J/ApJ/649/63 DRaGONS survey (Schmidt+, 2006)
The DRaGONS survey: a search for high-redshift radio galaxies and heavily
obscured active galactic nuclei.
Schmidt S.J., Connolly A.J., Hopkins A.M.
<Astrophys. J., 649, 63-78 (2006)>
=2006ApJ...649...63S 2006ApJ...649...63S
ADC_Keywords: Surveys ; Galaxies, radio ; Infrared sources
Keywords: galaxies: evolution - radio continuum: galaxies
Abstract:
We present the first results from the Distant Radio Galaxies Optically
Non-detected in the SDSS (DRaGONS) survey. Using a novel selection
technique for identifying high-redshift radio galaxy (HzRG)
candidates, a large sample is compiled using bright (S1.4GHz>100mJy)
radio sources from the FIRST survey having no optical counterpart in
the SDSS. Near-IR K-band imaging for 96 targets allows preliminary
identification of HzRG candidates through the well-known K-z relation,
for subsequent spectroscopic observation. We measure magnitudes
brighter than K∼19.5 for 70 of the 96, and limiting magnitudes for the
remainder. Redshifts based on a linear fit to the K-z diagram give a
mean =2.5 and median z=2.0, showing that this method should be
efficient at identifying a large number of HzRGs.
Description:
We acquired K-band images for 96 of the 172 unique candidates on the
Kitt Peak National Observatory (KPNO) 4m Mayall telescope over two
sets of four nights, 2003 April 2023 and 2004 May 31-June 3, using the
Florida Multi-object Imaging Near-IR Grism Observational Spectrometer
(FLAMINGOS) instrument.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 115 117 Detections
table2.dat 88 34 Non-detections
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See also:
VIII/71 : The FIRST Survey Catalog, Version 03Apr11 (Becker+ 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- DRaGONS Object Name (JHHMM+DDMM)
11 A1 --- m_DRaGONS [abc] Multiplicity index on DRaGONS (G1)
13 A1 --- n_DRaGONS [c-g] Note on DRaGONS (1)
15- 24 A10 "YYYY/MM/DD" Date Observation Date
25- 27 A3 --- n_Date Second day of observation
29- 30 I2 h RAh ? Radio right ascension (J2000) (G2)
32- 33 I2 min RAm ? Radio right ascension (J2000) (G2)
35- 40 F6.3 s RAs ? Radio right ascension (J2000) (G2)
42 A1 --- DE- Radio declination sign (J2000) (G2)
43- 44 I2 deg DEd ? Radio declination (J2000) (G2)
46- 47 I2 arcmin DEm ? Radio declination (J2000) (G2)
49- 53 F5.2 arcsec DEs ? Radio declination (J2000) (G2)
55 A1 --- Ext? [YN] Extended source ? (G3)
57- 58 I2 h RAIh ? Infrared right ascension (J2000)
60- 61 I2 min RAIm ? Infrared right ascension (J2000)
63- 67 F5.2 s RAIs ? Infrared right ascension (J2000)
69 A1 --- DEI- Infrared declination sign (J2000)
70- 71 I2 deg DEId ? Infrared declination (J2000)
73- 74 I2 arcmin DEIm ? Infrared declination (J2000)
76- 80 F5.2 arcsec DEIs ? Infrared declination (J2000)
82- 88 F7.2 mJy Fpeak ? Peak 1.4GHz flux density from the FIRST
(VIII/71) catalog
90- 96 F7.2 mJy Fint ? Integrated 1.4GHz flux density from the
FIRST (VIII/71) catalog
97 A1 --- l_Kmag Limit flag on Kmag
98-102 F5.2 mag Kmag ? Apparent K magnitude for the infrared
object (G4)
104-107 F4.2 mag e_Kmag ? rms uncertainty on Kmag (2)
109-111 F3.1 arcsec Seeing ? FWHM seeing measured for the field, for
radio observations
112 A1 --- l_z Limit flag on z
113-115 F3.1 --- z ? Estimated redshift, for radio
observations (3)
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Note (1): Individual notes as follows:
c = This object is an extended double lobe with a corresponding faint
match in SDSS and should not have been included in our sample.
