mapping the interstellar medium alyssa a. goodman harvard-smithsonian center for astrophysics (on...
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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
2000
2000
1990
1990
1980
1980
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1970
1960
1960
1950
1950
Year
100
101
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104
Nch
an
nels, S
/N in
1 h
our, N
pix
els
102
103
104
105
106
107
108
(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
50
05
10
15
20
25
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
102
103
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