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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 (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), 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). 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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 78 351 Summary of Offset AGN Candidates
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
Bytes Format Units Label Explanations
1- 4 A4 --- --- [SDSS] 6- 24 A19 --- SDSS SDSS designation ( 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
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.
History: From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 08-Mar-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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