J/A+A/698/A120 MeerKAT Absorption Line Survey (MALS). DR3 (Gupta+, 2025)
The MeerKAT Absorption Line Survey (MALS) data release 3:
Cold atomic gas associated with the Milky Way.
Gupta N., Kerp J., Balashev S.A., Morelli A.P.M., Combes F., Krogager J.-K.,
Momjian E., Borgaonkar D., Deka P.P., Emig K.L., Jose J., Jozsa G.I.G.,
Kloeckner H.-R., Moodley K., Muller S., Noterdaeme P., Petitjean P.,
Wagenveld J.D.
<Astron. Astrophys. 698, A120 (2025)>
=2025A&A...698A.120G 2025A&A...698A.120G (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Interferometry ; H I data ; Morphology
Keywords: techniques: interferometric - ISM: clouds - dust, extinction -
ISM: structure - Galaxy: halo - radio lines: ISM
Abstract:
We present results of a blind search for Galactic HI 21-cm absorption
lines toward 19130 radio sources, using 390 pointings of MALS, each
pointing centered on a source brighter than 200mJy. We detected 3640
HI absorption features. This represents the largest Galactic HI
absorption line catalog to date. Based on the strong correlation
between the HI 21-cm emission line column densities (NHI) and the
visual extinction (A_V) measured toward the pointing center, along
with the confinement of the absorption features to a narrow range in
radial velocities (-25<vLSR[km/s]<+25), we infer that the
detected absorption lines form a homogeneous sample of HI clouds in
the local interstellar medium (LISM). The HI 21-cm absorption optical
depth is linearly correlated to NHI and AV, up to AV of about 1 mag.
Above this threshold, AV traces the total hydrogen content, and
consequently, AV and NHI scale, differently. The slopes of NHI
distributions of central sight lines with HI 21-cm absorption
detections and non-detection differ at >2σ. A similar difference
is observed for H2 detections and non-detections in damped Lyman-alpha
systems at z>1.8, implying that turbulence-driven WNM-to-CNM
conversion is the common governing factor for the presence of HI 21-cm
and H2 absorption. Through a comparison of central and off-axis
absorption features, we find that the slope of rms fluctuations in the
optical depth variations in the quiescent gas associated with LISM is
shallower than the earlier measurements in the disk. The densities
(20-30cm-3) inferred from the optical depth variations are typical
of the CNM values. The negligible velocity shifts between central and
off-axis absorbers are in line with the hypothesis that the CNM and
LNM clouds freeze out of the extended WNM phase.
Description:
The third data release of the MeerKAT Absorption Line Survey (MALS)
consists of wideband continuum catalogues of 391 pointings observed at
L band. It consists of a blind search for Galactic HI 21-cm absorption
lines toward 19130 radio sources brighter than 1mJy at 1.4GHz. The
spectral resolution, the median spatial resolution, and the median 3σ
optical depth sensitivity (τ_3σ) are 5.5km/s, ∼9'', and
0.381, respectively
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 1028 19274 Source catalogue
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See also:
J/A+A/673/A113 : MALS ten pointings continuum catalogue (Wagenveld+ 2023)
J/ApJS/270/33 : MeerKAT Absorption Line Survey (MALS). I. DR1 (Deka+, 2024)
J/A+A/690/A163 : MeerKAT Absorption Line Survey DR2 (Wagenveld+ 2025)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Seq Sequential number
