J/ApJ/900/79 Chandra obs. of SDSS AGN pairs at zmed∼0.1 (Hou+, 2020)
A Chandra X-ray survey of optically selected AGN pairs.
Hou M., Li Z., Liu X.
<Astrophys. J., 900, 79 (2020)>
=2020ApJ...900...79H 2020ApJ...900...79H
ADC_Keywords: Active gal. nuclei; Redshifts; Optical; X-ray sources; Surveys
Keywords: Black hole physics ; Galaxy pairs ; Galaxy nuclei ;
X-ray active galactic nuclei
Abstract:
We present a Chandra archival study of optically selected active
galactic nucleus (AGN) pairs at a median redshift z∼0.1. Out of
1286 AGN pairs (with projected separations rp<100kpc and velocity
offsets Δv<600km/s) optically identified from the Sloan Digital
Sky Survey Seventh Data Release, we find 67 systems with archival
Chandra observations, which represents the largest sample of optically
selected AGN pairs studied in the X-ray. Among the 67 AGN pairs,
21 systems have both nuclei detected in the X-ray, 36 have one nucleus
detected in the X-ray, and 10 have no X-ray detection. The X-ray
detection rate, 78/134=58% (±7% 1σ Poisson errors), is
significantly higher than that (23/134=17%±4%) of a comparison
sample of star-forming galaxy pairs, lending support to the optical
AGN classification. In the conservative case where X-ray contamination
from star formation is removed, the X-ray detection rate becomes
27%±4%, consistent with predictions from the latest galaxy merger
simulations. The 2-10keV X-ray luminosity L2-10keV increases with
decreasing projected separation in AGN pairs for rp≳15kpc, suggesting
an enhancement of black hole accretion even in early-stage mergers. On
the other hand, L2-10keV appears to decrease with decreasing projected
separation at rp≲15kpc, which is contradictory to predictions from
merger simulations. The apparent decrease in L2-10 keV of AGN pairs at
rp≲15kpc may be caused by (i) enhanced absorbing columns from
merger-induced gas inflows, (ii) feedback effects from early-stage
mergers, and/or (iii) small number statistics. Future X-ray studies
with larger samples are needed to put our results on firmer
statistical ground.
Description:
We start from the 1286 optically selected AGN pairs or multiples at a
median redshift z∼0.1 from Liu+ (2011, J/ApJ/737/101).
Our final sample consists of 67 AGN pairs with Chandra archival
observations from the optically selected AGN pairs. Among them, 22
pairs are observed as the prime target. These include one triple AGN
candidate, SDSS J0858+1822, observed in Chandra Program GO-14700279
(PI: Liu); one triple AGN candidate, SDSS J1027+1749, optically
identified by Liu+ 2011ApJ...736L...7L 2011ApJ...736L...7L ; and five systems of AGN pairs
studied by Hou+ (2019ApJ...882...41H 2019ApJ...882...41H). The remaining 45 pairs were
serendipitously observed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 107 134 Information of AGN pairs with Chandra observation
table2.dat 152 78 X-ray properties of AGN pairs
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
J/AJ/129/2138 : Centers of early-type galaxies with HST (Lauer+, 2005)
J/AJ/131/1 : Binary quasars in the SDSS (Hennawi+, 2006)
J/AJ/131/2766 : Quasar luminosity function from SDSS-DR3 (Richards+, 2006)
J/ApJ/678/635 : Spectroscopy of quasar binary candidates (Myers+, 2008)
J/ApJS/182/216 : Surface photometry of Virgo ellipticals (Kormendy+, 2009)
J/ApJ/719/1672 : SDSS binary quasars at high redshift. I. (Hennawi+, 2010)
J/ApJ/737/101 : AGN pairs from SDSS-DR7. I. (Liu+, 2011)
J/ApJS/201/23 : Spectroscopy of 88 z<0.7 SDSS QSOs (Eracleous+, 2012)
J/ApJ/746/L22 : Dual AGNs in the nearby Universe (Koss+, 2012)
J/AJ/144/125 : Photometry & spectroscopy of Markarian 266 (Mazzarella+, 2012)
J/ApJ/789/140 : SDSS quasars balmer emission lines (Liu+, 2014)
J/A+A/578/A110 : Isolated galaxies, pairs & triplets (Argudo-Fernandez+, 2015)
J/MNRAS/453/1562 : CRTS close supermassive black hole binaries (Graham+, 2015)
J/ApJ/876/53 : Chandra X-ray point sources in the Fornax cluster (Jin+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- SDSS Identifier (JHHMMSS.ss+DDMMSS.s)
21- 29 F9.5 deg RAdeg Right Ascension (J2000) (1)
31- 39 F9.5 deg DEdeg Declination (J2000) (1)
41- 46 F6.4 --- z [0.02/0.2] Spectroscopic redshift
from Liu+ 2011, J/ApJ/737/101
48- 51 F4.1 kpc rp [2.3/99] Projected physical separation
of AGN pair
53- 56 F4.1 [Msun] logM* [8.8/11.4]? log stellar mass
58- 63 F6.1 10-17mW/m2 FOIII [5/4902]? The [OIII] emission line
flux; 10-17erg/s/cm2
65- 68 F4.1 10-17mW/m2 e_FOIII [1/35]? The 1σ uncertainty in FOIII
70- 74 F5.2 Msun/yr SFR [-1/17.4] Star Formation Rate (2)
76- 80 F5.2 Msun/yr E_SFR [0/45] Upper uncertainty in SFR
82- 86 F5.2 Msun/yr e_SFR [0/16] Lower uncertainty in SFR
88- 92 I5 --- ObsID [868/20466] Chandra observation identifier
93- 93 A1 --- f_ObsID [*] Flag on ObsID (3)
95- 99 F5.1 ks Exp [1.7/592.2] Exposure time
101-105 F5.2 [10-7W] logLX [39.38/42.05] log 0.5-8keV limiting X-ray
luminosity for source detection; erg/s
107-107 I1 --- Flag [0/1] Detection flag (1=detection)
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Note (1): Centroid position of the AGNs.
