J/AJ/171/17 MDW Halpha Sky Survey DR1 (Aftab+, 2026)
The MDW Hα Sky Survey: Data Release 1.
Aftab N., Zhang X., Walker S., Di Cicco D., Mittelman D.R., Gupta S.,
Saydjari A.K., Putman M., Schiminovich D.
<Astron. J. 171, 17 (2026)>
=2026AJ....171...17A 2026AJ....171...17A (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Photometry, hydrogen-line
Keywords: Sky surveys - Amateur astronomy - Astronomy data reduction -
H II regions
Abstract:
The Mittelman-di Cicco-Walker (MDW) Hα Sky Survey is an
autonomously operated all-sky narrowband (3nm) Hα imaging
survey. The survey was founded by amateur astronomers, and the
northern sky (decl. ≥0°) is presented here in its second stage of
refinement for academic use. Each 3.6 deg2 MDW field has 12 20
minutes individual exposures with a pixel scale of 3.2", a typical
point-spread function of 6", and a stack point-source depth of 16-17
mag. The northern MDW Survey Data Release 1 (DR1) includes calibrated
mean and individual images, star-removed mean fields, and point-source
catalogs for all images matched to Data Release 1 of the Panoramic
Survey Telescope and Rapid Response System (Pan-STARRS1) and the INT
Galactic Plane Survey. (All DR1 components are available at
https://mdw.astro.columbia.edu. The catalogs are also made available
in the AAS Journals Zenodo repository: doi:10.5281/zenodo.17307324.)
Our initial study of Hα filament widths finds a typical FWHM of
30"-45" in the Lyra region. The matched catalogs (with a median match
distance of ∼0.5"), combined with our distinctive narrowband
photometry, are also used to identify Hα variable and excess
sources. These initial studies highlight some of the many scientific
uses of the MDW Hα survey.
Description:
Our catalog of mean-combined sources a total of ∼50 million row (of
which ∼40 million are unique. Our images overlap with each other, so
some sources appear twice!). This is a catalog of all Pan-STARRS
matches found in our mean-combined, stacked fields. We set a match
distance limit of 1.5" (∼half a pixel). We further match the
Pan-STARRS sources to the IGAPS survey of the Northern Galactic Plane,
with a limit of 0.12" on the match distance.
Built from a combination of dr1v2meancatalogplane.fits.gz and
dr1v2meancataloghalo.fits.gz
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
mdw_dr1.dat 733 53689158 MDW catalog sources
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See also:
V/165 : IGAPS. merged IPHAS and UVEX of northern Galactic plane
(Monguio+, 2020)
II/389 : The Pan-STARRS release 1 (PS1) Survey - DR2 (Magnier+, 2025)
https://mdw.astro.columbia.edu/index.html : Columbia University MDW home page
https://www.mdwskysurvey.org : MDW Sky Survey home page
Byte-by-byte Description of file: mdw_dr1.dat
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Bytes Format Units Label Explanations
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1- 24 E24.17 deg RAdeg The MDW source's J2000 Right Ascension
(RAdeg)
26- 49 E24.17 deg DEdeg The MDW source's J2000 Declination
(DEdeg)
51- 74 E24.17 deg GLON The MDW source's Galactic longitude
(GLON)
76- 99 E24.17 deg GLAT The MDW source's Galactic longitude
(GLAT)
101-124 E24.17 mag Hamag The MDW source's calibrated H-alpha
AB magnitude (Ha_mag)
126-149 E24.17 mag Hainstmag The MDW source's instrument H-alpha
magnitude, calculated from
Hainstrflux (Hainstrmag)
151-174 E24.17 ct HainstFlux The MDW source's instrument flux,
measured via PSF photometry
(Hainstrflux)
176-199 E24.17 pix fittedFWHM The FWHM of this source, fitted to an
exponential per DR1 paper
(fitted_fwhm) (1)
201-224 E24.17 pix initialFWHM The initial FWHM of this source
(initial_fwhm)
226-245 I20 --- Field The field number this source is found
in (field) (2)
247-305 A59 --- FileName Name of the mean-combined FITS file
this source is found in (file_name)
307-330 E24.17 deg RAPdeg [0/360] The matched PanSTARRS source's
J2000 Right Ascension (ps1_RAJ2000)
332-355 E24.17 deg DEPdeg [-90/90] The matched PanSTARRS source's
J2000 Declination (ps1_DEJ2000)
357-376 I20 --- ps1objID The matched PanSTARRS object ID
(ps1_objID)
378-401 E24.17 mag PS1gmag The matched PanSTARRS source's g
AB magnitude (ps1gmag)
403-426 E24.17 mag PS1rmag The matched PanSTARRS source's r
AB magnitude (ps1rmag)
428-451 E24.17 mag PS1imag The matched PanSTARRS source's i
AB magnitude (ps1imag)
453-472 I20 --- NPS1nearby The number of nearby PanSTARRS objects
within 6 arcsec of this MDW source
(nps1nearby)
474-497 E24.17 deg RAIdeg [0/360]?=-999 The matched IGAPS
source's J2000 Right Ascension
(igaps_RAJ2000)
499-522 E24.17 deg DEIdeg [-90/90]?=-999 The matched IGAPS
source's J2000 Declination
(igaps_DEJ2000)
524-533 A10 --- IGAPSName The matched IGAPS source's name
(igaps_name)
535-558 E24.17 mag IGAPSrmag ?=-999 The matched IGAPS source's
r AB magnitude (igapsrmag)
560-583 E24.17 mag IGAPSimag ?=-999 The matched IGAPS source's
i AB magnitude (igapsimag)
585-608 E24.17 mag IGAPSgmag ?=-999 The matched IGAPS source's
g AB magnitude (igapsgmag)
610-633 E24.17 mag IGAPSHamag ?=-999 The matched IGAPS source's
H-alpha AB magnitude (igapsHamag)
635-658 E24.17 --- MDWx The MDW source centroid's x coordinate
(mdw_x)
660-683 E24.17 --- MDWy The MDW source centroid's y coordinate
(mdw_y)
685-708 E24.17 arcsec MDW-PS1-sep2d ?=-3596400 The 2D separation distance
between the MDW source and the matched
PanSTARRS source (mdwps1sep2d)
710-733 E24.17 arcsec PS1-IGAPS-sep2d ?=-3596400 The 2D separation distance
between the matched PanSTARRS and
IGAPS sources (ps1igapssep2d)
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Note (1): 1 pixel ∼ 3.17 arcsec in the MDW Survey.
Note (2): It is possible for a source to be found in 2 fields, if it sits in the
overlap margin when observations are taken.
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Acknowledgements:
Caden Gobat, cgobat(at)sdsu.edu
References:
Aftab et al., 2024AJ....168..260A 2024AJ....168..260A, MDW Data release 0
License: CC-BY-4.0 [see https://spdx.org/licenses/]
(End) Patricia Vannier [CDS] 20-Apr-2026