAST has been equipped with a real-time information system for the active reflector system and hierarchical commissioning scheme for the feed support system,which ultimately achieves safe operation of the two systems.For meeting the high-performance indices,a highprecision measurement system was set up based on the effective control methods that were implemented for the active reflector system and feed support system.Since the commissioning of the FAST,a low-frequency ultra-wideband receiver and 19-beam1.05-1.45 GHz receiver have been mainly used.Telescope efficiency,pointing accuracy,and system noise temperature were completely tested and ultimately achieved the acceptance indices of the telescope.The FAST has been in the process of national acceptance preparations and has begun to search for pulsars.In the future,it will still strive to improve its capabilities and expand its application prospects.展开更多
The Five-hundred-meter Aperture Spherical radio Telescope(FAST) is expected to complete its commissioning in 2019. FAST will soon begin the Commensal Radio Astronomy FasT Survey(CRAFTS), a novel and unprecedented comm...The Five-hundred-meter Aperture Spherical radio Telescope(FAST) is expected to complete its commissioning in 2019. FAST will soon begin the Commensal Radio Astronomy FasT Survey(CRAFTS), a novel and unprecedented commensal drift scan survey of the entire sky visible from FAST. The goal of CRAFTS is to cover more than 20000 deg2 and reach redshift up to about 0.35. We provide empirical measurements of the beam size and sensitivity of FAST across the 1.05 to 1.45 GHz frequency range of the FAST L-band array of 19-beams(FLAN). Using a simulated HI-galaxy catalogue based on the HI Mass Function(HIMF), we estimate the number of galaxies that CRAFTS may detect. At redshifts below 0.35, over 6 × 105 HI galaxies may be detected. Below the redshift of 0.07, the CRAFTS HIMF will be complete above a mass threshold of 109.5 M⊙. FAST will be able to investigate the environmental and redshift dependence of the HIMF to an unprecedented depth, shedding light onto the missing baryon and missing satellite problems.展开更多
The Five-hundred-meter Aperture Spherical radio Telescope(FAST)has the largest aperture and a 19-beam L-band receiver,making it powerful for investigating the neutral hydrogen atomic gas(HI)in the universe.We present ...The Five-hundred-meter Aperture Spherical radio Telescope(FAST)has the largest aperture and a 19-beam L-band receiver,making it powerful for investigating the neutral hydrogen atomic gas(HI)in the universe.We present HiFAST(https://hifast.readthedocs.io),a dedicated,modular,and self-contained calibration and imaging pipeline for processing the H?data of FAST.The pipeline consists of frequency-dependent noise diode calibration,baseline fitting,standing wave removal using an FFT-based method,flux density calibration,stray radiation correction,and gridding to produce data cubes.These modules can be combined as needed to process the data from most FAST observation modes:tracking,drift scanning,On-The-Fly mapping,and most of their variants.With HiFAST,the root-mean-square(RMS)noises of the calibrated spectra from all 19 beams were only slightly(~5%)higher than the theoretical expectation.The results for the extended source M33 and the point sources are consistent with the results from Arecibo.The moment maps(0,1 and 2)of M33 agree well with the results from the Arecibo Galaxy Environment Survey(AGES)with a fractional difference of less than 10%.For a common sample of 221 sources with signal-to-noise ratio S/N>10 from the Arecibo Legacy Fast ALFA(ALFALFA)survey,the mean value of fractional difference in the integrated flux density,Sint,between the two datasets is approximately 0.005%,with a dispersion of 15.4%.Further checks on the integrated flux density of 23 sources with seven observations indicate that the variance in the flux density of the source with luminous objects(Sint>2.5 Jy km s-1)is less than 5%.Our tests suggest that the FAST telescope,with the efficient,precise,and user-friendly pipeline HiFAST,will yield numerous significant scientific findings in the investigation of the H?in the universe.展开更多
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.11988101,12203044,and 12473023)by the Leading Innovation and Entrepreneurship Team of Zhejiang Province of China grant No.2023R01008+2 种基金by Key R&D Program of Zhejiang grant No.2024SSYS0012by the University Annual Scientific Research Plan of Anhui Province(No.2023AH030052,No.2022AH010013)Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS。
文摘We present the first search for pulsed CH maser emission potentially stimulated by PSR J1644-4559,conducted using the ultra-wide-bandwidth low-frequency receiver on Murriyang,CSIRO's Parkes Radio Telescope.Observations targeted three CHΛ-doublet transitions at 3264,3335,and 3349 MHz,with a variability timescale of78 ms.We detected ten CH emission features at 3335 and 3349 MHz,and seven features at 3264 MHz,during both pulsar-ON and pulsar-OFF phases.The observed velocities align with the OH emission and absorption reported by a previous study,suggesting a close spatial association between CH and OH molecules.The derived column densities for CH clouds within the Parkes beam range from 0.05 to 9.8×10^(13)cm^(-2),indicating that these clouds are likely in diffuse and translucent states.Upper limits for CH column densities within the pulsar beam ranged from 0.3 to 9.8×10^(13)cm^(-2).Comparison of these column densities suggests that CH clouds may exhibit clumpiness and substructure.No significant stimulated emission feature was detected in the optical depth spectra.Additionally,as part of our search for pulsed stimulated emission,we investigated the potential CH absorption of the pulsar signal and found none,in agreement with astrophysical expectations.The upper limits for the potential maser amplification factors towards PSR J1644-4559 at 3264,3335,and 3349 MHz are 1.014,1.009,and 1.009,respectively.This study demonstrates the feasibility of detecting pulsed CH maser emission in the interstellar medium stimulated by pulsar photons.
