Accreting flows at (sub) Accreting flows at (sub) millimeter wavelengthsmillimeter wavelengths

P. IvanovP. Ivanov

P.N. Lebedev Physical InstituteP.N. Lebedev Physical Institute

Radiatively inefficient accreting flows onto Radiatively inefficient accreting flows onto

supermassive black holessupermassive black holes Perhaps the most studied Perhaps the most studied

example is the source in our example is the source in our own Galaxy - own Galaxy - Sagittarius A*Sagittarius A*

BasicBasic parameters: distance D parameters: distance D ~~ 8kpc, mass M 8kpc, mass M ~~ 4*10 4*1066MM☼☼, ,

bolometric luminosity ~ bolometric luminosity ~ 3*103*103636ers/s, gravitational radius ers/s, gravitational radius rrgg=2GM/c=2GM/c22

~ 10~ 101212cm, cm,

angular size ~ rangular size ~ rgg/D ~10/D ~10μμas as

(observed structures are of (observed structures are of order of this size)order of this size)

Exhibits variability at time scales Exhibits variability at time scales of minutes to hours in NIR, X-of minutes to hours in NIR, X-rays and submillimeter bandsrays and submillimeter bands

Spectral energy distribution of the emission from Sgr A*. This plot shows the extinction and absorption corrected luminosities. All error bars are ±1 sigma and include statistical and systematic errors. Black triangles denote the radio spectrum of Sgr A*. Open grey circles mark various infrared upper limits from the literature. The three X-ray data ranges are (from bottom to top) the quiescent state as determined with Chandra (black; Baganoff et al., 2003), the autumn 2000 Chandra flare (red; Baganoff et al., 2000), and the autumn 2002 flare observed by XMM (light blue; Porquet et al., 2003). Open red squares with crosses mark the de-reddened peak emission (minus quiescent emission) of the four NIR flares. Open blue circles mark the de-reddened H, KS, and L' luminosities of the quiescent state, derived from the local background subtracted flux density of the point source at the position at Sgr A*, thus eliminating the contribution from extended, diffuse light due to the stellar cusp around Sgr A*.

http://www.mpe.mpg.de/ir/GC/res_general.php?lang=en

VariabilityVariability

Physical ConditionsPhysical Conditions The small value of luminosity of Sgr AThe small value of luminosity of Sgr A* * implies that either implies that either

the accretion rate in the innermost region of the system the accretion rate in the innermost region of the system

is rather small (dM/dt is rather small (dM/dt ~ 10~ 10-9-9-10-10-8 -8 MM☼☼/yr) /yr) oror efficiency of efficiency of conversion of gravitational energy to radiation is quite conversion of gravitational energy to radiation is quite small small ~ 10~ 10-6-6. The former case is preferred by numerical . The former case is preferred by numerical modeling. In this case the accreting flow is geometrically modeling. In this case the accreting flow is geometrically

thick with h/r ~ 0.5, hot (Tthick with h/r ~ 0.5, hot (Tpp ~ 10 ~ 101111-10-1012 12 K, TK, Tee ~ 10 ~ 101010-10-1011 11

K), optically thin, with ratio of magnetic field energy to K), optically thin, with ratio of magnetic field energy to the thermal energy of order of 10the thermal energy of order of 10-3 --3 -1010-1-1. The density . The density profile is rather “flat” n ~ r profile is rather “flat” n ~ r -3/2+p -3/2+p , with p=0.5-1. Close to , with p=0.5-1. Close to black hole n ~ 10black hole n ~ 1066- 10- 1088cmcm-3-3. The energy conversion . The energy conversion factor is of order of 10factor is of order of 10-3-3 for this case. for this case.

