We’ve got the smoke, but where’s the gun? We’ve got the smoke, but where’s the gun? IR astronomy, paradigms of star formation, IR astronomy, paradigms of star formation,

andand A search for high-mass protostars. A search for high-mass protostars.

Murray Campbell, 25 years of Colby students, and colleagues at UofA, UT Austin, BU, CfA, Keck, UKIRT, Cornell, Gemini, and MPIfA

Current students at Colby:Frank Fung, Tomas Vorobjov, Cliff Johnson, and Ry Brooks

Special thanks to Mike Ramstrom, and John Kuehne,

?

Only on the Only on the largest largest cosmological cosmological scales is scales is astronomy astronomy simple!simple!

The complexity you see here is only the beginning…

Hubble:Advanced Camera for Surveys Ground ESO-MPI 2.2m La Silla Filters:F435W (B) F555W (V) F658N (Ha) F775W (i) F850LP(z)ESO842 (B) ESO856 (Ha) ESO857 ([S II]) ESO859 ([O III])

A new composite view of the Orion nebula.

More beauty.More complexity.

The Simple Analysis Party is Busted!The Simple Analysis Party is Busted! Astronomy ought to be Astronomy ought to be

a study of atoms, a study of atoms, gravity, nuclear physics, gravity, nuclear physics, and newsworthy exotic and newsworthy exotic forces.forces.

Dust, clumpiness, and Dust, clumpiness, and turbulence spoil the turbulence spoil the party.party.

The universe is 90% H, The universe is 90% H, and clouds are mostly in and clouds are mostly in H or HH or H22, but you can’t , but you can’t see them in visible light.see them in visible light.

Interstellar H or H2 cloud in visible light:

Orion is a rare H+ = HII cloud (HII region)

Shit Happens.

Redeeming graces of DustRedeeming graces of Dust

Wavelength shifter Wavelength shifter and integrator:and integrator:

Absorbed light is re-Absorbed light is re-emitted in IR.emitted in IR.

IR is often THE best IR is often THE best estimator of estimator of luminosity!luminosity!

Great Observatories Origins Deep Survey

Figure 24-36Figure 24-36Dusty DonutDusty Donut

Chaisson and McMillan, Astronomy Today, 5th ed. (2005)

The Virial Theorem Rules Many The Virial Theorem Rules Many Processes, including Star Processes, including Star

FormationFormation

As an object collapses to a smaller size, the As an object collapses to a smaller size, the magnitude of its Gravitational Potential Energy gets magnitude of its Gravitational Potential Energy gets bigger.bigger.

But only half of the kinetic energy released can go But only half of the kinetic energy released can go into heating the gas, or it violates the theorem.into heating the gas, or it violates the theorem.

If it can’t radiate, it can’t collapse!If it can’t radiate, it can’t collapse!

€

1

2Gas,etc

∑ mv 2 =1

2Gravitational Potential Energy

€

Dust is a key player: IDust is a key player: I

H and HH and H22 don’t radiate in most cloud don’t radiate in most cloud conditions.conditions.

Dust can absorb energy from gas through Dust can absorb energy from gas through collisions and radiate it in the IR.collisions and radiate it in the IR.

Dust’s IR efficiency can keep the cloud at Dust’s IR efficiency can keep the cloud at its ORIGINAL TEMPERATURE.its ORIGINAL TEMPERATURE.

So the collapse is initially FREE FALL!So the collapse is initially FREE FALL! Density variations cause fragmentation Density variations cause fragmentation

into many cores.into many cores.

Dust is a key player: IIDust is a key player: II

Each collapse is inside out: a collapsing core Each collapse is inside out: a collapsing core becomes a protostar inside an envelope.becomes a protostar inside an envelope.

The outside envelope’s dust absorbs the The outside envelope’s dust absorbs the protostar’s emission and reradiates it in the protostar’s emission and reradiates it in the IR.IR.

So we can find where the process is going So we can find where the process is going on.on.

