Download Accreting Supermassive Black Holes and their

Accreting Supermassive Black Holes and
their Implication on Galactic Evolution
Shubhrangshu Ghosh
CAPSS, Bose Institute, Kolkata
WAPP 2015, Darjeeling
Supermassive BH accretion:

Center of all galaxies harbor supermassive black hole (SMBH)
~ 10^(6-10) solar mass.

SMBH accretes: In the center of galaxies SMBH accrets gaseous plasma to
the nuclear/central regions from the ambient medium in host galaxies

Accretion persists due to turbulent viscous transport of angular momentum
outwards forming a disk like structure.
Most efficient process of generating energy in the
universe.

Activities (SMBH+accretion):
→ Nuclear region produce high luminosity due
to radiation emitted from accretion flow
L_bol > 10^(40 – 45) erg/s
often called AGNs/quasars.

On many occassions Accreting plasma
produces collimated relativistic jets ~0.99c
jet range
several Kpc to Mpc scale .
Accretion flow models:

.
Geometry/optical structure of accretion flow depends on mass accretion rate
supplied from the accreting source  different accretion mode
1)

High mass accretion flow ~ Eddington rate (L_Edd / c^2)
Geometrically thin Keplerian disk (h/r << 1): Radiatively efficient accretion
flow generating high luminosity, spectrum ➙ optically thick peaks in soft
X-rays.
Accretion flow models:
2) Low mass accretion flow ~ sub-Eddington rate ( < 10^(-1) L_Edd /c^2 )
 Geometrically thick advective flow (h/r ~ 1). Accretion flow is two
temperature hot magnetized plasma, Radiatively inefficient accretion flow
generating low luminosity. Spectrum  optically thin peaks in hard X-rays.
 Outflows/jets originate from geometrically thick advective accretion flow
Outflows/jets:
●
Relativistic jets emit in all wave lengths (from radio to gamma), mostly
emit in radio synchrotron (radio jets)
●
AGNs with powerful relativistic radio jets (with strong radio emission)
→ Radio galaxies/Radio AGNS/Radio loud AGNs
●
)
What makes Radio galaxies/Radio loud AGNs important?
●
The host galaxies are massive/giant elliptical galaxies → Many of them
are old and evolved lying in center of galaxy clusters.

Hot spots and radio lobes are the ideal sites for particle acceleration to
extreme high energies (extra galactic UHECR)

Powerful relativistic jets interact with ISM/IGM/ICM and deposit
energy → AGN feedback regulating cooling flows in the center
of galaxy cluster
•
This AGN feedback may again influence acceleration of
particles in hot spots of radio jets

AGN feedback plays a significant role in latest phase of
massive galaxy formation and evolution
Effect of cosmological constant on AGN feedback
log(r/r_s)
Central dominant Galaxy – IC 1101 (super giant elliptical galaxy)
At the center of Abell 2029 galaxy cluster
Extended envelope with radius ~ 600 Kpc
(Ghosh & Banik 2015)
Cosmological constant may substantially influence particle acceleration in hot
spots of radio jets in radio galaxies.
AGN/Radio galaxy dichotomy :
Most classification of AGNs related to emission lines/continuum, line of
sight, radio loudness, historical significance (e.g. LINER, Seyfert, radio-quiet
quasars, FR Ⅰ, FR Ⅱ, radio galaxies, BL Lac )


Distinct classification of AGNs can be made based on radio power
⇓
Radio-quiet (no jets/tweak jets)
(negligible radio emission)
Radio loud (powerful radio jets)
(strong radio emission)
⇓
High excitation radio galaxy
(HERG)
(radio loud quasars)
Low excitation radio galaxy
(LERG)
Radio galaxy/Radio AGN dichotomy :

