Transcript Centimeter and Millimeter Observations of Very Young Binary Systems

Centimeter and Millimeter Observations
of Very Young Binary and Multiple
Systems
-Orbital Motions and Mass Determination
-Truncated Protoplanetary Disks
-The OMC1S Region in Orion
Luis F. Rodríguez
CRyA, UNAM
ORBITAL MOTIONS IN BINARY AND
MULTIPLE PROTOSTARS
L. Loinard, M. Rodríguez, & P. D’Alessio (CRyAUNAM, Morelia)
S. Curiel, J. Cantó, & A. C. Raga (IAUNAM, México City)
J. M. Torrelles (IEEC, Spain), J. M. Girart (U. Barcelona, Spain)
David J. Wilner & Paul T. P. Ho (CfA, USA)
High angular resolution (0.1”) Very Large Array
observations of young stellar systems that allow
measurement of orbital proper motions and estimate
of stellar masses.
BACKGROUND
• Most information on stellar masses comes
from studies of orbital motions
• Work at optical band toward visible stars
has been going on for 200 years
• In the last decade, near-IR speckle and
adaptive optics has been used to investigate
T Tauri binaries
• What about heavily obscured protostars, not
detectable even at near-IR wavelengths?
RADIO OBSERVATIONS
• Remarkably, protostars can be tracked at
radio wavelengths due to three processes:
1. Gyrosynchrotron from active stellar
magnetosphere
2. Free-free emission from ionized outflows
3. Thermal emission from circumstellar disks
No extinction. However, processes (2) and (3)
produce extended sources. These emissions are
not always present.
Very Large Array
0.1” resolution at 2 cm
HEAVILY OBSCURED SOURCES:
•
•
•
•
L1551 IRS5
YLW 15
L1527 (= IRAS 04368+2557)
IRAS 16293-2422
L1551 IRS5
Ha
[SII]
Cont.
Reipurth & Bally 2001
ESO NTT
Free-free from
ionized outflow
dominates cm
range, while thermal
emission from dust
in disk dominates
mm range
L1551 IRS5
VLA-A 2 cm
Proper Motions
• Large proper motions due to large scale
motion of region with respect to Sun and
agree very well with Jones & Herbig (1979)
• However, proper motions not identical for N
and S components, indicating relative
(orbital) motions
Orbital Proper Motions
• Observed changes in separation and
position angle imply relative velocity in the
plane of the sky of 2.3+-0.5 km/s
• A (very) conservative lower limit to the
total mass can be derived from
(M/Msun)>0.5 (V/30 km/s)^2 (R/AU)
• We obtain (M/Msun)>0.1
An attempt to correct for projection effects...
• Assume plane of orbit parallel to plane of
disks (Bate et al. 2000)
• Circular orbit
• => M = 1.2 Msun; P = 260 yr
• In the main sequence, luminosity will be of
order 1 solar luminosity, while now Lbol is
of order 30 Lsun => accretion main source
of luminosity
YLW 15
VLA-A 3.5 cm
1990.41
2002.18
YLW 15
YLW 15
• Relative velocity in the plane of the sky of
6.4+-1.8 km/s, implying:
• M > 1.7 Msun
• Assuming observed separation is close to
true separation, P < 360 yr
• Lbol = 13 Lsun
L1527
VLA-A
7 mm
Relative Velocity in Plane of the Sky = 4+-2 km/s
M > 0.1 Msun, most likely 0.5 Msun
Lbol about 2.5 Lsun
Up to now, binary systems, what
about multiples (i. e. triples)?
• IRAS 16293-2422
IRAS 16293-2422, VLA-A, 3.5 cm,
average proper motion subtracted
IRAS 16293-2422
• Relative velocity of about 15 km/s and
separation of about 30 AU between
components A1 and A2, implies relatively
large mass of about 4 Msun
• However, A1 has been proposed in the past
to be shock with ambient medium
CONCLUSIONS OF ORBITAL
MOTIONS
• Orbital motions in protostars will provide
important constraints on the early phases of
stellar evolution
• We are getting reasonable results, but must
follow “strange” cases such as IRAS 162932422
What do we know about protoplanetary disks?
• Radii of 100s of AU in T Tauri stars.
• They last between 2 and 10 million years.
• But little is known about their formation,
about their earliest stages.
• It can be argued theoretically that the disks
should start small and grow with time…
The binary disks in
L1551 IRS5 are much
smaller than the disks
found around T Tauri
stars, but their small
size is most likely due
to tidal truncation.
Other small disks
found are also part of
binary systems…
Anglada et al. (2004)
IRAS 04368+2557 =
L1527
VLA-A 7 mm
VLA
7 mm
Detailed modeling of disk allows estimate of parameters:
Disk Mass= 0.3-0.4 solar masses.
Disk Radius = 26 AU.
B
A
But…
Conclusions on Truncated
Protoplanetary Disks
• Given multiplicity in star formation it will
be hard to find truly isolated protoplanetary
disks to study their evolution, without the
effects of companion stars.
OMC-1S: A Cluster in Formation
• SMA and VLA observations of OMC1S:
part of Ph. D. Thesis of Luis Zapata (see his
poster).
Optical image of
O´Dell & Doi
(2003).
OMC-1S is a
region with
bolometric
luminosity of
10,000 solar
luminosities from
which many optical
outflows emanate.
VLA-A 3.6 cm
Zapata et al.
(2004)
VLA-B 1.3 cm
Hypercompact
HII Regions
Ionized by Early
B-type stars?
Higher angular
resolution
VLA-A
observations at
7-mm reveal
that at least
two of the
sources are
close binaries:
139-409 and
134-411.
SMA SiO (5-4)
Molecular Outflows in OMC-1S
• Highly collimated, young CO outflow.
• Multiple SiO outflows.
• CO and SiO observations complementary:
the CO outflow is not evident in SiO and
viceversa.
The Next Frontiers in Star Formation
• With the availability of the SMA and the future
construction of other interferometers we will start
to study star formation with new frontiers:
• Binary and multiple star formation
• Star formation in the extremes (very massive stars
and brown dwarfs)
• Starbursts and cosmological star formation (the
first stars)