But the protostar itself may be obscured.But the protostar itself may be obscured.

Shit Happens.

Dust is a key player: IIIDust is a key player: III

In far-IR (50-200In far-IR (50-200m), dust emission gives m), dust emission gives virtually total luminosity (power in watts).virtually total luminosity (power in watts).

In millimeter and submillimeter In millimeter and submillimeter wavelengths, dust emission can be used wavelengths, dust emission can be used to measure the mass of a molecular cloud, to measure the mass of a molecular cloud, and its star forming cores.and its star forming cores.

Galaxies, Dust, and Galaxies, Dust, and StarburstsStarbursts

Oops.

I forgot to say that “naturally occurring” interstellar clouds are stable against collapse.

The density is too low to have enough gravitational potential energy and the collisional coupling between gas and dust is too weak for dust cooling.

They only become unstable with help from a compression, as happens in galactic collisions.

Hubble close-up of a galactic collision that triggered star formation in NGC1275. The star formation is in the optically dark clouds.

A Brief HistoryA Brief History The first observation of dust in The first observation of dust in

emission was made by physicists emission was made by physicists who built IR detectors and put who built IR detectors and put them on telescopes.them on telescopes.

The first important far-ir source The first important far-ir source was the Galactic Center, was the Galactic Center, discovered by a one-inch discovered by a one-inch telescope on a high altitude telescope on a high altitude balloon.balloon.

It’s luminosity comes largely from It’s luminosity comes largely from formation of high-mass stars.formation of high-mass stars.

The Infrared Astronomy Satellite The Infrared Astronomy Satellite (IRAS) discovered that many (IRAS) discovered that many galaxies are strong IR emitters, galaxies are strong IR emitters, especially colliding galaxies!especially colliding galaxies!

The Galactic Center and plane of the the Milky Way at 100 m are shown in the background, but Spitzer is best for galaxies and low-mass stars.

More History…More History…

The bright far-IR The bright far-IR sources were all dust sources were all dust clouds around high-clouds around high-mass stars.mass stars.

Radio astronomers Radio astronomers mapping molecules’ mapping molecules’ rotation lines rotation lines discovered incredible discovered incredible outflows!outflows!

The outflows were The outflows were associated with low-associated with low-mass protostars.mass protostars.

Most astronomers focused on low-mass star formation.

Low-Mass Star Formation: Paradigms for the Low-Mass Star Formation: Paradigms for the cloud core’s evolution.cloud core’s evolution.

The core is the most The core is the most easily observed easily observed componentcomponent

Before collapse, the Before collapse, the core has uniform core has uniform temperature, and temperature, and density ~rdensity ~r-2-2, or , or something else.something else.

A uniform core would A uniform core would experience a experience a homologous collapse.homologous collapse.

Dense parts collapse Dense parts collapse fastest.fastest.A cloud forms many A cloud forms many cores.cores.In each core, the In each core, the protostar pulls away protostar pulls away from the outer core: from the outer core: inside out-collapse.inside out-collapse.Rotation is Rotation is important…important…

A (Simplified) Realistic ModelA (Simplified) Realistic Model

An outer envelope, An outer envelope, with density ~rwith density ~r-2-2..

A rotationally A rotationally flattened infalling flattened infalling envelope with density envelope with density determined by free determined by free fall, ~rfall, ~r-3/2-3/2..

An inner, flared An inner, flared accretion disk.accretion disk.

An outflow cavity.An outflow cavity. Barbara Whitney et al. 2003 ApJ 591, 1049

WHY SHOULD WE BELIEVE THE PARADIGM?WHY SHOULD WE BELIEVE THE PARADIGM?

Hydrodynamic models of Hydrodynamic models of collapsing clouds are roughly fit collapsing clouds are roughly fit by observations.by observations.

Hydrodynamic models of Hydrodynamic models of protostars give reasonable protostars give reasonable luminosities due to gravitational luminosities due to gravitational contraction, accretion, and the contraction, accretion, and the onset of nuclear fusion.onset of nuclear fusion.

