J/MNRAS/470/3071 PAH features of AGN (Jensen+, 2017)
PAH features within few hundred parsecs of active galactic nuclei.
Jensen J., Hoenig S.F., Rakshit S., Alonso-Herrero A., Asmus D., Gandhi P.,
Kishimoto M., Smette A., Tristram K.R.W.
<Mon. Not. R. Astron. Soc. 470, 3071 (2017)>
=2017MNRAS.470.3071J 2017MNRAS.470.3071J (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Spectra, infrared
Keywords: galaxies: active galaxies - galaxies: Seyfert - infrared: galaxies
Abstract:
Spectral features from polycyclic aromatic hydrocarbon (PAH) molecules
observed in the mid-infrared (mid-IR) range are typically used to
infer the amount of recent and ongoing star formation on kiloparsec
scales around active galactic nuclei (AGN) where more traditional
methods fail. This method assumes that the observed PAH features are
excited predominantly by star formation. With current ground-based
telescopes and the upcoming James Webb Space Telescope, much smaller
spatial scales can be probed and we aim at testing if this assumption
still holds in the range of few tens to few hundreds of parsecs. For
that, we spatially map the emitted 11.3um PAH surface flux as a
function of distance from 0.4-4 arcsec from the centre in 28 nearby
AGN using ground-based high-angular-resolution mid-IR spectroscopy. We
detect and extract the 11.3um PAH feature in 13 AGN. The fluxes
within each aperture are scaled to a luminosity-normalized distance
from the nucleus to be able to compare intrinsic spatial scales of AGN
radiation spanning about two orders of magnitude in luminosity. For
this, we establish an empirical relation between the
absorption-corrected X-ray luminosity and the sublimation radius in
these sources. Once normalized, the radial profiles of the emitted PAH
surface flux show similar radial slopes, with a power-law index of
approximately -1.1, and similar absolute values, consistent within a
factor of a few of each other as expected from the uncertainty in the
intrinsic scale estimate. We interpret this as evidence that the
profiles are caused by a common compact central physical process,
either the AGN itself or circumnuclear star formation linked in
strength to the AGN power. A photoionization-based model of an AGN
exciting dense clouds in its environment can reproduce the observed
radial slope and confirms that the AGN radiation field is strong
enough to explain the observed PAH surface fluxes within ∼10-500pc of
the nucleus. Our results advice caution in the use of PAH emission as
a star formation tracer within a kpc around AGN.
Description:
We use archival low-resolution 8-13um spectroscopic data from Very
Large Telescope Spectrometer and Imager for the mid-InfraRed (VISIR)
observations of a sample of local AGN (Hoenig et al.
2010A&A...515A..23H 2010A&A...515A..23H; Burtscher et al. 2013, Cat. J/A+A/558/A149). We
supplement these data with new, unpublished observations taken in
2005, 2008 and 2010, which represent VISIR spectra for Circinus, ESO
138-G001, F9, F49 and NGC 1068.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 221 28 Characteristics of our AGN mid-IR spectroscopic
sample
sp/* . 250 Individual spectra
fits/* . 250 Individual fits spectra
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See also:
J/A+A/418/465 : Mid-infrared and hard X-ray emission in AGN (Lutz+, 2004)
J/ApJ/697/506 : Mid-infrared galaxy luminosity function from AGN (Dai+ 2009)
J/A+A/558/A149 : VLTI/MIDI AGN Large Program observations (Burtscher+, 2013)
J/MNRAS/439/1648 : Subarcsecond mid-infrared atlas of local AGN (Asmus+, 2014)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Object Object name
14- 17 A4 --- Type AGN type (1)
20- 21 I2 h RAh Right ascension (J2000)
23- 24 I2 min RAm Right ascension (J2000)
26- 29 F4.1 s RAs RAm Right ascension (J2000)
31 A1 --- DE- Declination sign (J2000)
32- 33 I2 deg DEd Declination (J2000)
35- 36 I2 arcmin DEm Declination (J2000)
38- 39 I2 arcsec DEs Declination (J2000)
41- 46 F6.4 --- z Redshift from NED
48- 52 F5.1 Mpc DL Luminosity distance (2)
54- 56 I3 deg Slit Slit orientation
58- 62 F5.2 [10-7W] logLX Absorption-corrected 2-10keV luminosity from
Asmus et al. (2015MNRAS.454..766A 2015MNRAS.454..766A)
64- 67 F4.2 [10-7W] e_logLX rms uncertainty on logLX
69- 73 F5.3 pc rsub Dust sublimation radius (3)
75- 79 F5.3 pc e_rsub rms uncertainty on rsub
81 I1 --- Ref [1/3] Reference (4)
83- 85 A3 --- PAH [yes/no ] PAH detected ?
87- 97 A11 --- sp0 Name of spectrum file extracted slit position
r=0" in subdirectory sp
99-111 A13 --- sp0.4 Name of spectrum file extracted slit position
r=0.4" in subdirectory sp
113-125 A13 --- sp0.8 Name of spectrum file extracted slit position
r=0.8" in subdirectory sp
127-139 A13 --- sp1.2 Name of spectrum file extracted slit position
r=1.2" in subdirectory sp
141-153 A13 --- sp1.6 Name of spectrum file extracted slit position
r=1.6" in subdirectory sp
154-165 A12 --- sp2 Name of spectrum file extracted slit position
r=2" in subdirectory sp
167-179 A13 --- sp2.4 Name of spectrum file extracted slit position
r=2.4" in subdirectory sp
181-193 A13 --- sp2.8 Name of spectrum file extracted slit position
r=2.8" in subdirectory sp
195-207 A13 --- sp3.2 Name of spectrum file extracted slit position
r=3.2" in subdirectory sp
209-221 A13 --- sp3.6 Name of spectrum file extracted slit position
r=3.6" in subdirectory sp
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Note (1): from Veron-Cetty and Veron (2010A&A...518A..10V 2010A&A...518A..10V, Cat. VII/258)
Note (2): luminosity distance based on CMB reference frame redshifts from NED
and H0 = 73 km s-1 Mpc-1, Ωm = 0.27, and Ωvac = 0.73
Note (3): dust sublimation radius calculated from equation ??? in this work,
except for IC4329 A (kishimoto et al., 2011A&A...527A.121K 2011A&A...527A.121K),
NGC 3783 (Glass, 1992MNRAS.256p..23G 1992MNRAS.256p..23G), and
Mark 509, NGC 3227, and NGC 4593 (Koshida et al., 2014ApJ...788..159K 2014ApJ...788..159K).
Note (4): Reference for the VISIR spectroscopic data as follows:
1 = This work
2 = Honig et al., 2010A&A...515A..23H 2010A&A...515A..23H
3 = Burtscher et al., 2013, Cat. J/A+A/558/A149
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.5 um lambda Wavelength
11- 22 E12.10 Jy S Flux density
25- 35 E11.10 Jy e_S rms uncertainty on S
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Acknowledgements:
Jens Jual Jensen, juel(at)dark-cosmology.dk
(End) Patricia Vannier [CDS] 16-Jun-2017