J/MNRAS/475/5179 Spatially offset AGN cand. in CLASS survey (Skipper+, 2018)
Spatially offset AGN candidates in the CLASS survey.
Skipper C.J., Browne I.W.A.
<Mon. Not. R. Astron. Soc., 475, 5179-5193 (2018)>
=2018MNRAS.475.5179S 2018MNRAS.475.5179S (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Positional data ; Redshifts
Keywords: galaxies: active - galaxies: interactions - galaxies: nuclei
Abstract:
Prompted by a recent claim by Barrows et al. that X-ray active
galactic nuclei (AGNs) are often found significantly offset from the
centres of their host galaxies, we have looked for examples of compact
radio sources that are offset from the optical centroids of nearby
(z<0.2) galaxies. We have selected a sample of 345 galaxies from the
Sloan Digital Sky Survey (SDSS) galaxy catalogue, which have nearby
compact radio sources listed in the Cosmic-Lens All Sky Survey (CLASS)
catalogue. We find only three matches ∼0.87 per cent of the
sample) with offsets greater than 600 milliarcsec (mas), which is
considerably fewer than we would have expected from the Barrows et al.
X-ray survey. We fit our histogram of offsets with a Rayleigh
distribution with σ=60.5mas, but find that there is an excess
of objects with separations greater than ∼150mas. Assuming that
this excess represents AGNs with real offsets, we place an upper limit
of ∼17 per cent on the fraction of offset AGNs in our
radio-selected sample. We select 38 objects with offsets greater than
150mas, and find they have some diverse properties: Some are well
known, such as Mrk 273 and Arp 220, some have dust lanes, which may
have affected the optical astrometry, and a few are strong new
candidates for offset AGNs.
Description:
Our sample was constructed from the SDSS galaxy catalogue by cross
matching sources with the z<0.2 OSSY catalogue (Oh et al.,
2011ApJS..195...13O 2011ApJS..195...13O), and the CLASS catalogue (Myers et al.,
2003MNRAS.341....1M 2003MNRAS.341....1M, Browne et al., 2003MNRAS.341...13B 2003MNRAS.341...13B, Cat. VIII/72)
of compact radio sources. Our sample comprised 374 galaxies.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 257 345 *The high-offset galaxies
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Note on table1.dat: galaxies identified as AGNs, and with the closest matched
CLASS source offset by an angle of at least 150mas, and with a flux density
of at least 8mJy.
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See also:
VIII/72 : CLASS survey of radio sources (Myers+, 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- SDSS SDSS catalog ID (SDSS JHHMMSS.ss+DDMMSS.s)
26- 43 I18 --- OSSY OSSY catalog ID
45- 57 F13.9 deg RAdeg OSSY right ascension (J2000)
59- 70 F12.9 deg DEdeg OSSY declination (J2000)
72- 84 E13.7 --- z Redshift of galaxy from OSSY catalog
86-145 A60 --- OName Other common galaxy names (i.e. NGC, Messier,
UGC, IC, Markarian catalog IDs)
147-153 A7 --- Sy/LINER [SEYFERT LINER] Seyfert or LINER, based upon
the line strengths from the OSSY catalog
155-171 A17 --- CLASS CLASS catalog ID (GB6JHHMMSS+DDMMSS)
173-185 F13.9 deg RANdeg Right ascension (J2000) of nearest CLASS
source to galaxy position
187-198 F12.9 deg DENdeg Declination (J2000) of nearest CLASS source
to galaxy position
200-207 F8.3 mas OffsetN Offset between galaxy position and nearest
CLASS source
209-213 F5.1 mJy FluxN Flux density at 8.46GHz of
nearest CLASS source
215-228 F14.10 deg RABdeg ? Right ascension (J2000) of brightest CLASS
source (1)
230-242 F13.10 deg DEBdeg ? Declination (J2000) of brightest CLASS
source (1)
244-251 F8.3 mas OffsetB ? Offset between galaxy position and brightest
CLASS source (1)
253-257 F5.1 mJy FluxB ? Flux density at 8.46GHz of
brightest CLASS source (1)
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Note (1): The brightest CLASS source is usually the nearest to the galaxy
position, and in these instances the last four columns are unpopulated.
These four columns are only populated if there is a brighter CLASS detection
within the central bulge of the host galaxy, but further from the recorded
galaxy position.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 08-Apr-2021