J/MNRAS/453/1223 BCG high radio-frequency properties (Hogan+, 2015)
High radio-frequency properties and variability of brightest cluster galaxies.
Hogan M.T., Edge A.C., Geach J.E., Grainge K.J.B., Hlavacek-Larrondo J.,
Hovatta T., Karim A., McNamara B.R., Rumsey C., Russell H.R., Salome P.,
Aller H.D., Aller M.F., Benford D.J., Fabian A.C., Readhead A.C.S.,
Sadler E.M., Saunders R.D.E.
<Mon. Not. R. Astron. Soc., 453, 1223-1240 (2015)>
=2015MNRAS.453.1223H 2015MNRAS.453.1223H (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, radio
Keywords: galaxies: active - galaxies: clusters: general - galaxies: jets -
radio continuum: galaxies
Abstract:
We consider the high radio-frequency (15-353GHz) properties and
variability of 35 brightest cluster galaxies (BCGs). These are the
most core-dominated sources drawn from a parent sample of more than
700 X-ray selected clusters, thus allowing us to relate our results to
the general population. We find that ≥6.0 percent of our parent
sample (≥15.1 percent if only cool-core clusters are considered)
contain a radio source at 150GHz of at least 3mJy (∼1x1023W/Hz at
our median redshift of z∼0.13). Furthermore, ≥3.4 percent of the BCGs
in our parent sample contain a peaked component (Gigahertz Peaked
Spectrum, GPS) in their spectra that peaks above 2GHz, increasing to
≥8.5 percent if only cool-core clusters are considered. We see little
evidence for strong variability at 15GHz on short (week-month)
time-scales although we see variations greater than 20 percent at
150GHz over six-month time frames for 4 of the 23 sources with
multi-epoch observations. Much more prevalent is long-term
(year-decade time-scale) variability, with average annual amplitude
variations greater than 1 percent at 15GHz being commonplace. There is
a weak trend towards higher variability as the peak of the GPS-like
component occurs at higher frequency. We demonstrate the complexity
that is seen in the radio spectra of BCGs and discuss the potentially
significant implications of these high-peaking components for
Sunyaev-Zel'dovich cluster searches.
Description:
The sample of sources chosen for this study were selected primarily
from Hogan et al. (2015. Cat. J/MNRAS/453/1201) as having the
brightest (>10mJy at 5GHz), flat-spectrum cores (α<0.5) so a
detection above 100GHz was possible. The H15a sample covers an
all-sky, X-ray flux-limited sample of over 700 clusters as outlined
above, but the number of sources matching these flux and index cuts is
relatively small (<30 or <4 per cent). To increase the target list
we added seven bright (>50mJy at 5GHz) sources either in fainter
clusters and/or clusters misidentified until now.
We obtained data from three epochs, using GISMO to observe 29, 24 and
17 sources in 2012 April, November and 2013 April observing runs,
respectively, with as many source overlaps between runs as possible
23 sources were observed at 90GHz using the CARMA interferometer
in D-array between 2012 May 21-June 15, of which 20 overlap with our
GISMO sources.
We used the AMI-LA to observe 17 of our sources, with each target
visited either two or three times in 2012. Five of the sources in our
sample have been monitored as part of this OVRO monitoring campaign.
An additional 11 BCGs that were identified from this work as having
strong high radio-frequency emission, have been included within the
dynamic queue since 2013 January, allowing regular (typically every
10d) observations for these sources.
Observations were made using the SCUBA-2 instrument (Holland et al.
2013) on the James Clerk Maxwell Telescope (JCMT) as part of a poor
weather programme (JCMT weather Bands 4 and 5, τ225GHz=0.15-0.3)
as part of Canadian and UK projects (M12AC15, M12BC18, M12BU38,
M13AC16 and M13AU38) between 2012 February and 2013 July.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 97 68 GISMO (150GHz) fluxes of the observed clusters
table3.dat 91 17 AMI (16GHz) fluxes of the observed BCGs
table4.dat 63 22 CARMA (90GHz) fluxes of the observed BCGs
table5.dat 32 25 SCUBA-2 (353 GHz) fluxes of the observed BCGs
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See also:
J/MNRAS/453/1201 : Radio properties of brightest cluster galaxies (Hogan+ 2015)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 I1 --- Epoch [1/3] Epoch (1)
3- 14 A12 --- Cluster Cluster name
16- 25 A10 "date" Obs.Date Observation date
27- 28 I2 h RAh Right ascension (J2000)
30- 31 I2 min RAm Right ascension (J2000)
33- 37 F5.2 s RAs Right ascension (J2000)
39 A1 --- DE- Declination sign (J2000)
40- 41 I2 deg DEd Declination (J2000)
43- 44 I2 arcmin DEm Declination (J2000)
46- 49 F4.1 arcsec DEs Declination (J2000)
51- 54 F4.2 --- tau Optical extinction
56- 57 I2 min ExpTime Exposure time
59- 67 A9 --- Cruch CRUSH option (2)
69 A1 --- l_Flux Limit flag on Flux
70- 74 F5.1 mJy Flux GISMO flux at 150GHz
76- 79 F4.1 mJy e_Flux ? rms uncertainty on Flux
81 I1 --- neFlux [7]? Note on e_Flux
83- 86 F4.1 arcsec FWHM ?=- Full width at half-maximum
88- 92 F5.1 mJy FPeak ?=- Peak flux at 150GHz
94- 97 F4.1 --- rms Map RMS
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Note (1): Epoch as follows:
1 = Epoch 1 : April 2012
2 = Epoch 2 : November 2012
3 = Epoch 3 : April 2013
Note (2): CRUSH software package (Kovacs, 2008, Proc. SPIE Conf. Ser.
Vol. 7020, p. 70201s.) options.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Cluster Cluster name
12- 21 A10 "date" Obs.date1 First observation date
23- 28 F6.1 mJy Flux1 AMI flux at 16GHz at Obs.date1
30- 33 F4.1 mJy e_Flux1 rms uncertainty on Flux1
35- 37 F3.1 --- rms1 RMS at Obs.date1
39- 48 A10 "date" Obs.date2 Second observation date
50- 55 F6.1 mJy Flux2 AMI flux at 16GHz at Obs.date2
57- 60 F4.1 mJy e_Flux2 rms uncertainty on Flux2
62- 65 F4.1 --- rms2 RMS at Obs.date2
67- 76 A10 "date" Obs.date3 Third observation date
78- 82 F5.1 mJy Flux3 ? AMI flux at 16GHz at Obs.date3
84- 87 F4.1 mJy e_Flux3 ? rms uncertainty on Flux3
89- 91 F3.1 --- rms3 ? RMS at Obs.date3
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Cluster Cluster name
13- 22 A10 "date" Obs.Date Observation date
24- 25 I2 h RAh Right ascension (J2000)
27- 28 I2 min RAm Right ascension (J2000)
30- 34 F5.2 s RAs Right ascension (J2000)
36 A1 --- DE- Declination sign (J2000)
37- 38 I2 deg DEd Declination (J2000)
40- 41 I2 arcmin DEm Declination (J2000)
43- 46 F4.1 arcsec DEs Declination (J2000)
48 A1 --- l_Flux Limit flag on Flux
49- 53 F5.1 mJy Flux CARMA flux at 90GHz
55- 58 F4.1 mJy e_Flux ? rms uncertainty on Flux
60- 63 F4.1 --- rms RMS
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Cluster Cluster name
13- 22 A10 "date" Obs.Date Observation date
24- 27 F4.1 mJy Flux ?=- SCUBA-2 flux at 353GHz
29- 32 F4.1 --- rms RMS
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 16-Feb-2016