J/A+A/703/A17 Nine quasar pair fields JCMT/SCUBA-2 data (Herwig+, 2025)
Submillimeter galaxy overdensities around physically associated quasar pairs.
Herwig E., Arrigoni Battaia F., Chen C.-C., Obreja A., Nowotka M.,
Remus R.-S., Yajima H.
<Astron. Astrophys. 703, A17 (2025)>
=2025A&A...703A..17H 2025A&A...703A..17H (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Millimetric/submm sources ; QSOs
Keywords: galaxies: evolution - galaxies: high-redshift -
galaxies: interactions - quasars: general -
large-scale structure of Universe - submillimeter: galaxies
Abstract:
A commonly employed method to detect protoclusters in the young
universe is the search for overdensities of massive star forming
galaxies, such as submillimeter galaxies (SMGs), around high-mass
halos, including those hosting quasars. In this work, we study the
Megaparsec environment surrounding nine physically associated quasar
pairs between z=2.45 and z=3.82 with JCMT/SCUBA-2 observations at
450µm and 850µm covering a field of view of roughly 13.7 arcmin
in diameter (or 32Mpc2 at the median redshift) for each system. We
identify a total of 170 SMG candidates and 26 non-SMG and interloper
candidates.
A comparison of the underlying 850µm source models recovered with
Monte Carlo simulations to the blank field model reveals galaxy
overdensities in all fields, with a weighted average overdensity
factor of deltacumul=3.4±0.3.
From this excess emission at 850µm, we calculate a star formation
rate density of 1700±100M☉/yr/Mpc3, consistent with
predictions from protocluster simulations and observations. Compared
to fields around single quasars, those surrounding quasar pairs have
higher excess counts and more centrally peaked star formation, further
highlighting the co-evolution of SMGs and quasars. We do not find
preferential alignment of the SMGs with the quasar pair direction or
their associated Lyα nebulae, indicating that cosmic web
filaments on different scales might be traced by the different
directions. Overall, this work substantiates the reliability of quasar
pairs to detect overdensities of massive galaxies and likely sites of
protocluster formation. Future spectroscopic follow-up observations
are needed to confirm membership of the SMG candidates with the
physically associated quasar pairs and definitively identify the
targeted fields as protoclusters.
Description:
The dataset for the nine quasar pair fields studied in this work were
acquired with the Submillimetre Common-User Bolometer Array 2
(SCUBA-2) on the James Clerk Maxwell Telescope (JCMT) under the
program IDs M22AP049 and M22BP025 covering a field of view of around
13.7 arcmin in diameter each and using the DAISY scanning pattern
centered on one of the quasars in the pair. Information on the
exposure time and the observing conditions for each field can be found
in Table 1 of the paper. For each field, a map at 850µm and at
450µm is available.
Here, we provide the source catalogs of low-z interloper and non-SMG
candidates based on the flux ratio between the two bands, and SMG
candidate catalogs with 850µm detections above 4σ or
detections above 3σ in both bands.
Sources are named according to the ID of the field they were found in, as
listed in Table 1 of the paper. Entries with no values have -99.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb.dat 104 26 Interloper and non-SMG candidates in the quasar
pair fields based on the 450µm to 850µm
flux ratio (table B1)
tablec.dat 127 170 SMG candidates in the quasar pair fields
(tables C1-C9)
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Byte-by-byte Description of file: tableb.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Interloper name
17- 18 I2 h RAh Right ascension (J2000)
20- 21 I2 min RAm Right ascension (J2000)
23- 26 F4.1 s RAs Right ascension (J2000)
30 A1 --- DE- Declination sign (J2000)
31- 32 I2 deg DEd Declination (J2000)
34- 35 I2 arcmin DEm Declination (J2000)
37- 40 F4.1 arcsec DEs Declination (J2000)
42- 46 F5.1 arcsec ePos ?=-99 Error on Position
50- 53 F4.1 mJy F850 Flux density at 850um
56- 58 F3.1 mJy e_F850 Error on flux density at 850um
63- 67 F5.1 mJy F850D ?=-99 Deboosted flux density at 850um
68- 72 F5.1 mJy e_F850D ?=-99 Error on Deboosted flux density at 850um
78- 82 F5.1 mJy F450 Flux density at 450um
85- 88 F4.1 mJy e_F450 Error on flux density at 450um
93- 97 F5.1 mJy F450D ?=-99 Deboosted flux density at 450um
100-104 F5.1 mJy e_F450D ?=-99 Error on Deboosted flux density at 450um
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Byte-by-byte Description of file: tablec.dat
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Bytes Format Units Label Explanations
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3- 4 A2 --- Field Table number (C1-C9)
8- 22 A15 --- Name SMG candidate name
26- 27 I2 h RAh Right ascension (J2000)
31- 32 I2 min RAm Right ascension (J2000)
36- 39 F4.1 s RAs Right ascension (J2000)
43 A1 --- DE- Declination sign (J2000)
44- 45 I2 deg DEd Declination (J2000)
49- 50 I2 arcmin DEm Declination (J2000)
54- 57 F4.1 arcsec DEs Declination (J2000)
59- 64 F6.2 arcsec ePos ?=-99 Error on Position
67- 70 F4.1 mJy F850 Flux density at 850um
75- 77 F3.1 mJy e_F850 Error on flux density at 850um
79- 83 F5.1 mJy F850D ?=-99 Deboosted flux density at 850um
86- 90 F5.1 mJy e_F850D ?=-99 Error on Deboosted flux density at 850um
94 A1 --- forced [y/n] Forced flux at 450 um flag (y=yes, n=no)
100-104 F5.1 mJy F450 Flux density at 450um
108-111 F4.1 mJy e_F450 Error on flux density at 450um
116-120 F5.1 mJy F450D ?=-99 Deboosted flux density at 450um
123-127 F5.1 mJy e_F450D ?=-99 Error on Deboosted flux density at 450um
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Acknowledgements:
Eileen Herwig, eherwig(at)mpa-garching.mpg.de
(End) Patricia Vannier [CDS] 02-Sep-2025