Download Living alongside Monsters: Matter around Central Massive Black Holes Q. Daniel Wang

Living alongside Monsters:
Matter around Central Massive Black Holes
Q. Daniel Wang
University of Massachusetts
Issues to be addressed
•  Why galactic nuclear regions? Why M31 and our GC?
•  Activities of the SMBHs
–  Quiescent accretion flow vs. flare
–  Relation to the ambient gas and stellar properties
•  How did nuclear stellar clusters (NCs) form?
•  What is the star formation (SF) mode?
–  in clusters and/or small groups
–  in burst or continuous fashion
•  How do massive stars interact with the ISM?
•  How do activities in nuclear regions affect galaxy
ecosystem?
Galactic nuclear regions play a key role
in galaxy formation and evolution
•  Every galaxy probably contains
a SMBH and/or a nuclear stellar
cluster.
•  Their masses are correlated.
•  How these correlations are
achieved is not clear.
•  SMBHs accrete gas in two
modes :
–  Quasars: radiating ~10% of the
rest-mass energy
–  Local SMBHs: radiatively
inefficient
•  But SMBHs can also grow by
mergers
Graham & Spitler 2009
Little is known about the interplay
among stars, the ISM, and SMBHs
Lopsided stellar disks: relics of
SMBH accretion in quasar mode?
Dry mergers destroy such
disks, as in massive spheroids
Hopkins & Quataert 2010
M31: Double stellar nuclei and SMBH
P1
P2 (M31*)
HST view of the M31 center
(Lauer et al. 1998)
•  A red star cluster forming a
lopsided disk (Tremaine 1995)
•  Mbh ~ 1.4 x 108 Msun
•  Apparent young (A-type)
stars (t ~ 200 Myr) around
the SMBH
•  Alternatively, they may be
post-HB stars formed from
stripped redgiants and/or
stellar mergers (e.g.,
Demargue & Virani 2007).
M31*: Chandra view
•  40 HRC observations and 58
ACIS observations taken
from late 1999 to early
2010
•  Sources associated with P1,
SSS and S1 are probably Xray binaries
•  P2 – M31*
•  Lx ~ 10-5 Lbondi
•  Lbondi ~ 3 x1041 (η/0.1)erg s-1,
η - radiation efficiency
Li, Z. et al. (2010)
A major outburst seen on Jan. 6, 2006
M31* brightened by ~102
After the outburst, M31* remained active
with the mean flux ~ 7x quiescent one
10-yr Chandra light curve
An outburst
A quiescent state
An active state
What’s happening…
•  The outburst is similar in
relative amplitude to the Xray flares detected in Sgr A*.
•  Both phenomena may be
caused by episodic ejection of
relativistic plasma blobs
(“jets”) – analogous to coronal
mass ejection in the Sun.
•  Activities after the outburst,
Empirical and theoretical
may also due to many small
predictions for the
outbursts/ejection events.
mechanical feedback - up
to a few % of Lbondi
SMBH feedback: a major heating
source of the nuclear region?
HST/WFPC2 Hα Image
Large [NII]/Hα ~ 1.3-2.7, similar to LINERS, cannot
be explained purely by photo ionization.
Heating by low-energy cosmic-ray from the SMBH
feedback may be responsible.
Li & Wang 2009
Dense stellar pop.  dynamic
formation of X-ray binary
Radial X-ray source number density
distribution in the M31 bulge
With 1’ radius:
•  Lx > 1036 erg/s: an
enhanced number
density  dynamic
formation of LMXB
Voss & Gilfanov 2007
•  But in 1036 > Lx > 1035: a
deficit  destruction of
loosely bound LMXB?
•  A normal Sx/Sk ratio
toward the center
indicates little effect
on the CV pop.
Nuclear stellar feedback:
driving hot gas outflow
• Stellar contribution
(including CVs and
coronally active
binaries) subtracted
• characteristics of hot
gas in the bulge:
• z0 ~ 600 pc;
• T~ 0.3 keV;
• L0.5-2 keV ~ 3×1038 erg/s
Diffuse soft X-ray emission
IRAC 8 micro, K-band, 0.5-2 keV
Hydro-simulation of SNRs, bulge wind,
nuclear disk, and SMBH accretion
•  Full box size =4 kpc
•  Adaptive mesh refinement
down to 0.5 pc (FLASH code)
•  A cool gas inflow is assumed to
continuously feed the nuclear
disk around the SMBH.
•  Injection of Ia SN (4x10-4 /
yr), and stellar mass loss
follows the stellar light.
•  The injection drives a bulge
wind and also reduces the
accretion to the SMBH.
•  The disk is being evaporated
 mass loading to the hot gas.
Density cut
800 pc
Tang et al. 2009
~ 1055 erg, or > 104
SNe is needed over
the past 2 x 107 years!
ROSAT Survey (1.5-keV Band)
Chandra deep survey of the
Galactic center
Red: 1-2.5 keV Green: 2.5-4 keV Blue: 4-9 keV
X-ray close-up: the Galactic nuclear region
Bridge
X-ray reverberation of a Sgr A*
burst ~ 200 years ago
Ponti et al. 2010
A Panoramic HST Infrared View of
the Galactic Center
1.87 and 1.90 μm narrow bands: on and off Pα line; Wang et al. 2009
1.9 µm band detection limit
•  0.6 million stars
•  Accounting for >
80% light
•  Including all stars
with M > 10 M and
evolved lower mass
ones.