Hydrodynamic models of Hydrodynamic models of accreting protostars are accreting protostars are consistent with reasonable consistent with reasonable accretion rates.accretion rates.

Observed Spectral Energy Observed Spectral Energy Distributions (SEDs) can be Distributions (SEDs) can be explained by evolving disks and explained by evolving disks and envelopes.envelopes.

Jets are a natural consequence of Jets are a natural consequence of rotation, even if hard to understand rotation, even if hard to understand in detail.in detail. Disks are observed.Disks are observed.

Interstellar Cloud Evolution Shown Explains a “Sequence” of SEDsInterstellar Cloud Evolution Shown Explains a “Sequence” of SEDs

Protostar Class 0/I Class II/III Star

Chaisson and McMillan (2005)

If a protostar’s a gun, what forms does If a protostar’s a gun, what forms does the smoke take?the smoke take?

DustDust Far-ir continuum emissionFar-ir continuum emission Mid-ir cont. emission and Mid-ir cont. emission and

solid state bandssolid state bands mm and sub-mm cont. mm and sub-mm cont.

emissionemission Ionized gas (HII regions) Ionized gas (HII regions)

around young high-mass around young high-mass starsstars cm continuumcm continuum mid-ir ionic lines [NeII]mid-ir ionic lines [NeII]

Molecular hydrogen, HMolecular hydrogen, H22 Near-ir lines from shock Near-ir lines from shock

frontsfronts

Molecules--thermalMolecules--thermal mm emission linesmm emission lines Velocity maps of outflowsVelocity maps of outflows Velocity maps of disksVelocity maps of disks

Molecules--non-thermal Molecules--non-thermal (Masers)(Masers) HH22OO CHCH33OH (methanol)OH (methanol) SiO, OH, etc.SiO, OH, etc.

Visible images of disks and Visible images of disks and jets around low-mass jets around low-mass protostarsprotostars

Embedded low-mass young Embedded low-mass young stars (YSOs) visible in near-irstars (YSOs) visible in near-ir

So, what’s the problem for So, what’s the problem for high-mass star formation?high-mass star formation?

Very high accretion rates are required.Very high accretion rates are required. Nuclear fusion should begin in the core before the outer layer is finished Nuclear fusion should begin in the core before the outer layer is finished

accretion from its parent cloud core.accretion from its parent cloud core. Radiation pressure should stop accretion before a star can reach its final Radiation pressure should stop accretion before a star can reach its final

mass.mass. High-mass stars only form in clusters, so isolating individuals is difficult: High-mass stars only form in clusters, so isolating individuals is difficult:

Almost no HMPOs have been unambiguously identified at specific star-Almost no HMPOs have been unambiguously identified at specific star-like points on the sky that can be easily observed in isolation from like points on the sky that can be easily observed in isolation from nearby already formed high-mass stars.nearby already formed high-mass stars.

High-mass stars are rare, so high-mass protostars (HMPOs) are even High-mass stars are rare, so high-mass protostars (HMPOs) are even less common, especially nearby.less common, especially nearby.

HMPOs are more deeply embedded than low-mass counterparts, so HMPOs are more deeply embedded than low-mass counterparts, so there are no certain visible light images of disks and jets.there are no certain visible light images of disks and jets.

Obscuration by clumps of dense gas and dust make identification of Obscuration by clumps of dense gas and dust make identification of individual protostars difficult.individual protostars difficult.

No details are really pinned down in the process.No details are really pinned down in the process.

Why are HMPOs important?Why are HMPOs important?

High-mass stars dominate the luminosity High-mass stars dominate the luminosity of galaxies they are in.of galaxies they are in.

High-mass stars’ nucleosynsthesis High-mass stars’ nucleosynsthesis dominates the chemical evolution of dominates the chemical evolution of galaxies, and the universe.galaxies, and the universe.

