J/ApJ/799/72 Binary AGNs from the VLA Stripe 82 survey (Fu+, 2015)
Radio-selected binary active galactic nuclei from the Very Large Array
Stripe 82 survey.
Fu H., Myers A.D., Djorgovski S.G., Yan L., Wrobel J.M., Stockton A.
<Astrophys. J., 799, 72 (2015)>
=2015ApJ...799...72F 2015ApJ...799...72F
ADC_Keywords: Active gal. nuclei ; Radio continuum ; Photometry, SDSS; Redshifts
Keywords: galaxies: active; galaxies: interactions; galaxies: nuclei;
radio continuum: galaxies
Abstract:
Galaxy mergers play an important role in the growth of galaxies and
their supermassive black holes. Simulations suggest that tidal
interactions could enhance black hole accretion, which can be tested
by the fraction of binary active galactic nuclei (AGNs) among galaxy
mergers. However, determining the fraction requires a statistical
sample of binaries. We have identified kiloparsec-scale binary AGNs
directly from high-resolution radio imaging. Inside the 92deg2
covered by the high-resolution Very Large Array survey of the Sloan
Digital Sky Survey (SDSS) Stripe 82 field, we identified 22 grade A
and 30 grade B candidates of binary radio AGNs with angular
separations less than 5" (10kpc at z=0.1). Eight of the candidates
have optical spectra for both components from the SDSS spectroscopic
surveys and our Keck program. Two grade B candidates are projected
pairs, but the remaining six candidates are all compelling cases of
binary AGNs based on either emission line ratios or the excess in
radio power compared to the Hα-traced star formation rate. Only
two of the six binaries were previously discovered by an optical
spectroscopic search. Based on these results, we estimate that ∼60% of
our binary candidates would be confirmed once we obtain complete
spectroscopic information. We conclude that wide-area high-resolution
radio surveys offer an efficient method to identify large samples of
binary AGNs. These radio-selected binary AGNs complement binaries
identified at other wavelengths and are useful for understanding the
triggering mechanisms of black hole accretion.
Description:
About a third of the Stripe 82 area has been mapped by the VLA at
1.4GHz in its most extended configurations between 2007 and 2009
(Hodge et al. 2011AJ....142....3H 2011AJ....142....3H). The VLA-Stripe82 survey covers a
total area of ∼92deg2. The VLA survey has an angular resolution of
1.8" and a median rms noise of 52uJy/beam.
We obtained longslit spectroscopy during part of 2011 October 23 (UT)
with the Low Resolution Imaging Spectrometer (LRIS) on the Keck I
telescope.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 95 44 *Grade A candidate binary radio AGNs
table2.dat 95 60 *Grade B candidate binary radio AGNs
table3.dat 96 12 *Properties of spectroscopically confirmed pairs
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Note on table1.dat, table2.dat and table3.dat: every two lines is a pair.
See Note (1) of table3 for the grade definition.
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See also:
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
J/MNRAS/441/1802 : Low-redshift QSOs in SDSS Stripe 82 (Karhunen+, 2014)
J/MNRAS/436/3581 : X-ray observations of Stripe 82 (LaMassa+, 2013)
J/ApJ/753/42 : Double-peaked AGN. I. Dual AGN candidates (Comerford+, 2012)
J/ApJ/746/L22 : Dual AGNs in the nearby Universe (Koss+, 2012)
J/A+A/525/A37 : Variability index of QSOs in SDSS Stripe 82 (Meusinger+, 2011)
J/ApJ/737/101 : AGN pairs from SDSS-DR7. I. (Liu+, 2011)
J/ApJ/716/866 : SDSS search for binary AGN (Smith+, 2010)
J/ApJ/708/427 : Type 2 AGNs with double-peaked [OIII] lines (Liu+, 2010)
J/ApJ/705/L76 : AGNs with double-peaked [OIII] lines (Wang+, 2009)
J/ApJ/690/20 : Models of the AGN and black hole populations (Shankar+, 2009)
J/A+A/487/993 : MAMBO Mapping of c2d Clouds and Cores (Kauffmann+, 2008)
