Circumstellar Disks and Young Clusters

Elizabeth Lada University of Florida Karl Haisch University of Florida (PhD Thesis) Charles Lada Smithsonian Astrophysical Observatory Joao Alvcs European Southern Observatory Gus Muench SAO/Florida Program Objectives

• Determine how often disk formation accompanies formation in clusters. • Measure the duration of the circumstellar disk phase using clusters as chronometers. • Determine how this depends on stellar mass and formation environment.

• Investigate disk evolution. How often do disks in clusters evolve to produce planetary systems? Why Young and Embedded Clusters?

H Clusters contain statistically significant #s of covering a large range of mass with similar chemical composition in a relatively small volume at the same distance from the .

H The ages of clusters can be determined from the HR diagram.

H A significant fraction of all stars in the Milky Way originate in embedded clusters. Clusters and Evolution The The Embedded Cluster: L1654 Clusters and Evolution

The NGC 2362 Cluster Why Infrared? Why Infrared? Circumstellar Disk SED

•SED broader than a blackbody & declines longward of 2 mm in power-law fashion. Infrared Color-Color Diagram

Reddening K-Band Excess in Embedded Clusters Frequency of Protoplanetary Disks 80

NGC 2024

60 NGC 1333 Mon R2

Rho Oph

40 NGC 2071 Taurus NGC 2264 20 IC 348

0 NGC 2362 Fraction of NIR Excess Sources

0 2 4 6 Age (Myr) Messy Problems

H Only about 1/2 the stars with circumstellar disks will exhibit significant 2.2 micron excess.

H Excess at 2.2 microns can be produced by other physical causes, such as reflection nebulosity.

H Significant age spreads in young clusters make age determinations somewhat ambiguous. Frequency of Protoplanetary Disks 80

NGC 2024

60 NGC 1333 Mon R2

Rho Oph

40 NGC 2071 Taurus NGC 2264 20 IC 348

0 NGC 2362 Fraction of NIR Excess Sources

0 2 4 6 Age (Myr) Why Longward of 2 Microns?

Star + disk l

K5 star SOFIA

2.2mm Why Longward of 2 Microns?

Disk with Hole

2.2mm Trapezium Cluster

JHK L

SAO 1.2 meter INFRARED EXCESS FRACTION

JHK = 42% JHKL = 95% NGC 2024 JHK L INFRARED EXCESS FRACTION: NGC 2024

JHK = 59% JHKL = 93% Mid-IR Survey of NGC 2024

Detected 33 sources. Disk fraction ~ 75% Haisch, Lada, & Pina 1999 Mass Distribution of Disks

limit Solar Nebular

Taurus Ophiuchus

100X Mdust

Beckwith & Sargent 1996 Nature 383, 139 Trapezium Disk Masses

• Masses of disks associated with proplyds are poorly determined • Previous attempts to measure disk masses using mm observations resulted in only upper limits of < 0.15 solar masses – (Mundy, Looney & Lada 1995) IRAM Observations • Two Trapezium fields observed using the IRAM Interferometer on the Plateau de Bure. These fields contained 20 Proplyds and 34 NIR sources • Observing Frequency: 109 GHz & 222 GHz – 2.7mm & 1.3mm • Resolution: – 3”.1 x 1”.7 & 2” x 1” • RMS Sensitivity: – 1 mJy & 1 mJy • Mass sensitivity ~ 0.005 masses IRAM Interferometer Results • Detected three sources at l=1.3 mm • Detections are coincident with know Proplyds & NIR sources

Lada, Dutrey, Mundy & Guilloteau 1999 IRAM Results Fluxes Source l=1.3 mm l=2.7mm HST170-337 9.9mJy <1 mJy HST171-340 10.1mJy 4.9 mJy HST158-327 11.3mJy <1 mJy

Masses for these 3 sources ~ 0.01 M¤ Comparable to the minimum mass solar Detection Rates • 1.3 mm continuum emission detected for 3 – out of 20 proplyds Þ 15% – out of 34 NIR sources Þ 10% Taurus - Trapezium - NGC 2071

Trapezium MID-IR Images of the Trapezium

10mm

OSCIR IMAGES Lada, Pina, Telesco 1998 Disk Dispersal in the Trapezium

Mass Loss Rate Þ Disk Survival

Initial mass for Trapezium Disks ~ 0.1 M¤ Mass now ~ 0.01 M¤

6 -7 mass loss/age » 0.1 M¤ /10 yr ~10 M¤ /yr

It will take 105 years to loose rest of material

Disk lifetimes in Trapezium-like environments are short Circumstellar Disk Lifetimes in Clusters

H Duration of the K-band excess phase (i.e., optically thick disk phase) is < 5-6 million years. However,

H Disk lifetimes are probably a function of the mass of the central star, and are likely longer around less massive stars. Moreover,

H Disk Lifetimes likely depend on the cluster environment at time of formation. THE END Modeling Cluster Luminosity Functions

Input IMFs: two power-law segments with break at 1/2

THE END (really)