Narrow line radio galaxies are like Seyfert 2's - their Seyfert 1/quasar nuclei are blocked by a dusty molecular torus seen edge-on.
Sy1 Sy2
Narrow line radio galaxies are like Seyfert 2's - their Seyfert 1/quasar nuclei are blocked by a dusty molecular torus seen edge-on.
Sy1 Sy2
If true, expect to observe molecular absorption against the compact, flat spectrum radio cores of NLRGs and (not only confirm the torus model, but also derive valuable physical and kinematic information on the torus material itself.) OH surveys OH surveys at 18 cm • Schmelz et al. 1986, • Staveley-Smith et al. 1992, • Baan et al. 1992 • ...
CO, HCN and HNC searches • Drinkwater et al. 1997 • Conway & Blanco (1995) Observed 300 galaxies Low detection rates (absorption towards two Seyferts, maser emission in five).
OH megamaser emission searches based on IR properties and result in detection rates of a few percent. Either OH is present at lower abundances or selection criteria are inadequate .
(Of any galaxies Cygnus should have a torus!) NLRG large X-ray absorbing column (10 23.5
very bright core (at 3mm) cm -2 ) Cygnus A: No CO Absorption from a Molecular Torus
(Barvainis & Antonucci 1994 )
Search for OH
H2CO
non detection non detection
Conway & Blanco (1995) found HI absorption against core of Cygnus A (atomic torus?) Mundell et al (1995) found core abs. in N4151 But in larger surveys of Seyfert 2 galaxies, Gallimore et al (1999) find that HI absorption tends to avoid the nucleus Conway & Blanco, Cyg A HI
Maloney, Begelman, & Rees (1994) postulate that lack of absorption is due to radiative excitation by nonthermal radio source: High T
ex
depletes lower rotational levels, decreasing optical depth Alternatively, clouds much smaller than the continuum source, with covering factor ~1, would produce many shallow lines over 100-300 km/s, hard to detect. Torus models predict large molecular abundance (Krolik & Lepp 1989) OH non-detection is OH radiatively excited ?
Black (1995) predicts radiative excitation effects to affect the 18 cm OH line: Searches for 5 cm and 2.2 cm may be more profitable...
Our approach
Search for highly excited rotational states of OH: 2 P 3/2 J=5/2: 6035 MHz & 6030 MHz; 6049 MHz & 6016 MHz (120 K above the ground level) 2 2 P (182 K) P 1/2 3/2 J=1/2: 4750 MHz; 4765 MHz & 4660 MHz J=7/2: 13434 MHz & 13441 MHz; 13442 MHz & 13433 MHz (290 K)
The sample
• Selected 31 Seyfert 2 galaxies • with a high X-ray absorbing columns 10 23 • S 5cm > 50 mJy (high T B ) • HPBL (indicate obscured BLR) cm -2
Results
31 sources with S 5cm > 50 mJy were selected for Effelsberg observations: Hydra A Cygnus A NGC 1052 NGC 1068 NGC 1167 NGC 1275 NGC 1365 NGC 1808 NGC 2110 NGC 2639 NGC 2992 NGC 3079 NGC 4151 NGC 4261 NGC 4388 NGC 5135 NGC 5506 NGC 5793 NGC 6240 NGC 7130 NGC 7674 Mrk 3 Mrk 348 Mrk 463E Mrk 1210 Mrk 1073 F01475-0740 IRAS 05414+5840 IRAS 1345+1232 Mrk 231 Mrk 273 ... Mrk 3 one of our best candidates!!
