J/A+A/530/A147 Megamaser detection in Seyfert galaxies (Ramolla+, 2011)
Megamaser detection and nuclear obscuration in Seyfert galaxies.
Ramolla M., Haas M., Bennert V.N., Chini R.
<Astron. Astrophys. 530, A147 (2011)>
=2011A&A...530A.147R 2011A&A...530A.147R
ADC_Keywords: Galaxies, Seyfert ; Masers ; Galaxies, IR ; X-ray sources
Keywords: galaxies: Seyfert - galaxies: nuclei - masers - X-rays: galaxies -
infrared: galaxies
Abstract:
We revisit the relation between H2O maser detection rate and nuclear
obscuration for a sample of 114 Seyfert galaxies, drawn from the CfA,
12um and IRAS F25/F60 catalogs. These sources have mid-infrared
spectra from the Spitzer Space Telescope and they are searched for
X-ray and [OIII] (5007Å) fluxes from the literature. We use the
strength of the [OIV] (25.9um) emission line as tracer for the
intrinsic AGN strength. After normalization by [OIV] the observed
X-ray flux provides information about X-ray absorption. The
distribution of X-ray/[OIV] flux ratios is significantly different for
masers and non-masers: The maser detected Seyfert-2s (Sy 1.8-2.0)
populate a distinct X-ray/[OIV] range which is, on average, about a
factor four lower than the range of Seyfert-2 non-masers and about a
factor of ten lower than the range of Seyfert-1s (Sy 1.0-1.5).
Non-masers are almost equally distributed over the entire X-ray/[OIV]
range. This provides evidence that high nuclear obscuration plays a
crucial role for the probability of maser detection. Furthermore,
after normalization with [OIV], we find a similar but weaker trend for
the distribution of the maser detection rate with the absorption of
the 7um dust continuum. This suggests that the obscuration of the 7um
continuum occurs on larger spatial scales than that of the X-rays.
Hence, in the AGN unified model, at moderate deviation from edge-on,
the 7um dust absorption may occur without proportionate X-ray
absorption. The absorption of [OIII] appears unrelated to maser
detections. The failure to detect masers in obscured AGN is most
likely due to insufficient observational sensitivity.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 49 163 *Master sample
table3.dat 75 163 Measured fluxes and literature values for
sample and off-sample sources
refs.dat 46 71 References
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Note on table1.dat: All Seyferts from the three catalogs for which we
performed a search in the Spitzer archive:
* The magnitude limited complete sample of the CfA Redshift
Survey by Huchra & Burg (1992ApJ...393...90H 1992ApJ...393...90H)
* the 12um Active Galaxy Sample by Spinoglio & Malkan (1989ApJ...342...83S 1989ApJ...342...83S)
* the IRAS F25/F60 flux-ratio selected sample by de Grijp et al.
(1992A&AS...96..389D 1992A&AS...96..389D), as refined by Schmitt et al. (2003ApJS..148..327S 2003ApJS..148..327S)
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1 A1 --- n_Name [s] s for sample sources (G1)
3- 16 A14 --- Name Name
18- 27 F10.6 deg RAdeg J2000 right ascension in degrees
29- 38 F10.6 deg DEdeg J2000 declination in degrees
40- 49 A10 --- OName Other name
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1 A1 --- n_Name [sa] a for Additional off-sample data (G1)
3- 16 A14 --- Name Source name
18- 22 A5 --- Ref [abc, ] Catalog references for Name (1)
24- 27 F4.1 [Lsun] logLM ? H2O isotropic maser luminosities obtained
from Bennert et al., 2009ApJ...695..276B 2009ApJ...695..276B
(- for maser undetected source)
28 A1 --- n_logLM [?*] Flag on maser luminosity (2)
30- 32 F3.1 --- Type Seyfert type
34 A1 --- l_F[OIV] Limit flag on F[OIV]
35- 39 I5 aW/m2 F[OIV] ?=- [OIV] flux measurement from Ramolla
(2009, Thesis, Ruhr-Universitat, Bochum)
41- 44 I4 aW/m2 e_F[OIV] ? rms uncertainty on F[OIV]
46- 50 I5 aW/m2 F[OIII] ? [OIII] literature flux
52- 53 I2 --- r_F[OIII] ? Reference for F[OIII], in refs.dat file
55- 59 I5 10aW/m2 Fx ?=- 2-10keV literature flux (in 10-14erg/cm2/s)
61- 62 I2 --- r_Fx ? Reference for F2-10keV, in refs.dat file
64 A1 --- l_F7um Limit flag on F7um
65- 69 I5 10aW/m2 F7um ?=- 7um flux measurement from Ramolla
(2009, Thesis, Ruhr-Universitat, Bochum)
71- 75 I5 10aW/m2 e_F7um ? rms uncertainty on F7um
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Note (1): Catalog references for Names as follows:
a = CfA sample (Huchra & Burg, 1992ApJ...393...90H 1992ApJ...393...90H)
b = 12um sample (Spinoglio & Malkan, 1989ApJ...342...83S 1989ApJ...342...83S)
c = IRAS F25/F60 sample (de Grijp et al., 1992A&AS...96..389D 1992A&AS...96..389D)
Note (2): Flag on maser luminosity as follows:
? = sources unobserved for masers
* = MRK938 and NGC1320 are listed as Maser in Zhang et al.
(2010ApJ...708.1528Z 2010ApJ...708.1528Z) but have no luminosity information available
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference number
4- 22 A19 --- BibCode BibCode
24- 46 A23 --- Aut Author's name
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Global Notes:
Note (G1): 126 sources with [s] (sample) flag are common to tables 1 and 3.
Acknowledgements:
Michael Ramolla, Astronomisches Institut, Ruhr-Universitaet Bochum,
ramolla(at)astro.rub.de
(End) Patricia Vannier [CDS] 11-Feb-2011