High-mass stars luminosities, outflows, High-mass stars luminosities, outflows, and winds dominate the evolution of the and winds dominate the evolution of the interstellar medium, and hence on-going interstellar medium, and hence on-going star formation. star formation.

What should we look for?What should we look for?

Sources of mid- and far-ir with a variety of Sources of mid- and far-ir with a variety of sensible spectral energy distributions sensible spectral energy distributions (SEDs).(SEDs).

Hot, high density molecular cores that are Hot, high density molecular cores that are internally heated.internally heated.

Evolution of SEDsEvolution of SEDs

Star, "Disk", and Envelope: Av Disk = 0.5 Av Envelope = 200

1.00E-11

1.00E-10

1.00E-09

1.00E-08

1.00E-07

1.00E-06

0.1 1 10 100 1000

Wavelength in Microns

Lambda F(lambda) in erg sec-1 cm-2

Star, "Disk", and Envelope: Av Disk = 0.05 Av Envelope = 10

1.00E-11

1.00E-10

1.00E-09

1.00E-08

1.00E-07

1.00E-06

0.1 1 10 100 1000

Wavelength in Microns

Lambda F(lambda) in erg sec-1 cm-2

Star, "Disk", and Envelope: Av Disk = 0.01 Av Envelope = 0

1.00E-11

1.00E-10

1.00E-09

1.00E-08

1.00E-07

1.00E-06

0.1 1 10 100 1000

Wavelength in Microns

Lambda F(lambda) in erg sec-1 cm-2

Star, "Disk", and Envelope: Av Disk = 0.0 Av Envelope = 0

1.00E-11

1.00E-10

1.00E-09

1.00E-08

1.00E-07

1.00E-06

0.1 1 10 100 1000

Wavelength in Microns

Lambda F(lambda) in erg sec-1 cm-2

Very approximate calculations by Cliff Johnson and me for high-mass protostars.

Color-Color PlotsColor-Color Plots The shapes of SEDs can The shapes of SEDs can

be analysed by ratios of be analysed by ratios of logs of photometric points.logs of photometric points.

Ratios of logs are Ratios of logs are proportional to differences proportional to differences in astronomical in astronomical magnitudes, that are magnitudes, that are called “Color Indices”called “Color Indices”

““Color-Color” plots can be Color-Color” plots can be used to select classes of used to select classes of objects from a photometric objects from a photometric database.database.

Wood and Churchwell derived color-color criteria for deeply embedded high-mass stars with ultracompact HII regions (UC HIIs).[1989 ApJ, 340, 265)]

Sridharan, Beuther, Schilke and Sridharan, Beuther, Schilke and Menten Survey of HMPOs IMenten Survey of HMPOs I

Criteria for sources:Criteria for sources: Detected in previous CS Detected in previous CS

survey.survey. IRAS IR colors meeting Wood IRAS IR colors meeting Wood

and Churchwell UCHII region and Churchwell UCHII region criteria.criteria.

Bright in far-ir in IRAS survey. Bright in far-ir in IRAS survey. (IRAS F(60 m) > 90 Jy and F(100 m) > 500 Jy)

Not detected in cm surveys for Not detected in cm surveys for HII regions. HII regions. (F(cm) < 25 mJy)

Number satisfying criteriaNumber satisfying criteria 6969

Observations:Observations: Search for mid-ir sources in Search for mid-ir sources in

Midcourse Space Expreiment Midcourse Space Expreiment (MSX) archive.(MSX) archive.

Search for cm emission at Very Search for cm emission at Very Large Array.Large Array.

Survey thermal molecular lines at Survey thermal molecular lines at Institut de Radioastronomie Institut de Radioastronomie Millimetrique (IRAM) 30 m Millimetrique (IRAM) 30 m telescope and MPIfR Effelsberg telescope and MPIfR Effelsberg 100m telescope .100m telescope .

Search for masers at MPIfR Search for masers at MPIfR Effelsberg 100m telescope.Effelsberg 100m telescope.

