Mapping the Interstellar Medium

Alyssa A. GoodmanHarvard-Smithsonian Center for Astrophysics

(on sabbatical 2001-2 at Yale University)cfa-www.harvard.edu/~agoodman

Barnard’s Interstellar

Medium

“Barnard’s Method”: Star Counting

Observations by Alves, Lada & Lada 1999

Counts of stars per unit area measure how much material must be producing obscuration.

Barnard’s Interstellar

Medium

The “Modern”

Interstellar Medium

The “Modern”

Interstellar Medium

Telescopes Used in Our Mapping of the ISM

NTT, VLT (Chile)

FCRAO & CfA (Mass.)

JCMT (Hawaii)

IRAM 30-m(Spain)

ATCA+Parkes(Australia)

KPNO 12-m & HHT

(Arizona)

HST, IRAS(Earth Orbit) SIRTF

(Sun Orbit)

Arecibo(Puerto Rico)

Nagoya 4-m(Japan)

The “Modern” ISM

IRAS Satellite Observation, 1983

Barnard’s Optical Photograph of

Ophiuchus

Remember: Cold (10K) dust glows, like a blackbody, in the far-infrared.

Tutorial: Absorption, Scattering, Emission & Extinction

Emitter

Absorber

“Emission”

Note: Absorption + Scattering = “Extinction”

“Scattering”

“Absorption”

Scatterer

Multiwavelength Milky Way

Advanced Tutorial: “Wavelength Dependence of

Extinction”

“Dust Grain”

“DustGrain”

Light is “Extinguished”& Does not Reach Us

Light Goes Right by& Reaches Us

Bok Globule (Core)

Seeing “through” the CloudsNear-Infrared

Optical

Multiwavelength Milky Way

Galaxy

"Velocity Coherent" Dense Core

Young Stellar Object +Outflow

Stars

time

Self-Similar, Turbulent,"Larson's Law" Clouds

Star Star FormationFormation

(a.k.a. GMC or Cloud Complex)

Thermal Dust

Emission in the OrionStar-

Forming Region

Outflows

MagnetohydrodynamicWaves

Thermal Motions

MHDTurbulence

InwardMotions

SNe/GRBH II Regions

Star Formationin the ISM

The “Modern” ISM

IRAS Satellite Observation, 1983

Barnard’s Optical Photograph of

Ophiuchus

Remember: Cold (10K) dust glows, like a blackbody, in the far-infrared.

The Very Cold ISM: 850 m Emission (T~15K)

Motte, André & Neri 1998

The “Modern” ISM

M. Pound 1

99

8Contours show Molecular Line (CO) Map

Galactic Longitude

Velo

city

What NASA Didn’t Explain…but I will…

“Molecular Hydrogen” (is really a CO map)

Spectral Lines Give VELOCITY

Galactic LongitudeGala

ctic

Lati

tud

e

Molecular Clouds: The Stuff of New Stars

Red Plate, Digitized Palomar Observatory Sky Survey

The Oschin telescope, 48-inch aperture wide-field Schmidt camera

at Palomar

Radio Spectral-line Observations of Interstellar Clouds

Spectral Line Observations

Tutorial:Velocity from Spectroscopy

1.5

1.0

0.5

0.0

-0.5

Inte

nsit

y

400350300250200150100

"Velocity"

Observed Spectrum

All thanks to Doppler

Telescope Spectrometer

1.5

1.0

0.5

0.0

-0.5

Inte

nsit

y

400350300250200150100

"Velocity"

Observed Spectrum

Telescope Spectrometer

All thanks to Doppler

Tutorial:Velocity from Spectroscopy

Radio Spectral-line Observations of Interstellar Clouds

Spectral Line Observations

Alves, Lada & Lada 1999

Radio Spectral-Line Survey

Radio Spectral-line Observations of Interstellar Clouds

Velocity as a "Fourth" DimensionSpectral Line Observations

Mountain RangeNo loss ofinformatio

n

Loss of1 dimension

Giant Outflow from a Young

Star (PV Ceph)

Goodman & Arce 2002

Molecular or Dark Clouds

"Cores" and Outflows

Rotation, Outflow & Turbulence all rely on Velocity Measurements

Jets and Disks

Solar System Formation

1 p

c = 3

lyr

Molecular Spectral Line Mapping

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nels, S

/N in

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our, N

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els

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(S/N

)*N

pix

els

*Nch

an

nels

Npixels

S/N

Product

Nchannels

That’s a one-thousand-fold“improvement” in 20 years.

Real & Simulated Spectral

Line Maps

Based on work of Padoan, Nordlund, Juvela, et al. simulation shown used in Padoan & Goodman 2002.

The Value of MHD Simulations

Stone, Gammie & Ostriker 1999•Driven Turbulence; M K; no gravity•Colors: log density•Computational volume: 2563

•Dark blue lines: B-field•Red : isosurface of passive contaminant after saturation

=0.01 =1

T / 10 K

nH 2 / 100 cm-3 B / 1.4 G 2

How Well do Numerical Models Match Reality?

Pow

er-

Law

Slo

pe o

f S

CF

vs.

Lag

Magnitude of Spectral Correlation at 1 pc

Padoan & Goodman 2002

“Reality”

Scaled “Superalfvenic”Models

“Stochastic”Models

“Equipartition”Models

Galactic Scale Heights from the SCF (v.2.0)

Padoan, Kim, Goodman & Stavely-Smith 2001

HI map of the LMC from ATCA & Parkes Multi-Beam, courtesy Stavely-Smith, Kim, et al.

Galaxy

"Velocity Coherent" Dense Core

Young Stellar Object +Outflow

Stars

time

Self-Similar, Turbulent,"Larson's Law" Clouds

Mapping Mapping Everything?Everything?

