The FAST HI 21-cm absorption blind survey. II. -- Statistic Exploration for Associated and Intervening systems

Abstract

We present an extragalactic HI 21-cm absorption lines catalog from a blind search at z $⩽$ 0.35, using drift-scan data collected in 1325.6 hours by the ongoing Commensal Radio Astronomy FasT Survey (CRAFTS) and FAST All Sky HI Survey (FASHI), which spans a sky area of 6072.0 deg${}^2$ and covers 84533 radio sources with a flux density greater than 12 mJy. 14 previously identified HI absorbers and 20 newly discovered HI absorbers were detected, comprising 15 associated systems, 10 intervening systems, and 9 systems with undetermined classifications. Through spectral stacking, the mean peak optical path, mean velocity-integrated optical path, mean FWHM and mean HI column density are measured to be 0.47 and 0.30; 27.19 and 4.36 km s${}^{-1}$; 42.61 and 9.33 km s${}^{-1}$; 0.49 and 0.08 T${}_s\times$ 10${}^{20}$cm${}^{-2}$K${}^{-1}$, for the associated and intervening samples, respectively. Statistical analysis also reveals that associated systems tend to be hosted by red ($g-r>$0.7) galaxies at lower redshifts, whereas galaxies hosting intervening HI absorption are typically found at higher redshifts and are of a bluer ($g-r⩽$0.7) type. A noticeable difference is observed in the positions of foregrounds, backgrounds of intervening systems, and high-redshift and low-redshift associated systems on the WISE color-color diagram. All identified foreground sources in our sample have W1-W2 magnitudes below 0.8, suggesting no Active Galactic Nuclei (AGN). In contrast, backgrounds of intervening systems tend to have W1-W2 magnitudes above 0.8, indicating AGN presence. For associated absorption, most low-redshift ($z⩽$0.5) systems show W1-W2 values below 0.8, while higher-redshift associated absorption ($z>$0.5) displays a broader range of W1-W2 values.

33 pages, 41 figures, 5 tables

References in corpus (47)

• The Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) Project
• CRATES: An All-Sky Survey of Flat-Spectrum Radio Sources
• The VLA Low-frequency Sky Survey
• The VLBA Imaging and Polarimetry Survey at 5 GHz
• The Arecibo Legacy Fast ALFA Survey: IV. Strategies for Signal Identification and Survey Catalog Reliability
• Probing radio source environments via HI and OH absorption
• The HI absorption "Zoo"
• The FAST all sky HI survey (FASHI): The first release of catalog
• A Giant Metrewave Radio Telescope search for associated H{\sc i} 21\,cm absorption in GHz-peaked-spectrum sources
• An accurate low-redshift measurement of the cosmic neutral hydrogen density
• Probing the gas content of radio galaxies through HI absorption stacking
• The First Large Absorption Survey in HI (FLASH): I. Science Goals and Survey Design
• FLASH Early Science -- Discovery of an intervening HI 21-cm absorber from an ASKAP survey of the GAMA 23 field
• Correlation between X-ray and radio absorption in compact radio galaxies
• A Search for Intrinsic HI 21 cm and OH 18 cm Absorption Toward Compact Radio Sources
• A comparative study of intervening and associated HI 21-cm absorption profiles in redshifted galaxies
• HiFAST: an HI data calibration and imaging pipeline for FAST
• A successful search for intervening 21 cm HI absorption in galaxies at 0.4 < z <1.0 with the Australian Square Kilometre Array Pathfinder (ASKAP)
• GASKAP Pilot Survey Science II: ASKAP Zoom Observations of Galactic 21-cm Absorption
• The Relativistic Jet Orientation and Host Galaxy of the Peculiar Blazar PKS 1413+135
• Using 21-cm absorption surveys to measure the average HI spin temperature in distant galaxies
• The FAST Core Array
• The HI absorption zoo: JVLA extension to $z\sim 0.4$
• Resolving the HI in Damped Lyman-α systems that power star-formation
• A pilot search for extragalactic OH absorption with FAST
• uGMRT detection of associated HI 21 cm absorption at $z\approx 3.5$
• Extragalactic HI 21-cm absorption line observations with the Five-hundred-meter Aperture Spherical radio Telescope
• The cosmic atomic hydrogen mass density as a function of mass and galaxy hierarchy from spectral stacking
• HI absorption towards low luminosity radio-loud AGNs of different accretion modes and WISE colours
• A statistical measurement of the HI spin temperature in DLAs at cosmological distances
• HI absorption at z~0.7 against the lobe of the powerful radio galaxy PKS 0409-75
• Parsec-scale HI absorption structure in a low-redshift galaxy seen against a Compact Symmetric Object
• FLASH Pilot Survey: Detections of associated 21 cm HI absorption in GAMA galaxies at 0.42 < z <1.00
• H I absorption towards radio Active Galactic Nuclei of different accretion modes
• Detections of 21-cm absorption with a blind FAST survey at z $⩽$ 0.09
• The Atomic Hydrogen Content of Galaxies as a function of Group-Centric Radius
• Redshift evolution of the HI detection rate in radio-loud active galactic nuclei
• Mapping HI 21-cm in the Klemola 31 group at z = 0.029: emission and absorption towards PKS2020-370
• Observations of cold extragalactic gas clouds at $z=0.45$ towards PKS 1610-771
• The potential of tracing the star formation history with HI 21-cm in intervening absorption systems
• Cold neutral hydrogen gas in galaxies
• Toward a direct measurement of the cosmic acceleration: The pilot observation of H I 21cm absorption line at FAST
• HI Absorption in Low-power Radio AGNs Detected by FAST
• HI absorption associated with Norma's brightest cluster galaxy
• Statistical distribution of HI 21cm intervening absorbers as potential cosmic acceleration probes
• PKS1413+135: OH and HI at z = 0.247 with MeerKAT
• Emergence of a new HI 21-cm absorption component at z~1.1726 towards the gamma-ray blazar PKS~2355-106

Cited by in corpus (2)

• Analyzing the 21cm forest with Wavelet Scattering Transform: Insight into non-Gaussian features of the 21cm forest
• HI 21-cm Absorption Associated with Foreground Galaxies on Top of Quasars