Search for molecular tori Violette

Impellizzeri

Alan Roy

Christian Henkel

Max-Planck-Institut für RadioastronomieMax-Planck-Institut für Radioastronomie Max-Planck-Institut für RadioastronomieMax-Planck-Institut für Radioastronomie

AGN unification Scheme: Type I and II AGN

The Unified AGN Scheme explains the difference between types 1 and 2 as due to different viewing angle towards fundamentally the same type of source/ physical system.

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

AGN unification Scheme: Type I and II AGN

The Unified AGN Scheme explains the difference between types 1 and 2 as due to different viewing angle towards fundamentally the same type of source/ physical system.

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

Dusty AGN torus is molecular gas rich

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

Observed 300 galaxies Low detection rates (absorption towards two Seyferts, maser emission in five).

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) 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.

No Molecular Absorption Lines (Of any galaxies Cygnus should have a torus!)

NLRGlarge X-ray absorbing column (1023.5 cm-2)very bright core (at 3mm)

Cygnus A: No CO Absorption from a Molecular TorusCygnus A: No CO Absorption from a Molecular Torus(Barvainis & Antonucci 1994 )

Search for OH non detection H2CO non detection

What about HI Absorption Lines?

Conway & Blanco (1995) found HI absorption against core of Cygnus A (atomic torus?)

Mundell et al (1995) found core abs. in N4151But 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

No Molecular Absorption Lines

Maloney, Begelman, & Rees (1994) Maloney, Begelman, & Rees (1994) postulate that lack of postulate that lack of absorption is due to radiative excitation by nonthermal absorption is due to radiative excitation by nonthermal

radio source:radio source:

High High TTex ex depletes lower rotational levels, decreasing opticaldepletes lower rotational levels, decreasing optical depth

Alternatively, clouds much smaller than the continuum source, Alternatively, clouds much smaller than the continuum source, with covering factor ~1, would produce many shallow lines with covering factor ~1, would produce many shallow lines

over over

100-300 km/s, hard to detect100-300 km/s, hard to detect.

Torus models predict large molecular abundance (Krolik & Lepp Torus models predict large molecular abundance (Krolik & Lepp 1989) 1989)

OH non-detection OH non-detection is OH radiatively excited ? is OH radiatively excited ?

Black (1995) predicts radiative excitation effects to affect the 18 Black (1995) predicts radiative excitation effects to affect the 18 cm OH line: cm OH line: Searches for 5 cm and 2.2 cm may be more Searches for 5 cm and 2.2 cm may be more profitable... profitable...

Our approach

Search for highly excited rotational states of OH:

2P3/2 J=5/2: 6035 MHz & 6030 MHz; 6049 MHz & 6016 6035 MHz & 6030 MHz; 6049 MHz & 6016 MHzMHz(120 K above the ground level)2P1/2 J=1/2: 4750 MHz; 4765 MHz & 4660 MHz4750 MHz; 4765 MHz & 4660 MHz (182 K)2P3/2 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 1023 cm-2 • S5cm > 50 mJy (high TB)• HPBL (indicate obscured BLR)

Results

Hydra ACygnus ANGC 1052NGC 1068NGC 1167NGC 1275NGC 1365NGC 1808NGC 2110NGC 2639NGC 2992NGC 3079NGC 4151

NGC 4261NGC 4388NGC 5135NGC 5506NGC 5793NGC 6240NGC 7130NGC 7674Mrk 3Mrk 348Mrk 463EMrk 1210Mrk 1073

F01475-0740IRAS 05414+5840IRAS 1345+1232Mrk 231Mrk 273

31 sources with S5cm > 50 mJy were selected for Effelsberg observations:

... Mrk 3 one of our best candidates!!

Results

Hydra ACygnus ANGC 1052NGC 1068NGC 1167NGC 1275NGC 1365NGC 1808NGC 2110NGC 2639NGC 2992NGC 3079NGC 4151

NGC 4261NGC 4388NGC 5135NGC 5506NGC 5793NGC 6240NGC 7130NGC 7674Mrk 3Mrk 348Mrk 463EMrk 1210Mrk 1073

F01475-0740IRAS 05414+5840IRAS 1345+1232Mrk 231Mrk 273

31 sources with S5cm > 50 mJy were selected for Effelsberg observations:

We detect rotationally excited OHClose to (or at) systemic velocity

VLBA Obsat 2 cm

5GHz OH detections

NGC 3079 NGC 3079 NGC 5793NGC 5793

•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 1022 cm-2

from X-rays: NH = 1.6 1022 cm-2

•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

13.434 GHz13.441 GHz

BW 16 MHz = 357km/s

Core:OH 0.125

FWHM: 90 km/s

NH= ... Coming soon!

rms ~ 5 mJy2 pc

90 km/s

Conclusions

• Detect highly excited, broad absorption lines (5 of 27, 19%)Detect highly excited, broad absorption lines (5 of 27, 19%)

• Most detections seen also in at least one other OH transitionMost 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 !!!!!!!!!!! Tentative detection of OH toward Cygnus A !!!!!!!!!!!

• All lines detected in absorption (1.6 GHz mainly only in emission)All lines detected in absorption (1.6 GHz mainly only in emission)

• Line widths few 100s-2,000 km sLine widths few 100s-2,000 km s-1-1 (close to nuclear region ?) (close to nuclear region ?) But still most non-detections must be explained !! Bimodal distribution of absorptions Bimodal distribution of absorptions very compact clouds ? very compact clouds ? Broad lines Broad lines infall/outflow ? Not a simple rotating torus ? infall/outflow ? Not a simple rotating torus ? X-ray absorber may be non-molecular in most galaxies ??X-ray absorber may be non-molecular in most galaxies ??

Cygnus A

Effelsberg observations

Each of the sources observed for 3 hours, PSW40MHz BW and 512 channelsAchieve a sensitivity level of 3.5 mJy (5)Corresponding to a line opacity of 0.002 to 0.07(and a column density of Nh cm-2 –black? &Compare to xray columns)

Total velocity covered in bw 2000 km s-1 (4 km s-1 per channel)Efbg resolution at 6 GHz 125´´

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 103

opacity in 6 GHz transition suppressed by factor 102

opacity in 13.4 GHz transition will increase slightly by factor 2.

Thus, absorption will strongly depend on transition one choosesto 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???)

Radiative excitation effects

Spiral Galaxy in Ursa MajorDistance: 15 Mpc (50 million light-years)Dimensions: The full image 4.9´( 21 kpc)Sy2 galaxy Nh = 1.6 1022 cm-2

FIR excess: Lfir = 19 109 Lsun

OH + HI broad absorption against nucleus (Baan & Irwin 1995)Most luminous H2O megamaser known

Baan & Irwin 1995

Say that we detect absorption,Two overlapping transitionsHigh vel extreme vel, near nucleusThat this can only take place in frontOf a strong continuum source –show 5cm Cont emission sjow where that is

We have two transitions of this source can find TexBaan, Henkel upper limit to 4.7 GHz (1987)See abs against a b c e?

Vel of our line compared with HI + OH absorptionNeed to do large vel gradient modellinf

•Width ~ 800 km s-1

•Line opcacity ~0.05

Middelberg et al. 2003

NGC 5793•Edge-on disk galaxy, Sy 2, 46 Mpc • Bright compact nucleus in radio continuum emission •The total flux density 191 mJy 6 cm•peculiar H2O 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)

www.nro.nao.ac.jp/ ~kotaro/Gals/gals.html

Hagiwara et al. 2000

Narrower line componentsBut total line width may be extending to few hundred km s-1

: 0.034