Map dust continuum at IRAM.Map dust continuum at IRAM.

Sridharan, Beuther, Schilke and Sridharan, Beuther, Schilke and Menten Survey of HMPOs IIMenten Survey of HMPOs II

Some Results:Some Results: Derived Luminosities from IRAS.Derived Luminosities from IRAS. Found most sources in 18Found most sources in 18 MSX MSX

survey.survey. Found some to be weak cm sources Found some to be weak cm sources

indicative of young UCHII regions.indicative of young UCHII regions. Found many with wide CO lines Found many with wide CO lines

indicating outflows.indicating outflows. Found many HFound many H220 and CH0 and CH330H masers.0H masers. Mapped all in 1.2 mm dust continuum.Mapped all in 1.2 mm dust continuum.

Why Follow-up Sridharan Why Follow-up Sridharan Survey on IRTF?Survey on IRTF?

IRAS and MSX surveys were low resolution, with IRAS and MSX surveys were low resolution, with beams (1beams (1x5x5 and 18 and 18) covering whole proto-) covering whole proto-clusters, so hope to:clusters, so hope to:

Identify individual HMPOs with beams of 1-2Identify individual HMPOs with beams of 1-2. . (IRTF would primarily detect compact objects)(IRTF would primarily detect compact objects)

Determine statistics of HMPOs in each proto-Determine statistics of HMPOs in each proto-cluster, the initial mass function (IMF).cluster, the initial mass function (IMF).

Make approximate models of dust around each Make approximate models of dust around each HMPO.HMPO.

Observations at IRTF on Observations at IRTF on Mauna Kea, HawaiiMauna Kea, Hawaii

• In collaboration with Shridharan, Beuther, and MIRSI Team.In collaboration with Shridharan, Beuther, and MIRSI Team.• High sensitivity images at 10.4High sensitivity images at 10.4m covering about a square m covering about a square

arc minute.arc minute.• Images at 24.8Images at 24.8m.m.• Low resolution “grism” spectra from 8-13Low resolution “grism” spectra from 8-13m.m.• Telescope was controlled from my office 9/13-15/2003.Telescope was controlled from my office 9/13-15/2003.• Frank Fung worked on planning and initial data processing.Frank Fung worked on planning and initial data processing.• Tomas Vorobjov helped with planning.Tomas Vorobjov helped with planning.• Frank, Glen Munkhold, and my wife kept logs during parts Frank, Glen Munkhold, and my wife kept logs during parts

of the observations.of the observations.

Criteria and Initial ResultsCriteria and Initial Results

Chose 1/3 of survey members with Chose 1/3 of survey members with brightest, most compact MSX 12brightest, most compact MSX 12m m emission.emission.

Found compact sources in 18 of 23 fields.Found compact sources in 18 of 23 fields. Found multiple sources in 7 fields.Found multiple sources in 7 fields. On average, brightest source in each field On average, brightest source in each field

accounts for 40% of large beam flux.accounts for 40% of large beam flux. Typical spectra have moderately deep Typical spectra have moderately deep

silicate absorption.silicate absorption.

Analysis in ProgressAnalysis in Progress

Studying two fields that have been mapped on Studying two fields that have been mapped on the Plateau de Bure Interferometer (PdBI) or the the Plateau de Bure Interferometer (PdBI) or the Submillimeter Array (SMA) .Submillimeter Array (SMA) .

Reducing and analyzing spectra--begun by Ry Reducing and analyzing spectra--begun by Ry Brooks.Brooks.

Beginning to make approximate models of SMA Beginning to make approximate models of SMA sources--begun by Cliff Johnson.sources--begun by Cliff Johnson.

