J/ApJ/777/64 A search for double-peaked AGNs in AGES (Comerford+, 2013)
Dual supermassive black hole candidates in the AGN and Galaxy Evolution Survey.
Comerford J.M., Schluns K., Greene J.E., Cool R.J.
<Astrophys. J., 777, 64 (2013)>
=2013ApJ...777...64C 2013ApJ...777...64C
ADC_Keywords: Active gal. nuclei ; Redshifts ; Spectra, red ; Surveys
Keywords: galaxies: active; galaxies: interactions; galaxies: nuclei
Abstract:
Dual supermassive black holes (SMBHs) with kiloparsec-scale
separations in merger-remnant galaxies are informative tracers of
galaxy evolution, but the avenue for identifying them in large numbers
for such studies is not yet clear. One promising approach is to target
spectroscopic signatures of systems where both SMBHs are fueled as
dual active galactic nuclei (AGNs), or where one SMBH is fueled as an
offset AGN. Dual AGNs may produce double-peaked narrow AGN emission
lines, while offset AGNs may produce single-peaked narrow AGN emission
lines with line-of-sight velocity offsets relative to the host galaxy.
We search for such dual and offset systems among 173 Type 2 AGNs at
z<0.37 in the AGN and Galaxy Evolution Survey (AGES), and we find two
double-peaked AGNs and five offset AGN candidates. When we compare
these results to a similar search of the DEEP2 Galaxy Redshift Survey
and match the two samples in color, absolute magnitude, and minimum
velocity offset, we find that the fraction of AGNs that are dual SMBH
candidates increases from z=0.25 to z=0.7 by a factor of ∼6 (from 2/70
to 16/91, or 2.9-1.9+3.6% to 18-5+5%). This may be associated
with the rise in the galaxy merger fraction over the same cosmic time.
As further evidence for a link with galaxy mergers, the AGES offset
and dual AGN candidates are tentatively ∼3 times more likely than the
overall AGN population to reside in a host galaxy that has a companion
galaxy (from 16/173 to 2/7, or 9-2+3% to 29-19+26%). Follow-up
observations of the seven offset and dual AGN candidates in AGES will
definitively distinguish velocity offsets produced by dual SMBHs from
those produced by narrow-line region kinematics, and will help sharpen
our observational approach to detecting dual SMBHs.
Description:
Our sample consists of a catalog of optical galaxy spectra observed
for AGES (Kochanek et al. 2012, J/ApJS/200/8; Cool et al.
2012ApJ...748...10C 2012ApJ...748...10C). Using Hectospec, an optical fiber-fed
spectrograph with 1.5" fibers on the MMT 6.5m telescope, AGES observed
7.7deg2 of the Bootes field in the NOAO Deep Wide-Field Survey
(Jannuzi & Dey 1999ASPC..191..111J 1999ASPC..191..111J). The resultant spectra have a
wavelength coverage of 3700-9200Å, and the spectral resolution is
6Å, yielding R∼1000.
We measured the fluxes of nine emission lines (Hβ; [OIII]
λλ4959, 5007; [OI] λ6300; Hα; [NII]
λλ6548, 6584; [SII] λλ6716, 6731) covered
in the wavelength range of our sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 125 175 Observed properties of the 173 AGN and Galaxy
Evolution Survey (AGES) Type 2 AGNs
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See also:
J/ApJ/769/95 : [NeV] or [NeIII] double peaked SDSS quasars (Barrows+, 2013)
J/ApJS/201/23 : Spectroscopy of 88 z<0.7 SDSS QSOs (Eracleous+, 2012)
J/ApJ/753/42 : Double-peaked AGN. I. Dual AGN candidates (Comerford+, 2012)
J/ApJS/200/8 : AGES: the AGN and Galaxy Evolution Survey (Kochanek+, 2012)
J/ApJ/746/L22 : Dual AGNs in the nearby Universe (Koss+, 2012)
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/614/91 : Black hole mass and accretion rate of AGNs (Wu+, 2004)
J/AJ/126/1720 : ugriz and Hα of double-peaked AGN (Strateva+, 2003)
J/AJ/126/1183 : Major galaxy mergers at z≲3 (Conselice+, 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- --- [NDWFS]
7- 25 A19 --- NDWFS Source identifier (JHHMMSS.ss+DDMMSS.s) (1)
27- 32 F6.4 --- z [0.04/0.37] Host galaxy redshift (2)
34- 39 F6.1 km/s HbVoff [-239/221] The Hβ velocity offset
41- 45 F5.1 km/s e_HbVoff [11/286] Uncertainty in HbVoff
47- 52 F6.1 km/s O3Voff [-372/228] The [OIII] velocity offset
54- 58 F5.1 km/s e_O3Voff [3/387] Uncertainty in O3Voff
60- 65 F6.1 km/s HaVoff [-191/227] The Hα velocity offset
67- 71 F5.1 km/s e_HaVoff [8/196] Uncertainty in HaVoff
73- 77 F5.2 --- O3/Hb [1/14] The [OIII] 5007 to Hβ ratio
79- 82 F4.2 --- e_O3/Hb [0.01/7] Uncertainty in O3/Hb
84- 87 F4.2 --- N2/Ha The [NII] 6584 to Hα ratio
89- 92 F4.2 --- e_N2/Ha Uncertainty in N2/Ha
94- 98 F5.2 --- S2/Ha The [SII] 6716,6731 to Hα ratio
100-103 F4.2 --- e_S2/Ha Uncertainty in S2/Ha
105-108 F4.2 --- O1/Ha The [OI] 6300 to Hα ratio
110-113 F4.2 --- e_O1/Ha Uncertainty in O1/Ha
115-123 A9 --- Class Classification of double-peaked AGNs and offset
AGN candidates from table 2; column added by CDS
125 A1 --- n_Class [b] Also consistent with Seyfert class (3)
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Note (1): The double-peaked AGNs have two entries each; the first gives the
properties of the blueshifted component, while the second gives the
properties of the redshifted component.
Note (2): The uncertainties on the host galaxy redshifts are 0.0003.
Note (3): b = The line ratios, within their errors, are consistent with
classification as a Seyfert.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 07-Apr-2015