文摘The distribution of ultraviolet(UV)radiation field provides critical constraints on the physical environments of molecular clouds.Within 1 kpc of our solar system and fostering protostars of different masses,the giant molecular clouds in the Gould Belt present an excellent opportunity to resolve the UV field structure in star-forming regions.We performed spectral energy distribution(SED)fitting of the archival data from the Herschel Gould Belt Survey(HGBS).Dust radiative transfer analysis with the DUSTY code was applied to 23 regions in 14 molecular complexes of the Gould Belt,resulting in the spatial distribution of the radiation field in these regions.For 10 of 15 regions with independent measurements of star formation rate,their star formation rate and UV radiation intensity largely conform to a linear correlation found in previous studies.
基金the support of the China National Key Program for Science and Technology Research and Development of China(2022YFA1602901,2023YFA1608204)the National Natural Science Foundation of China(Nos.11988101,11873051,12125302,12373011,12041305,12173016)the CAS Project for Young Scientists in Basic Research grant(No.YSBR-062)。
文摘Accurate flux density calibration is essential for precise analysis and interpretation of observations across different observation modes and instruments.In this research,we first introduce the flux calibration model that incorporated in Hi FAST pipeline,and designed for processing HⅠ21 cm spectra.Furthermore,we investigate different calibration techniques and assess the dependence of the gain parameter on the time and environmental factors.A comparison is carried out in various observation modes(e.g.,tracking and scanning modes)to determine the flux density gain(G),revealing insignificant discrepancies in G among different methods.Long-term monitoring data shows a linear correlation between G and atmospheric temperature.After subtracting the G-Temperature dependence,the dispersion of G is reduced to<3%over a one-year timescale.The stability of the receiver response of Five-hundred-meter Aperture Spherical radio Telescope(FAST)is considered sufficient to facilitate HⅠobservations that can accommodate a moderate error in flux calibration(e.g.,>~5%)when utilizing a constant G for calibration purposes.Our study will serve as a useful addition to the results provided by Jiang et al.Detailed measurement of G for the 19 beams of FAST,covering the frequency range 1000-1500 MHz,can be found on the Hi FAST homepage:https://hifast.readthedocs.io/fluxgain.
基金supported by the National Natural Science Foundation of China (Grant No.12588202)Renzhi Suceived the support from the National SKA Program of China (Grant No.2025SKA0130100)+5 种基金the Shanghai Super Postdoctoral Incentive Program (Grant No.2025322)the China Postdoctoral Science Foundation (Grant No.2025M783232)supported by the National Natural Science Foundation of China (Grant No.12473019)the Shanghai Pilot Program for Basic Research-Chinese Academy of Sciences,Shanghai Branch (Grant No.JCYJ-SHFY-2021-013)the National SKA Program of China (Grant No.2022SKA0120102)the China Manned Space Project (Grant No.CMSCSST-2025-A07)。
文摘We report a constraint on the cosmological variation of the proton g-factor,g p.By comparing the measured redshifts between mboxH[131612871054103210261171106210321026817374340333324]21 cm and OH 18 cm lines observed with the newly commissioned Five-hundred-meter Aperture Spherical radio Telescope(FAST)toward PKS 1413+135 at z=0.24671,we obtain Δg _(p)/g_(p)=(−4.3±2.5)×10^(−5),which is more than two orders of magnitude more sensitive than previous constraints.In addition,we obtain sensitive constraints ofΔ(μα^(2))/(μα^(2))=(2.0±1.2)×10^(−5) and Δ(μα^(2)g_(p)^(0.64))/(μα^(2)g_(p)^(0.64))=(−4.7±1.9)×10^(−6).