Modeling of spectraModeling of spectra

Possible sourcesPossible sources ofof variabilityvariability in the sub mm rangein the sub mm range could be: 1) intrinsic variability due to MHD turbulencecould be: 1) intrinsic variability due to MHD turbulence

2) reconnection events/hot spots in the disc 3) excitation2) reconnection events/hot spots in the disc 3) excitation of different modes of disc’s pulsations (e.g. so-called of different modes of disc’s pulsations (e.g. so-called

“corrugation” or “twisted” modes). These possibilities are“corrugation” or “twisted” modes). These possibilities are exploited in recent numerical models of Sgr Aexploited in recent numerical models of Sgr A** . .

However, to disentangle However, to disentangle them more observations in them more observations in different wavebands, longer sets of data and more different wavebands, longer sets of data and more resolution are required. Polarization measurements are resolution are required. Polarization measurements are also important. also important.

The last three possibilities are provided by The last three possibilities are provided by Millimetron. Millimetron.

Numerical modelsNumerical models

Dexter et al, 2010

Recent simulationsRecent simulations

Other galaxiesOther galaxies

Sensitivity and resolution requirementsSensitivity and resolution requirements

In the interferometer mode Millimetron will have sensitivity of order of 10In the interferometer mode Millimetron will have sensitivity of order of 10 -3-3Jy Jy at at λλ~ 0.3mm. The corresponding minimal flux F~ 0.3mm. The corresponding minimal flux Fminmin==ννFFνν ~ 10~ 10-15-15ergs/cmergs/cm22. . From the constraint that the received flux should be larger than FFrom the constraint that the received flux should be larger than Fmin min we get we get L > 10L > 103636DD11

22ergs/s, where L is a typical source luminosity in the ergs/s, where L is a typical source luminosity in the submillimeter waveband, D is the distance from the source and submillimeter waveband, D is the distance from the source and DD11=D/1Mpc. =D/1Mpc.

As a typical interferometer base I take B=1.5*10As a typical interferometer base I take B=1.5*1066km. The corresponding km. The corresponding resolution limit resolution limit θθcrit crit ~ 2*10~ 2*10-13-13Rad at Rad at λλ~ 0.3mm. In order to get something ~ 0.3mm. In order to get something really interesting scales smaller than or of the order of Rreally interesting scales smaller than or of the order of Rgg should be should be resolved. Accordingly, we should have resolved. Accordingly, we should have θθgg= R= Rgg/D > /D > θθcrit crit . From this condition . From this condition

one obtains: Mone obtains: M88 > 10 > 10-2-2 D D11, where M, where M8 8 =M/(10=M/(1088MM☼☼). ). It turns out that assuming that the submillimeter luminosity is of the orderIt turns out that assuming that the submillimeter luminosity is of the order of a typical X-ray luminosity both conditions are fulfilled for of a typical X-ray luminosity both conditions are fulfilled for almost all nearby supermassive black holes. almost all nearby supermassive black holes.

R= R= θθcritcrit / /θθgg Circles correspond to detection threshold 1010-4-4Jy, squares – 10Jy, squares – 10-2-2 Jy, and Jy, and diamonds - 10diamonds - 10-1-1JyJy

Additionally, potential intermediate mass black holes within our Galaxy may have R ~ 1. For example, for GC M15 (D ~ 1. For example, for GC M15 (D ~ 10kpc and M ~ 10kpc and M ~ 4*10~ 4*103 3 MM☼☼), IMBH may have ), IMBH may have

R R ~ 2. ~ 2.

The record breakersThe record breakers: : Sgr ASgr A* * , R=2*10, R=2*10-3-3, M87, R=5*10, M87, R=5*10-3-3, NGC 4649, , NGC 4649, R=8*10R=8*10-3-3, NGC 4594 (Sombrero), R=10, NGC 4594 (Sombrero), R=10-2-2, IC 1459, R=1.16*10, IC 1459, R=1.16*10-2-2, NGC 5128 , NGC 5128 (Cen A), R=1.75*10(Cen A), R=1.75*10-2-2, NGC 4472 (M49), R=2*10, NGC 4472 (M49), R=2*10-2-2. .