IRAS 19410+2336IRAS 19410+2336

Spitzer Space Telescope Spitzer Space Telescope GLIMPSE IRAC Image GLIMPSE IRAC Image

44oox4x4oo

Blue=3.6Blue=3.6mm

Green=5.8Green=5.8m (Hm (H22))

Red=8.0 Red=8.0 m (PAH)m (PAH)

Galactic Legacy Infrared Midplane Survey ExtroidinairePI: Ed Churchwell, Wisconsin

Collaborator Joe Hora (CfA) hasaccessed the Spitzer database, and processed the IRAC images.

Shocked HShocked H22 and CO Outflows and CO Outflows

Beuther, Schilke&Stanke2003A&A 408,601

Our region of interest

Our region of interest

Dust Continuum (1.2mm, 3 mm, 1.3mm) Beuther & Schilke 2004 Dust Continuum (1.2mm, 3 mm, 1.3mm) Beuther & Schilke 2004 Science 303, 1167Science 303, 1167

MM and Mid-IR Compared: Scales allignedMM and Mid-IR Compared: Scales alligned

Blue: IRAC 8m; Green IRTF 10.4m; Red IRTF 24.8m

IRAC Positions

Right: 1.3mm Plateau de Bure Interferometer

What is the optical depth of the dust in the mid-ir?What is the optical depth of the dust in the mid-ir?

Absorption/emissivity properties of Absorption/emissivity properties of diffuse interstellar dust are diffuse interstellar dust are dramatic function of wavelength.dramatic function of wavelength.

Based on 1.2 mm dust emission, Based on 1.2 mm dust emission, expect Aexpect Avv = 1000 in core. = 1000 in core.

Don’t expect to see any mid-ir at Don’t expect to see any mid-ir at all!all!

Source might be on near edge of Source might be on near edge of cloud core--would violate cloud core--would violate paradigm for high-mass star paradigm for high-mass star formation in center of core.formation in center of core.

Source might be viewed through Source might be viewed through an outflow cavity aimed right at us.an outflow cavity aimed right at us.

Should try imaging disk at shorter Should try imaging disk at shorter ir (5ir (5m)!m)!Li & Draine 2001 ApJ 554, 778

Why don’t we see a cluster of sources?Why don’t we see a cluster of sources?

Clump mass function looks like the Initial Mass Clump mass function looks like the Initial Mass Function--Maybe we see only the single brightest star.Function--Maybe we see only the single brightest star.

Fig. 2. The mass spectrum of IRAS 19410+2336. The clump-mass bins are [1.7(3),4], [4,6], [6,8], [8,10], and [10,25] M, and the axes are in logarithmic units. The error bars represent the standard deviation of a Poisson distribution . The solid line shows the best fit to the data N/M M–a, with a = 2.5. The dashed and dotted lines present the IMFs derived from Salpeter with a = 2.35 (15) and Scalo with a = 2.7 (17), respectively.

What about all the Shocked HWhat about all the Shocked H22 and CO Outflows? and CO Outflows?

Maybe they all go with the lower mass stars.Maybe the high-mass star has passed the outflow stage:

There is a weak cm (UC HII region) near the brightest mm peak.But there are also an H2O maser and a CH3OH maser near the brightest mm peak.

Originally observed in partly cloudy skies--to be observed on Gemini.

IRAS 18089-1732IRAS 18089-1732

Spitzer Space Spitzer Space Telescope GLIMPSE Telescope GLIMPSE IRAC Image IRAC Image

44oox4x4oo

Blue=3.6Blue=3.6mm

Green=5.8Green=5.8m (Hm (H22))

Red=8.0 Red=8.0 m (PAH)m (PAH)

Galactic Legacy Infrared Midplane Survey ExtroidinairePI: Ed Churchwell, Wisconsin

Collaborator Joe Hora (CfA) hasaccessed the Spitzer database, and processed the IRAC images.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

IRAS 18089-1732 in Sub-mmIRAS 18089-1732 in Sub-mm

In mm and sub-mm In mm and sub-mm dust continuum it’s dust continuum it’s only one source!only one source!

UC HII and HUC HII and H22O O maser are at center.maser are at center.

CHCH33OH maser is OH maser is offset from center.offset from center.

