Present and past activity at the Galactic center - Gabriele Ponti INAF OA Brera - MPE - INAF OAS

Present and past activity at the
 Galactic center

 Gabriele Ponti
 INAF OA Brera - MPE

How do galaxies evolve?
How do galaxies evolve?

 NGC 7331 Hubble

The Baryon cycle
Tumlinson +17

 106-7 K

 Hot Baryons:
 Bulk of Baryons
 Re-condensation
 Driver outflows

AGN - Starbursts influence CGM
AGN Starburst

 M 82: Hubble/Spitzer/Chandra

 Outstanding progress
 ➜ Understand feedback between
 nuclear activity and CGM
MS 0735.6+7421: Chandra/Hubble/VLA

Do galaxies influence their CGM?
 Quiescent galaxy

 Does the nuclear activity of quiescent galaxies
 influence their CGM?

 ➜ Let’s look to the Milky Way

M83: Subaru/ESO/Hubble

The structure of the Milky Way
Galactic bar mass
Mass ~ 7×109 MSun
Size ~ 3 kpc

 Binney +91; Bally +10; Ridley +17

From Spitzer/GLIMPSE data Churchwell +09

The central degrees of the Milky Way
 Molinari+11

 Central Molecular Zone
 Herschel column density map

 Sgr A*

 140 pc
 1 deg

 Molinari+11

 Abundant gas reservoir ~3×107 MSun
Peculiar environment: forming stars at extremely low rate (10 times lower than expected)
 Nevertheless ➜ Mini starburst

The Central Molecular Zone in X-rays
 Exposure > 1.5 Ms (central 15’)
 More than 100 EPIC observations
 > 200 ks in the plane

 X-ray binaries No powerful starburst! Ponti+15

 Sgr A*
 ➜ Very faint!

 What is the present activity of Sgr A*?

 Can Sgr A* influence our CGM?

 140 pc
 1 deg

ESA News/XMM-Newton/G. Ponti+15

The Central Molecular Zone in X-rays
 Exposure > 1.5 Ms (central 15’)
 More than 100 EPIC observations
 > 200 ks in the plane
 Ponti+15
 X-ray binaries
 Sgr A*
 ➜ Very faint!

 140 pc
 1 deg

ESA News/XMM-Newton/G. Ponti+15

The Central Molecular Zone in X-rays
 Exposure > 1.5 Ms (central 15’)
 More than 100 EPIC observations
 > 200 ks in the plane
 Ponti+15
 X-ray binaries
 Sgr A*
 ➜ Very faint!

 Sgr A’s
 bipolar lobes

Gillessen +09; +12

 140 pc
 1 deg

 ESA News/XMM-Newton/G. Ponti+15
 Ponti +15

Sgr A*’s quiescent emission
 X-ray (Chandra) Wang+13 0.08 pc
 NIR (VLT-NACO) 2 arcsec
 1.1 pc

 LSgr A* ~ 10-9 LEdd
 0.5 arcmin
 Optically thin synchrotron
 Best target to study low luminosity accretion r ~ 10 RS
 Linearly polarised Marrone +06
 Yuan +03; Ponti +17b Thermal e- (ɣe~10)
 ne ~ 106 cm-3 Loeb +07; Genzel +10
 B ~ 20-50 G
 Soon ➜ Event horizon telescope!
 RIAF radial dependence
 Radio flattening
 matter > 90 % outflow!
 Likely from a compact jet
 Falcke +98; Moscibrodzska +10

 ADAF/RIAF
 Quiescent Sgr A*’s activity ➜ No influence on CGM

 Wang+13
 Wang +13
 Bremsstrahlung
 r ~ 105 RS
 extended (~1”) accretion from stars wind
Falcke +98; Markoff +01; Yuan +03; Zhao +03; +04; Baganoff +03; kTe ~ 7×107 K Melia +92; Quataert
Herrnstein +04; An +05; Xu +06; Marrone +06; +07; Schoedel +07; 02; Baganoff +03;
+11; Dodds-Eden +09; Trap +11; Wang +13; Bower +15; +18; +19; ne ~ 100 cm-3
 Cuadra +05; Xu +06;
Brinkerink +15; Liu +16; Stone +16; Witzel +18; Lu +18; von Wang +13
Fellenberg 18; Fazio +18; Iwata +20 ; Gravity Coll. +20

X-ray flares of Sgr A* Ponti +15b

 Chandra
 (1999-2006)