Non-active galaxies exhibiting x-ray flares on time-scale of a few yearsNon-active galaxies exhibiting x-ray flares on time-scale of a few years

(tidal disruption event candidates)(tidal disruption event candidates) potential candidates: NGC 5905 (eg. Komossapotential candidates: NGC 5905 (eg. Komossa

and Bade 1999), Dand Bade 1999), D~ 40 Mpc, M ~ 10~ 40 Mpc, M ~ 1077-10-1088MM☼☼

R ~ 0.4-4, R ~ 0.4-4, RXJ 1242-1119A (eg. Komossa etRXJ 1242-1119A (eg. Komossa et

al, 2004),Dal, 2004),D~200 Mpc, M ~ 10~200 Mpc, M ~ 1088MM☼ ☼ and,and,

accordingly, R ~ 2. It would be VERYaccordingly, R ~ 2. It would be VERYinteresting to look for sub-mm radiation frominteresting to look for sub-mm radiation fromsuch galaxies using Millimetron. such galaxies using Millimetron.

Swift J1644+57/Swift J1644+57/GRB 110328AGRB 110328A It was as an extra long It was as an extra long

GRB coming from a GRB coming from a distance of order of distance of order of 3.8Gpc. It is interpreted 3.8Gpc. It is interpreted as emission of a jet as emission of a jet formed after a tidal formed after a tidal disruption event. The disruption event. The source emits in radio and source emits in radio and microwave bands, see microwave bands, see the Fig. The the Fig. The MILLIMETRON could MILLIMETRON could probe scales order of 10probe scales order of 10--

33pc at such distances! pc at such distances! This could help to confirm This could help to confirm or refute the tidal or refute the tidal disruption hypothesis for disruption hypothesis for sources of such type on sources of such type on a quite solid basis. a quite solid basis.

CONCLUSIONSCONCLUSIONS1) Millimetron is able to resolve scales of order of gravitational radius for almost all 1) Millimetron is able to resolve scales of order of gravitational radius for almost all

nearby SMBH (D < 50Mpc). Also, its sensitivity is sufficient for this task. For many nearby SMBH (D < 50Mpc). Also, its sensitivity is sufficient for this task. For many extragalactic objects Millimetron is able to resolve structures several order of extragalactic objects Millimetron is able to resolve structures several order of magnitude smaller than rmagnitude smaller than rgg..

2) Practically all nearby SMBH are underluminous (L << L2) Practically all nearby SMBH are underluminous (L << Leddedd). In this regime the ). In this regime the radiatively inefficient accretion is likely to occur. If so, the flow may be expected to radiatively inefficient accretion is likely to occur. If so, the flow may be expected to be optically thin in the (sub) mm waveband, close to black hole. Thus, Millimetron be optically thin in the (sub) mm waveband, close to black hole. Thus, Millimetron may be able to see black holes themselves, and probe the structure of the flow in may be able to see black holes themselves, and probe the structure of the flow in the very vicinity of BH. This may enable to determine both mass and angular the very vicinity of BH. This may enable to determine both mass and angular momentum of BH’s and parameters of the flow: its geometrical structure (including momentum of BH’s and parameters of the flow: its geometrical structure (including the possibility of jet/outflow), orientation, physical conditions in the flow as well as the possibility of jet/outflow), orientation, physical conditions in the flow as well as to clarify the origin of time variability of such accreting flows.to clarify the origin of time variability of such accreting flows.

3) It will be quite interesting to have a possibility to measure flux variability from the 3) It will be quite interesting to have a possibility to measure flux variability from the sources at short time scales, from minutes to hours.sources at short time scales, from minutes to hours.

4) Millimetron may be quite useful for observing many other disc-like structures 4) Millimetron may be quite useful for observing many other disc-like structures within our own Galaxy, such as e.g. the debris discs.within our own Galaxy, such as e.g. the debris discs.