7- 25 A19 --- Source MALS name of the source,
JHHMMSS.ss+DDMMSS.s (Source_name)
27- 45 A19 --- PointId The MALS pointing ID based on the
position of the central source in NVSS
or SUMSS (Pointing_id)
52- 67 A16 "date" ObsDateL The date and time (UTC) of the start of
L-band observing block(s) in the
format YYYY-MM-DDThh:mm (ObsdateL)
71 A1 --- ObsBand [L] Observing band L=L-band (Obs_band)
73- 80 A8 --- SPWId This identifies the SPW corresponding
to the spectrum (SPW_id)
82- 85 F4.1 arcsec Majcbeam The major axis of the restoring beam of
the cube (Maj_cbeam)
87- 90 F4.1 arcsec Mincbeam The minor axis of the restoring beam of
the cube (Min_cbeam)
92- 96 F5.1 deg PAcbeam The position angle of the restoring
beam of the cube (PA_cbeam)
98- 99 I2 h RAh Right ascension (J2000) of the pixel
corresponding to flux density peak
(Peak_pos)
100 A1 --- --- [:]
101- 102 I2 min RAm Right ascension (J2000) of the pixel
corresponding to flux density peak
(Peak_pos)
103 A1 --- --- [:]
104- 109 F6.3 s RAs Right ascension (J2000) of the pixel
corresponding to flux density peak
(Peak_pos)
111 A1 --- DE- Declination sign (J2000) of the pixel
corresponding to flux density peak
(Peak_pos)
112- 113 I2 deg DEd Declination (J2000) of the pixel
corresponding to flux density peak
(Peak_pos)
114 A1 --- --- [:]
115- 116 I2 arcmin DEm Declination (J2000) of the pixel
corresponding to flux density peak
(Peak_pos)
117 A1 --- --- [:]
118- 123 F6.3 arcsec DEs Declination (J2000) of the pixel
corresponding to flux density peak
(Peak_pos)
125- 144 F20.16 deg GLON The Galactic longitude of the Peak_pos
(Peakposl)
146- 165 F20.16 deg GLAT The Galactic latitude of the Peak_pos
(Peakposb)
167- 186 F20.16 arcmin DistPoint The distance of the source from the
pointing center (Distance_pointing)
188- 205 F18.16 --- ScaleFactor The scale factor applied for the
primary beam correction (Scale_factor)
207- 228 F22.16 mJy/beam PeakFlux The peak flux density of the source
(Peak_flux)
230- 248 F19.16 mJy/beam Specrms The spectral rms per channel in the
unsmoothed spectrum, in mJy/beam/ch
(Spec_rms)
250- 254 A5 --- VisFlag Boolean indicating whether an
absorption feature based on visual
inspection is detected in the spectrum
(Vis_flag) (1)
256- 258 F3.1 --- Nclump ? The number of well detached
absorption features detected in the
spectrum (n_clump)
260- 262 F3.1 --- Ncomp The total number of Gaussian components
fit to the absorption features
detected in the spectrum (n_comp)
264- 282 F19.16 --- tauMax ? The peak optical depth of the
absorption feature (taumaxval)
284- 301 F18.16 --- E_tauMax ? The positive 1sigma error on
taumaxval (taumax+err)
303- 320 F18.16 --- e_tauMax ? The negative 1sigma error on
taumaxval (taumax-err)
322- 342 F21.16 km/s PosMax ? The position of the taumaxval
(pos_max)
344- 363 F20.16 km/s tauInt ? The integrated optical depth
(tauintval)
365- 383 F19.16 km/s E_tauInt ? The positive 1sigma error on
tauintval (tauint+err)
385- 403 F19.16 km/s e_tauInt ? The negative 1sigma error on
tauintval (tauint-err)
405- 424 F20.16 km/s deltav ? The velocity width containing 50% of
the tauintval (delta_v)
426- 443 F18.16 --- C1Amp ? The amplitude of the 1^th Gaussian
component fit to the absorption line
(comp1amp)
445- 462 F18.16 --- E_C1Amp ? The positive 1sigma error on
