分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The 2-m aperture Chinese Space Station Telescope (CSST), which observes at wavelengths ranging from 255 to 1000 nm, is expected to start science operations in 2024. An ultra-deep field observation program covering approximately 10 square degrees is proposed with supernovae (SNe) and other transients as one of its primary science drivers. This paper presents the simulated detection results of type Ia supernovae (SNe Ia) and explores the impact of new datasets on the determinations of cosmological parameters. The simulated observations are conducted with an exposure time of 150 s and cadences of 10, 20, and 30 days. The survey mode covering a total of 80 observations but with a random cadence in the range of 4 to 14 days is also explored. Our simulation results indicate that the CSST can detect up to \sim 1800 SNe Ia at z < 1.3. The simulated SNe Ia are then used to constrain the cosmological parameters. The constraint on \Omega_m can be improved by 37.5% using the 10-day cadence sample in comparison with the Pantheon sample. A deeper measurement simulation with a 300 s exposure time together with the Pantheon sample improves the current constraints on \Omega_m by 58.3% and \omega by 47.7%. Taking future ground-based SNe Ia surveys into consideration, the constraints on \omega can be improved by 59.1%. The CSST ultra-deep field observation program is expected to discover large amounts of SNe Ia over a broad redshift span and enhance our understanding of the nature of dark energy.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The 2-m aperture Chinese Space Station Telescope (CSST), which observes at wavelengths ranging from 255 to 1000 nm, is expected to start science operations in 2024. An ultra-deep field observation program covering approximately 10 square degrees is proposed with supernovae (SNe) and other transients as one of its primary science drivers. This paper presents the simulated detection results of type Ia supernovae (SNe Ia) and explores the impact of new datasets on the determinations of cosmological parameters. The simulated observations are conducted with an exposure time of 150 s and cadences of 10, 20, and 30 days. The survey mode covering a total of 80 observations but with a random cadence in the range of 4 to 14 days is also explored. Our simulation results indicate that the CSST can detect up to \sim 1800 SNe Ia at z < 1.3. The simulated SNe Ia are then used to constrain the cosmological parameters. The constraint on \Omega_m can be improved by 37.5% using the 10-day cadence sample in comparison with the Pantheon sample. A deeper measurement simulation with a 300 s exposure time together with the Pantheon sample improves the current constraints on \Omega_m by 58.3% and \omega by 47.7%. Taking future ground-based SNe Ia surveys into consideration, the constraints on \omega can be improved by 59.1%. The CSST ultra-deep field observation program is expected to discover large amounts of SNe Ia over a broad redshift span and enhance our understanding of the nature of dark energy.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Xiao-Hang Luan
Zhen-Zhao Tao
Hai-Chen Zhao
Bo-Lun Huang
Shi-Yu Li
Cong Liu
Hong-Feng Wang
Wen-Fei Liu
Tong-Jie Zhang
Vishal Gajjar
Dan Werthimer
摘要： The search for extraterrestrial intelligence (SETI) is to search for technosignatures associated with extraterrestrial life, such as engineered radio signals. In this paper, we apply the multibeam coincidence matching (MBCM) strategy, and propose a new search mode based on the MBCM which we call MBCM blind search mode. In our recent targeted SETI research, 33 exoplanet systems are observed by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). With this blind search mode, we search for narrowband drifting signals across 1.05-1.45 GHz in two orthogonal linear polarization directions separately. There are two special signals, one of which can only be detected by the blind search mode while the other can be found by both blind and targeted search modes. This result reveals huge advantages of the new blind search mode. However, we eliminate the possibility of the special signals being ETI signals based on much evidence, such as the polarization, drift, frequency and beam coverage characteristics. Our observations achieve an unprecedented sensitivity and our work provides a deeper understanding to the polarization analysis of extraterrestrial signals.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Xiao-Hang Luan
Zhen-Zhao Tao
Hai-Chen Zhao
Bo-Lun Huang
Shi-Yu Li
Cong Liu
Hong-Feng Wang
Wen-Fei Liu
Tong-Jie Zhang
Vishal Gajjar
Dan Werthimer
摘要： The search for extraterrestrial intelligence (SETI) is to search for technosignatures associated with extraterrestrial life, such as engineered radio signals. In this paper, we apply the multibeam coincidence matching (MBCM) strategy, and propose a new search mode based on the MBCM which we call MBCM blind search mode. In our recent targeted SETI research, 33 exoplanet systems are observed by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). With this blind search mode, we search for narrowband drifting signals across 1.05-1.45 GHz in two orthogonal linear polarization directions separately. There are two special signals, one of which can only be detected by the blind search mode while the other can be found by both blind and targeted search modes. This result reveals huge advantages of the new blind search mode. However, we eliminate the possibility of the special signals being ETI signals based on much evidence, such as the polarization, drift, frequency and beam coverage characteristics. Our observations achieve an unprecedented sensitivity and our work provides a deeper understanding to the polarization analysis of extraterrestrial signals.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Zhen-Zhao Tao
Hai-Chen Zhao
Tong-Jie Zhang
Vishal Gajjar
Yan Zhu
You-Ling Yue
Hai-Yan Zhang
Wen-Fei Liu
Shi-Yu Li
Jian-Chen Zhang
Cong Liu
Hong-Feng Wang
Ran Duan
Lei Qian
Cheng-Jin Jin
Di Li
Andrew Siemion
Peng Jiang
Dan Werthime
Jeff Cobb
摘要： As a major approach to looking for life beyond the Earth, the search for extraterrestrial intelligence (SETI) is committed to detecting technosignatures such as engineered radio signals that are indicative of technologically capable life. In this paper, we report a targeted SETI campaign employing an observation strategy named multi-beam coincidence matching (MBCM) at the Five-hundred-meter Aperture Spherical radio Telescope (FAST) towards 33 known exoplanet systems, searching for ETI narrow-band drifting signals across 1.05-1.45 GHz in two orthogonal linear polarization directions separately. A signal at 1140.604 MHz detected from the observation towards Kepler-438 originally peaked our interest because its features are roughly consistent with assumed ETI technosignatures. However, evidences such as its polarization characteristics are almost able to eliminate the possibility of an extraterrestrial origin. Our observations achieve an unprecedented sensitivity since the minimum equivalent isotropic radiated power (EIRP) we are able to detect reaches 1.48 x10^9 W.
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