…and AGN

Marcello Giroletti

Dipartimento di Astronomia, UniBOIstituto di Radioastronomia, INAF

A L M A & A G N

Active Galactic Nuclei

ALMA --> Science with ALMA --> Cosmology & Extragalactic Astronomy --> Active Galactic Nuclei

AGN can be studied "in depth", because of the low synchrotron and dust opacity and the unprecedented angular resolution of millimeter VLBI. The ALMA will provide millijansky VLBI sensitivity, corresponding to brightness temperatures as low as 100-10000 K. The optically-obscured molecular tori and the circumnuclear starbursts of nearby galaxies can be resolved. The presence of central black holes can be studied kinematically in a large number of galaxies.

(from http://www.eso.org/projects/alma/science/cosmo.html)

A L M A & A G N

ALMA frequency and resolution

ALMAmm-VLBI

A L M A & A G N

The central engine of AGN

New possibilities opened by ALMA Study jet physical properties and production

mechanisms Discover new classes of AGN, youngest objects Observations of the galactic center Structure of the torus and ISM in the vicinity of the

AGN operating as

independent interferometer most sensitive element of a mm-VLBI array

A L M A & A G N

Nuclei of radio loud AGN

mm and sub-mm observations can probe closer to the base of the jet than any other

waveband except X-ray much closer than cm observations because

synchrotron self-absorption opacities are lower monitoring of variability and polarization of

thousand of blazars study correlation between mm and -ray flares

derive time lags linear/quadratic, SSC/IC

A L M A & A G N

As mm-VLBI element

hundreds of possible targets not only brightest/closest/most

peculiar see jet collimation region acceleration/deceleration velocity structures relation to other wavelenghts may even include ARISE (90

GHz, 30 m, space VLBI)

mm-VLBI current with ALMA

sensitivity 100 mJy 10 mJy

resolution 50 as 10 as

(Ly et al. 2004)

A L M A & A G N

The youngest AGN?

compact symmetric objects are YOUNG

anticorrelation between linear size and turnover frequency

high frequency surveys are expected to detect newly born AGN

stand-alone and mm-VLBI follow ups can constrain formation mechanisms and rates of expansion

expect the unexpected…

(O’Dea 1998)

A L M A & A G N

mm-VLBI observations of SgrA*

(Falcke et al. 2000)

General Relativity

calculation VLBI at 0.6 mm VLBI at 1.3 mm

maximally rotating BH

non rotating BH

A L M A & A G N

Molecular gas around AGN

molecular lines such as 12CO (J=2-1) are good tracers of gas mass in the torus (cold, dense, clumpy)

confirm unified models separate

AGN/starbursts study inhomogeneities interactions between jet

and ISM probe physical and

chemical conditions at unmatched resolution(Wada & Tomisaka 2004)

A L M A & A G N

Conclusions

ALMA can be most fruitful also for AGN study high frequency: low opacity, cores & young sources

(HFP) sensitivity: surveys and monitoring lines: condition of the ISM surrounding the central

engine mm-VLBI

is already feasible will yield resolution better than any other astronomical

instrument ever will shed light on the vicinity of SMBHs