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¹Center for Astrophysics and Space Astronomy (CASA)

Department of Astrophysical and Planetary Sciences (APS)

University of Colorado, Boulder, USA

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The CMZ Asymmetries: Feeding or Feedback?

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John Bally¹

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The Inner CMZ 8 um 24 um N(H₂)

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+2.0^o -2.0^o

Central Molecular Zone (CMZ)

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Denser, more turbulent than disk GMCs: M_gas ~ 2 – 5 x 10⁷ M_o

Star Formation Rate (SFR): ~ 0.04 to 0.1 M_o yr ^-1

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Infall Rate from Disk: ~ 1 M_o yr ^-1

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• The Two Asymmetries:

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Gas & dust: > 3/4 at POSITIVE longitude, + velocity

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24 μm sources: > 2/3 at NEGATIVE longitude

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• Short orbit times & Shear : t_orbit ~ 6.3 Myr R_{100 pc} / V_{100 km/s}

(1 to 10 Myr)

1 GHz 70 um 8 um (MeerKAT: Heywood+2022; Hi-GAL)

1 degree (144 pc)

Sgr B2 SgrB1 Galactic Center Bubble Sgr A Sgr C Wray 17-96 (LBV)

Sgr B2 SgrB1 Galactic Center Bubble Sgr A Sgr C Wray 17-96 (LBV)

1 GHz (MeerKAT: Haywood+ 2022 ) 24 um 8 um

(Herschel Hi-GAL)

1 degree (144 pc)

N(H₂) 1 GHz (MeerKAT: Heywood+ 2022)

(Herschel Hi-GAL)

1 degree (144 pc)

Sgr B2 SgrB1 Galactic Center Bubble Sgr A Sgr C Wray 17-96 (LBV)

N(H₂) from Hi-GAL 24 um Spitzer

1 degree (144 pc)

Sgr B2 SgrB1 Galactic Center Bubble Sgr A Sgr C Wray 17-96 (LBV)

N(H₂)

Negative longitudes

Sgr C

SgrA

1 degree (144 pc)

24 um

Negative longitudes

Negative longitudes

Sgr C

SgrA

1 degree (144 pc)

1 GHz

Negative longitudes

Sgr C

SgrA

1 degree (144 pc)

1 GHz 24 um 8 um

Negative longitudes

Sgr C

SgrA

1 degree (144 pc)

N(H₂)

Positive longitudes

Sgr B2 SgrB1 Galactic Center Bubble Sgr A

Brick

1 degree (144 pc)

24 um

Sgr B2 SgrB1 Galactic Center Bubble Sgr A

Positive longitudes

Brick

1 degree (144 pc)

1 GHz

Sgr B2 SgrB1 Galactic Center Bubble Sgr A

Positive longitudes

Brick

1 degree (144 pc)

1 GHz 24 um 8 um

Sgr B2 SgrB1 Galactic Center Bubble Sgr A

Positive longitudes

Brick

1 degree (144 pc)

Life in a Bar:

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X₁ to X₂

orbits

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(Ridley+ 2017)

To Sun

X₁

X₂

Milky Way bar-shock / leading-edge dust lanes (Sormani, Barnes 2019)

NGC 1097(HST)

Most CMZs are symmetric

Nuclear Rings in Galaxies (Peeples & Martini 2006)

Most CMZs are symmetric

ALMA

Phangs

CO

JWST NGC1300

Most CMZs are symmetric

JWST NGC1365

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Most CMZs are symmetric

Magnetized CMZ Models (Tress+ 2023)

Asymmetric Feeding of CMZ?

“Wiggle instabilities” in bar shocks (leading-edge dust lanes)?

(Kim+ 2014; Sormani+ 2017; Mandowara, Sormani+ 2022)

x₁ to x₂ orbits in Bar Models

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“Wiggle instabilities” in bar shocks? => Infalling clumps => Asymmetries

(Sormani+2018)

HI

CO

CO

x₁ to x₂ orbits in Bar Models (Sormani+2018)

“Wiggle instabilities” in bar shocks? => Infalling clumps => Asymmetries

CMZ Models (Sormani+2018)

“Wiggle instabilities” in bar shocks? => Infalling clumps => Asymmetries

HI

CO

CO

Galactic Ecology: Star Formation & the Interstellar Medium

50 - 100 Myr

Cycle

Feedback

Star Formation, a Self-Regulated Process

EUV & wind feedback in W5

Post-Main-sequence Feedback:

WR stars, LBVs, RSGs,

Close-binaries & mergers

η-Carina

Ou4 (Corradi 2014)

in Sh2-129

V838 Mon

Cas A SNR: X-ray Hα IR

Post-Main-sequence Feedback:

WR stars, SNe, neutron stars, BHs

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NGC 2359

A wind-bubble

blown by a

massive star

HD 56925

Galactic Center Bubble: 8 μm 70 μm 350 μm

W50 / SS433 relativistic jet

Feedback?