基金supported by the National Natural Science Foundation of China(Grant Nos.11673039,11573044,11673002,11803051,11503048,and 11203048)the Youth Innovation Promotion Association CAS+4 种基金the Open Project Program of the Key Laboratory of FAST,NAOC,Chinese Academy of Sciencesthe Young Researcher Grant of National Astronomical Observatories,Chinese Academy of Sciencessupported by the Special Funding for Advanced Users,budgeted and administrated by Center for Astronomical Mega-Science,Chinese Academy of Sciences(CAMS)the National Key Research and Development Program of China(Grant No.2017YFA0402600)the CAS"Light of West China"Program
文摘The Five-hundred-meter Aperture Spherical radio Telescope(FAST)was completed with its main structure installed on September 25,2016,after which it entered the commissioning phase.This paper aims to introduce the commissioning progress of the FAST over the past two years.To improve its operational reliability and ensure effective observation time,FAST has been equipped with a real-time information system for the active reflector system and hierarchical commissioning scheme for the feed support system,which ultimately achieves safe operation of the two systems.For meeting the high-performance indices,a highprecision measurement system was set up based on the effective control methods that were implemented for the active reflector system and feed support system.Since the commissioning of the FAST,a low-frequency ultra-wideband receiver and 19-beam1.05-1.45 GHz receiver have been mainly used.Telescope efficiency,pointing accuracy,and system noise temperature were completely tested and ultimately achieved the acceptance indices of the telescope.The FAST has been in the process of national acceptance preparations and has begun to search for pulsars.In the future,it will still strive to improve its capabilities and expand its application prospects.
基金supported by the National Key R&D Program of China(Grant Nos.2017YFA0402600,and 2016YFA0400702)the National Natural Science Foundation of China(Grant Nos.11690024,11725313,11590783,and 11803051)+2 种基金the International Partnership Program of Chinese Academy of Sciences(Grant No.114A11KYSB20160008)the Young Researcher Grant of National Astronomical Observatories,Chinese Academy of Sciencesthe CAS "Light of West China" Program
文摘The Five-hundred-meter Aperture Spherical radio Telescope(FAST) is expected to complete its commissioning in 2019. FAST will soon begin the Commensal Radio Astronomy FasT Survey(CRAFTS), a novel and unprecedented commensal drift scan survey of the entire sky visible from FAST. The goal of CRAFTS is to cover more than 20000 deg2 and reach redshift up to about 0.35. We provide empirical measurements of the beam size and sensitivity of FAST across the 1.05 to 1.45 GHz frequency range of the FAST L-band array of 19-beams(FLAN). Using a simulated HI-galaxy catalogue based on the HI Mass Function(HIMF), we estimate the number of galaxies that CRAFTS may detect. At redshifts below 0.35, over 6 × 105 HI galaxies may be detected. Below the redshift of 0.07, the CRAFTS HIMF will be complete above a mass threshold of 109.5 M⊙. FAST will be able to investigate the environmental and redshift dependence of the HIMF to an unprecedented depth, shedding light onto the missing baryon and missing satellite problems.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1602901)the National Natural Science Foundation of China(Grant Nos.11988101,11873051,12125302,and 12373011)+3 种基金the CAS Project for Young Scientists in Basic Research Grant(Grant No.YSBR-062)the K.C.Wong Education Foundationthe science research grants from the China Manned Space Projectsupport from the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS。
文摘The Five-hundred-meter Aperture Spherical radio Telescope(FAST)has the largest aperture and a 19-beam L-band receiver,making it powerful for investigating the neutral hydrogen atomic gas(HI)in the universe.We present HiFAST(https://hifast.readthedocs.io),a dedicated,modular,and self-contained calibration and imaging pipeline for processing the H?data of FAST.The pipeline consists of frequency-dependent noise diode calibration,baseline fitting,standing wave removal using an FFT-based method,flux density calibration,stray radiation correction,and gridding to produce data cubes.These modules can be combined as needed to process the data from most FAST observation modes:tracking,drift scanning,On-The-Fly mapping,and most of their variants.With HiFAST,the root-mean-square(RMS)noises of the calibrated spectra from all 19 beams were only slightly(~5%)higher than the theoretical expectation.The results for the extended source M33 and the point sources are consistent with the results from Arecibo.The moment maps(0,1 and 2)of M33 agree well with the results from the Arecibo Galaxy Environment Survey(AGES)with a fractional difference of less than 10%.For a common sample of 221 sources with signal-to-noise ratio S/N>10 from the Arecibo Legacy Fast ALFA(ALFALFA)survey,the mean value of fractional difference in the integrated flux density,Sint,between the two datasets is approximately 0.005%,with a dispersion of 15.4%.Further checks on the integrated flux density of 23 sources with seven observations indicate that the variance in the flux density of the source with luminous objects(Sint>2.5 Jy km s-1)is less than 5%.Our tests suggest that the FAST telescope,with the efficient,precise,and user-friendly pipeline HiFAST,will yield numerous significant scientific findings in the investigation of the H?in the universe.
