J/other/PASA/43.65 ASKAP-FLASH catalog (Roster+, 2026)
The ASKAP-FLASH survey: A first look at the multiwavelength properties and
redshift distribution of compact radio sources.
Roster W., Sadler M., Mahony E.K., Salvato M., Yoon H., Kluge M.,
Shirley R., Kerrison E., Buchner J., Igo Z., Davies R., Allison J.R.,
Shabala S.S., Moss V.A., Starck H., Whiting M., Nandra K., Weller J.
<Publ. Astron. Soc. Australia, 43, 65 (2026)>
=2026PASA...43...65R 2026PASA...43...65R (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Radio sources ; Redshifts ; Photometry, infrared ;
Optical
Keywords: catalogues - galaxies: active - galaxies: distances and redshifts -
galaxies: photometry - radio continuum: galaxies
Abstract:
We present the characterisation, including a photometric redshift
(photo-z) analysis, of the optical counterparts (CTPs) to over 45000
bright (S856MHz≥30mJy) compact radio sources, identified across all
ASKAP First Large Absorption Survey in HI (FLASH) fields observed up
to April 2025. These sources constitute a large, homogeneous
population of background continuum sightlines specifically selected to
enable statistical studies of cold gas at intermediate redshifts of
0.42≤z≤1. As spectroscopic redshift measurements are not available
for the majority of these candidate absorbers, we estimate photo-zs
for the CTPs of all FLASH continuum sources cross-matched to the tenth
data release of the DESI Legacy Imaging Surveys (LS10). Using these
estimates, we establish the redshift distribution and find that
approximately 13% of continuum sources lie at z<0.42 (foreground), 35%
within the detectability range of FLASH ('in-band'), and 52% at z>1
(background). We examine the subset of FLASH continuum sources with
CTPs in the eROSITA X-ray survey, providing additional insight into
their AGN content, multiwavelength properties, and environments.
Finally, we discuss how this information can be used as a statistical
prior to aid in distinguishing between associated and intervening HI
absorption systems and estimating the total comoving absorption path
length of the survey, establishing a framework for incorporating
redshift-based priors in future large radio absorption surveys. We
release a catalogue of LS10 counterparts to FLASH continuum sources,
providing photo-z estimates, associated uncertainties, and measures of
redshift degeneracies.
Description:
We determine optical CTPs for FLASH continuum sources using the
Bayesian cross-matching tool NWAY (Salvato et al., 2018, Cat.
J/MNRAS/473/4937), which combines astrometric information with
photometric priors to improve the reliability of associations.
We compare the FLASH-based CTPs with those obtained by running NWAY on
RACS sources in the area jointly covered by LS10 and the footprint of
eROSITA.
The final catalogue comprises 45113 unique FLASH continuum sources
with optical CTPs in LS10. Among these, 6305 cases correspond to
instances where multiple FLASH entries (with distinct source IDs) are
associated with the same optical CTP.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 524 45113 ASKAP-FLASH catalog
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See also:
J/MNRAS/473/4937 : AllWISE ctp to ROSAT/2RXS & XMMSLEW2 catalogs
(Salvato+, 2018)
J/A+A/692/A260 : PICZL. Image-based photo-z for AGN (Roster+, 2024)
J/A+A/704/A344 : eRASS1 counterparts and classification (Salvato+, 2025)
https://www.legacysurvey.org/dr10 : DESI LS10 Home Page
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 22 A22 --- FLASHcompid Concatenation of FLASH SBID and unique
component identifier (FLASHcomponentid)
24- 30 A7 --- FLASHSBID FLASH tile (FLASH_SBID)
32- 41 F10.6 deg RAdeg Right Ascension (J2000) of the radio
source in the parent catalog (FLASH_RA)
43- 52 F10.6 deg DEdeg Declination (J2000) of the radio source
in the parent catalog (FLASH_DEC)
54- 62 F9.3 mJy FpeakFLASH Peak flux (712- 1000MHz) of the
radio source (FLASHfluxpeak)
64- 70 F7.3 mJy e_FpeakFLASH Peak flux (712-1000MHz) error of the
radio source (FLASHfluxpeak_err)
72- 80 F9.3 mJy FintFLASH Integrated flux (712-1000MHz) of the
radio source (FLASHfluxint)
82 I1 --- FLASHdup Binary flag indicating whether the same
radio source is detected across
different SBIDs (FLASH_duplicate)