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The Feedback Ladder

Progression of ever stronger feedback impacts ….

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Protostar Outflows => local, all M_*, couples directly to cloud

FUV/heating =>

EUV/ionization =>

Stellar winds =>

Radiation pressure =>

M.S. dynamic interactions / mergers =>

Post-M.S. outflows =>

SNe => global, high M_* ; P, E

Black holes vented away from SFRs.

Feedback failure => High SFE, bound clusters?

Stellar Feedback in the CMZ

OB stars: Outflows, FUV, HII, stellar winds, post-MS mass-loss, SNe, black holes

M_{gas, CMZ} ~ 2-5 x 10⁷ M_o ΔV_gas ~ 10 - 20 km/s

M_GMC ~ 10⁵ M_o , R_gmc ~3 – 10 pc

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1 GMC:

Self-gravity (E_G ~ GM_g²/R_c): ~ 1 – 3 x10⁵⁰ erg

Molecular binding energy (E_mol ~ M_gmc [4.8 eV] /μm_H ) ~ 3 x 10⁵⁰ erg

Energy to disrupt 10⁵ M_o GMC: ~ 10⁵¹ erg (~ 1 SN)

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100 GMCs (10⁷ M_o= 20% of CMZ):

Energy to disrupt: ~ 10⁵³ erg (~100 SNe)

H₂ => 21 cm HI + HII

To eject from R₁₀₀ pc to infinity: ~ 10⁵⁵ – 10⁵⁶ erg

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Likely need SMBH feedback => Fermi-LAT Bubbles?

or Face Accumulation problem !

Summary

Asymmetries:

Gas-dust: 2/3 to 3/4 at Positive longitude & velocity

24 μm compact sources: 2/3 to 3/4 at Negative longitude

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Accumulation Problem: M / SFR => t > 10⁸ yr

Shear should symmetricize CMZ!

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Compact 24 μm Sources ?

MYSO (t < 0.1 Myr) ? (Sgr B1, Sgr B2)

Main-Sequence stars in CMZ ISM ? (Impostor MYSOs)?

post-Main-Sequence OH/IR, RSGs? (t >3 to 30 Myr old massive stars)

(Jang & An+ 2022)

>10⁵ M_o, tidally sheared cluster 10 to 30 Myr ago?

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We Underestimate Feedback E,P Injection Rates: “Tre Are No Perfect Tracers”

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Did CMZ Star Formation Feedback disrupt a quandant of the CMZ?:

UV, winds,~10^2-3 SNe, accreting Dark Remnants, …:

=> Dissociate, “puff-up” a CMZ sector

Mass-load Fermi Bubble, aided by the SMBH ?

Does stellar feedback prevent SMBH growth?

“Nature is Truth; Observations & Simulations are approximations”

Hα MDW Survey (David Mittelmann, Dennis Di Cicco, Sean Walker)

Superbubbles …

Orion H-alpha

350 pc

Questions:

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Infall rate from R ~ 3 kpc? ~ 1 M_o/yr ? (Tress+ 2020)

Why so asymmetric? (t _{orbit 100pc} ~ 6 Myr)

Stochastic infall? (Sormani+ 2018) Starburst feedback ?

Star Formation Rate: ~0.04 – 0.1 M_o/yr ? (Sormani+ 2020)

Quasi-periodic bursts ~ 30 -50 Myr ? (Armillotta+ 2019, 2020)

Negative-longitude 24 um sources?

Conveyor-Belt? (Kruijjsen, Longmore 2015, 2019)

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Where Does Most Gas Go?

Stars or Ejected ?

What ejects it?

OB star feedback + Transient AGN outbursts? => Fermi/LAT ?