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Molecular Absorption Lines in the Circumnuclear Region
Satoko Sawada-Satoh 澤田-佐藤 聡子 Kagoshima University 鹿児島大学
Background & Motivations
AGN circumnuclear torusFuel tank of mass accretion onto SMBHInvented by astronomers, to explain Seyfert 1 & 2The size : < 10pc
How can we confirm it ?Requirement of 1 milliarcsec (mas) resolution to imageVLBI can acheive it
Urry & Padovani 1995
<10pc
AGN torus/disk & VLBI
1990s mid ~ :A pc-scale masering molecular disk surrounding a SMBH.A pc-scale dense absorbing gas torus.
2000s ~ :A torus model with several physical-phase layers inside.
Miyoshi+ 1995
340pc
HST VLBAFerranres+ (1996)
Jones & Wehrle (1997)
Molecular lines & VLBI
Molecular gas in AGN regionImportant clues to study AGN fuelingCompact (pc scale)High column density (1023-24 cm-2)
Advantages of VLBI for absorptionCan display thermal absorption in silhouette against a background synchrtron emission.Not detect the thermail emission
No contamination of emissionsSensitive to detect the compact and dense absorbing gas
beam size smaller, filling factor larger
Emitting gas Absorbing gas
HI absorption with VLA
Irwin & Seaquist 1991
VLA-CVLA-BVLA-A
higher resolution
NGC3079
The target NGC 1052 (1)
A nearby radio gal.AGN : LINER/Sy2Two-sided radio jet
AGN torus suggestedSeveral layersFree-free absorption (FFA) due to plasmaH2O maserOH absorptionRedshifted from Vsys
Ongoing infall ?1 pc
Eastern approaching jet
Western receding jet
Circumnuclear torus
Plasma gas region
XDR
Centralengine Lines of sight
B
C3
C2
6 4 0 -4 -62 -2
4
2
0
-2
-4Relat
ive D
eclin
atio
n [m
as]
Relative Right Ascension [mas]
0
-1
1600 1650 1700 1750 1800VLSR (km s-1)
0 -1 -2
-16-14-12-10-8-6-4-2 0 2 4 6
1300 1400 1500 1600 1700
Flux D
ensit
y (Jy
/bea
m)
Velocity (km/s)
-4
-3
-2
-1
0
1
2
3
4
5
1300 1400 1500 1600 1700
Flux D
ensit
y (Jy
/bea
m)
Velocity (km/s)
-6
-4
-2
0
2
4
6
8
10
1300 1400 1500 1600 1700
Flux D
ensit
y (Jy
/bea
m)
Velocity (km/s)
NGC 1052
-10
-8
-6
-4
-2
0
2
4
6
8
1300 1400 1500 1600 1700
Flux D
ensit
y (Jy
/bea
m)
Velocity (km/s)
NGC 1052 − VLBA 2 cm
0.2 pc
Blank field
(a)
(b)
(c)
(d)
(e)approaching jet
receding jet
H2O maser spots
FFA opacity
OH absorption
0.1pc
Radio Continuum
0.2pc
Vsys
0.2pc
Sawada-Satoh+ 2008
Sawada-Satoh+ 2008
Impellizzeri+ 2009
Kameno+ 2003
Past VLBI images of NGC 1052
The target NGC 1052 (2)
Molecular absorption at mm bandHCO+(1-0), HCN(1-0), CO(1-0)Velocity: 1400-1800 km/sRedshifted with respect to Vsys
Similar to OH and H2OInfall from the torus ? or, another motion ? Location of the absorption is a key !
Need a high resolution image
Liszt & Lucas 2004 (PdBI)
Kameno+ 2008
H2O maser
Vsys
HCN (1-0) absorption
The first VLBI map of HCN (1-0) (Sawada-Satoh+ ApJ 830 L3, 2016)
Two redshifted features, detected.The features around Vsys, not detected.Localized on the receding jet side.A depth of >10%, deeper with PdBI
HCN 1-0 optical depth maps HCN spectral profileOptical Depth0 0.1 0.2 0.3
DEC
Offs
et [m
as]
RA Offset [mas]6 4 2 0 -2 -4 -6
4
2
0
-2
-4
1698-1741 km s-1(b)
Optical Depth0 0.1 0.2 0.3
DEC
Offs
et [m
as]
RA Offset [mas]6 4 2 0 -2 -4 -6
4
2
0
-2
-4
1634-1677 km s-1(a)
-40
-20
0
1400 1500 1600 1700Flu
x Den
sity [
mJy]
Radial Velocity [km s-1]
HCN(1-0)
Vsys (a) (b)
(c)
0.2pc 0.2pcreceding jetreceding jet
1656 1719
Sawada-Satoh+ (2016)
I
KVN
(I) (II)
II
0.00
-0.05
-0.10
line/
cont
inuu
m
(I) (II)
Vsys
Liszt & Lucas 2004PdBI
A possible model
Several layers + clumpy HCN clouds (Sawada-Satoh+ 2016)
High opacity localized on the receding jet => Inclined torusAt least two narrow absorptions => Inhomogeneous, clumpy Redshifted velocity => Ongoing infall onto SMBH
(maser)
The line of sightHCN clouds
(b)(a)
Circum-nuclear
torus
Eastern approaching
jet
Westernreceding
jet
XDRPlasmaregion
Sawada-Satoh+ ApJ 830 L3, 2016
0.2pc
Physical properties
N(H2) : 1024-1025 cm-2 (HCN-to-H2 ratio of 109; Smith & Wardle 14)1-2 order higher than N(e) by FFA opacity (~1023; Kameno+ 01)
Infall rate : ~0.05-0.5 Msun/yrComparable to the rate estimated from X-ray luminosities (~0.04 ; Wu & Cao 06)
Label Vp Vp-Vsys Δv NHCN(T=100K) NHCN(T=230K)
[km/s] [km/s] [km/s] [1014 cm-2] [1014 cm-2]
I 1656 149 31.7 9.5 50II 1719 212 52.9 20 101
M = fvRinNHmHVin�
Column density of HCN 1-0 absorption Sawada-Satoh+ ApJ 830 L3, 2016
Summary
Conducted KVN observations of the HCN(1-0) & HCO+(1-0) absorption in NGC 1052.Our HCN results are naturally explained by an AGN tors
Two HCN absorption features are identified at redshifted velocities.Reached a depth of >10%, deeper than that of PdBI.Found N(H2) of 1024--1025 cm-2 (HCN-to-H2 ratio of 109), assuming a Tex of 100--200 KHigh opacity of HCN absorption localized on the receding jetHCN gas is clumpy, and traces ongoing infall onto SMBH.
The first VLBI detection of HCO+(1-0) absorption A broad absorption feature (~500km/s), unlike HCNLocalised on the receding jet side. Torus ?