 Sgr A*’s flare distribution
 Neilsen+13

 ~ 1.9±0.3

 Flaring rate ~ 1 day-1
 Flares L>1035 erg s-1 ~ 0.1 day-1

Baganoff+01; Goldwurm+03; Porquet+03;+08; Belanger+05; Nowak+12; Neilsen+13;+15; Degenaar+13; Barriere+14;
 Ponti+15; Mossoux+16; Yuan+16; Zhang+17; Capellupo+17; Yuan+18; Leibowitz+18;+20; Fazio+18; Okuda+19;
 Boyce+19; Haggard+19; Bouffard+19; Gutierrez+20; Ball+20; Subroweit+20; Ripperda+20; Gravity Coll+20

Sgr A*’s emission during X-ray flares?
 Best target to study low luminosity accretion

 During flares ➜ IR ~ 1.6
 IR polarised ➜ Synchrotron

 ɣe>106 ∆ =0.5
 ADAF
 ɣe~102 ∆ =whatever

Yuan +03
Ponti +17b

For 15 years we wondered…
 Genzel +10
What is the radiative
 process in X-ray?

First NIR and X-ray spectrum of a flare
 Second brightest flare ever detected by XMM
 XMM
 NuSTAR
 Sinfoni

 Ponti +17b

First NIR and X-ray spectrum of a flare
 Ponti +17b
 IR = 1.7±0.1; X = 2.27±0.12 ➜ ∆ = 0.57±0.09
 ➜ B = 9±3 G

 XMM+NuSTAR

 Synchrotron with cooling break! ɣe>106

 Is this flare peculiar?
 We want spectroscopy of more flares

Sgr A*’s present activity

 Was Sgr A* brighter in
 the past?

Ponti +13; +14; +15b; +17b

 Current activity ➜ No influence on CGM

Clouds: mirrors of past activity
Sunyaev +93
 ➜ Tool to study Sgr A*’s past activity
 Molinari +11

 ➜ Tomography
 Central of cloud distribution
 Molecular Zone
 Herschel column density map

 Sgr A*

 L
 d
 A, nH

 140 pc
 1 deg

 nH × A× I FeK
 LSgrA* ∝
 Molinari +11 d2

Clouds as X-ray mirrors
 GRANAT: Hard X-ray/MC ASCA: Fe K from some MC

Sunyaev +93 Koyama +96

Are clouds reflecting Sgr A* radiation?
 Puzzling result: constant FeK emission
 Cosmic ray electrons

 Is theFeK ;
 Contours: 850μm; X-ray emission
 20cm
 Revnivtsev +04 induced by cosmic rays?
 Yusef-Zadeh +02+07

Cosmic ray protons

 HESS TeV on FeK map

 Aharonian +06

Super-luminal echo ➜ clouds as mirrors
XMM: Fe K emission
 Ponti +10

 Significant
 variation of the
 Fe K emission

 Super-luminal
 Fe K 
 LSgr A* ~ 2×1039 erg s-1 (106 times brighter) propagation
 Implies:
 ~102 years ago

 ➜ Rule out
 cosmic rays

 ➜ Clouds are
 mirrors of past
 activity
 Corroborated by several other super-luminal echoes
 Clavel +13; Terrier +18
 e.g. Ponti +10;+13

Some recent major results
Mori +15;
Zhang +15 NuSTAR: 10-20 keV

 Emission in hard X-rays
 ➜ Reflection
Clavel +13 Chandra light curves Clavel +13

 2 years event 10 years event

 Multiple outbursts?

Some recent major results Terrier+18
 Fe K⍺ emission

 All Fe K⍺ bright regions are variable
See also Ponti+10;+13;+14; Clavel+13;+14; Yusef-Zadeh+13a,b;+19; Marin+14; Koyama+14;+18; Zhang+15; Mori+15;
 Nobukawa+15; +16; Walls+16; Krivonos+14;+17; Churazov+17a,b,c; Chuard+18; Chernyshov+18; Kuznetsova+19;
 Di Gesu+20; Khabibullin+20a,b

Future prospects: X-ray polarisation!
Reflection
 Degree Compton
 of scattered
 polarisation
 Fe K⍺ emission Cloud distribution in central molecular zone
 Kruijssen +15 Churazov+17b
 ➜ polarised

 Angle and degree of polarisation
 Achievable with IXPE (2021) EXTP (2027)
 Churazov+02+17b; Di Gesu+20; Khabibullin+20b
Churazov+17b
See also Churazov+02;
Di Gesu +20; Khabibullin+20b
 ➜ Derive Sgr A*’s light curve
 Churazov+17b
 ➜ Reconstruct 3-d distribution of clouds

See also Ponti+10;+13;+14; Clavel+13;+14; Yusef-Zadeh+13a,b;+19; Marin+14; Koyama+14;+18; Zhang+15; Mori+15;
 Nobukawa+15; +16; Walls+16; Krivonos+14;+17; Churazov+17a,b,c; Chuard+18; Chernyshov+18; Kuznetsova+19;
 Di Gesu+20; Khabibullin+20a,b

Sgr A*’s present and past activity

 LSgr A* ~ 2×1039 erg s-1
 ~102 years ago

 Can we go further
 back in time?

