J/A+A/647/A195 Unknown active galactic nuclei study (Giuliani+, 2021)
A new panchromatic classification of unclassified Burst Alert Telescope
active galactic nuclei.
Giuliani L., Ghisellini G., Sbarrato T.
<Astron. Astrophys., 647, A195 (2021)>
=2021A&A...647A.195G 2021A&A...647A.195G (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Energy distributions ; Gamma rays ;
X-ray sources
Keywords: radiation mechanisms: non-thermal - radiation mechanisms: thermal -
galaxies: active - galaxies: jets - X-rays: general - galaxies: nuclei
Abstract:
We collect data at all frequencies for the new sources classified as
unknown active galactic nuclei (AGNs) in the latest Burst Alert
Telescope all-sky hard X-ray catalog. Focusing on the 36 sources with
measured redshift, we compute their spectral energy distribution (SED)
from radio to γ-rays with the aim to classify these objects. We
apply emission models that attempt to reproduce the obtained SEDs,
including: (i) a standard thin accretion disk together with an
obscuring torus and a X-ray corona; (ii) a two temperature thick
advection-dominated flow; (iii) an obscured AGN model, accounting for
absorption along the line of sight at kiloelectronvolt energies and in
the optical band; and (iv) a phenomenological model to describe the
jet emission in blazar-like objects. We integrate the models with the
SWIRE template libraries to account for the emission of the host
galaxy. For every source we found a good agreement between data and
our model. Considering that the sources were selected in the hard
X-ray band, which is rather unaffected by absorption, we expected and
found a large fraction of absorbed radio-quiet AGNs (31 out of 36) and
some additional rare radio-loud sources (5 out of 36), since the jet
emission in hard X-rays is important for aligned jets owing to the
boost produced by the beaming effect. With our work we can confirm the
hypothesis that a number of galaxies, whose optical spectra lack AGN
emission features, host an obscured active nucleus. The approach we
used proved to be efficient in rapidly identifying objects, which
commonly used methods were not able to classify.
Description:
Considering that the sources are selected in the hard X-ray band,
which is rather unaffected by absorption, we expected and found a
relatively large fraction of absorbed radio-quiet AGNs and some more
rare radio-loud sources. In fact, the jet emission in hard X-rays
becomes important for aligned jets as a result of the boost produced
by the beaming effect.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 125 31 Fit results for the sources SWIFT soft-X spectra
table2.dat 124 5 Fit parameters for the unknown AGNs
(phenomenological jet model with accretion
disk) identified as blazars
table3.dat 103 31 Fit parameters for unknown AGNs
(obscured AGN emission model)
table4.dat 37 36 BAT 105 unknown AGNs classification as results
from our work
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- Source Source name (SWIFT JHHMM.m+DDSS)
20- 24 F5.3 --- z Source redshift
26- 29 F4.1 ks ttot ?=- Total exposure time
31- 36 F6.3 --- alpha0.3-2 ?=- Photon index in the 0.3-2keV band (1)
38- 43 F6.3 --- b_alpha0.3-2 ?=- Lower value of alpha0.3-2 interval
45- 50 F6.3 --- B_alpha0.3-2 ?=- Upper value of alpha0.3-2 interval
52- 59 E8.3 mW/m2 f0.3-2 ?=- Total flux in the 0.3-2keV band
61- 68 E8.3 mW/m2 b_f0.3-2 ?=- Lower value of f0.3-2 interval
70- 77 E8.3 mW/m2 B_f0.3-2 ?=- Upper value of f0.3-2 interval
79- 84 F6.3 --- alpha2-10 ?=- Photon index in the 2-10keV band (1)
86- 91 F6.3 --- b_alpha2-10 ?=- Lower value of alpha2-10 interval
93- 98 F6.3 --- B_alpha2-10 ?=- Upper value of alpha2-10 interval
100-107 E8.3 mW/m2 f2-10 ?=- Total flux in the 2-10keV
109-116 E8.3 mW/m2 b_f2-10 ?=- Lower value of f2-10 interval
118-125 E8.3 mW/m2 B_f2-10 ?=- Upper value of f2-10 interval
--------------------------------------------------------------------------------
Note (1): The spectral indices alpha are defined as in Eq. (1).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- Source Source name (SWIFT JHHMM.m+DDMM)
20- 24 F5.2 --- CD Compton dominance ratio
26- 33 E8.3 10-7W nuLS Synchrotron peak luminosity in nuL(nu)
35- 38 F4.2 --- a1 a1 power-law slope
40- 43 F4.2 --- a2 a2 power-law slope
45- 48 F4.2 --- a3 a3 power-law slope
50- 56 E7.2 Hz nus Synchrotron peak frequency
58- 64 E7.2 Hz nuc Inverse-Compton peak frequency
66- 72 E7.2 Hz nucuts Cutoff frequency for low-energy spectra
74- 80 E7.2 Hz nucutc Cutoff frequency for high-energy spectra
82- 88 E7.2 Hz nuT Self-absorption frequency
90- 94 F5.2 --- ar Power-law slope for nu<nuT
96- 99 F4.2 Msun/yr dM/dt ?=- Accretion ratio
101-108 E8.3 Msun MBH ?=- Black hole mass (1)
110-113 F4.2 pc RT ?=- Obscuring torus radius (1)
115-118 F4.2 deg thetaT ?=- Obscuring torus covering angle (1)
120-124 F5.3 --- lEdd ?=- Accretion disk Eddington ratio (1)
--------------------------------------------------------------------------------
Note (1): We only found the emission signature of an accretion disk in the
first three objects.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- Source Source name (SWIFT JHHMM.m+DDMM)
20- 24 F5.2 Msun/yr dM/dt Accretion ratio
26- 33 E8.3 Msun M Black hole mass
35- 39 F5.3 --- lEdd Accretion disk Eddington ratio
41- 46 F6.2 pc RDB ?=- Dust belt radius
48- 51 F4.2 deg thetaDB ?=- Dust belt covering angle
53- 57 F5.2 pc RT Obscuring torus radius
59- 62 F4.2 deg thetaT Obscuring torus covering angle
64- 68 F5.3 --- f Intrinsic corona scattered component
(as fraction of the total flux)
70- 77 E8.3 cm-2 NH Hydrogen column density
79- 86 E8.3 cm-2 NHgal Hydrogen column density from host galactic gas
88- 91 F4.2 --- gamma gamma X-ray corona power-law index
93- 97 F5.2 --- G G normalization coefficient for the galaxy
emission template
99-103 F5.3 mag AB AB extinction at wavelength λB=0.44um
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- Source Source name (SWIFT JHHMM.m+DDMM)
20- 37 A18 --- Class Classification
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 31-May-2021