Transcript HD 100453: An Evolutionary link between

HD 100453
An Evolutionary Link Between
Protoplanetary Disks
and Debris Disks
Karen Collins
Master’s Thesis Defense
April 24th, 2008
University of Louisville
Department of Physics and Astronomy
Supported by a Fellowship from the Kentucky Space Grant Consortium
Thesis Directors
Dr. Gerard Williger - UofL
Dr. Carol Grady - NASA GSFC
Journal Paper Co-authors
Co-authors(s)
Affiliation
Contribution
C. A. Grady
Eureka Scientific and NASA GSFC
overall direction, science mentor, HST and Chandra PI, and day-to-day support
K. Hamaguchi & R. Petre
X-ray Astrophysics Laboratory
NASA/GSFC
Chandra observations, data reduction, and results
J. P. Wisniewski
NASA/GSFC, NPP Fellow
HST ACS HRC observations, data reduction, and results
S. Brittain
Clemson University
Gemini South observations of warm CO, data reduction, and results
M. Sitko & W. J. Carpenter
SSI, University of Cincinnati
SED and modeling data, general support
G. M. Williger
University of Louisville
FUSE observations, data reduction, results, and general day-to-day support
R. van Boekel
Max-Planck-Institut für Astronomie
VLT NACO NIR observations, data reduction, common proper motion results, and
related photometric results
A. Carmona
Max-Planck-Institut für Astronomie,
ESO, ISDC & Geneva Observatory
VLT SINFONI NIR spectroscopy, data reduction, spectral typing, and other related
results.
M. E. van den Ancker
European Southern Observatory
VLT SINFONI NIR spectroscopy, data reduction, spectral typing, and other related
results.
G. Meeus
Astrophysikalisches Institut Potsdam
FEROS Ca II spectroscopic data
J. P. Williams,
G. S. Mathews
University of Hawaii
JCMT HARP CO spectroscopic observations, data reduction, dust mass calculations,
gas mass calculations, and related results
X. P. Chen
Max-Planck-Institut für Astronomie
VLT NACO Brγ common proper motion data reduction
B. E. Woodgate
NASA/GSFC
overall scientific interpretation
Karen Collins
Master's Thesis Defense
4/24/2008
Star Formation Overview
 Start with molecular cloud
 Four phases of collapse
 dense rotating core forms
 collapses from inside out
 bipolar outflows
 carry away angular momen. (L)
 star and disk revealed
Shu et al. 1987
 Conservation of L
 cloud rotates slowly
 star rotates more rapidly
 High L material forms disk
 disk accretes onto star
Wood 1997
Karen Collins
Master's Thesis Defense
4/24/2008
Pre-Main Sequence Stars
 Pre-main sequence (PMS) stars
 fully revealed stars
 still gravitationally contracting toward main sequence
 hydrogen fusion not started yet
 PMS stars are called
 T Tauri if
0.1 M < M < 2 M (M, K, G, F type stars)
 Herbig Ae/Be if 2 M < M < 8 M (F, A, B type stars)
 higher mass stars emerge from cloud on main sequence
 Observable characteristics
 Balmer emission lines in stellar spectrum (Hα, Hβ, Hγ, …)
transition (32, 42, 52, …)
 infrared excess due to circumstellar dust (next slides)
Karen Collins
Master's Thesis Defense
4/24/2008
Spectral Energy Distribution
 Spectral Energy Distribution (SED)
 plot of radiated energy
vs. wavelength
 Stellar photosphere
~blackbody
 peaks in optical
 Sun
5778 K
 A-type stars
7500-10,000 K
 M-type stars
3000-4000 K
Karen Collins
Master's Thesis Defense
4/24/2008
Infrared Excess
 IR excess
 total emission − stellar contribution
 stellar contribution determined from a model fit to UV and Optical data
 source is circumstellar dust
 dust absorbs stellar radiation
 re-radiates as thermal emission
 IR excess source
 inner disk
 NIR (1 - 7 μm)
 outer disk
 MID to FIR (10 - 50 μm)
 disk midplane
 FIR to mm (>50 μm)
Karen Collins
adapted from M.Sitko simulation
Master's Thesis Defense
4/24/2008
Disk Evolution
 Protoplanetary Disks (initial phase)
 gas rich + small dust grains (submicron)
 gas:dust ~100:1 (as in interstellar medium (ISM))
 high accretion rates (> ~1108 M yr1)
 gas and dust well mixed
 hydrostatic equilibrium
 dust material supported above midplane
 disk can maintain scale height
 disk expected to “flare”
Karen Collins
Master's Thesis Defense
4/24/2008
Flared Disk
 "bowl" shaped disk
 h  r, where  > 1.0
 relatively flat SED in IR
 inner rim  NIR BB
 disk surface  MIR - FIR
 disk midplane  FIR - mm
Dullemond et al. 2006
Dullemond et al. 2006
Karen Collins
Master's Thesis Defense
4/24/2008
Disk Vertical Structure