•  A high-res
database for
stellar pop., dist.,
and formation
Pα + stellar continuum: Preliminary Results
•  Ionized gas features
resolved into arrays of
organized linear
filaments  strong local
magnetic fields.
•  ~200 stars show enhanced Pα emission (green dots).
•  ~2/3 of them are located outside the three known clusters.
•  13 have been followed up spectroscopically, confirming that they are
indeed massive stars
 a new population of massive stars.
Sickle HII Region
Detailed structure
of ionized gas
pillars sculpted by
the intense
radiation and wind
from the
Quintuplet cluster.
But magnetic field
may also play a
critical role.
Red: radio continuum Green: Pα Blue: 1.9µm
Detailed views of
individual compact HII regions
Nuclear Spiral/Torus
Sgr A*
•  Ionized gas around the
supermassive black hole is
confined to a spiral
embedded in a
circumnuclear dusty torus.
•  Evidence for ionized gas
outflows from this torus.
Red: 8µm (IRAC) Green: Pα Blue: 1.9µm
X-ray Flare from Sgr A*
• Mbh ~ 3 x 106 M
• Peak L(2-10 keV) ∼1035 erg s-1
• Lasted for about 3 hrs
• Variability ~ a few minutes
Baganoff et al. (2003)
Spectra of extended X-rayemitting features
Sgr A*
PWN
IRS 13
Diffuse
The spectra of Sgr A*, IRS 13, and diffuse X-ray emission all show the Fe K
line at ~6.6 keV  NEI emission from gas heated recently (net~103 cm-3 yr).
Nuclear cluster and extinction mapping
NICMOS image:
Red: H, Green: 1.9 Blue: K
Extinction map from SED fits
for individual stars
Spitzer/IRAC 4.5 µm Intensity Map
IRAC 4.5/3.6 µm Intensity Map
Extinction contour overlaid on the
HST 1.9 µm image
Great Observatory Survey of the GC
Summery
•  An unprecedented high-resolution infrared
panorama of the Galactic center. Initial results:
–  a new population of very massive stars in relative
isolation and with strong winds.
–  Fine filamentary structures of ionized diffuse gas
indicating profound influence of local strong magnetic
field.
–  Compact nebulae, tracing various stages of massive
star evolution
–  Construction of a high-res extinction map toward the
GC.
–  Evidence for a SF burst ~ a few 108 yrs ago, in
addition to continuum SF over the life time of the
Galaxy.
Summary Cont.
•  X-ray flare and flux variation are detected from
M31*, a scaled-up version of Sgr A* activities.
•  Cool gas in the nuclear regions of M31 and our GC
both has a small filling factor and are embedded in
hot gas.
•  Evaporation of cool gas by hot gas may lead to the
starvation of SMBHs
•  The mass-loaded hot gas undergoes outflows,
affecting the global ecosystem of the galaxies.
•  We aim to understand the formation modes of
massive stars and their interplay with the extreme
environment in galactic nuclei.
CMZ
T ≤107 K
Filling factor?
Composition?
Physical properties?
Heating and cooling?
Mass loading?
Corona
Galactic disk
Magnetic loops
Galactic Center: Environment
•  Strong absorption from NIR to soft X-ray
•  Strong scattering and dispersion of low
frequency radio wave
•  Large amounts of molecular gas (~ 107 Msun)
–  But small filling factor (< 10%)
•  Very active in star formation
–  Close to 10% of the SF in the Galaxy
–  SN rate ~ 1 per 103 yrs  1041 ergs/s
•  Short orbital period (~ a few x 106 yr)
–  Large tidal and shear forces
•  Very high B field (up to ~ 1 mG)
–  Toroidal B field in dense clouds
–  Poloidal B field in intercloud gas
•  Very hard diffuse X-ray emission
–  Much harder than spectra of SNRs
HST/NICMOS 1.90µm Map of the
Galactic Center
l
Foreground dusty clouds
Quintuplet cluster
b
15’ (115 light-year)
Arches cluster
Sgr A*
39’ (300 light-year)
•  Distance to the Galactic center: 26,000 light-year
•  Resolution: 0.025 light-year (0.2”)
•  144 HST orbits, taken between Feb and June, 2008
 144X4X4=2304 images for each of the two wavelength filters
HST/NICMOS 1.87µm Map of the
Galactic Center
Arched HII filaments
Arches cluster
Sickle HII region
Quintuplet cluster
Sgr A*
•  The 1.9µm filter is sensitive to the stellar continuum emission.
•  The 1.87µm filter covers the Pα line.
•  Subtracting the 1.9µm map from the 1.87µm map adaptively.
 A net Pα line emission map (see the poster by Dong et al.; 415.01) .
Net Pα Map of the Galactic Center
Why do we need the HST?
•  Excellent imaging stability
•  Only observable from the space
•  Little background due to the Earth’s warm atmosphere
Living alongside Monsters:
Matter around Central Massive Black Holes
Q. Daniel Wang
University of Massachusetts
But most of SMBHs are not active in
nearby galaxies. They are starved. Why?
•  Little gas falls into the galaxy
center?
•  Or the infalling gas is being removed,
due to episodic AGN feedback or
some continuous processes?
Answering these questions will help to
understand the formation of SMBHs
and galaxies in general.
Outline
•  Review of nuclear regions in M31 and
our Galactic center
•  key components
•  interesting unique phenomena
•  their interplay
•  What need to be done?
M31 (d=780 kpc)
IRAC 8 micro
0.5-2 keV
2-8 keV
Li & Wang 2007