84 I1 --- FLASHdupApp ? Count of how often the same radio source
is detected across different SBIDs
(FLASHduplicateappearances)
86- 97 E12.6 --- FLASHdupMSep ?=- Maximum positional separation of the
same radio source detected across
different SBIDs
(FLASHduplicatemax_separation)
99-116 A18 --- LS10 Legacy survey DR10 unique identifier of
the CTP by concatenation of RELEASE,
BRICKID and OBJID (LS10_FULLID)
118-132 F15.11 deg RALdeg Legacy survey DR10 J2000 right Ascension
of the CTP (LS10_RA)
134-148 F15.11 deg DELdeg Legacy survey DR10 J2000 declination of
the CTP (LS10_DEC)
150 I1 --- InAllLS10 Binary flag indicating whether the CTP is
detected in *all* optical LS10 bands
(InAllLS102025)
152 I1 --- InAnyLS10 Binary flag indicating whether the CTP is
detected in *any* optical LS10 bands
(InAnyLS102025)
154-156 A3 --- LS10type LS10 morphological classification
(LS10_type)
158-179 F22.15 3.63uJy FW1LS10 Dereddened LS10 flux in WISE W1 band in
nanomaggy (LS10deredflux_w1)
181-202 F22.15 3.63uJy FW2LS10 Dereddened LS10 flux in WISE W2 band in
nanomaggy (LS10deredflux_w2)
204-225 F22.15 3.63uJy FW3LS10 Dereddened LS10 flux in WISE W3 band in
nanomaggy (LS10deredflux_w3)
227-249 F23.15 3.63uJy FW4LS10 Dereddened LS10 flux in WISE W4 band in
nanomaggy (LS10deredflux_w4)
251-272 F22.15 3.63uJy FgLS10 Dereddened LS10 flux in WISE g band in
nanomaggy (LS10deredflux_g)
274-295 F22.15 3.63uJy FrLS10 Dereddened LS10 flux in WISE r band in
nanomaggy (LS10deredflux_r)
297-318 F22.15 3.63uJy FiLS10 Dereddened LS10 flux in WISE i band in
nanomaggy (LS10deredflux_i)
320-341 F22.15 3.63uJy FzLS10 Dereddened LS10 flux in WISE z band in
nanomaggy (LS10deredflux_z)
343-365 A23 --- LS10Qual SNR quality class for optical LS10 bands
(LS10snrquality)
367-387 F21.19 --- LS10radio CTP probability to of being a radio
emitter based on the Random Forest model
(NWAYLS10radio)
389-396 F8.6 arcsec sepFLASH-LS10 Distance between FLASH and LS10 source
(NWAYseparationFLASH_LS10)
398-405 F8.5 --- Distbf Logarithm of ratio between prior and
posterior, from separation, positional
error and number density
(NWAYdistbayesfactor) (1)
407-414 F8.6 --- Distpost Distance posterior probability comparing
this association vs. no association
(NWAYdistpost) (1)
416-424 F9.6 --- Bias Probability weighting introduced by the
LS10-based prior. 1 indicates no change
(NWAYbiasLS10radioproba)
426-433 F8.6 --- psingle Same as dist_post, but weighted by the
prior (NWAYpsingle) (1)
435-442 F8.6 --- pany For each entry in the radio catalogue,
the probability that there is a
counterpart in LS10 (NWAYpany) (1)
444-451 F8.6 --- pi Relative probability of the FLASH/LS10
match (NWAYpi) (1)
453 I1 --- MatchFlag Match flag (NWAYmatchflag) (2)
455-466 E12.6 --- purityatpany Sample purity if cut at p_any
(NWAYpurityatpany)
468-479 E12.6 --- complatpany Sample completeness if cut at p_any
(NWAYcompletenessatpany)
481-485 F5.3 --- PICZLzph PICZL photometric redshift
(PICZLzphot) (3)
487-492 A6 --- PICZLpdfdegen PICZL PDF degeneracy class
(PICZLpdfdegeneracy)
494-498 F5.3 --- PICZLsPeakPSF ?=- PICZL PDF secondary peak for LS10_type
(PICZLsecondarypeak_PSF)
500-504 F5.3 --- PICZLsPeakHz ?=- PICZL PDF secondary peak for CTPs at
low redshift
(PICZLsecondarypeakhighz)
506-510 F5.3 --- PICZLbestzph Recommended PICZL photo-z solution
(PICZLbestz_phot)
512-516 F5.3 --- e_PICZLbestzph Photo-z lower 1 sigma error
(PICZLlower1sig)
518-522 F5.3 --- E_PICZLbestzph Photo-z upper 1 sigma error
(PICZLupper1sig)
524 I1 --- PICZLmperr Binary flag indicating whether the 1 sigma
error range includes more than 1
significant PDF peak
(PICZLmultipeak_errors)
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Note (1): see Appx. in Salvato et al. (2018MNRAS.473.4937S 2018MNRAS.473.4937S,
Cat. J/MNRAS/473/4937) for clarifications
Note (2): Match flag as follows:
1 = for the most probable match, if existing
2 = almost as good solutions (p i/p ibest ≥ 0.5)
Note (3): see Roster et al. (2024A&A...692A.260R 2024A&A...692A.260R, Cat. J/A+A/692/A260)
for more details)
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Acknowledgements:
William Roster, wroster(at)mpe.mpg.de
License: CC-BY-4.0 [see https://spdx.org/licenses/]
(End) Patricia Vannier [CDS] 12-Mar-2026