Infrared Dark Clouds as precursors to star clusters

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1. Infrared Dark Clouds as precursors to star clusters
2. Infrared Dark CloudsClouds that exhibit significant mid-IR
3. Contours 1.2 mm; colour 8 m MSXRathborne
4. Are the IRDC cores forming stars?Detected 140
5. Strong mm/sub-mm continuum Broad linewidths in
6. Are IRDC cores forming single stars or
7. A high-mass protostarM = 800
8. An early stage of high-mass star formation, a hot molecular core
9. The “hot core” lines are unresolved; 13CO
10. A cluster of protostarsSpitzer/MIPS 24mmM = 200 MLbol = 104 LAngular resolution6’’IRAM PdeBI
11. A high- and low-mass protostarSpitzer/MIPS 24mmM = 230 MLbol = 103.4 L
12. Cluster formation in IRDCs
13. Jeans masses, Jeans lengths, and hierarchical fragmentationThese
14. SummaryIRDCs have sizes and masses comparable to
15. IRDCs are important laboratories to study the very earliest stage in the formation of star clusters
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Infrared Dark CloudsClouds that exhibit significant mid-IR opacity Extreme propertiesCold (104 cm-3)Enormous column densities (>1023 – 1025 cm-2)Dark at 100 m Sizes (few pc) and masses

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Infrared Dark Clouds as precursors to star clusters

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Слайд 1Infrared Dark Clouds as precursors to star clusters
Jill Rathborne, James

Jackson, Edward Chambers, Robert Simon, Qizhou Zhang

Слайд 2Infrared Dark Clouds
Clouds that exhibit significant mid-IR opacity
Extreme properties
Cold

(104 cm-3)
Enormous column densities (>1023 – 1025

cm-2)
Dark at 100 m
Sizes (few pc) and masses (few 1000 M) comparable to warm, cluster-forming molecular clumps
Colder and with little obvious star formation

Perault et al. 1996; Egan et al. 1998; Carey et al. 1998, 2000; Hennebelle et al. 2001; Simon et al. 2006; Rathborne et al. 2006

GLIMPSE 8 mm image

Infrared Dark CloudsClouds that exhibit significant mid-IR opacity Extreme propertiesCold (104 cm-3)Enormous column densities (>1023 – 1025

Слайд 3Contours 1.2 mm; colour 8 m MSX
Rathborne et al. 2006
IRDCs

in 1.2 mm continuum: dust emission reveals compact cores
Sizes < 0.5

pc
Masses ~ 75 M 

These properties are what we expect for cores that will give rise to high-mass protostars

Contours 1.2 mm; colour 8 m MSXRathborne et al. 2006IRDCs in 1.2 mm continuum: dust emission reveals

Слайд 4Are the IRDC cores forming stars?
Detected 140 compact, cold cores

2/3 of the cores show no evidence for star formation

Massive

starless cores?

GLIMPSE 3-color image (3.6, 4.5, 8.0 m)

Are the IRDC cores forming stars?Detected 140 compact, cold cores 2/3 of the cores show no evidence

Слайд 5 Strong mm/sub-mm continuum
Broad linewidths in CS, HCN

Strong SiO emission
Extended, enhanced 4.5 m emission
Compact, bright

24 m emission
High bolometric luminosities >104 L
Bright (>1 Jy) water maser emission

Active star formation in IRDC cores

Chambers et al. 2005, Rathborne et al. 2005, 2007, Wang et al. 2006

Strong mm/sub-mm continuum Broad linewidths in CS, HCN Strong SiO emission Extended, enhanced 4.5 m emission

Слайд 6Are IRDC cores forming single stars or star clusters?
Some IRDCs

are forming high-mass stars
High-mass stars form in clusters with many

lower-mass stars
If IRDCs are forming clusters, then they should also contain many lower-mass protostars
Because IRDCs are distant, most observations have lacked the sensitivity and angular resolution to detect lower-mass protostars and separate multiple protostars

Sensitive, high angular resolution mm/submm observations can distinguish between these two scenarios

Are IRDC cores forming single stars or star clusters?Some IRDCs are forming high-mass starsHigh-mass stars form in

Слайд 7A high-mass protostar
M = 800 M
Lbol =

104.5 L
MIPS 24m

6 ” angular resolution

Слайд 8An early stage of high-mass star formation, a hot molecular

core

Слайд 9The “hot core” lines are unresolved; 13CO 3-2 reveals circumstellar structure
Color:

SO2 (116,6-125,7)
Contours: 13CO 3-2
Red: 61 km s-1
Blue: 55 km

s-1

The “hot core” lines are unresolved; 13CO 3-2 reveals circumstellar structureColor: SO2 (116,6-125,7) Contours: 13CO 3-2Red: 61

Слайд 10A cluster of protostars
Spitzer/MIPS 24mm
M = 200 M
Lbol

= 104 L
Angular resolution
6’’
IRAM PdeBI

Слайд 11A high- and low-mass protostar
Spitzer/MIPS 24mm
M = 230

M
Lbol = 103.4 L

Слайд 12Cluster formation in IRDCs

Слайд 13Jeans masses, Jeans lengths, and hierarchical fragmentation
These results support the

idea that gravitational collapse is occurring within the IRDCs and

that fragmentation process has stopped at these protostellar scales

Jeans masses, Jeans lengths, and hierarchical fragmentationThese results support the idea that gravitational collapse is occurring within

Слайд 14Summary
IRDCs have sizes and masses comparable to warm, cluster-forming molecular

clouds
High-mass and multiple protostars found within IRDC cores
The properties of

IRDCs, their cores and protostellar condensations provide broad support for hierarchical fragmentation within IRDCs

SummaryIRDCs have sizes and masses comparable to warm, cluster-forming molecular cloudsHigh-mass and multiple protostars found within IRDC

Слайд 15IRDCs are important laboratories to study the very earliest stage

in the formation of star clusters

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