J/A+A/613/A20 r' magnitudes and sizes of Oph cluster galaxies (Durret+, 2018)
The optical properties of galaxies in the Ophiuchus cluster.
Durret F., Wakamatsu K., Adami C., Nagayama T., Omega Muleka Mwewa Mwaba J.M.
<Astron. Astrophys. 613, A20 (2018)>
=2018A&A...613A..20D 2018A&A...613A..20D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, photometry ; Morphology
Keywords: clusters: individual: Ophiuchus - large-scale structure of Universe
Abstract:
Ophiuchus is one of the most massive clusters known, but due to its
low Galactic latitude its optical properties remain poorly known.
We investigate the optical properties of Ophiuchus to obtain clues on
the formation epoch of this cluster, and compare them to those of the
Coma cluster, which is comparable in mass to Ophiuchus but much more
dynamically disturbed.
Based on a deep image of the Ophiuchus cluster in the r' band
obtained at the Canada France Hawaii Telescope with the MegaCam
camera, we have applied an iterative process to subtract the
contribution of the numerous stars that, due to the low Galactic
latitude of the cluster, pollute the image, and have obtained a
photometric catalogue of 2818 galaxies fully complete at r'=20.5mag
and still 91% complete at r'=21.5mag. We use this catalogue to derive
the cluster Galaxy Luminosity Function (GLF) for the overall image and
for a region (hereafter the "rectangle" region) covering exactly
the same physical size as the region in which the GLF of the Coma
cluster was previously studied. We then compute density maps based on
an adaptive kernel technique, for different magnitude limits, and
define three circular regions covering 0.08, 0.08, and 0.06 deg2,
respectively, centred on the cluster (C), on northwest (NW) of the
cluster, and southeast (SE) of the cluster, in which we compute the
GLFs.
The GLF fits are much better when a Gaussian is added to the usual
Schechter function, to account for the excess of very bright galaxies.
Compared to Coma, Ophiuchus shows a strong excess of bright galaxies.
The properties of the two nearby very massive clusters Ophiuchus and
Coma are quite comparable, though they seem embedded in different
large-scale environments. Our interpretation is that Ophiuchus was
built up long ago, as confirmed by its relaxed state (see paper I,
Durret et al., 2015, Cat. J/A+A/583/A124) while Coma is still in the
process of forming.
Description:
The study presented here is based on the full exploitation of the
CFHT/MegaCam image that we obtained in the r' band. Magnitudes have
been measured in the AB photometric system. At the redshift of
Ophiuchus, the 1x1 deg2 MegaCam field corresponds to a region of
about 2.1x2.1 Mpc2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 86 2818 A photometric catalogue of galaxies in the
Ophiuchus cluster
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See also:
J/A+A/583/A124 : Ophiuchus r'g'z' photometry and redshifts (Durret+, 2015)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- Name Galaxy name (OPHJHHMMSS.ss+DDMMSS)
23- 31 F9.5 deg RAdeg Right ascension (J2000.0)
33- 41 F9.5 deg DEdeg Declination (J2000.0)
43- 48 F6.3 mag r'mag Measured r' band magnitude with no extinction
correction (1)
50- 55 F6.3 mag r'magc1 r' band magnitude corrected for a constant
extinction value of 1.357mag (1)
57- 62 F6.3 mag r'magc2 r' band magnitude corrected for its individual
extinction correction (1)
64- 68 F5.1 arcsec aaxis Major axis (2)
71- 74 F4.1 arcsec baxis Minor axis (2)
76- 80 F5.1 deg PA Position angle of the major axis
83- 86 F4.1 deg e_PA Error on the position angle
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Note (1): We do not give individual errors on the observed magnitudes, but their
typical values are given in Table A.1. of the paper.
Note (2): the error bars on these two quantities are typically 0.1 arcsec,
so they are not given for every galaxy.
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Acknowledgements:
Florence Durret, durret(at)iap.fr
References:
Durret et al., Paper I, 2015A&A...583A.124D 2015A&A...583A.124D, Cat. J/A+A/583/A124
(End) Patricia Vannier [CDS] 25-Jan-2018