(a.k.a. GMC or Cloud Complex)

SIRTF’s1st Plan for

Star-FormingRegions

The SIRTFLegacySurvey

“From Molecular Cores to Planet-Forming Disks”Neal J. Evans, II, Principal Investigator (U. Texas)

Lori E. Allen (CfA)Geoffrey A. Blake (Caltech) Paul M. Harvey (U. Texas)

David W. Koerner (U. Pennsylvania)Lee G. Mundy (Maryland)

Philip C. Myers (CfA) Deborah L. Padgett (SIRTF Science Center)

Anneila I. Sargent (Caltech)Karl Stapelfeldt (JPL)

Ewine F. van Dishoeck (Leiden)

SIRTF Legacy Survey

Perseus Molecular Cloud Complex(one of 5 similar regions to be fully mapped in far-IR by SIRTF Legacy)

SIRTF Legacy Survey

MIRAC Coverage

2 degrees ~ 10 pc

Our Plan for theFuture:

COMPLETE

The COordinated Molecular Probe Line Extinction Thermal Emission Survey

Alyssa A. Goodman, Principal Investigator (CfA)João Alves (ESA, Germany)

Héctor Arce (Caltech)Paola Caselli (Arcetri, Italy)

James DiFrancesco (Berkeley)Doug Johnstone (HIA, Canada)

Scott Schnee (CfA)Mario Tafalla (OAS, Spain)Tom Wilson (MPIfR/SMTO)

2MASS/NICER Extinction Map of Orion

Un(coordinated) Molecular-Probe Line, Extinction

and Thermal Emission

Observations

5:41:0040 20 40 42:00

2:00

55

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10

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30

R.A. (2000)

1 pc

SCUBA

5:40:003041:003042:00

2:00

1:50

10

20

30

40

R.A. (2000)

1 pc

SCUBA

Molecular Line Map

Nagahama et al. 1998 13CO (1-0) Survey

Lombardi & Alves 2001Johnstone et al. 2001 Johnstone et al. 2001

The Value of CoordinationC18ODust EmissionOptical

Image

NICER Extinction Map

Radial Density Profile, with Critical

Bonnor-Ebert Sphere Fit

Coordinated Molecular-Probe Line, Extinction & Thermal Emission Observations of Barnard 68

This figure highlights the work of Senior Collaborator João Alves and his collaborators. The top left panel shows a deep VLT image (Alves, Lada & Lada 2001). The middle top panel shows the 850 m continuum emission (Visser, Richer & Chandler 2001) from the dust causing the extinction seen optically. The top right panel highlights the extreme depletion seen at high extinctions in C18O emission (Lada et al. 2001). The inset on the bottom right panel shows the extinction map derived from applying the NICER method applied to NTT near-infrared observations of the most extinguished portion of B68. The graph in the bottom right panel shows the incredible radial-density profile derived from the NICER extinction map (Alves, Lada & Lada 2001). Notice that the fit to this profile shows the inner portion of B68 to be essentially a perfect critical Bonner-Ebert sphere

Is this Really Possible Now?

10-4

10-3

10-2

10-1

100

101

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Time (hours)

20152010200520001995199019851980

Year

1 Hour

1 Minute

1 Day

1 Second

1 Week

SCUBA-2

SEQUOIA+

NICER/8-m

NICER/SIRTFNICER/2MASS

AV~5 mag, Resolution~1'

AV~30 mag, Resolution~10"

13CO Spectra for 32 Positions in a Dark Cloud (S/N~3)

Sub-mm Map of a Dense Core at 450 and 850 m

1 day for a 13CO map then

1 minute for a 13CO map now

COMPLETE, Part 1

Observations:Mid- and Far-IR SIRTF Legacy Observations: dust temperature and column density maps ~5 degrees mapped with ~15" resolution (at 70 m)

NICER/2MASS Extinction Mapping: dust column density maps, used as target list in HHT & FCRAO observations + reddening information ~5 degrees mapped with ~5' resolution

HHT Observations: dust column density maps, finds all "cold" source ~20" resolution on all AV>2”

FCRAO/SEQUOIA 13CO and 13CO Observations: gas temperature, density and velocity information ~40" resolution on all AV>1

Science:Combined Thermal Emission (SIRTF/HHT) data: dust spectral-energy distributions, giving emissivity, Tdust and Ndust

Extinction/Thermal Emission inter-comparison: unprecedented constraints on dust properties and cloud distances, in addition to high-dynamic range Ndust map

Spectral-line/Ndust Comparisons Systematic censes of inflow, outflow & turbulent motions will be enabled—for regions with independent constraints on their density.

CO maps in conjunction with SIRTF point sources will comprise YSO outflow census

5 degrees (~tens of pc)

SIRTF Legacy Coverage of Perseus

COMPLETE, Part 2

Observations, using target list generated from Part 1:

NICER/8-m/IR camera Observations: best density profiles for dust

associated with "cores". ~10" resolution SCUBA Observations: density and temperature profiles for dust associated with "cores" ~10" resolutionFCRAO+ IRAM N2H+ Observations: gas temperature, density and velocity information for "cores” ~15" resolution

Science:Multiplicity/fragmentation studies

Detailed modeling of pressure structure on <0.3 pc scales

Searches for the "loss" of turbulent energy (coherence)

FCRAO N2H+ map with CS spectra superimposed.

(Le

e,

Mye

rs &

Ta

falla

20

01

).

Mapping the Interstellar MediumAlyssa A. GoodmanHarvard-Smithsonian Center for Astrophysics

(on sabbatical 2001-2 at Yale University)cfa-www.harvard.edu/~agoodman