J/MNRAS/498/5065 NEPSC2, the North Ecliptic Pole SCUBA-2 survey (Shim+, 2020)
NEPSC2, the North Ecliptic Pole SCUBA-2 survey:
850-µm map and catalogue of 850-µm-selected sources over 2deg2.
Shim H., Kim Y., Lee D., Lee H.M., Goto T., Matsuhara H., Scott D.,
Serjeant S., Ao Y., Barrufet L., Chapman S., Clements D.L., Conselice C.J.,
Greve T.R., Hashimoto T., Hwang H.S., Im M., Jeong W.-S., Jiang L., Kim M.,
Kim S.J., Kong A.K.H., Koprowski M., Marchetti L., Michalowski M.J.,
Parsons H., Pearson C., Seo H., Toba Y., White G.
<Mon. Not. R. Astron. Soc., 498, 5065-5079 (2020)>
=2020MNRAS.498.5065S 2020MNRAS.498.5065S (SIMBAD/NED BibCode)
ADC_Keywords: Millimetric/submm sources ; Galaxy catalogs ; Positional data
Keywords: galaxies: evolution - galaxies: photometry - galaxies: starburst -
submillimetre: galaxies
Abstract:
We present an 850-µm mosaic map and extracted catalogue of
submillimetre sources in the extended North Ecliptic Pole (NEP) region
over about 2deg2. The 850-µm map is constructed using newly
obtained observations by SCUBA-2 at the East Asian Observatory's James
Clerk Maxwell Telescope, carried out using the observatory's large
programme opportunities. The recent 850-µm survey has extended the
submillimetre data coverage by almost a factor of 4 compared to
previous surveys, with a depth of σrms=1.0-2.3mJy/beam. The
catalogue contains 549 sources selected above a significance level of
4σ, where the false-detection rate is 10 per cent; a higher
threshold of 4.5σ is required in order to achieve a
false-detection rate below 3 per cent, which results in 342 sources
being selected. Despite the large spatial variation of the noise, the
deboosted flux density of sources is comparable to results from the
SCUBA-2 Cosmology Legacy Survey, which covered the central 0.6deg2
of our survey area with better sensitivity. We construct the source
counts at 850µm, finding results in agreement with other 850-µm
surveys in cosmological blank fields over S850=4-15mJy. We find a
slight excess of bright galaxies (S850>15mJy), which can be
considered to be at zphot=2-4. The 850-µm data add valuable
long-wavelength information to mid-infrared-selected sources from the
AKARI NEP-deep and NEP-wide surveys, which will be helpful in
preparing for future near-infrared to millimetre wavelength
observations in the NEP region. Our 850-µm mosaic map and source
catalogue will be made publicly available.
Description:
The NEPSC2 data presented in this publication were observed as part of
JCMT program ID M17BL007. The data were obtained with the SCUBA-2
instrument (Holland et al. 2013MNRAS.430.2513H 2013MNRAS.430.2513H) at 850µm over the
period from 2017 July to 2019 November. In order to obtain 850-µm
images over a wide (4deg2) area centred on the NEP (RA=18h00m00s,
Dec=+66°33'38.5"), we used multiple 30-arcmin maps in a tiling
pattern to provide even coverage, with each individual field referred
to as a 'subfield'. Each 30-arcmin map, known as a PONG1800 map
(Holland et al. 2013MNRAS.430.2513H 2013MNRAS.430.2513H; Thomas & Currie
2014StarC..21.....T 2014StarC..21.....T), provides uniform sensitivity in the inner
circular region of 30arcmin (1800arcsec) diameter. Each PONG1800
observation took 40min of on-sky integration time and each subfield
was observed 28 times so that the total integration time for a single
subfield was 18.7h.
As of 2019 December, observations of nine subfields (NEP1 to NEP9)
have been completed, with approximately 170h of total integration time
(Table 1). The actual time spent by the programme is longer, since
there are some subfields that were observed only a few times and are
not included in this work.
Currently, the areal coverage of the NEPSC2 survey is still smaller
than that of the S2COSMOS project (Simpson et al. 2019ApJ...880...43S 2019ApJ...880...43S,
Cat. J/ApJ/880/43), which provides uniform sensitivity over 2deg2.
The observations are expected to be completed by 2022 through the
recently approved large programme extension; we will then have
approximately 4deg2 coverage with a sensitivity comparable to that
of the currently existing data.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 88 549 850-µm source catalogue from the NEPSC2
survey covering approximately 2deg2
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 21 A21 --- Name Source name (NEPSC2_JHHMMSS-DDMMSS)
23- 24 I2 h RAh Right ascension (J2000)
26- 27 I2 min RAm Right ascension (J2000)
29- 32 F4.1 s RAs Right ascension (J2000)
34 A1 --- DE- Declination sign (J2000)
35- 36 I2 deg DEd Declination (J2000)
38- 39 I2 arcmin DEm Declination (J2000)
41- 44 F4.1 arcsec DEs Declination (J2000)
46- 50 F5.1 mJy S850obs Observed 850um flux density
52- 54 F3.1 mJy e_S850obs Error on S850obs (1)
56- 60 F5.1 --- S/N Signal to noise ratio
62- 66 F5.1 mJy S850deb Deboosted 850um flux density
68- 70 F3.1 mJy e_S850deb Error on S850deb (2)
72- 75 F4.2 --- C Completeness (3)
77- 83 F7.2 --- logF Logarithm of the false-detection rate (4)
85- 88 F4.2 arcsec dtheta Positional uncertainty of the 850um source
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Note (1): Instrumental noise
Note (2): Total uncertainty. The total uncertainty is the quadrature sum of the
instrumental noise, confusion noise, and deboosting error.
Note (3): The completeness is defined as the ratio between the number of
recovered sources and the number of total injected sources
Note (4): The false-detection rate is defined as the ratio between the number
of extracted sources in the jackknife noise map and the flux-density
map per signal-to-noise bin
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 09-Aug-2023