inner-most part of the disk is dust free

beyond sublimation temperature

the inner rim is illuminated face-on from the star, the gas heats up
more and causes an increased scale height (i.e. it "puffs up")

as the disk ages, the dust grains grow in size

disk becomes vertically stratified


larger grains in midplane
smaller grains in upper layers
Dullemond et al. 2006
Karen Collins
Master's Thesis Defense
4/24/2008
Disk Evolution Continued
 accretion rates ~10 - 100x lower than
protoplanetary disks
 IR excess similar to pp disk at >10 μm
Van den Ancker 1999
 Transitional Disks (intermediate phase)
Protoplanetary Disk
 IR excess significantly less at <10 μm
 result of less dust, or optically thin dust,
in the inner disk
Transitional Disk
 photoevaporation
 grain growth until optically thin
 gap creation by massive planet
Karen Collins
Master's Thesis Defense
4/24/2008
Disk Evolution Continued
Protoplanetary Disk
 Debris Disks (final phase)
 accretion has stopped
 moderate IR excess at >10 μm
 very little to no IR excess at <10 μm
Transitional Disk
 no inner disk at all
 primordial dust has grown to rocks,
protoplanets, and terrestrial planets
 remaining dust is second generation
 gas-poor
Karen Collins
Master's Thesis Defense
Van den Ancker 1999
from collisions of massive bodies
Debris Disk
4/24/2008
Meeus Groups
 Meeus et al. (2001) divided 14 Herbig stars into two groups
 Group I
 blackbody in MIR
 high fraction of IR excess (LIR/L* ~ 0.5)
 steep submm slope (i.e. small grains)
 Group II
 no blackbody in MIR
 low fraction of IR excess (LIR/L* ~ 0.2)
 shallow submm slope (i.e. larger grains)
 Meeus et al. suggested Group I
sources evolve to Group II sources
Meeus et al. 2001
Karen Collins
Master's Thesis Defense
4/24/2008
Meeus Physical Model
 3 components
 disk midplane - optically thick
 inner disk with scale height
 outer disk
 Group I
 inner disk optically thin
 outer disk is directly illuminated
 outer disk heats & flares
 creates MIR BB
 Group II
 inner disk optically thick
 outer disk shielded
 outer disk stays flat
 no MIR BB
Karen Collins
Master's Thesis Defense
4/24/2008
Thesis Goal
 Test idea that Meeus Group I sources
evolve to Meeus Group II sources
 at time of Meeus et al. (2001) paper, many age
estimates were not available
 accretion rates were not considered
(recall that accretion rate is tied to disk evolution)
Karen Collins
Master's Thesis Defense
4/24/2008
Thesis Approach
 Compare ages and accretion rates between the groups
 we focus on HD 100453 in this work because:




Herbig AeBe stars are difficult to date after about 5 Myr
low-mass stars are easier to date and often form together with A-stars
we can determine the age of the A-star from a companion low-mass star
a candidate low-mass companion was recently reported for HD 100453A
(Chen et al. 2006)
 determine age and accretion rate for HD 100453A (this work)
 determine age and accretion rate for other stars from the
literature
Karen Collins
Master's Thesis Defense
4/24/2008
HD 100453A
 Southern Hemisphere
(Lower Centaurus-Crux Assn)
 Distance 114 pc
 v=7.78
(not visible by naked eye)
 Spectral Type A9Ve
 Age > ~10 Myr
Karen Collins
Master's Thesis Defense
4/24/2008
Summary of Observations
Instrument
Chandra
K. Hamaguchi
Direct
Image

HST ACS HRC
J. Wisniewski

HST ACS HRC
J. Wisniewski
HST ACS SBC
VLT NACO
C. Grady
K. Collins
R van Boekel
VLT SINFONI
A. Carmona

NIR
Spectral Type of Companion
FUSE
G.M. Williger

FUV
Accretion Rate
Phoenix
S. Brittain

NIR
Warm Gas Limits
JCMT HARP
J. Williams
G. Mathews
G. Meeus
K. Collins

Submm
Cold Gas Limits

Optical
Accretion Rate
FEROS
Karen Collins
Prime
Coron.
Image
Spectra
Wavelength
Scientific Purpose

X-ray
Accretion Rate
Optical
Companion Location &
Photometry
Optical
Disk Detection & Photometry
FUV
Companion Detection
NIR
Companion Proper Motion &
Photometry