Two classes of Radio AGNs → LERGs and HERGs are distinctly different
both observationally and morphologically.
NRAO-VLA sky survey,
z<0.1, L_1.4GHZ
Best & Heckman 2012
Radio galaxy/Radio AGN dichotomy :
⇓
Low excitation radio galaxies
High excitation radio galaxies
•
Reddest galaxies and at the last
stage of massive galaxy formation.
Mostly lie in center of galaxy clusters.
•
Star formation rate very less
•
No such emission
•
Radiatively inefficient
L_Bol < 10^40 erg/s
•
No such feature
younger than LERGs
higher than LERGs
Optical broad and narrow emission
lines and absorption lines due to
obscuring cold molecular torus
Radiatively very efficient
L_Bol > 10^40 erg/s (10^(45-46) erg/s)
Optical to UV emission characterized
by “Big blue bump”
What makes HERGs/LERGs observationally different ?
➤
Differences due to source/fueling of accretion
✶ LERGs
→ SMBH accretes gaseous plasma quasi-spherically from hot X-ray emitting
phase of gaseous halo surrounding the host galaxy or from hot phase of
IGM/ICM (at ~ 10^7 K) with high sub-Eddington mass accretion rate
~ < 10^(-3) L_Edd/c^2
→ forming a geometrically thick advective accretion flow which is
radiatively very inefficient and optically thin
→ Accretion flow extends up to million Schwarzschild radius.
Geometrically thick advective accretion flow remarkably explain
LERGs
What makes HERGs/LERGs observationally different ?
✶ HERGs
→ SMBH accretes gas from cold molecular torus most likely with moderately
sub-Eddington mass accretion rate ~ (10^(-2) - 10^(-1)) L_Edd/c^2
 forming a outer geometrically thin, optically thick Keplerian accretion disk
& inner moderately thick, opticlaly thin
advective accretion flow
 Accretion flow extends up to few
thousand Schwarzschild radius.
(Ghosh & Konar 2015)
How jet - accretion flow are correlated ?
●
Acceleration of particles in the hot spots is directly related to
jet-trigerring mechanism.
●
Jet launching a MHD process
 plasma gets
accelerated magnetocentrifugally along open
field lines with the help of poloidal magnetic field.
BH spin directly powers jets.
●
Symbiotic picture:
 jet
extracts matter, energy
& momentum from advective
accretion flow.
Accretion-outflow-BH
symbiotically
correlated/coupled through
conservation laws: matter, momentum
& energy .
2.5 - D magnetized advective accretion-outflow model eqns:
2.5 - D magnetized advective accretion-outflow model eqns:
Ghosh 2015 a,b
Pseudo-Newtonian-potentials:
●
GR information of the BH simulated through PseudoNewtonian-potential (PNPs) or Pseudo-GR potentials.
➤ Generic BH (rotating/non-rotating) Ghosh & Mukhopadhyay (2007)
●
Recently developed most correct PNPs those can accurately reproduce all
GR features (Ghosh, Sarkar & Bhadra 2014; Sarkar, Ghosh & Bhadra
2014; Ghosh, Sarkar & Bhadra 2015).
➤ The potentials are velocity dependent potentials
➤ For rotating/Kerr BH, the corresponding PNP contains explicit information
of frame dragging.
Solid and long-dashed curves are for T_i with M_{accr} (a) = 10^(-4) , (b) = 10^(-3)
(c) = 10^(-2) & (d) = 10^(-2). short-dashed and dotted curves are for T_e with same
parameters. M_BH = 10^9 solar mass. M_{accr} in Edd unit. (Ghosh 2015b )
Solid, long-dashed & short-dashed curves in Fig. (a) for M_{accr} = 10^(-4). Dotted, long
dot-dashed & short dot-dashed curves in (a) for M_{accr} = 10^(-3). Fig (b) for
M_{accr} = 10^(-2). M_BH = 10^9 solar mass
Ghosh 2015b
Variation of (a) luminosity/jet power with BH spin
Bhattacharya, Ghosh & Mukhopadhyay 2010
Advective accretion flow and radio AGN unification
“Mass accretion rate of accreting gas around central SMBHs in HERGs
is apparently to be in order of ~ (10^(-2) - 10^(-1)) L_Edd/c^2 or
moderately sub-Eddington” with
'Inner moderately advective flow region + outer geometrically thin
Keplerian disk' with a transition in-between
SMBH in HERGs attain extremal spin by galactic mergers and baryonic accretion
Ghosh &
Konar 2015
Advective accretion flow and radio AGN unification
Spectrum of outer Keplerian disk:
Λ~1100 Å
T ~ 10^4 K
Ghosh & Konar 2015
Final Thoughts :

HERGs occur in a transitional evolutionary state linking between spiral star
forming galaxy to massive red elliptical galaxies (LERGs).
HERGs may eventually evolve to LERGs.

Proper modeling of accretion-outflow/jet coupled region necessary for
high energetic particle acceleration in hot spots of jets.

Spin of SMBH, AGN feedback as well as cosmological constant
substantially influence particle acceleration in hot spots.

Spin of SMBH may play a predominant role in final state of galaxy
evolution.
The sky in black holes, > 10^7 solar mass. Aitoff projection in galactic coordinates of
5,978 candidate sources in the case of a complete sub sample (the Galactic plane
remains obscured). The choice was made from a complete sample of 10,284
candidate brighter than 0.03 Jy at 2 micron, and selected at z< 0.025; this uses the 2
micron all sky survey, limited in a 20 degree band in the Galactic plane. The color code
is Black, Blue, Green, Orange, Red corresponding to redshifts betwen 0, 0.005, 0.01,
0.015, 0.02, 0.025:
Caramete et al. (2008)