Salts in Orion

Adam Ginsburg

Assistant Professor, University of Florida

Brett McGuire, John Bally, Ciriaco Goddi, Dick Plambeck, Melvyn Wright
Slides available at https://keflavich.github.io/talks/salts_orion.html
Ginsburg+ 2018c, Ginsburg+ 2019b
Press Release on "ALMA salt star"

Data, Papers, Source Code

Bally+ 2017
Bally+ 2017
Bally+ 2017
Src I, X, and BN were in the same location around 500 years ago.
The Explosion was around 500 years ago.
Probably the same event.
Farias+ 2018

What happened in Orion 500 years ago?

  • There was a non-hierarchical multiple system (unstable)
  • Dynamical interactions happened and flung out BN, I, X
  • A bunch of material was flung out. E~1047 erg
    • Did a star fly through another's disk?
    • Was there a stellar collision?
  • Src I has a disk, which is dynamically OK
    • \(v < v_{esc} = 23 \mathrm{~km~s}^{-1} \left(\frac{M_I}{15 \mathrm{M}_{\odot}}\right)^{1/2} \left(\frac{r}{50~\mathrm{AU}}\right)^{-1/2}\)
    • \(v_I \approx 11.5 \mathrm{~km~s}^{-1}\)

Orion Source I
a disk around a 15 M⊙ YSO

Salt: NaCl
Image: Ginsburg, NRAO
1 mm continuum
NaCl v=3 J=7-6
1 mm continuum
NaCl v=1 J=18-17
1 mm continuum
NaCl v=2 J=26-25
SiO v=5 J=8-7
NaCl v=2 J=26-25
SiO v=0 J=8-7
SiO v=5 J=8-7
NaCl v=2 J=26-25
880 μm continuum

Observing the Keplerian rotation profile of a disk is the most direct way to measure a protostar's mass

(we can only see the disk, not the star itself)

Salts are seen in other HMYSO disks

Luke Maud et al (2019) in G17.64+0.16 (\(d\sim2.2\) kpc)

Why do we see salt?

  • Previously, NaCl & KCl only in AGB* atmospheres,
    associated with dust formation
  • Most likely dust destruction here
    Dust destruction happens immediately as the outflow is launched?
  • What about excitation? We see vibrationally excited lines at v>1, which are not seen in AGB*s

Temperature?

Temperature?

We do not have a viable model to explain these temperatures

A strong non-blackbody radiation field from 25-40 µm may explain them.
Forsterite (MgSiO4) has some emission bands in that range. Maybe?
UV/optical electronic excitation is possible, but would likely dissociate the molecules

A contrived model

Electronic excitation analog

Kaplan+ 2017

Possible future uses for these lines?

  • Metallicity measurement in deeply embedded star-forming environments? (at least of Na, K, Cl) [probably not]
  • Disk kinematics of high-mass stars, which are otherwise unobservable (τ>1 at mm wavelengths)
  • Disk kinematic measurements at early stages?
  • Probe dust destruction (and/or formation?) in outflows, disks?
  • Probe radiation environment around HMYSOs?