Chemistry in the Molecular Disk of Active Galactic

Nuclei

Nanase HaradaEric Herbst

Todd Thompson

The Ohio State University

What’s an active galactic nucleus (AGN)?

High luminosity from the galactic central region

Lbol ~ 1044-46erg/s High X-ray luminosity Supermassive black

hole at the center of the galaxy

MBH=106-10M

mass accretion

What’s an active galactic nucleus (AGN)?

Star burst (M82)

AGN-dominant(NGC 1068) (U)LIRG

(Arp220)

Milky Way

AGN-dominant

AGN Star-formation

What’s an active galactic nuclei (AGN)?

Star burst (M82)

AGN-dominant(NGC 1068) (U)LIRG

(Arp220)

Milky Way

(Ultra-) Luminous Infrared Galaxies ((U)LIRG)•dense gas•high infrared luminosity LIR>1011Lsun

(AGN) Star-

formation

What’s an active galactic nuclei (AGN)?

Star burst (M82)

AGN-dominant(NGC 1068) (U)LIRG

(Arp220)

Milky Way

Starburst

Star-formation

What’s an active galactic nuclei (AGN)?

Star burst (M82)

AGN-dominant(NGC 1068) (U)LIRG

(Arp220)

Milky Way

Milky Way

Star-formation

Molecular Observations in Galaxies

AGNs› High CN, HCN

abundances in central region of the galaxy (XCN≡[CN]/[Htot]~10-7)

(U)LIRGs› High HCN, HC3N, C2H2

abundances› (XHCN~10-7 -10-6,

› XC2H2>10-7)

Starburst› Higher HCO+/HCN ratio

than AGNs

Molecular Observations in Galaxies

AGNs› High CN, HCN

abundances in central region of the galaxy

› (XCN≡[CN]/[Htot]~10-7)

(U)LIRGs› High HCN, HC3N, C2H2

abundances› (XHCN~10-7 -10-6,

› XC2H2>10-7)

Starburst› Higher HCO+/HCN ratio

than AGNs

What causes the differences between these galaxies?Can molecules tell us about the X-ray activity in the galaxy with AGN?Can molecules tell us about the star formation rate?

This Work: Molecular abundance modeling of a molecular accretion disk of an AGN-dominant galaxy to 100 pc

1+1-dimensional model of a cylindrically symmetric disk

Chemical network: High-temperature OSU network (Harada et al. ApJ submitted)

Top View

Side View

Physical Conditions of an AGN disk

Blackbody Temperature T ~750 K(L/2x1045erg/s)1/4(r/pc)-

1/2

Density

)/exp()(

2

2

0

2

2

3

2

0

hzzG

vQ

rr

GM

GQ

s

BH

NGC 1068Lbol=2x1045erg/sMBH=1x107M

LX~1042erg/s (obs)Total hydrogen density (cm-3)

r(pc)

z(pc)

30

r 20

rInner region Outer regionh/r=0.1

Sources of Ionization

Ionization rate› X-rays › UV-photons› Cosmic-rays

Star formation

SupernovaeE~1051erg

OB starsLOB~104Lsun

Cosmic-rays

Cosmic-rays

UV-photons

AGN core

X-raysCosmic-

rays?

Sources of Ionization

Ionization rate› X-rays › UV-photons› Cosmic-rays

Star formation

SupernovaeE~1051erg

OB starsLOB~104Lsun

Cosmic-rays

Cosmic-rays

UV-photons

AGN core

X-raysCosmic-

rays?

Calculation of the Ionization rate

Cosmic-rays Star formation rate per

volume

ν=star formation efficiency (10-5 – 10-2) Assume some fraction of

energy from supernovae or OB stars go to ionization.

* tdyn

X-rays

max

min

)()(

)exp(4

sec

2

E

E

X

XX

dEEFEN

r

LF

Maloney et al (1996)

ResultsCN

•Observed abundances (source size ~70pc, inclination 40º)• XCN=(0.2-1)x10-

7

•More abundant at the outer radius

Star formation efficiency = 10-5

Star formation efficiency = 10-2

X-ray + low SF

X-ray + high SF

r(pc)

ResultsHCN

Star formation efficiency = 10-5

•Observed abundances • XHCN=(0.8-1)x10-7

•More abundant at the inner disk

Star formation efficiency = 10-2

X-ray + low SF

X-ray + high SF

r(pc)

ResultsHCO+

Star formation efficiency = 10-5

•Observed abundances • XHCO+=(0.6-2)x10-7

Star formation efficiency = 10-2

X-ray + low SF

X-ray + high SF

r(pc)

Discussion

Cosmic-ray penetration› The ionization rate may not be uniform

Disk structure› h/r may be r-dependent

UV-photons Radiative transfer Clumpiness Metalicity Shock waves

› How much does it dissociate? › Effect of sputtering?

Summary

X-rays alone can produce close to the lower limit of the observed abundances of CN, HCN although some star formation can help produce more.

We predict that the chemistry will be different in the inner core - less CN and more HCN.

Higher-resolution observation of ALMA can reveal gas properties in AGN disks in greater detail through molecular observations.

As a future work, comparison with other types of galaxies will be interesting.

Acknowledgments

Yuri Aikawa, Hideko Nomura George Hassel, Paul Rimmer, and Yezhe

Pei