Note (2): Given by the MPA-JHU DR7 catalog inferred from Dn(4000).
Note (3): Flag on ObsID as follows:
* = target with multiple Chandra observations. The observation ID of all
available observations are listed here (the ID listed in table is
the one observation with the longest exposure time).
J1259+2757 = 555 556 1086 1112 1113 1114 9714 10672 13993 13994 13995
13996 14406 14410 14411 14415
J0320+4123 = 11715 11716 12037
J0924+0225 = 5604 11562 11563 11564 11565 11566
J1605+1746 = 4996 19592 20086 20087
J0805+2410 = 9270 19496 20888 20889 20890 20891
J1415+5204 = 5853 5854 6222 6223 6366 7187
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- SDSS Identifier (JHHMMSS.ss+DDMMSS.s)
21- 29 F9.5 deg RAdeg Right Ascension (J2000) (2)
31- 38 F8.5 deg DEdeg Declination (J2000) (2)
40 A1 --- l_Cts Limit flag on Cts
42- 47 F6.1 ct Cts [2/3836] Observed net counts in
0.5-8keV band
49- 52 F4.1 ct E_Cts [2/66]? Upper uncertainty in Cts
54- 57 F4.1 ct e_Cts [1/65]? Lower uncertainty in Cts
59 A1 --- l_F0.5-2 Limit flag on F0.5-2
61- 67 F7.2 10-6ph/cm2/s F0.5-2 [0.2/289] Observed 0.5-2keV photon
flux
69- 73 F5.2 10-6ph/cm2/s E_F0.5-2 [0.1/12]? Upper uncertainty in F0.5-2
75- 79 F5.2 10-6ph/cm2/s e_F0.5-2 [0.08/12]? Lower uncertainty in F0.5-2
81 A1 --- l_F2-8 Limit flag on F2-8
83- 88 F6.2 10-6ph/cm2/s F2-8 [0.16/364] Observed 2-8keV photon flux
90- 93 F4.2 10-6ph/cm2/s E_F2-8 [0.07/8]? Upper uncertainty in F2-8
95- 98 F4.2 10-6ph/cm2/s e_F2-8 [0.05/8]? Lower uncertainty in F2-8
100 A1 --- l_logL0.5-2 Limit flag on logL0.5-2
102- 107 F6.2 [10-7W] logL0.5-2 [39.3/43.6] Log 0.5-2keV unabsorbed
luminosity
109- 112 F4.2 [10-7W] E_logL0.5-2 [0.01/0.3]? Upper uncertainty in
logL0.5-2
114- 117 F4.2 [10-7W] e_logL0.5-2 [0.01/0.5]? Lower uncertainty in
logL0.5-2
119 A1 --- l_logL2-10 Limit flag on logL2-10
121- 126 F6.2 [10-7W] logL2-10 [39.5/44] Log 2-8keV unabsorbed
luminosity
128- 131 F4.2 [10-7W] E_logL2-10 [0.01/0.3]? Upper uncertainty in
logL2-10
133- 136 F4.2 [10-7W] e_logL2-10 [0.01/0.4]? Lower uncertainty in
logL2-10
138- 142 F5.2 --- HR [-0.96/0.96] Hardness ratio (3)
144- 147 F4.2 --- E_HR [0/0.6] Upper uncertainty in HR
149- 152 F4.2 --- e_HR [0.01/0.61] Lower uncertainty in HR
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Note (2): Centroid position of the x-ray counterpart.
Note (3): HR=(H-S)/(H+S) where "H"=2-8keV and "S"=0.5-2keV.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 16-Dec-2021