21 research outputs found
Forecasting the Cross-Correlation of the CSST galaxy survey with the FAST HI Intensity Map
The cross-correlation of optical galaxies with the neutral hydrogen (HI)
radiation intensity can enhance the signal-to-noise ratio (SNR) of the HI
intensity measurement. In this paper, we investigate the cross-correlation of
the galaxy samples obtained by the spectroscopic survey of the China Space
Station Telescope (CSST) with the HI Intensity mapping (IM) survey of the
Five-hundred-meter Aperture Spherical Telescope (FAST). Using the IllusitrisTNG
simulation result at redshift , we generate mock data of the CSST
survey and a FAST L-band drift scan survey. The CSST spectroscopic survey can
yield a sample of galaxies with a high comoving number density of 10^{-2}
(\unit{Mpc}/h)^{-3} at . We cross-correlate the foreground-removed
radio intensity with the CSST galaxies, including both the whole sample, and
red and blue galaxy sub-samples separately. We find that in all cases the HI
and optical galaxies are well correlated. The total HI abundance can be
measured with a high precision from this correlation. A relative error of for could be achieved at for an
overlapping survey area of 10000 \unit{deg}^2.Comment: 16 pages, 10 figure
Cross-Correlation Forecast of CSST Spectroscopic Galaxy and MeerKAT Neutral Hydrogen Intensity Mapping Surveys
Cross-correlating the data of neutral hydrogen (HI) 21cm intensity mapping
with galaxy surveys is an effective method to extract astrophysical and
cosmological information. In this work, we investigate the cross-correlation of
MeerKAT single-dish mode HI intensity mapping and China Space Station Telescope
(CSST) spectroscopic galaxy surveys. We simulate a survey area of
of MeerKAT and CSST surveys at using Multi-Dark N-body
simulation. The PCA algorithm is applied to remove the foregrounds of HI
intensity mapping, and signal compensation is considered to solve the signal
loss problem in the HI-galaxy cross power spectrum caused by the foreground
removal process. We find that from CSST galaxy auto and MeerKAT-CSST cross
power spectra, the constraint accuracy of the parameter product can reach to , which is about one order
of magnitude higher than the current results. After performing the full MeerKAT
HI intensity mapping survey with 5000 deg survey area, the accuracy can be
enhanced to . This implies that the MeerKAT-CSST cross-correlation can
be a powerful tool to probe the cosmic HI property and the evolution of
galaxies and the Universe.Comment: 17 pages, 11 figures, 3 tables. Accepted for publication in RA
Detecting HI Galaxies with Deep Neural Networks in the Presence of Radio Frequency Interference
In neutral hydrogen (HI) galaxy survey, a significant challenge is to
identify and extract the HI galaxy signal from observational data contaminated
by radio frequency interference (RFI). For a drift-scan survey, or more
generally a survey of a spatially continuous region, in the time-ordered
spectral data, the HI galaxies and RFI all appear as regions which extend an
area in the time-frequency waterfall plot, so the extraction of the HI galaxies
and RFI from such data can be regarded as an image segmentation problem, and
machine learning methods can be applied to solve such problems. In this study,
we develop a method to effectively detect and extract signals of HI galaxies
based on a Mask R-CNN network combined with the PointRend method. By simulating
FAST-observed galaxy signals and potential RFI impacts, we created a realistic
data set for the training and testing of our neural network. We compared five
different architectures and selected the best-performing one. This architecture
successfully performs instance segmentation of HI galaxy signals in the
RFI-contaminated time-ordered data (TOD), achieving a precision of 98.64% and a
recall of 93.59%.Comment: 17 pages, 9 figures, 1 tables. Accepted for publication in RA
A Fast Transient Backend to Detect FRBs with the Tianlai Dish Pathfinder Array
The Tianlai Dish Pathfinder array is a radio interferometer array consisting
of 16 six meter dish antennas. The original digital backend integration time is
at the seconds level, designed for HI intensity mapping experiment. A new
digital backend with millisecond response is added to enable it to search for
fast radio burst (FRB) during its observations. The design and calibration of
this backend, and the real time search pipeline for it are described in this
paper. It is capable of forming 16 digital beams for each linear polarisation,
covering an area of 19.6 square degrees. The search pipeline is capable of
searching for, recording and classifying FRBs automatically in real time. In
commissioning, we succeeded in capturing the signal pulses from the pulsars PSR
B0329+54 and B2021+51.Comment: 16 pages, 14 figures, RAA accepte
A Fast Transient Backend to Detect FRBs with the Tianlai Dish Pathfinder Array
The Tianlai Dish Pathfinder array is a radio interferometer array consisting of 16 six meter dish antennas. The original digital backend integration time is at the seconds level, designed for HI intensity mapping experiment. A new digital backend with millisecond response is added to enable it to search for fast radio burst (FRB) during its observations. The design and calibration of this backend, and the real time search pipeline for it are described in this paper. It is capable of forming 16 digital beams for each linear polarisation, covering an area of 19.6 square degrees. The search pipeline is capable of searching for, recording and classifying FRBs automatically in real time. In commissioning, we succeeded in capturing the signal pulses from the pulsars PSR B0329+54 and B2021+51
FAST drift scan survey for HI intensity mapping: I. preliminary data analysis
International audienceThis work presents the initial results of the drift-scan observation for the neutral hydrogen (HI) intensity mapping survey with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The data analyzed in this work were collected in night observations from 2019 through 2021. The primary findings are based on 28 hours of drift-scan observation carried out over seven nights in 2021, which covers sky area. Our main findings are: (i) Our calibration strategy can successfully correct both the temporal and bandpass gain variation over the -hour drift-scan observation. (ii) The continuum maps of the surveyed region are made with frequency resolution of kHz and pixel area of . The pixel noise levels of the continuum maps are slightly higher than the forecast assuming , which are mK (for 10.0 s integration time) at the -- MHz band, and mK (for 16.7 s integration time) at the -- MHz band, respectively. (iii) The flux-weighted differential number count is consistent with the NRAO-VLA Sky Survey (NVSS) catalog down to the confusion limit . (iv) The continuum flux measurements of the sources are consistent with that found in the literature. The difference in the flux measurement of isolated NVSS sources is about . Our research offers a systematic analysis for the FAST HI intensity mapping drift-scan survey and serves as a helpful resource for further cosmology and associated galaxies sciences with the FAST drift-scan survey
FAST drift scan survey for HI intensity mapping: I. preliminary data analysis
International audienceThis work presents the initial results of the drift-scan observation for the neutral hydrogen (HI) intensity mapping survey with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The data analyzed in this work were collected in night observations from 2019 through 2021. The primary findings are based on 28 hours of drift-scan observation carried out over seven nights in 2021, which covers sky area. Our main findings are: (i) Our calibration strategy can successfully correct both the temporal and bandpass gain variation over the -hour drift-scan observation. (ii) The continuum maps of the surveyed region are made with frequency resolution of kHz and pixel area of . The pixel noise levels of the continuum maps are slightly higher than the forecast assuming , which are mK (for 10.0 s integration time) at the -- MHz band, and mK (for 16.7 s integration time) at the -- MHz band, respectively. (iii) The flux-weighted differential number count is consistent with the NRAO-VLA Sky Survey (NVSS) catalog down to the confusion limit . (iv) The continuum flux measurements of the sources are consistent with that found in the literature. The difference in the flux measurement of isolated NVSS sources is about . Our research offers a systematic analysis for the FAST HI intensity mapping drift-scan survey and serves as a helpful resource for further cosmology and associated galaxies sciences with the FAST drift-scan survey