J/A+A/587/A23 CFHT r- and z-band images 28 Planck sources (van der Burg+, 2016)
Prospects for high-z cluster detections with Planck, based on a follow-up of
28 candidates using MegaCam at CFHT.
van der Burg R.F.J., Aussel H., Pratt G.W., Arnaud M., Melin J.-B.,
Aghanim N., Barrena R., Dahle H., Douspis M., Ferragamo A., Fromenteau S.,
Herbonnet R., Hurier G., Pointecouteau E., Rubino-Martin J.A.,
Streblyanska A.
<Astron. Astrophys. 587, A23 (2016)>
=2016A&A...587A..23V 2016A&A...587A..23V (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Photometry
Keywords: galaxies: clusters: general - galaxies: photometry
Abstract:
The Planck catalogue of SZ sources limits itself to a significance
threshold of 4.5 to ensure a low contamination rate by false cluster
candidates. This means that only the most massive clusters at redshift
z>0.5, and in particular z>0.7, are expected to enter into the
catalogue, with a large number of systems in that redshift regime
being expected around and just below that threshold. In this paper, we
follow-up a sample of SZ sources from the Planck SZ catalogues from
2013 and 2015. In the latter maps, we consider detections around and
at lower significance than the threshold adopted by the Planck
Collaboration. To keep the contamination rate low, our 28 candidates
are chosen to have significant WISE detections, in combination with
non-detections in SDSS/DSS, which effectively selects galaxy
cluster candidates at redshifts z≳0.5. By taking r- and z-band
imaging with MegaCam@CFHT, we bridge the 4000Å rest-frame break
over a significant redshift range, thus allowing accurate redshift
estimates of red-sequence cluster galaxies up to z∼0.8. After
discussing the possibility that an overdensity of galaxies coincides
-by chance- with a Planck SZ detection, we confirm that 16 of the
candidates have likely optical counterparts to their SZ signals, 13
(6) of which have an estimated redshift z>0.5 (z>0.7). The richnesses
of these systems are generally lower than expected given the halo
masses estimated from the Planck maps. However, when we follow a
simplistic model to correct for Eddington bias in the SZ halo mass
proxy, the richnesses are consistent with a reference mass-richness
relation established for clusters detected at higher significance.
This illustrates the benefit of an optical follow-up, not only to
obtain redshift estimates, but also to provide an independent mass
proxy that is not based on the same data the clusters are detected
with, and thus not subject to Eddington bias
Description:
Reduced CFHT MegaCam r-, and z-band FITS images of the 28 Planck
candidates studied in the paper. WCS information (calibrated w.r.t.
USNO-B1) is included. Exposure times are 2000 seconds in each filter.
Magnitude zero points are calibrated w.r.t. SDSS (where there is
overlap), or else using the Universal stellar locus in combination
with WISE Channel 1, as detailed on in the accompanying paper. The
MAGZP keywords correspond to the best estimates (with uncertainty
∼0.05), in the AB magnitude system. Images are centred on the Planck
SZ position, and have a size (15'x15') that is several times larger
than the Planck beam, to allow for a study of optical counterparts to
the SZ detections.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sources.dat 42 28 The sample of 28 cluster candidates studied here
list.dat 115 56 List of fits files in r and z bands
fits/* . 112 Individual fits files
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See also:
VIII/88 : Planck Early Release Compact Source Catalogue (Planck, 2011)
VIII/91 : Planck Catalog of Compact Sources Release 1 (Planck, 2013)
J/A+A/536/A8 : Planck early results. VIII. ESZ sample. (Planck+, 2011)
J/A+A/578/A44 : Map of foreground masks for Planck (Axelsson+, 2015)
J/A+A/581/A14 : Updated Planck catalogue PSZ1 (Planck+, 2015)
Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
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1 A1 --- Status [CI] Confirmed or Invalided candidate
3- 19 A17 --- Name Source name
21- 22 I2 h RAh Right ascension (J2000) (1)
24- 25 I2 min RAm Right ascension (J2000) (1)
27- 30 F4.1 s RAs Right ascension (J2000) (1)
32 A1 --- DE- Declination sign (J2000) (1)
33- 34 I2 deg DEd Declination (J2000) (1)
36- 37 I2 arcmin DEm Declination (J2000) (1)
39- 42 F4.1 arcsec DEs Declination (J2000) (1)
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Note (1): Location that maximizes the richness measurement.
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- Name Source name (PLCKGLLL.ll+BB.bb,
PSZ1GLLL.ll+BB.bb or PSZ2GLLL.ll+BB.bb)
19- 27 F9.5 deg RAdeg Right Ascension of center (J2000)
28- 36 F9.5 deg DEdeg Declination of center (J2000)
38- 42 F5.3 arcsec/pix scale [0.185] Scale of the image
44- 47 I4 --- Nx [5000] Number of pixels along X-axis
49- 52 I4 --- Ny [5000] Number of pixels along Y-axis
54- 58 I5 Kibyte size [97757/98004] Size of FITS file
60- 83 A24 --- FileName1 Name of FITS image file, in subdirectory fits
85-115 A31 --- FileName2 Name of FITS weight file,
in subdirectory fits
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Acknowledgements:
Remco van der Burg, rfjvanderburg(at)gmail.com
(End) Patricia Vannier [CDS] 11-Feb-2016