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Hot Cores:
Sites of early feedback

Adam Ginsburg

Assistant Professor
Department of Astronomy
University of Florida, Gainesville

with the ALMA-IMF team (incl. Timea Csengeri, Melisse Bonfand, Thomas Nony), postdoc Allison Towner, and students Desmond Jeff, Theo Richardson, Alyssa Bulatek, Nazar Budaiev, and Savannah Gramze
Slides available at https://keflavich.github.io/talks/ascona2022_feedback.html

Hot Cores are the sites of high-mass star formation

While the star is still accreting rapidly, before it has contracted enough to produce ionizing radiation, it cooks a warm, dusty envelope.
W51e2e
$r\sim0.06$ pc
$T=350$ K
G+ 2017
W51e2e:
20-30 $M_\odot$ star accreting at $>10^{-4} M_\odot$ yr$^{-1}$ surrounded by $\sim300$ $M_\odot$ of fresh material
G+ 2017
Goddi+ 2020
HCs suppress fragmentation, drive mass function higher
Jeans Mass MJ ∝ T3/2 ρ−1/2
Ginsburg+ 2017

ALMA-IMF: $\sim800$ cores

www.almaimf.com/data.html
Pouteau+ 2022 W43-MM2/3
Hot cores in ALMA-IMF: From rare objects to a population ($\sim50$)
Cores with line forests
TD>50 K
TG ≳100K
Brouillet+, resubmitted
Observationally, hot cores exhibit "line forests"
Cores with line forests
TD>50 K
TG ≳100K
Brouillet+, resubmitted
Bonfand+: CH3OCHO HC catalog ($T\gtrsim100$ K)
Many lines of CH3OCHO toward W51-E2

ALMA-IMF:
The CMF is shallow (top-heavy) in HMSFRs

Pouteau+ 2022 W43-MM2/3 CMF
Motte+ 2018 W43-MM1 CMF: α≳-1

How does the observed CMF transform to the IMF?




Offner+ 2014 PPVI review

Top-heavier IMFs are seen in high-mass clusters,
CMFs in protoclusters

Hosek+ 2019
https://tinyurl.com/IMF-figure

Hot cores are the most massive cores

Hot cores are mostly small ($\lesssim5000$ AU)

HCs are the centers of protoclusters

where $F_{grav} > F_{feedback}$

W51-E

HCs are the centers of protoclusters

where $F_{grav} > F_{feedback}$

W51-IRS2
Hot cores are more prevalent in the Galactic center
$\sim 10^{-5}$ kpc$^{-2}$ in the disk, $\sim10^{-3}$ kpc$^{-2}$ in the CMZ
Desmond Jeff:
Ten hot cores in Sgr B2 DS
TG ~ 200-500 K
M ~ 200 - 2900 M⊙

Hot cores in the CMZ are a bit hotter and more massive

Summary:

  • IR feedback from HMYSOs heats gas
  • The CMF (and IMF?) appear shallower in HMSFRs
  • Hot cores likely affect the CMF locally, driving up the average mass

ACES progress report

Data are about half delivered!
Talk 2: Sgr B2 is a template for clusters in starbursts

SSCs in starbursts drive outflow

NGC 253 protoclusters (Leroy+2018)
NGC 4945 protoclusters (Emig+2020)

Levy+ 2021

Our Galaxy's center, the CMZ, has denser gas than the Galactic average

Image: NRAO, Ginsburg
Mills, Ginsburg+ 2018; Kruijssen & Longmore 2013
Cold Dust
Hot, ionized gas
Hot dust/PAHs

The proto-Super Star Cluster Sgr B2 is forming in the CMZ

Image: NRAO, Ginsburg
Ginsburg+ 2018a

The proto-Super Star Cluster Sgr B2 is forming in the CMZ

Image: NRAO, Ginsburg
Ginsburg+ 2018a

Sgr B2 N is rapidly accreting...

Schwörer+ 2019
M(gas)=2000-4000 M⊙
Ṁ(in)=0.16 M⊙ yr -1

...and driving a massive outflow

Smallest example of a cluster-driven outflow?
(not from 1 YSO!)
Schwörer+ 2021 (subm.)
Ṁ(out) =0.044 M⊙ yr -1



Sgr B2: the most massive & star-forming cloud in the Galaxy
Ginsburg+ 2018a
Ginsburg+ 2018a
Ginsburg+ 2018a
Ginsburg+ 2018a
Hot cores are more prevalent in the Galactic center
$\sim 10^{-5}$ kpc$^{-2}$ in the disk, $\sim10^{-3}$ kpc$^{-2}$ in the CMZ
Desmond Jeff:
Ten hot cores in Sgr B2 DS
TG ~ 200-500 K
M ~ 200 - 2900 M⊙

Hot cores in the CMZ are a bit hotter and more massive

Nazar Budaiev: Low-mass YSOs in Sgr B2M
49 at 0.5" →
169 at 0.05"
Nazar Budaiev: Low-mass YSOs in Sgr B2N
26 at 0.5" →
209 at 0.05"
Sgr B2 is filled with pressure-confined HII regions
Meng+ 2019, 2022/subm
Sgr B2's HII regions accelerate cosmic rays
Meng+ 2019, Padovani+ 2019

The "Bound Cluster Fraction" is higher in CMZs

Kruijssen 2012
Ginsburg & Kruijssen 2018
Γ is the fraction of stars forming in bound clusters
Galaxy averages
CMZ prediction
Sgr B2 data

ACES progress report

Data are about half delivered!
Summary 2:
  • Sgr B2 is the local reference for SSCs!
  • It is the best local analog to super star clusters in other galaxies
  • It contains examples of:
    • Cluster-driven molecular outflow
    • Feedback-heated molecular gas
    • CR acceleration in HII regions
    • Pressure-confined HII regions

Aside about HII regions

Related to Shyam Menon's and Grace Olivier's talks:
  • HII regions are optically thin in the near-IR, so IR trapping is ineffective
  • Hot cores are very optically thick ($\Sigma \gtrsim 1$ g cm$^{-2}$) but also massive and gravitationally dominated