There is a jet in SiO.There is a jet in SiO. There is a disk in There is a disk in

HCOOOCHHCOOOCH3.3.

Beuther et al. 2005 ApJ 628, 800. * is dust peak position.

Beuther et al.2004 ApJL 616, L23

Four Mid-IR Views of IRAS Four Mid-IR Views of IRAS 18089-173218089-1732

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

The action’s here!

IRAS 18089-1732 in Sub-mmIRAS 18089-1732 in Sub-mm

Beuther et al. 2005 ApJ 628, 800. * is dust peak position.

Beuther et al.2004 ApJL 616, L23

A

B

Cool Image!Cool Image!

Shit Happens!

The image at source B clearly indicates a temperature gradient!

But it does not fit well into any simple symmetry.

And it does not indicate where the protostar is.

A

B

Interpretation:Interpretation:

For now we’re stuck!For now we’re stuck! Maybe malicious cold clumps are causing Maybe malicious cold clumps are causing

the asymmetry, like the situation the the asymmetry, like the situation the famous BN/KL high-mass star forming famous BN/KL high-mass star forming region.region.

Ultimately, we have to interpret the SED of Ultimately, we have to interpret the SED of each HMPO.each HMPO.

Observed SEDs in IRAS Observed SEDs in IRAS 18089-173218089-1732

IRAC and IRTF data suggest IRAC and IRTF data suggest moderately deeply embedded moderately deeply embedded source, not Asource, not Avv=1000 suggested by =1000 suggested by

mm dust continuum.mm dust continuum. Sources are on Gemini list for Sources are on Gemini list for

spectra and astrometry.spectra and astrometry. Ry started processing low Ry started processing low

resolution spectra of HMPOs resolution spectra of HMPOs between 8 and 13between 8 and 13m. m.

Cliff is beginning to make Cliff is beginning to make spherically symmetric models to spherically symmetric models to get rough estimates of the sizes get rough estimates of the sizes and densities of the disks and and densities of the disks and envelopes. envelopes.

IRAS 18089-1732

0.001

0.01

0.1

1

10

100

0 5 10 15 20 25 30

Wavelength - Microns

Flux Density - Jy

A

B

A

BSpitzer - IRAC IRTF - MIRSI

Models of deeply embedded low-mass protostars for Models of deeply embedded low-mass protostars for different angles of incidence suggest interpretations…different angles of incidence suggest interpretations…

Whitney, et al. 2003 ApJ 598, 1079

What have we learned?What have we learned?

A significant fraction of A significant fraction of regions of high-mass star regions of high-mass star formation have a single, formation have a single, compact mid-ir source.compact mid-ir source.

IR images of star IR images of star formation regions are formation regions are very hard to interpret.very hard to interpret.

SEDs are critically SEDs are critically dependent on the model dependent on the model assumptions, e.g. assumptions, e.g. orientation of the outflow orientation of the outflow cavity, and the shape and cavity, and the shape and density of the disk.density of the disk.

IRAS 19410 from GLIMPSE

What’s next?What’s next? Studying high-mass star Studying high-mass star

formation is like looking for a formation is like looking for a serial killer. serial killer.

We’ve got to look at each crime We’ve got to look at each crime scene (each HMPO’s images scene (each HMPO’s images and spectrum), looking for and spectrum), looking for commonalities and commonalities and idiosyncrasies.idiosyncrasies.

We need to make computer We need to make computer models that match the SED’s models that match the SED’s and image sizes as a way of and image sizes as a way of estimating the physical estimating the physical conditions in the disks, the conditions in the disks, the envelopes, and the outflows.envelopes, and the outflows.

In the end, patterns will emerge In the end, patterns will emerge that pin down details of the steps that pin down details of the steps and their time scales.and their time scales.

IRAS 18247-1147 from GLIMPSE

I hope!

Next week, Dr. Lori Allen (CfA) will show more stunning Spitzer images and some of the successes in the study of low- mass star formation.