Master's Thesis Defense
4/24/2008
Test of Companion Status
 To date an A-star from a low-mass companion, we need to know
that they are physical companions
 Two tests:
 determine motion of A-star & candidate companion
 If motion through space is common,
they are likely physical companions
 determine spectral type of companion
 for the brightness contrast between the two stars,
a physical companion would be a low-mass star
Karen Collins
Master's Thesis Defense
4/24/2008
The Candidate Companion
 HST optical direct image
 B located 1.05 @ 126° east of north
 mv = 15.87 (A:B = 1500:1 contrast)
optical
HST ACS HRC F606W
Karen Collins
Master's Thesis Defense
4/24/2008
Candidate Companion Spectral Type
 Need high spatial resolution spectroscopy
to separate the light from the two stars
 Optical Spectroscopy is first choice
 need A/O for ~1 separation
 none available
 NIR is good second choice
 SINFONI on VLT with A/O
 Integral Field Spectrograph
 0.8 x 0.8 field of view
 J, H, K band gratings (NIR)
Karen Collins
Master's Thesis Defense
4/24/2008
Candidate Companion Spectral Type
 Compare to 4 standard stars
 M3.5V
 M4.0V
 M4.5V
 M5.0V
 Find closest match to
features in all 3 bands
 Spectral Type is
M4.0V - M4.5V
Karen Collins
Master's Thesis Defense
4/24/2008
Relative Proper Motion
 Determine movement of A star over 3 years
 Hipparcos data  0.111 ± 0.003
 Determine relative motion of candidate companion over 3 years
 use VLT NACO Brγ imagery
 2003 data (Chen et al. 2006)
 2006 data (this work)
 compare change in position
of B w.r.t. A  0.020 ± 0.010
 Common proper motion
confirmed
 Residual could be
orbital motion
Karen Collins
Master's Thesis Defense
4/24/2008
Candidate Confirmation
 Common proper motion
 suggests both stars originated from same cloud
 suggests physically companions
 Spectral Type M4.0V - M4.5V
 class “V”  not a distant red giant (high luminosity)
 A9:M4 has proper contrast ratio
 Confirmation that candidate companion
is a physical companion
Karen Collins
Master's Thesis Defense
4/24/2008
Companion Photometry
Object
Mode
Filter
magnitude
HD 100453B
Direct
mF606W
15.6
HD 100453B
Coron
mF606W
15.8
HD 100453B
Combined
mF606W
15.7  0.2
Notes
(prime)
HST HRC
(J. Wisniewski)
HST HRC
(J. Wisniewski)
(J. Wisniewski)
HD 100453B
Direct
Ks
10.66  0.1
HD 100453B
Coron
L
10.13  0.1
HD 100453B
Coron
M
9.99  0.1
HD 100453B
Calculated
V
15.87  0.2
(Chen et al. 2006)
VLT NACO
(R. van Boekel)
VLT NACO
(R. van Boekel)
(K. Collins)
HD 100453B
Calculated
K
10.64  0.1
(K. Collins)
HD 100453B
Calculated
L
10.27  0.1
(K. Collins)
• Key Point: Candidate companion has NO IR Excess
 Can use K-band in H-R diagram for age estimate
Karen Collins
Master's Thesis Defense
4/24/2008
Age Determination (from A-star)
 PMS H-R diagram - derived from Siess et al. stellar models
 if we know magnitude and effective temperature
 we can determine age and mass
 HD 100453A
 mv = 7.7
 A9Ve  Teff = 7400 K
 Results
 age: 10 Myr - ZAMS
 mass: 1.6 - 1.8 M
 Age is not well constrained
because of compressed
isochrones at >10 Myr
Karen Collins
Master's Thesis Defense
4/24/2008
Age Determination (from Companion)
 Note wider separation of isochrones for low-mass stars
 HD 100453B (input data)
 mK = 10.64 ± 0.1
 M4.0V – M4.5V
Teff = 3300 K – 3400 K
 Results (Siess Model)
 age: 10  15 Myr
 mass: 0.21  0.23 M
 Results (Baraffe Model)
 age: 11  18 Myr
 mass: 0.24  0.30 M
 Results (Combined)
 age: 14 ± 4 Myr
 mass: 0.21  0.30 M
Karen Collins
Master's Thesis Defense
4/24/2008
Mass Accretion onto A-star
 Mass accretion rate gives insight into the
evolutionary phase of the disk
 We investigate the following accretion indicators:
 enhanced FUV continuum
 Herbig-Haro knots in Lyα
 enhanced emission of
 Ca II λ8662 Å
 Hard X-rays
 Hα (6563 Å)
 Brγ (2.166 μm)
Karen Collins
Master's Thesis Defense
4/24/2008
Accretion - FUV Continuum
 FUV continuum upper limit
 from FUSE spectra
 <1.51015 ergs s1 cm2 Å1 (1σ)
(-14.8 in log space)
Karen Collins
Master's Thesis Defense
4/24/2008
Accretion - FUV Continuum
 Plot accretion rate vs. FUV continuum
 accretion rates based on Brγ
(Garcia Lopez et al. 2006)
 FUV values from literature
 note power law trend
except HD 100453
Karen Collins
Master's Thesis Defense
4/24/2008
Accretion - FUV Continuum
 Plot accretion rate vs. FUV continuum
 accretion rates based on Brγ
(Garcia Lopez et al. 2006)
 FUV values from literature
 note power law trend
except HD 100453
 relocate HD 100453 to fit trend
 log (Accr Rate) < -9.6
 < 2.5x10-10 M yr-1 (1σ)
 Stellar activity can also be a source of Brγ emission
 HD 100453 Brγ emission is contaminated by stellar activity
Karen Collins
Master's Thesis Defense
4/24/2008
Accretion - Herbig-Haro Knots
 HH knots from jets
FUV
 Are Lyα bright in FUV
 Use scaling argument
 HD 163296 has HH knots
(Wassell et al. 2006)
 F122M = 2.0 cnts s1 arcsec2
 accretion ~1×107 M yr1
 HD 100453 - no knots detected
HST ACS SBC F122M
 3σ upper limit
<1.1x10-4 cnt s-1 arcsec-2
 scaling  ~<6×1011 M yr1
Karen Collins
Master's Thesis Defense
4/24/2008
Accretion- Ca II 8662 Å emission
 Use scaling argument again
 HD 163296
 Ca II 8662 Å EW = 4.18 Å
(Hamann & Persson 1992)
 accretion rate ~1×107 M yr1
(Wassel et al. 2006)
 HD 100453
 in absorption
 find emission upper limit
 Ca II 8662 Å EW <410-3 Å
 assume linear relation
 accretion rate <1×1010 M yr1 (4σ)
Karen Collins
Master's Thesis Defense
4/24/2008
Accretion - Hα
 HD 100453 Hα emission
 variable, weak
 lowest EW of 91 Herbig Ae/Be stars
(Manoj et al. 2006)
 at best a very weak accretor
Karen Collins
Master's Thesis Defense
4/24/2008
Accretion - X-ray
Chandra
 In A-stars:
 accretion produces hard X-rays
 winds produce soft X-rays
 HD 100453A produces soft X-rays
 not a strong accretor
Chandra X-ray
HD 100453A
HD 100453B
energy (keV)
Karen Collins
1
red
0.35 − 0.70 keV
green 0.70 − 0.90 keV
blue 0.90 − 2.00 keV
2
Master's Thesis Defense
4/24/2008
Accretion Rate Summary
Accretion Indicator
Accretion Level
Significance
FUV Continuum
< 2.5×1010 M yr1
1
Lack of Ca II 8662 Å emission line
< 1.0×1010 M yr1
4
Lack of HH Knots in Ly
< ~6×1011 M yr1
factor of 10
weak accretor