Results
31 sources with S 5cm > 50 mJy were selected for Effelsberg observations: Hydra A
Cygnus A NGC 1052
NGC 1068 NGC 1167 NGC 1275 NGC 1365 NGC 1808 NGC 2110 NGC 2639 NGC 2992 NGC 3079 NGC 4151 NGC 4261 NGC 4388 NGC 5135 NGC 5506 NGC 5793 NGC 6240 NGC 7130 NGC 7674 Mrk 3 Mrk 348 Mrk 463E Mrk 1210 Mrk 1073 F01475-0740 IRAS 05414+5840 IRAS 1345+1232 Mrk 231 Mrk 273 5GHz OH detections VLBA Obs at 2 cm We detect rotationally excited OH Close to (or at) systemic velocity
NGC 3079
•Width ~ 800 km s
-1
•Line opcacity
~ 0.05
•4.7 GHz non-detection •1.6 GHz abs (Baan et al. 1995)
NH = 1.7 10 22 cm -2 from X-rays: NH = 1.6 10 22 cm -2
NGC 5793
•Width ~ up to 1000 km s
-1
•Line opcacity
~ 0.034
•1.6 GHz abs (Hagiwara et al. 2000) •Narrower line components extending to 1000 km s -1 : 0.034
Cygnus A - VLBA
BW 16 MHz = 357km/s Core:
OH
0.125
FWHM: 90 km/s N H = ... Coming soon!
2 pc
90 km/s
rms ~ 5 mJy
• Detect highly excited, broad absorption lines (5 of 27, 19%) • Most detections seen also in at least one other OH transition (so far does not support radiative excitation models alone to explain the lack of detections) • Tentative detection of OH toward Cygnus A !!!!!!!!!!! • All lines detected in absorption (1.6 GHz mainly only in emission) • Line widths few 100s-2,000 km s -1 (close to nuclear region ?)
But still most non-detections must be explained !!
Bimodal distribution of absorptions very compact clouds ? Broad lines infall/outflow ? Not a simple rotating torus ?
X-ray absorber may be non-molecular in most galaxies ??
Cygnus A
Effelsberg observations Each of the sources observed for 3 hours, PSW 40MHz BW and 512 channels Achieve a sensitivity level of 3.5 mJy (5 Compare to xray columns) ) Corresponding to a line opacity of 0.002 to 0.07
(and a column density of Nh cm-2 –black? & Total velocity covered in bw 2000 km s -1 Efbg resolution at 6 GHz 125´´ (4 km s -1 per channel)
Radiative excitation effects Calculations of radiative excitation effects carried out on for Cygnus A by Maloney et al (1994) on CO molecule.
Similar calculations done by Black (1997) on OH. Results show that for torus located 10 pc from AGN: opacity in 1.6 GHz transition suppressed by factor 10 3 opacity in 6 GHz transition suppressed by factor 10 2 opacity in 13.4 GHz transition will increase slightly by factor 2.
Thus, absorption will strongly depend on transition one chooses to observe and how close gas is located to nucleus.
For 1-10 pc scale torus, radiative excitation effects strong at 1.6GHz
Gas could be found by looking at higher order transitions.
If molecular gas extends to 300 pc radiative excitation effects become minor.(are we looking at the right transitions???)
•Width ~ 800 km s -1 •Line opcacity ~ 0.05
Spiral Galaxy in Ursa Major Distance: 15 Mpc (50 million light-years) Dimensions: The full image 4.9´( 21 kpc) Sy2 galaxy N h = 1.6 10 22 cm -2 FIR excess: L fir = 19 10 9 L sun
Middelberg et al. 2003
OH + HI broad absorption against nucleus (Baan & Irwin 1995) Most luminous H 2 O megamaser known Say that we detect absorption, Two overlapping transitions High vel extreme vel, near nucleus That this can only take place in front Of a strong continuum source –show 5cm Cont emission sjow where that is We have two transitions of this source can find Tex Baan, Henkel upper limit to 4.7 GHz (1987) See abs against a b c e?
Vel of our line compared with HI + OH absorption Need to do large vel gradient modellinf Baan & Irwin 1995
NGC 5793
Narrower line components But total line width may be extending to few hundred km s -1
: 0.034
• •
Edge-on disk galaxy, Sy 2, 46 Mpc Bright compact nucleus in radio continuum emission
•
The total flux density 191 mJy 6 cm
•
peculiar H 2 O maser features in its center, indicating the presence of a rotating disk/torus (r = 0.13 pc)
•
Many molecules (CO, HI, OH..)
•
18 cm OH absorption (200 km s -1) ) Optical depth: 0.065
gas on pc scales could trace a compact molecular gas disk/torus (Hagiwara 2000)
Hagiwara et al. 2000
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