J/ApJ/789/112 Offset AGN Candidates (Comerford+, 2014)
Offset active galactic nuclei as tracers of galaxy mergers and supermassive
black hole growth.
Comerford J.M., Greene J.E.
<Astrophys. J., 789, 112 (2014)>
=2014ApJ...789..112C 2014ApJ...789..112C (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Redshifts ; Spectroscopy
Keywords: galaxies: active - galaxies: interactions - galaxies: nuclei
Abstract:
Offset active galactic nuclei (AGNs) are AGNs that are in ongoing
galaxy mergers, which produce kinematic offsets in the AGNs relative
to their host galaxies. Offset AGNs are also close relatives of dual
AGNs. We conduct a systematic search for offset AGNs in the Sloan
Digital Sky Survey by selecting AGN emission lines that exhibit
statistically significant line-of-sight velocity offsets relative to
systemic. From a parent sample of 18,314 Type 2 AGNs at z < 0.21, we
identify 351 offset AGN candidates with velocity offsets of
50 km/s <|Δv| < 410 km/s. When we account for projection effects
in the observed velocities, we estimate that 4%-8% of AGNs are offset
AGNs. We designed our selection criteria to bypass velocity offsets
produced by rotating gas disks, AGN outflows, and gravitational recoil
of supermassive black holes, but follow-up observations are still
required to confirm our candidates as offset AGNs. We find that the
fraction of AGNs that are offset candidates increases with AGN
bolometric luminosity, from 0.7% to 6% over the luminosity range
43 < log (Lbol) [erg/s] <46. If these candidates are shown to be
bona fide offset AGNs, then this would be direct observational
evidence that galaxy mergers preferentially trigger high-luminosity
AGNs. Finally, we find that the fraction of AGNs that are offset AGN
candidates increases from 1.9% at z = 0.1 to 32% at z = 0.7, in step
with the growth in the galaxy merger fraction over the same redshift
range.
Description:
Our selection criteria for offset AGNs are as follows. In the OSSY
catalog (Oh et al. 2011ApJS..195...13O 2011ApJS..195...13O), all forbidden lines are
forced to have the same kinematics, while all the Balmer lines are fit
with a separate kinematical model (e.g., Tremonti et al.
2004ApJ...613..898T 2004ApJ...613..898T). We use the velocities of the forbidden lines,
Balmer lines, and stellar absorption features measured in OSSY to
derive line-of-sight velocity offsets of the forbidden and Balmer
lines relative to the stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 78 351 Summary of Offset AGN Candidates
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See also:
J/MNRAS/392/1509 : Distribution of AGNs in galaxy clusters (Gilmour+, 2009)
J/MNRAS/398/1165 : AGN in nearby galaxies (Goulding+, 2009)
J/MNRAS/405/2062 : AGN candidates from 2MASS/ROSAT catalogs
(Kouzuma+, 2010)
J/MNRAS/407/2399 : AGN activity and black hole mass (McKernan+, 2010)
J/other/RMxAA/47.361 : AGN activity in isolated SDSS galaxies (Coziol+, 2011)
J/ApJS/218/8 : Swift AGN and Cluster Survey (SACS). I. (Dai+, 2015)
J/MNRAS/454/3722 : AGN in nearby low-mass galaxies (Sartori+, 2015)
J/ApJS/222/13 : Swift AGN and Cluster Survey (SWCL). II. SDSS
(Griffin+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [SDSS]
6- 24 A19 --- SDSS SDSS designation (JHHMMSS.ss+DDMMSS.s)
26- 33 F8.6 --- z Host galaxy redshift
35- 42 F8.6 --- e_z Uncertainty in z
44- 49 F6.1 km/s DelVB Line-of-sight velocity offset of
Balmer emission lines (1)
51- 54 F4.1 km/s e_DelVB Uncertainty in DelVB
56- 61 F6.1 km/s DelVF Line-of-sight velocity offset of
forbidden emission lines (1)
63- 66 F4.1 km/s e_DelVF Uncertainty in DelVF
68- 73 F6.1 km/s DelVW Weighted line-of-sight velocity offset (2)
75- 78 F4.1 km/s e_DelVW Uncertainty in DelVW
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Note (1): Relative to stellar absorption features.
Note (2): Mean of the Balmer and forbidden line-of-sight velocity offsets,
weighted by their inverse variances.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 08-Mar-2017