The object has SDSS magnitudes g=23.25, r=22.29, i=21.26, and z=19.90.
d = This object, 3C 257, was previously identified as a radio galaxy
(Hewitt & Burbidge, 1991, Cat. VII/178). The K band contains
Halpha emission, leading to the underestimate of redshift from
the K-z diagram (for details see van Breugel et al.,
1998ApJ...502..614V 1998ApJ...502..614V).
e = This object is a wide-separation double lobe with several
candidate objects along the radio axis. The probable match is
faintly detected in SDSS with magnitudes of g=22.6, r=22.13,
i=21.32 and z=20.27.
f = Object J1411+0124 was observed on subsequent nights for a total
integration time of 40 minutes.
g = This object has a match in SDSS g=22.86, r=22.45, i=22.11, and
z=21.12 and was improperly targeted because it is a weak double lobe.
Note (2): Errors are those output by SExtractor.
Note (3): Estimated redshift based on a fit to the Hubble K-z relation,
given by K=4.62logz+17.2. For non-detections (Table 2), the estimated
redshift is given as a lower limit for the 2σ limiting
magnitude.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- DRaGONS Object Name
11 A1 --- m_DRaGONS [abc] Multiplicity index on DRaGONS (G1)
13 A1 --- n_DRaGONS [h-i] Note on DRaGONS (1)
15- 30 A16 --- Date Observation Date
32- 33 I2 h RAh ? Radio right ascension (J2000) (G2)
35- 36 I2 min RAm ? Radio right ascension (J2000) (G2)
38- 43 F6.3 s RAs ? Radio right ascension (J2000) (G2)
45 A1 --- DE- Radio declination sign (J2000) (G2)
46- 47 I2 deg DEd ? Radio declination (J2000) (G2)
49- 50 I2 arcmin DEm ? Radio declination (J2000) (G2)
52- 56 F5.2 arcsec DEs ? Radio declination (J2000) (G2)
58 A1 --- Ext? [YN] Extended source ? (G3)
60- 65 F6.2 mJy Fpeak ? Peak 1.4GHz flux density from the FIRST
(VIII/71) catalog
67- 72 F6.2 mJy Fint ? Integrated 1.4GHz flux density from the
FIRST (VIII/71) catalog
74 A1 --- l_Kmag Limit flag on Kmag
75- 79 F5.2 mag Kmag ? 2σ limit K magnitude for the infrared
object (G4)
81- 83 F3.1 arcsec Seeing ? FWHM seeing measured for the field, for
radio observations
85 A1 --- l_z Limit flag on z
86- 88 F3.1 --- z ? Estimated redshift, for radio
observations (2)
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Note (1): Individual notes as follows:
h = J1350+0352 was observed on both 2003 April 20 and 2004 June 2,
for a total integration time of 61 minutes with no detection.
i = J2242-0808 was observed on two nights in 2004 for a total
integration time of 29 minutes.
Note (2): Estimated redshift based on a fit to the Hubble K-z relation,
given by K=4.62logz+17.2. Here the estimated redshift is given as a
lower limit for the 2sigma limiting magnitude.
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Global notes:
Note (G1): Objects with double-lobe and multiple radio morphologies have
the infrared object reported first and the individual radio components
named a, b, c as necessary. Objects identified as DRaGONS JHHMM+DDMMa
in Simbad
Note (G2): Position of radio detection from the FIRST catalog (J2000.0).
Note (G3): Extended sources flag as follows:
Y = if the object shows visible extension in the FIRST image or if
the object is a double- or multiple-lobe radio source
N = if the object is unresolved in the radio image
Note (G4): Magnitudes are in the 2MASS system, which is slightly offset
from the CIT system, given by
Ks(2MASS)=K(CIT)+0.0000(J-K)CIT-0.024±0.003
(Carpenter, 2001AJ....121.2851C 2001AJ....121.2851C).
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 18-Jul-2008