J/MNRAS/450/1477 VLA 352MHz image of the Bootes field. I. (Coppejans+, 2015)
Megahertz peaked-spectrum sources in the Bootes field.
I. A route towards finding high-redshift AGN.
Coppejans R., Cseh D., Williams W.L., van Velzen S., Falcke H
<Mon. Not. R. Astron. Soc. 450, 1477 (2015)>
=2015MNRAS.450.1477C 2015MNRAS.450.1477C
ADC_Keywords: Surveys ; Active gal. nuclei ; Galaxies, radio ; Radio sources
Keywords: techniques: interferometric - catalogues - galaxies: active -
galaxies: high-redshift - radio continuum: galaxies
Abstract:
We present a 324.5MHz image of the NOAO Bootes field that was made
using Very Large Array (VLA) P-band observations. The image has a
resolution of 5.6"x5.1", a radius of 2.05 degrees and a central noise
of ∼0.2mJy/beam. Both the resolution and noise of the image are an
order of magnitude better than what was previously available at this
frequency and will serve as a valuable addition to the already
extensive multiwavelength data that are available for this field. The
final source catalogue contains 1370 sources and has a median 325 to
1400MHz spectral index of -0.72. Using a radio colour-colour diagram
of the unresolved sources in our catalogue, we identify 33 megahertz
peaked-spectrum (MPS) sources. Based on the turnover frequency linear
size relation for the gigahertz peaked-spectrum (GPS) and compact
steep-spectrum (CSS) sources, we expect that the MPS sources that are
compact on scales of tens of milliarcseconds should be young radio
loud active galactic nuclei at high (z>2) redshifts. Of the 33 MPS
sources, we were able to determine redshifts for 24, with an average
redshift of 1.3. Given that five of the sources are at z>2, that the
four faint sources for which we could not find redshifts are likely at
even higher redshifts and that we could only select sources that are
compact on a scale of ∼5", there is encouraging evidence that the
MPS method can be used to search for high-redshift sources.
Description:
The source and Gaussian component catalog presented here is derived
from 20 hours of observations with the VLA at 325MHz, centered at the
NOAO Bootes field. The resulting 13.2 square degree image has a
central noise level of 0.2mJy/beam and a resolution of 6".
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 103 1706 List of sources and Gaussian component in the
VLA 325MHz image
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See also:
J/AJ/123/1784 : 1.4GHz imaging of the Bootes field (de Vries+, 2002)
J/AJ/127/213 : LALA Bootes field X-ray source catalog (Wang+, 2004)
J/AJ/130/923 : Faint radio sources in the NOAO Bootes field (Wrobel+, 2005)
J/ApJ/634/L1 : 16 micron sources in the NOAO Bootes field (Kasliwal+, 2005)
J/ApJS/161/9 : X-ray survey of the NDWFS Bootes field (Kenter+, 2005)
J/ApJ/641/140 : Optical counterparts in the NDWFS Bootes field (Brand+, 2006)
J/A+A/535/A38 : Observations of NOAO Bootes field at 153Mhz (Intema+, 2011)
J/A+A/549/A55 : GMRT 153MHz (2m) Radio Mini Survey I (Williams+, 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Source Source identifier (JHHMMSS+DDMMSS) (1)
15 A1 --- m_Source [a-i] Gaussian component (2)
17- 25 F9.5 deg RAdeg Centroid right ascension (J2000)
27- 29 F3.1 arcsec e_RAdeg [0/2] rms uncertainty on RA (1σ)
31- 38 F8.5 deg DEdeg Centroid declination (J2000)
40- 42 F3.1 arcsec e_DEdeg [0/2] rms uncertainty on DEC (1σ)
44- 49 F6.1 mJy Si [0.1/2013] 325MHz integrated flux density
51- 55 F5.1 mJy e_Si rms uncertainty on Si (1σ)
57- 61 F5.1 mJy Sp [0.8/873] 325MHz peak flux density in mJy/beam
63- 67 F5.1 mJy e_Sp rms uncertainty on Sp (1σ) in mJy/beam
69- 72 F4.1 arcsec a Deconvolved major-axis
74- 76 F3.1 arcsec e_a rms uncertainty on a (1σ)
78- 81 F4.1 arcsec b Deconvolved minor-axis
83- 85 F3.1 arcsec e_b rms uncertainty on b (1σ)
87- 91 F5.1 deg phi [0/180] position angle φ
93- 97 F5.1 deg e_phi rms uncertainty on phi (1σ)
99-101 F3.1 mJy rms Local RMS image noise near source in mJy/beam
103 I1 --- Ng [1/9]? Number of gaussians out of which
the source is composed (2)
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Note (1): Note that in the catalogue the source names were mistakenly derived
by rounding the RA and DEC values to the nearest second instead of
truncating them as recommended by the IAU.
Note (2): The Gaussian components (if any) of the sources are given after the
sources. The components have the source name followed by an alphabetic symbol
(a,b,c,...) where "a" indicates the first Gaussian component,
"b" indicates the second ...
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Acknowledgements:
Rocco Coppejans, r.coppejans(at)astro.ru.nl
(End) Patricia Vannier [CDS] 31-Mar-2015