studies SED of disk lifetimes &
Long wavelength studies of disks
Ge/Ay133
Characterizinglargedisksamples?SEDModels:
HH30
G.J. van
Zadelhoff
2002
Chiang &
Goldreich
1997
IR
disk surface within several 0.1 several tens of AU
(sub)mm
disk surface at large radii, disk interior.
Details next!
UseSEDsurveys
toprobedisk
evolutionw/time,
accretionrate,etc.
Findveryfewobjects
withmoderateIR
excesses,mostdisk
systemsareoptically
thickoutto24m.
Disk Fraction Correlations
cTTs
wTTs
For wTTs sample projected on clouds, disk fraction increases
with H Equivalent Width (EW), declines with age.
Cieza et al. 2006
Disk Timescales
Big RED circle: has disk
Some wTTs do have disks,
not seen before w/IRAS.
But, only the young ones
(age < 3 to 6 MYr)
The ages are uncertain due
to models, but ~half the
young wTTs lack disks
(even at 0.8 to 1.5 Myr).
Thus, time is NOT the only
variable. How might disks
evolve?
Padgett et al., 2006; Cieza et al., 2006
Thatis,aretheremultiplepathsfromoptically
thicktoopticallythindisks?
Disk
Class II
Class II
Star
Class II
Class III
Mappingevolutionarypaths?
Evolutionary sequence: cTTs
wTTs
Debris
isthe
slopeof
theIR
excess,
towhere
thestar
anddisk
contribute
equallyto
theSED.
Statistically,howlongdodustgrainsindiskssurvive?
Basicresult:
Disksdissipate
withinafew
Myr,butwith
alargedisp.
foranySINGLE
system.When
theygo,however,
thedissipation
isFASTin
comparisonw/
disklifetime.
Gas???
Withmodernmmdetectors,cansensebeyondSEDknee:
Canthislongwavelengthphotometryhelpusunderstanddisk
evolutionanddissipation?(Imageslater)
Diskmodelingof(sub)mmwavefluxmeasurements:
Measure, must know distance.
derive
Assume
UNLESS the
disk is spatially
resolved.
ro Rd T (r ) (r )
optically thin, near peak of blackbody:
optically thin, R-J limit
0
Fortypicalassumptions,what
doyoufind?
Currentstudiesareflux
limitedat~10mJy:
SubmmContinuumImagingTWHya
The SMA continuum measurements agree well with the
predictions of the physically self-consistent irradiated
accretion model disk for TW Hya (Calvet et al. 2002)
The radial brightness distribution of the disk observed at
345 GHz is also consistent with the Calvet model.
So,weCANmeasuremanydiskparameters,butonlyforahandfulofsourcesfor
now.Usetheseresultstoguidecontinuumsurveys:
OnlysubstantialcorrelationiswithoverallSEDand/or
accretionrateindicators,otherwiseLARGEscatter!
Otherfactoids:
Submmfluxhighly
correlatedwith
thepresenceor
absenceofIR
excess.Almostno
disksw/weakIR
butstrongsubmm.
Verylittledependence
ofMAXIMUMdisk
massonage(thatis,
somefairlyOLDstars
have>MMSNdisks).
Otherfactoids:
Submmfluxhighly
correlatedwith
thepresenceor
absenceofIR
excess.Almostno
disksw/weakIR
butstrongsubmm.
Verylittledependence
ofMAXIMUMdisk
massonage(thatis,
somefairlyOLDstars
have>MMSNdisks).
Gas?
CO/Good Dynamical, T Tracer
T M(
)B K
Dent et al. 2005,
JCMT
vLSR (km/s)
The CO line shape is
Sensitive to:
Rdisk ,Mstar, Inc.
These can be
measured
w/resolved images:
M. Simon et al.
2001, PdBI
With multiple CO lines
CO 3-2
M.R. Hogerheijde code
TW Hya w/SMA
Qi et al. 2004,
ApJ 616, L7.
T gradients:
13
CO 2-1/TW Hya
Data
Model
(Rout 110 AU)
Model
(Rout 172 AU)
Onlysensitivetodisksurfacelayers,hardtogetmass.
CO 2-1
CO 3-2
Temperature Contour
Tau=1 Surfaces
CO 3-2
CO 2-1
Blue: Canonical Model (Calvet et al. 2002, Qi et al. 2004 )
Black: SMA data
Also,veryfew
transitional
disksarefound
(thatis,disksw/
innerholes):
Statisticsare~a
fewofmany
hundredsof
youngstars.
Calvet et al. 2005, ApJ, 630, L185
Atleastsomedisks
evolvefromthe
insideout.Does
thisapplymore
generally,orcan
disksdissipatein
avarietyofways?
Calvet et al. 2005, ApJ, 630, L185
Are there other examples? The case of LkH 330.
1
COv=10EmissionfromTransitionalDisks?
For dust sublimation
alone, the lines from T
Tauri disks should be
broader than those from
Herbig Ae stars+disks.
Often observed, but
The TW Hya lines are extremely
narrow, with i~7
R0.37 AU.
Similar for SR 9, DoAr 44, GM
Aur.
Rhot(KI) < R(CO) < Rdust(SED)