Star Formation in a Dynamic Interstellar Medium

Workshop hosted by the Yale University

Astronomy Department

May 20, 2002

Simulation is a preview of work by Bate, Bonnell &

Bromm…stay tuned

The PlanTime Speaker Topic

09:40 Alyssa Goodman (CfA/Yale) Introduction

10:00 Phil Myers (CfA) What are the properties of the observed environment for star formation?

10:40 Coffee Break

11:00 Richard Larson What are the real observational constraints on the IMF?

11:40 Paolo Padoan (Caltech/JPL) What have we learned from numerical simulations of the star-forming ISM, on >1 pc scales?

12:20 Lunch

1:50 Bruce Elmegreen (IBM) On what scale is an IMF determined, and how might the answer to this question change? (Opinion #1)

2:30 Ian Bonnell (U. St. Andrews) On what scale is an IMF determined, and how might the answer to this question change? (Opinion #2; simulation figure above from Bate, Bonnell & Bromm)

3:10 Coffee Break

3:30 Richard Larson (Yale) Thoughts, and an open fourm, on the day's presentations

4:00 Meeting Adjourns, but those interested stay on to chat

Questions Raised by a Dynamic View of Star Formation

Scale Names Static Dynamic

100-1 pc Giant MolecularClouds, Cloud

Complexes

Formation ofGMCs in SpiralDensity Wave

• Ho w importan t ar e supernov ae a nd oth er b igoutflo ws increati ng b igmolecula r cloud ?s

• Doe s turbulenc e nee d drivin g on thes e scales?

10-0.1 pc Dark Clouds,Cl oudCores

(Jeans-like)Instabiliti es within

clouds le ad tostructures

• Assuming turbulenc e determine s the "clump IMF", wi th ashallowe r sl opet han th e stella r IM F at th is scale, w hatisthe ri ghtclu mp IM ? F (log-normal?)

• Ho w muc h of a rol e d o outflows pla y on th is scal : e r -eshapin g m ass distributio , n drivin g turbulence?

1-0.01 pc Dense Cores,Coher entCores,

Kernels

Gravitationalcollap se of J eans-m ass fragments

• D o inwar d motion s an d "coherent" cores rea lly resul t fromcollidi ngstreams?

• I s th (e stella ) r IM F se t b y th e turbulenc e a t these scales?i. . e Do es the"cl ump IMF" of self-gravitati ng blob =s stellarIMF?

• Ho w muc h dointeraction s amongs t forming densit y peaksand/ oryo ungstar s ma ?tter

0.1 pc-200 AU

Kernel , s Pse -udodisks, Disks,

Star +sProtoplanetary

Disks

Disk instabilitiesfragmen t d isks into

multipl e pieces,depending on

or dero f instability

• W hata re th e interacti on among stblobs, star s an d d isks i n aformi ngclust ?er

• W hata re th e blob ?s

• Ho w lon g dostructur es las ?t

• A re man y planet s discar ?ded

“4. Powering source of (some)

outflows may move rapidly through ISM.”

Goodman & Arce 2002

“Giant” Herbig-Haro

Flow inPV Ceph

Reipurth, Bally & Devine 1997

1 pc

PV Ceph: Episodic ejections

from precessing or

wobbling moving source

Implied source motion ~7 km/s (3 mas/year)

assuming jet velocity ~100 km/s

Goodman & Arce 2002

“4. Powering source of (some)

outflows may move rapidly through ISM.”

Goodman & Arce 2002

Goodman & Arce 2002

HST WFPC2 Overlay: Padgett et al. 2002

Arce & Goodman 2002

Goodman & Arce 2002

Trail & Jet

How much gas will be pulled along for the ride?

Goodman & Arce 2002

Insights from a “Plasmon” Model4x1018

3

2

1

0

y knot positions (cm)

-4x1017

-2 0

x knot posns. w.r.t. star "now" (cm)

500x1015

400

300

200

100

0

Distance along x-direction (cm)

15x103

1050

Elapsed Time since Burst (Years)

70

60

50

40

30

20

10

0

Knot Offset/Star Offset (Percent)

Knot

Star

Star-KnotDifference

Star-KnotDifference

(%)

Initial jet 250 km s-1; star motion 10 km s-1

Insights from a “Plasmon” Model4x1018

3

2

1

0

y knot positions (cm)

-4x1017

-2 0

x knot posns. w.r.t. star "now" (cm)

1

2

3

4

5

6

7

8

9

10

"Dynamical Time"/Elapsed Time

3.0x1018

2.52.01.51.00.50.0

Distance of Knot from Source (cm)