Randolf Klein

SOFIA – USRA/NASA Ames

July 2014

AASTCS 4: Workshop on Dense Cores - Monterey, CA

Issues with SED Fitting, PMS Tracks, and the Birthline Exemplified with two

Cores near IRAS 05345+3157

WORKSHOP ON DENSE CORES - MONTEREY 2

OVERVIEW

July 2014

• How do massive stars form?Monolithic collapse and disk accretion, competitive accretion and runaway growth, or stellar collisions and mergers. (Zinnecker & Yorke 2007)

• Knowing the initial conditions of massive star formation would help to answer that question.

Thus, I want to study:

• Can we identify a similar classification like Class0 to Class II for massive stars?

• How do massive cores/clumps and their SEDs evolve?

• Extrapolate to the earliest stages

But first I get my tools ready while studying two intermediate mass protostars.

WORKSHOP ON DENSE CORES - MONTEREY 3

IRAS 05345+3157

• Infrared cluster with shell

• Two massive cores detected in mm-survey (Klein et al. 2005)

• Large separation from IRAS source MIPS observations (saturation)

• Pilot study to analyze SEDs of mm-cores and their evolution

THE MASSIVE CORES IN IRAS 05345+3157

July 2014

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• Green fuzzies (extended IRAC 4.5µm emission) Shocked gas? (cf. De Buizer&Vacca 2010)

• CARMA observations: CS 2-1 Infall signatures(Lee et al. 2011)

• Outflow (Fontani et al. 2009)

PROTOSTELLAR CORES?

July 2014

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SED FITTING (ROBITAILLE MODELS)

Northern Core

• M★=8.0M

• R★=30R

• T★=5800K

• Renv=86000AU

• Menv=180M

• Ltot=910L

• AV=260mag

• Age 5.6 104yr

Best model: 3007730

July 2014

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SED FITTING (ROBITAILLE MODELS)

Southern Core

• M★=5.8M

• R★=32R

• T★=4300K

• Renv=48000AU

• Menv=110M

• Ltot=320L

• AV=430mag

• Age: 1.2 104yr

Best model: 3003596

But these are not protostars!July 2014

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THE ROBITAILLE MODELS

YSO Grid by T. Robitaille et al (2007, ApJS, 169, 328):

• 20,000 Env.-Disk-Models with 14 parameters

• 10 inclination angles: 200,000 SEDs

• On-line access and fitting

Widely used to fit and interpret SEDs.

But don’t just use the best fit. Online Fitter returns 1000 best matches, which allows to estimate uncertainties and significances.

• I considered a fit good when χ2-χ2best < 5/data point leading to

a range of good parameters

July 2014

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THE ROBITAILLE MODELS

• A-priory selection 100L☉<L<1000 L ☉ & Menv>0.1M: 1456 models

• Statistical test if parameter distribution for a-priory and good model differs.

• Colored lines indicate that the fitted parameter distribution differs from the a-priory distribution.(All not listed parameters have the a-priory distribution except for the cavity angle)

Northern Core with interquartile range

• M★=8.0M 7.5...8.0

• R★=30R32…42

• T★=5800K 4300…4600

• Renv=86000AU 54000…94000

• Menv=180M 130…250

• Ltot=910L 660…720

• AV=260mag 160…230

• Age 56000yr 7800…26000

July 2014

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EVOLUTIONARY TRACKS• Robitaille’s model

grid was populated by randomly picking a mass and an age.

• Theoretical pre-main sequence tracks from Siess et al. 2000 and Bernasconi & Maeder 1996 were used to set the temperature and stellar radius accordingly.

Evolutionary tracks from 7.0 to 0.1M for a solar metallicity. Dashed isochrones at 106, 107 and 108. Siess et al. 2000

July 2014

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THE BIRTHLINE

Observational: upper envelope in the

HR-diagram for pre-MS-stars

Theoretical: locus of pre-MS-stars

with protostellar radii

HR diagram with visible stars driving molecular outflows:• Open circles – HAeBe• Filled circles – associated with CO• Theoretical birthline• Zero age main sequence• Pre-MS tracks with mass

What about PMS tracks above the birthline?

“The Formation of Stars”Stahler & Palla 2004 Wiley-VHC

July 2014

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THE PROBLEMThe protostar evolves along the birthline while accreting:

A. PS contracts

B. Central D-burning

C. PS contracts despite D-burning

D. Radiative coreD-burning in shell

E. Completely radiative

F. CNO-cycle creates convective core; PS joins MS

When the accretion stops, the evolution follows the PMS tracks.

Pre-main-sequence tracks above the birthline are unphysical.

Star formation with disc accretion and rotationBirthline and PMS-tracks - Haemmerlé et al (2013):July 2014

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PROTOSTAR AS CENTRAL SOURCE

• Replace the PMS star with a protostar emitting the same luminosity and recalculate the SED (Whitney, B. A. et al. 2003)

• L★=910L

T★=5800K8900KR★=30R13R

Still a good fit as all the emission is reprocessed.

Same for the southern core.

July 2014

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WHICH BIRTHLINE?

• Location of the birthline depends on the accretion rate

• Hosokawa & Omukai (2009) assume a constant accretion rate.

• In blue: Haemmerle et al. (2013) use an empirical relation Ṁacc(L) resulting in Ṁacc = 10-5...10-3 Myr-1

July 2014

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CONCLUSIONS

• The cores in IRAS 05345+3157 harbor intermediate-mass protostars.

• Infall signatures

• Deeply embedded heating source

• Outflows

• The SED is not sensitive to the central source (or disk) for such deeply embedded sources.

• Lessons learned:

• The central source in Robitaille’s modes and elsewhere where pre-MS-tracks are used may be unphysical.The radii are too large and thus the temperature too low for a given luminosity.

• The effect on the SED-fit? The total luminosity of the protostar gets reprocessed in the envelope. The emerging spectrum mainly depends on the luminosity.

• Outlook: study more envelopes.

July 2014

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OUTLOOK

Study candidates for very young, massive, star-forming cores

Selection criteria:

• No radio, IRAS, MIR, NIR sources within 10” of the core’s peak.

• Minimum mass of 100 M☉.

Single-dish mm continuum surveys:

• Faundez et al. (2004): CS sources from Bronfman et al. (1996) Fulfill the IRAS UC HII region color criterion.

• Sridharan et al. (2005): High-mass protostellar objects (HMPO) from the survey by Beuther et al. (2002) excluding cores associated with masers.

• Klein et al. (2005): FIR bright IRAS sources (F(100µm)>500Jy) in the outer Galaxy

• Beltran et al (2006): Uses source sample from Palla et al. (1991), which used an IRAS color criterion for compact molecular clouds and excluded HII regions.

July 2014

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OUTLOOK

• Selected 173 cores in 117 regions

• Compile SED from GLIMPSE, MIPS, HiGal and mm-surveys

July 2014

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OUTLOOK

And from SOFIA

THANK YOU!July 2014