 Ponti +13; +14; +15b; +17b

Although 106 times brighter ➜ No influence on CGM

Distribution of remnants and outflows Ponti +15
Si xiii, S xv, Ar xvii

 140 pc
 1 deg

 Possible
 Atlas of all (~15) influence
 SNR in the region on CGM?
 ➜ Powering outflows to
 3.5×10-4 yr-1 < SN rate < 15×10-4 yr-1
 Galactic center lobe?
 Law +11; Crocker +11; 12;
Massive kinetic energy input > 1.1×1040 erg s-1 Yoast-Hull +14; Jouvin +15

Discovery of high latitude hot plasma

 What is this?

 Ponti +15
 AFGL 5376

 Intensity of 1 keV
 Sgr A*
 thermal plasma

Galactic center radio lobe

 Radio emission
Galactic Center Radio
 Lobe

 Law +08

What is the origin of this hot plasma?
 Hot atmosphere of the Galactic center?

 Base of Galactic wind? Crocker +12

 Past Sgr A*’s AGN-like activity? Bland-Hawthorn & Cohen 03

 Extensive X-ray scan
 Ponti +15
 AFGL 5376

 Intensity of 1 keV
 Sgr A*
 thermal plasma

Suspense….

ESA News/XMM-Newton/G. Ponti 2019, Nature
 1.5-2.6 keV
 2.35-2.56 S xv
 2.7-3.0 keV

 Hot outflow

 Flow molecular matter

The Galactic
 ESA News/XMM-Newton/G. Ponti 2019, Nature 1.5-2.6 keV
 2.35-2.56 S xv
 2.7-3.0 keV

 center
 1

 Chimneys
 Ponti +2019, Nature

 Counts s-1 (keV-1 cm-2 arcmin-2)
 Ne ix Mg xi Si xiii S xv Ar xvii Ca xix Fe K
Galactic latitude

 b = 0º
 b = -1.5º

 10-5

 -1
 10-6
 -1

 1 2 5
 Energy (keV)

 ➜ Measure kT, n, p,
 abundances of hot plasma
 -2

 1 0 359
 Galactic longitude

ESA News/XMM-Newton/G. Ponti 2019, Nature Hot plasma properties

 Surface brightness
 10-3
 Conical
 outflow
 Sgr A’s
 1

 bipolar lobes

 10-4
 5
Galactic latitude

 Chimneys ➜ impact on CGM

 Density (cm-3)
 1
 0.5
 0.1
 -1

 Pressure (keV cm-3)
 1
 Hot plasma 0.1

 flow
 -2

 1 0 359 10 100
 Galactic longitude Latitudinal distance in pc from Sgr A*

The radio view of the Chimneys
 ESA News/XMM-Newton/G. Ponti 2019, Nature
 Radio traces edges of Chimneys
 MeerKAT
 1
Galactic latitude
 -1

 Heywood +19, Nature
 Hot plasma
 flow
 -2

 1 0
 Galactic longitude
 359
 Outflow has radio counterpart

Multi-phase multi-epoch Galactic outflow
 Ponti+20
 Hot plasma (X-rays)
 Coherent features
 warm dust (mid-IR) ➜
 on > 102 pc scales
 SNR shocks (radio)
 SNR ➜ Deeply interconnected and linked to
 the Galactic outflow
 ➜ Strong shocks at the chimney-ISM
 interface (radio + shorter-lived dust emission)
 ➜ AFGL 5376 > 0.1 kpc molecular shock
 Uchida+94

 Foreground

 Foreground
 SNR

 SNR

 X-rays: 1.5-2.6 keV
 Mid-IR: 22.2/12.08 μm
 Radio: 1.284 GHz

Large scale cold Galactic outflow
Ponti+20

 Base Fermi bubbles

 Base Fermi bubbles
 Di Teodoro+18 Di Teodoro+18

 McClure-Griffith+13; Di Teodoro+18;+20; Lockman+20

 AFGL 5376 similar to clouds at the base of the Fermi bubbles

Small scale molecular Galactic outflow
Ponti+20

 Molecular outflow
 (Polar Arc) Hsieh+16

 X-ray only Ponti+15

 Sgr A’s
 bipolar lobes

 Sgr A*
 .
 Molecular outflow
 (Hourglass feature)