not strong accretor

H
X-ray
Karen Collins
Master's Thesis Defense
4/24/2008
Constraints on Disk Structure
 From Meeus et al. 2001, 2002
 strong IR excess blackbody in NIR
 inner rim < ~0.5 AU
 From Habart et al. 2006
M. Sitko, private communication
 spatially resolved PAH features
out to ~0".3 (~40 projected AU)
  disk outer radius > ~40 AU
Habart et al. (2006)
Karen Collins
Master's Thesis Defense
4/24/2008
HST ACS Coronagraphy




Need ~1x106 contrast to image disk around A star
Use coronagraph to block light from central star
Use psf-subtraction to reduce remaining stray light
ACS HRC provides contrast of:
 ~1x105 in direct mode
 ~1x106 in coronagraphic mode
 ~1x107 in coronagraphic mode with psf-subtraction
 HRC has 0".9 radius spot size, but psf-subtraction
residuals out to ~2-3"
Clampin et al. 2003
Karen Collins
Master's Thesis Defense
4/24/2008
Constraints on Disk Structure
HST ACS HRC Coron w/psf-sub
 HD 100453 psf-subtracted
coronagraphic image
(HST ACS HRC F606W)
HD 100453
 Limiting surface brightness from
azimuthally averaged radial profile
 No detection of disk
in scattered light
 psf residuals dominate to ~2-3"
 scattered light disk < ~250 AU
Karen Collins
Master's Thesis Defense
4/24/2008
Constraints on Disk Structure
 Third object in field
 HST ACS - 2003 (red)
HST ACS - 2003 (red)
VLT NACO - 2006 (blue)
 VLT NACO - 2006 (blue)
 Overlay aligned by
diffraction spikes
 B positioned according to
relative motion determined
previously
 C has retrograde relative
motion compared to B
 C proper motion ~ zero
 Likely a background star
 Disk is optically thin in the
optical and IR by a projected
distance of ~90 AU
Karen Collins
Master's Thesis Defense
4/24/2008
Disk Structure Summary
Line of Sight
Outer Edge Optically Thin
<90 proj. AU (star C)
Inner Rim
<0.5 AU (NIR BB)
A
Scattered Light
Outer Radius <250 AU
Companion
120 proj. AU
Outer Radius
>40 AU (PAH)
i?
B
Gap (SED dip)?
C
Karen Collins
Master's Thesis Defense
4/24/2008
Gas and Dust in Inner Disk
 Carmona et al. (2008) found no evidence for
molecular hydrogen emission
 upper limit of ~0.2 MJ of optically thin warm H2 (150 K)
 upper limit of ~0.007 MJ of optically thin hot H2 (300 K and above)
 NIR BB in SED  hot dust
 We detected no warm CO emission (4.97 μm)
 unlike other HAeBe with
hot dust
 Could have optically thick gas
in disk midplane
 Low accretion rate suggests
little optically thick or thin gas
 dust-rich gas-poor
inner disk
Karen Collins
(after Brittain et al. 2007)
Master's Thesis Defense
4/24/2008
Gas and Dust in Outer Disk
 Cold gas (from submm emission line)
 we found no CO J = 32 (868 m) emission toward HD 100453
 cold gas mass of < 0.2 MJ (1000x depletion)
 Cold dust (from mm continuum)
 Strong 1.2 mm continuum flux of 265 mJy (Meeus et al. 2003)
 cold dust mass ~0.1 MJ
 Gas:dust upper limit is 2:1 (for 1000x depletion)
 typical protoplanetary disk is 100:1 (like ISM)
 Gas-poor outer disk
Karen Collins
Master's Thesis Defense
4/24/2008
Where Does It Belong?
 14 ± 4 Myr  transitional disk character
 High NIR excess  protoplanetary disk character
 Low accretion rate  transitional or debris disk character
 Gas-poor disk  debris disk character
 High total IR excess  flared disk? requires gas?
 HD 100453A does not fit in any
classically defined disk group
(protoplanetary, transitional, debris)
Karen Collins
Master's Thesis Defense
4/24/2008
Thesis Results
 Recall we set out to test idea that
Meeus Group I sources evolve to Group II ...
 by comparing ages & accretion between the groups
 determine for HD 100453
 collect new and updated data from literature
Karen Collins
Master's Thesis Defense
4/24/2008
Thesis Results
 Group I sources are
slightly older than
Group II on average
(but are within 1σ)
 Group I accretion rates
are slightly lower than
Group II accretion rates
on average
(but are within 1σ)
Karen Collins
Master's Thesis Defense
4/24/2008
Thesis Results
 Age range significantly




