J/ApJS/277/20 AstroSat UVIT survey of M31: compact sources (Leahy+, 2025)
AstroSat UVIT survey of M31: new compact source catalog.
Leahy D., Ranasinghe S., Mitra S., Rawal K.
<Astrophys. J. Suppl. Ser., 277, 20 (2025)>
=2025ApJS..277...20L 2025ApJS..277...20L
ADC_Keywords: Galaxies, nearby; Photometry, ultraviolet; Magnitudes
Keywords: Andromeda galaxy ; Ultraviolet astronomy ; Ultraviolet photometry
Abstract:
An ultraviolet survey of M31 was carried out during 2017-2023 with the
UltraViolet Imaging Telescope (UVIT) instrument on board the AstroSat
Observatory. Here we present far- and near-ultraviolet (FUV and NUV)
observations from the M31 UVIT survey, which covers a sky area of
∼3.5x1.3° with a spatial resolution of ∼1". The observations
included six filter bands in the wavelength range of 120-280nm.
Including the six bands, ∼115,000 sources with signal-to-noise ratio
(S/N)≥3 (∼95,000 sources with S/N≥5) were detected at FUV or NUV
wavelengths, with the largest set of detections (∼54,000 sources) in
the FUV 150nm band (F148W filter). This is considerably more than for
the first version of the M31 source catalog (published in 2020), in
part due to additional observations of M31 by UVIT and in part due to
improved data processing. The magnitude (mAB) at which incompleteness
sets in is ∼23.0 in the F148W band, with the other bands somewhat less
sensitive, with least sensitive band (in mAB units) N279N with
incompleteness for sources fainter than ∼20.3). The faintest sources
detectable in F148W have mAB∼25.4, with other bands having higher
minimum detectable brightness, and with N279N having a minimum
detectable limit of mAB∼22.1. The product of this work is the new M31
UVIT compact-source catalog, containing positions, fluxes, magnitudes,
and S/N for the sources.
Description:
This paper presents the new compact source catalog derived from the
full AstroSat UltraViolet Imaging Telescope (UVIT) M31 survey project,
with updated calibration, astrometry, and data processing. M31 was
observed, over a period of 2016 through 2024, with a set of 23
pointings, each with one to five observations in different filters, to
cover the galaxy.
The M31 UVIT survey used the FUV filters F148W, F154W, F169M, and
F172M and the NUV filters N219M and N279N. The whole area of M31
(except Field 21) was covered by the most sensitive (and broadest
band) FUV F148W filter, whereas the other filters only covered parts
of M31. The sky locations in R.A., decl. (J2000, decimal degrees) of
the field positions for the UVIT survey of M31 are shown in Figure 1.
Objects:
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RA (ICRS) DE Designation(s)
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00 42 44.33 +41 16 07.5 M31 = NAME Andromeda Galaxy
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 54 115285 Combined M31 source catalog for the six UVIT filters
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See also:
I/357 : Gaia DR3 Part 3. Non-single stars (Gaia Collaboration, 2022)
J/ApJS/173/185 : GALEX ultraviolet atlas of nearby galaxies (Gil de Paz+, 2007)
J/ApJ/703/614 : UV star-forming regions in M31 (Kang+, 2009)
J/AJ/144/142 : HST phot. of young stellar populations in M31 (Bianchi+, 2012)
J/ApJS/199/37 : GALEX catalog of star clusters in M31 (Kang+, 2012)
J/ApJS/215/9 : PHAT X. UV-IR photometry of M31 stars (Williams+, 2014)
J/ApJS/247/47 : Ultraviolet survey of M31 with UVIT on AstroSat (Leahy+, 2020)
J/AJ/161/215 : Far-ultraviolet variable sources in M31 (Leahy+, 2021)
J/AJ/162/199 : UV photometry of 548 variables stars in M31 (Leahy+, 2021)
J/AJ/164/183 : UVIT photometry of M31 PHAT stellar clusters (Leahy+, 2022)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Filt Filter used (1)
7- 13 A7 --- Field Observed field
15- 23 F9.6 deg RAdeg [9.16/12.6] Right ascension (J2000)
25- 33 F9.6 deg DEdeg [39.8/42.8] Declination (J2000)
35- 42 E8.2 cW/m2/nm Flux [2.2e-18/2e-13] Flux; erg/cm2/s/angstrom
44- 48 F5.1 --- S/N [3/650] Signal-to-noise ratio
50- 54 F5.2 mag mag [12.58/25.9] Apparent AB magnitude in Filt
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Note (1): UVIT filters, UC and flux to AB magnitude conversions as in Table 3:
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Filter lammean Δlam UC e_UC mAB
Å Å
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F148W 1481 500 2.864x10^-15 2.7x10^-17 24.24
F154W 1541 380 3.571x10^-15 4.0x10^-17 24.15
F169M 1608 290 4.574x10^-15 3.9x10^-17 24.06
F172M 1717 125 1.142x10^-14 1.7x10^-16 23.92
N219M 2196 270 4.920x10^-15 7.7x10^-17 23.38
N279N 2792 90 3.790x10^-15 3.8x10^-17 22.86
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UC = (counts per second to flux conversion factors; in erg/cm2/s/Å/(ct/s))
are based on the updated zero-point magnitudes given in
Tandon+ 2020AJ....159..158T 2020AJ....159..158T).
lam_mean = the mean wavelength, λmean, and the
bandwidth, Δλ, are from Table 3 in
Tandon+ (2017AJ....154..128T 2017AJ....154..128T)
mAB = AB magnitude equivalent of a flux of 10-17erg/cm2/s/Å
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Nov-2025