 Hsieh+15;+16

 Molecular outflow detected tens of parsec from Sgr A*
 15 pc

Multi-phase multi-epoch Galactic outflow
 Ponti+20
 Hot plasma (X-rays)
 Coherent features
 warm dust (mid-IR) ➜
 on > 102 pc scales
 SNR shocks (radio)
 SNR ➜ Deeply interconnected and linked to
 the Galactic outflow
 ➜ Strong shocks at the chimney-ISM
 interface (radio + shorter-lived dust emission)
 H3+ survey ➜ outflow
 of warm diffuse gas Oka+20 ➜ AFGL 5376 > 0.1 kpc molecular shock

 Foreground
 ➜ Multi-phase (hot, molecular, warm-diffuse)
 Foreground
 SNR ➜ Multi-scale and multi-epoch outflow

 SNR

 X-rays: 1.5-2.6 keV
 Mid-IR: 22.2/12.08 μm
 Radio: 1.284 GHz

Multi-phase multi-epoch Galactic outflow
 Ponti+20
 Hot plasma (X-rays)
 Coherent features
 warm dust (mid-IR) ➜
 on > 102 pc scales
 SNR shocks (radio)
 SNR ➜ Deeply interconnected and linked to
 the Galactic outflow
 n
 io
 s

 ➜ Strong shocks at the chimney-ISM
 ru
 ot
 Pr

 interface (radio + shorter-lived dust emission)
 ➜ AFGL 5376 > 0.1 kpc molecular shock

 Foreground
 ➜ Multi-phase (hot, molecular, warm-diffuse)
 Foreground
 SNR ➜ Multi-scale and multi-epoch outflow
 ➜ Vertical (dominant? B~0.1-1 mG) magnetic
 SNR field diverging beyond |b|~0.5º
 ➜ Hot (X-ray) plasma cannot drive outflow
 Relic? Dark? outflow
 What we do not understand:
 Radio: 1.284 GHz Origin of protrusion?
 X-rays: 1.5-2.6 keV Why not perfectly symmetric?
 Mid-IR: 22.2/12.08 μm Relic outflow? Dark outflow?
 Radio: 1.284 GHz AGN driven? Starburst?

5 kpc

Fermi RGB image Selig +15

The channel feeding the Fermi bubbles

 Does have an effect on CGM!

ESA News/XMM-Newton/G. Ponti et al. 2019, Nature

Summary X-ray polarisation
 ➜ Derive Sgr A*’s light curve
 ➜ 3-d distribution of clouds

 Normal galaxies hold outflows to CGM

Or longer-lived Starbursts?

 How is the disc-CGM exchange?
 Synchrotron with
 cooling break!

 ➜ Discovered the channel
 connecting the activity at the Milky
 Way center with the Fermi bubbles
 ➜ Outflow multi-phase,
 multi-epoch and multi-scale

 Ponti +13; +14; +15b; +17b

eROSITA (Spektr-RG)’s launch
 Baikonur, July 13th, 2019

Source: Roscosmos Merloni, Munich JAC, 30/4/2020 43

Map the flows of hot Galactic
 Baryons
Global outflow? Inner outflow
 outer inflow?

 ? ?

 ? Milky Way center ?
Fountains? Chaotic flow?

Conclusions X-ray polarisation
 ➜ Derive Sgr A*’s light curve
 ➜ 3-d distribution of clouds

 ➜ Discovered the channel connecting the
 activity at the Milky Way center with the
 Fermi bubbles
 ➜ Outflow multi-phase, multi-epoch and
 multi-scale
 Starbursts?

 eROSITA ➜ flows of hot Baryons
 between the Galactic disc and halo

 Synchrotron with
 cooling break!

Ponti +13; +14; +15b; +17b

How can a super-luminal echo happen?

Projector Wall

 Velocity observed on the screen 1m/1s

To change
 slide 1 s

 Wall distant 1 m

 e.g. Ponti +10;+13

How can a super-luminal echo happen?
 Wall

Projector

 Velocity observed on the screen 3c!!!

To change
 slide 1 s

 Wall distant ~900000 km

 The physical variations happens in the projector! e.g. Ponti +10;+13

Conclusions X-ray polarisation
 ➜ Derive Sgr A*’s light curve
 ➜ 3-d distribution of clouds

 Starburst?

 ➜ Discovered the channel connecting the Synchrotron with
 activity at the Milky Way center with the cooling break!
 Fermi bubbles
 ➜ Outflow multi-phase, multi-epoch and
 multi-scale

Ponti +13; +14; +15b; +17b