J/MNRAS/362/9 : Radio-loud AGN in SDSS (Best+, 2005)
J/ApJ/554/803 : New VLA Sky Survey (NVSS) Cat of IRAS 2 Jy Galaxies (Yun+ 2001)
http://www.sdss3.org/ : SDSS-III home page
Byte-by-byte Description of file: table[12].dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- RName Radio designation (HHMMSS.ss+DDMMSS.s; J2000)
20- 24 F5.2 mJy S1.4pk [0.3/23.2] 1.4GHz peak flux density
(in mJy/beam)
26- 29 F4.2 mJy e_S1.4pk [0.05/0.8] S1.4pk uncertainty
31- 35 F5.2 mJy S1.4int [0.3/43.5] 1.4GHz integrated flux density
37- 54 A18 --- OName Optical designation of the counterpart
(HHMMSS.ss+DDMMSS.s; J2000)
56- 58 F3.1 arcsec Sep [1.6/6] Angular separation between the optical
counterparts in the pair
60- 63 F4.1 mag umag [17.5/28.1]? SDSS u-band Petrosian AB magnitude
65- 68 F4.1 mag gmag [15.7/25.7]? SDSS g-band Petrosian AB magnitude
70- 73 F4.1 mag rmag [14.8/25.5]? SDSS r-band Petrosian AB magnitude
75- 78 F4.1 mag imag [14.2/25.5]? SDSS i-band Petrosian AB magnitude
80- 83 F4.1 mag zmag [14/23.6]? SDSS z-band Petrosian AB magnitude
85- 90 F6.4 --- z [0.04/1]? Spectroscopic redshift
92- 95 A4 --- Inst Instrument used to obtained the spectroscopic
redshift (SDSS, BOSS or LRIS)
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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- 18 A18 --- RName Radio designation (HHMMSS.ss+DDMMSS.s; J2000)
20 A1 --- Q [AB] Grade of the candidate binary (1)
22- 27 F6.4 --- z [0.04/0.4] Spectroscopic redshift
29- 32 A4 --- Inst Instrument used to obtained z: LRIS or SDSS
34- 36 F3.1 arcsec aSep [2.5/4.6] Angular separation between the
optical counterparts in the pair
38- 41 F4.1 kpc pSep [4.1/12] Projected separation in kiloparsecs
43- 47 F5.1 km/s DelV [20.9/137] Radial velocity separation ΔV
49- 52 F4.1 [W/Hz] logP1.4 [22/25] Logarithmic radio power computed from
the integrated source flux density at 1.4GHz
54 A1 --- l_logLHa Limit flag on logLHa
56- 59 F4.1 [10-7W] logLHa [39.4/42.4] Log Hα luminosity in erg/s;
corrected for reddening and aperture-loss
61- 64 F4.1 0.1nm EWHa [-3/51] Hα equivalent width in the
observed frame in Å
66- 68 F3.1 0.1nm e_EWHa [0.1/1.2] EWHa uncertainty
70- 72 F3.1 --- [NII]/Ha [0.5/1.7]? [NII]λ6584/Hα line
flux ratio
74- 76 F3.1 --- e_[NII]/Ha [0.1/0.4]? The 1σ error on [NII]/Ha
78- 80 F3.1 --- [OIII]/Hb [0.3/1.3]? [OIII]λ5007/Hβ line
flux ratio
82- 84 F3.1 --- e_[OIII]/Hb [0.1/0.7]? The 1σ error on [OIII]/Hb
86- 91 A6 --- Rcl "Excess" or "Normal" Radio classification (2)
93- 96 A4 --- BPTcl "Comp" or "AGN2" classification based on the
BPT line-ratio diagram in Figure 6 (3)
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Note (1): Grade is (see section 7):
A = Both optical sources are well enclosed by the radio structure and are
clearly associated with a discrete radio source (i.e.,
"secure optical IDs"). In such cases, the PA between the optical IDs is
well aligned with that of the radio structure (i.e., "aligned PAs").
B = Secure optical ID and aligned PAs, but the radio morphologies suggest
that one of the optical components could be either a projected source
within the radio lobe generated by the primary component or emission-line
gas ejected by the radio outflow. Projected pairs are a significant
concern because of the high source density of the deep co-added SDSS
images. On average, ∼36% of optical sources in the SDSS co-adds would
have a nearby optical source within 5". However, we note that there is
no clear boundary between grades A and B and the separation is quite
subjective.
Note (2): Radio classification based on the Kauffmann et al.
(2003MNRAS.346.1055K 2003MNRAS.346.1055K) classification in Figure 7.
Note (3): Classification from Baldwin et al. 1981PASP...93....5B 1981PASP...93....5B:
Comp = AGN-star forming composite galaxy
AGN2 = type 2 Seyfert or LINER
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 12-Jun-2015