Comp1amp (comp1amp_+err)
464- 481 F18.16 --- e_C1Amp ? The negative 1sigma error on
Comp1amp (comp1amp_-err)
483- 502 F20.15 km/s C1Pos ? The position of the 1^th Gaussian
component relative to pos_max
(comp1pos)
504- 523 F20.16 km/s E_C1Pos ? The positive 1sigma error on
Comp1pos (comp1pos_+err)
525- 544 F20.16 km/s e_C1Pos ? The negative 1sigma error on
Comp1pos (comp1pos_-err)
546- 564 F19.16 km/s C1Sigma ? The width (sigma) of the 1^th
Gaussian component (comp1sigma)
566- 583 F18.16 km/s E_C1Sigma ? The positive 1sigma error on
Comp1sigma (comp1sigma_+err)
585- 590 F6.3 km/s e_C1Sigma ? The negative 1sigma error on
Comp1sigma (comp1sigma_-err)
592- 609 F18.16 --- C2Amp ? The amplitude of the 2^th Gaussian
component fit to the absorption line
(comp2amp)
611- 628 F18.16 --- E_C2Amp ? The positive 1sigma error on
Comp2amp (comp2amp_+err)
630- 647 F18.16 --- e_C2Amp ? The negative 1sigma error on
Comp2amp (comp2amp_-err)
649- 655 F7.2 km/s C2Pos ? The position of the 2^th Gaussian
component relative to pos_max
(comp2pos)
657- 662 F6.2 km/s E_C2Pos ? The positive 1sigma error on
Comp2pos (comp2pos_+err)
664- 669 F6.2 km/s e_C2Pos ? The negative 1sigma error on
Comp2pos (comp2pos_-err)
671- 675 F5.2 km/s C2Sigma ? The width (sigma) of the 2^th
Gaussian component (comp2sigma)
677- 680 F4.2 km/s E_C2Sigma ? The positive 1sigma error on
Comp2sigma (comp2sigma_+err)
682- 686 F5.2 km/s e_C2Sigma ? The negative 1sigma error on
Comp2sigma (comp2sigma_-err)
688- 705 F18.16 --- C3Amp ? The amplitude of the 3^th
Gaussian component fit to the
absorption line (comp3amp)
707- 724 F18.16 --- E_C3Amp ? The positive 1sigma error on
Comp3amp (comp3amp_+err)
726- 743 F18.16 --- e_C3Amp ? The negative 1sigma error on
Comp3amp (comp3amp_-err)
745- 751 F7.2 km/s C3Pos ? The position of the 3^th
Gaussian component relative to
pos_max (comp3pos)
753- 757 F5.2 km/s E_C3Pos ? The positive 1sigma error on
Comp3pos (comp3pos_+err)
759- 763 F5.2 km/s e_C3Pos ? The negative 1sigma error on
Comp3pos (comp3pos_-err)
765- 769 F5.2 km/s C3Sigma ? The width (sigma) of the 3^th
Gaussian component (comp3sigma)
771- 774 F4.2 km/s E_C3Sigma ? The positive 1sigma error on
Comp3sigma (comp3sigma_+err)
776- 779 F4.2 km/s e_C3Sigma ? The negative 1sigma error on
Comp3sigma (comp3sigma_-err)
781- 785 F5.3 --- C4Amp ? The amplitude of the 4^th
Gaussian component fit to the
absorption line (comp4amp)
787- 804 F18.16 --- E_C4Amp ? The positive 1sigma error on
Comp4amp (comp4amp_+err)
806- 810 F5.3 --- e_C4Amp ? The negative 1sigma error on
Comp4amp (comp4amp_-err)
812- 818 F7.2 km/s C4Pos ? The position of the 4^th
Gaussian component relative to
pos_max (comp4pos)
820- 824 F5.2 km/s E_C4Pos ? The positive 1sigma error on
Comp4pos (comp4pos_+err)
826- 830 F5.2 km/s e_C4Pos ? The negative 1sigma error on
Comp4pos (comp4pos_-err)
832- 836 F5.2 km/s C4Sigma ? The width (sigma) of the 4^th
Gaussian component (comp4sigma)
838- 841 F4.2 km/s E_C4Sigma ? The positive 1sigma error on
Comp4sigma (comp4sigma_+err)
843- 846 F4.2 km/s e_C4Sigma ? The negative 1sigma error on
Comp4sigma (comp4sigma_-err)
848- 852 F5.3 --- C5Amp ? The amplitude of the 5^th
Gaussian component fit to the
absorption line (comp5amp)
854- 858 F5.3 --- E_C5Amp ? The positive 1sigma error on
Comp5amp (comp5amp_+err)