overlaps between the two
groups
Accretion slows as star ages
in both groups
Meeus suggested star and disk
evolution may be decoupled
for this sample
We find that the star, accretion rate, and disk evolve together.
We conclude that the hypothesis suggesting Meeus Group I
sources evolve to Meeus Group II sources does not hold.
Karen Collins
Master's Thesis Defense
4/24/2008
Possible Physical Explanation
 HD 100546 example (Group I)
after Bouwman et al. 2003)
 cavity confirmed by interferometry & STIS
(Lui et al. 2003) (Grady et al. 2005)
 inner rim of inner and outer disk creates




NIR and MIR blackbody components in SED
and high Lexcess/L*
possible giant planet in gap is causing
collisional cascade
collisions produce small dust grains
radiation pressure blows the grains onto
surface of cold outer disk
small grains cause steep submm slope
 Meeus groups may be more representative of differences in
disk structure rather than differences in disk evolution.
Karen Collins
Master's Thesis Defense
4/24/2008
Future Directions
 To lift disk structure degeneracy allowed by SED
 need high contrast, high spatial resolution imaging
 high spatial resolution interferometry
 NICMOS on HST (coron. imaging, 0.075 pixel1 , 0".3
hole)
 My collaborators have submitted a proposal (March
2008) for NICMOS observations of several T Tauri
and Herbig Ae/Be stars, including HD 100453.
 Near-term prospects
 HST SM4 (8/2008) set to repair other key instruments
 ACS (down since June 2006)
 coron. imaging mode, 0.025 pixel1, 0".9 radius spot
 STIS (down since 2004)
 coron. imaging mode, 0.05 pixel1, 0".5-2.8" wedges
Karen Collins
Master's Thesis Defense
HD 141569 (from Krist 2004)
 We can do this with existing instrumentation
4/24/2008
Long -Term Prospects
 Atacama Large Millimeter Array (ALMA)
 0.3 - 9.6 mm (cold dust and gas)
 0".01 resolution, no occulter needed
 64 x 12-meter antennas
 completion expected in 2012
 Simulation
 0.5 M star
 1 MJ planet
 5 AU orbit
 Mdisk = 10 MJ
Wolf & D'Angelo 2005
Karen Collins
Master's Thesis Defense
4/24/2008
Thank You!
A possible view of the HD 100453 system?
adapted from NASA/JPL-Caltech/T. Pyle (SSC)
Karen Collins
Master's Thesis Defense
4/24/2008