860- 864 F5.3 --- e_C5Amp ? The negative 1sigma error on
Comp5amp (comp5amp_-err)
866- 870 F5.2 km/s C5Pos ? The position of the 5^th
Gaussian component relative to
pos_max (comp5pos)
872- 874 F3.1 km/s E_C5Pos ? The positive 1sigma error on
Comp5pos (comp5pos_+err)
876- 879 F4.2 km/s e_C5Pos ? The negative 1sigma error on
Comp5pos (comp5pos_-err)
881- 884 F4.2 km/s C5Sigma ? The width (sigma) of the 5^th
Gaussian component (comp5sigma)
886- 889 F4.2 km/s E_C5Sigma ? The positive 1sigma error on
Comp5sigma (comp5sigma_+err)
891- 894 F4.2 km/s e_C5Sigma ? The negative 1sigma error on
Comp5sigma (comp5sigma_-err)
896- 900 F5.3 --- C6Amp ? The amplitude of the 6^th
Gaussian component fit to the
absorption line (comp6amp)
902- 906 F5.3 --- E_C6Amp ? The positive 1sigma error on
Comp6amp (comp6amp_+err)
908- 912 F5.3 --- e_C6Amp ? The negative 1sigma error on
Comp6amp (comp6amp_-err)
914- 918 F5.2 km/s C6Pos ? The position of the 6^th
Gaussian component relative to
pos_max (comp6pos)
920- 923 F4.2 km/s E_C6Pos ? The positive 1sigma error on
Comp6pos (comp6pos_+err)
925- 928 F4.2 km/s e_C6Pos ? The negative 1sigma error on
Comp6pos (comp6pos_-err)
930- 933 F4.2 km/s C6Sigma ? The width (sigma) of the 6^th
Gaussian component (comp6sigma)
935- 938 F4.2 km/s E_C6Sigma ? The positive 1sigma error on
Comp6sigma (comp6sigma_+err)
940- 943 F4.2 km/s e_C6Sigma ? The negative 1sigma error on
Comp6sigma (comp6sigma_-err)
945- 948 F4.2 --- C7Amp ? The amplitude of the 7^th
Gaussian component fit to the
absorption line (comp7amp)
950- 953 F4.2 --- E_C7Amp ? The positive 1sigma error on
Comp7amp (comp7amp_+err)
955- 958 F4.2 --- e_C7Amp ? The negative 1sigma error on
Comp7amp (comp7amp_-err)
960- 964 F5.1 km/s C7Pos ? The position of the 7^th
Gaussian component relative to pos_max
(comp7pos)
966- 969 F4.1 km/s E_C7Pos ? The positive 1sigma error on
Comp7pos (comp7pos_+err)
971- 974 F4.1 km/s e_C7Pos ? The negative 1sigma error on
Comp7pos (comp7pos_-err)
976- 979 F4.1 km/s C7Sigma ? The width (sigma) of the 7^th
Gaussian component (comp7sigma)
981- 983 F3.1 km/s E_C7Sigma ? The positive 1sigma error on
Comp7sigma (comp7sigma_+err)
985- 987 F3.1 km/s e_C7Sigma ? The negative 1sigma error on
Comp7sigma (comp7sigma_-err)
989- 992 F4.2 --- C8Amp ? The amplitude of the 8^th
Gaussian component fit to the
absorption line (comp8amp)
994- 997 F4.2 --- E_C8Amp ? The positive 1sigma error on
Comp8amp (comp8amp_+err)
999-1002 F4.2 --- e_C8Amp ? The negative 1sigma error on
Comp8amp (comp8amp_-err)
1004-1007 F4.1 km/s C8Pos ? The position of the 8^th
Gaussian component relative to pos_max
(comp8pos)
1009-1011 F3.1 km/s E_C8Pos ? The positive 1sigma error on
Comp8pos (comp8pos_+err)
1013-1015 F3.1 km/s e_C8Pos ? The negative 1sigma error on
Comp8pos (comp8pos_-err)
1017-1019 F3.1 km/s C8Sigma ? The width (sigma) of the 8^th
Gaussian component (comp8sigma)
1021-1023 F3.1 km/s E_C8Sigma ? The positive 1sigma error on
Comp8sigma (comp8sigma_+err)
1025-1028 F4.2 km/s e_C8Sigma ? The negative 1sigma error on
Comp8sigma (comp8sigma_-err)
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Note (1): Blank implies no visual inspection has been performed
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Acknowledgements:
Neeraj Gupta, ngupta(at)iucaa.in
(End) Neeraj Gupta [IUCAA], Patricia Vannier [CDS] 29-Apr-2025