Transcript From Cores to Disks with Spitzer Neal J. Evans II and the c2d Team.

From Cores to Disks with
Spitzer
Neal J. Evans II and the c2d Team
From Cores to Disks (c2d)
Science Goals
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Complete database for nearby (< 350 pc) regions
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Follow evolution: starless cores to planet-forming disks
Coordinate with FEPS team
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Low mass star and substar formation
ensure complete coverage of 0 to 1 Gyr
Cover range of other variables
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mass, rotation, turbulence, environment, …
separate these from evolution.
Are the times right?
Is the cartoon right?
Is this really an evolutionary
sequence?
P. Andre
What we can learn
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The initial conditions for collapse
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The nature of the collapse
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Use Spitzer MIR sensitivity to detect young disks
Timescales for disk evolution
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More complete, less biased surveys
How the disk initially forms
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Study early embedded phase
Timescales for various stages
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Study starless cores (extinction mapping, …)
Study large sample of stars (excess vs. age)
How planets form in the disk
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Debris disk statistics vs. time (e.g., George Rieke’s talk)
Observations
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(275 hr) IRAC and MIPS Mapping
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(50 hr) IRAC and MIPS Photometry
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~190 stars [~half obs., being analyzed]
(75 hr) Spectroscopy of disk material (IRS)
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Map ~5 large clouds (~20 sq. deg.) [Obs. done, being analyzed]
~135 smaller cores [most obs. done, being analyzed]
about 200 targets [about 1/3 obs., being analyzed]
Ancillary/complementary data from optical to mm
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Collecting a very large data base
Will be publicly available eventually
Large Clouds: Status
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Ophiuchus
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Chamaeleon
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Observed, some embargoed (Paul Harvey)
Lupus
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Observed, no embargo issues
Papers in progress
Serpens
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Observed, large areas embargoed (Lori Allen)
Observed, partial analysis (Lee Mundy)
Perseus
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Just observed, not analyzed
Ophiuchus AV = 3 and AORs
IRAC
AORS
Outline of AV = 3
1o
MIPS
AORs
High-extinction regions are dark
at 24 microns
Cuts:
Black is AV;
Red is emission
See Poster 33 by
Shih-Ping Lai
Red: 24 micron emission, Blue: extinction from 2MASS and
Weingartner and Draine extinction law, binned to 40” resolution.
Chamaeleon II
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Chamaeleon:
- Star forming region in the Southern sky
- Contains about 6 distinct molecular clouds
Cha II:
- Distance = 178 ± 18 pc (Whittet et al. 1997)
- Known to harbor sparsely grouped T Tauri type stars
and a couple of known Class I sources
- Also in the region: Ae star DK Cha, Star-forming
Core BHR 86, HH 54
AV map from
Cambrésy 1999
Chamaeleon II
IRAC 1, 2, 4
MIPS 1, 2, 3
Chamaeleon II (IRAC)
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About 40,000 sources detected
95% of 2-band detections are stars
Categories based on SED fitting
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72 candidates for “star+disk”
50 with rising SEDs to longer wavelengths
547 with mixed spectra
Porras et al. In prep.
IRAC Detection Statistics
Major Points:
IRAC 1 and 2 more
sensitive
Similar numbers of <13mag
sources in all bands
Bright “toe” in IRAC 3
and 4 bands – sources
with rising SEDs
Porras et al. In prep
IRAC Color-Color Diagram
For sources with detections
in all IRAC bands.
Star+ disk candidates show
many cold disks.
Rising sources should
represent Class I and
II sources + galaxies
Mixed spectrum sources
show wide range of
colors – including stellar
colors (0,0)
IRAC Colors of Young Stellar Objects
Disk models
D’Alessio 2004
Disk + protostellar
Envelope models
After Calvet 1994,
Kenyon, Calvet &
Hartmann 1993
Model IRAC colors
 Disk + envelope models
“Class I”
L = 0.1 - 100 Lsun
log r = -14 -- -12.5 g/cm3
Rc = 50, 300 AU
central
luminosity
envelope
density
 Disk models
“Class II”
Teff = 4000 K, t = 1 Myr
log (dM/dt) = -9 -- -6 Msun/yr
i = 30, 60 deg
accretion rate
inclination
grain size distribution, disk radius,
wall at disk inner rim
Allen et al. 2004 ApJS 154, 363
The Exgal Vermin Problem
Gray scale and
contours:
SWIRE catalog.
Big overlap with
Star + disk and
Class I (rising
spectrum) sources.
Porras et al. In prep
Separating the Vermin I
Use Color-magnitude diagram.
Gray scale and contours:
SWIRE catalog with same cuts
in magnitude as our catalog.
Points: Chamaeleon off-cloud
fields.
Consistent with all galaxies
and background stars.
Porras et al. In prep
Separating the Vermin II
Cham ON-cloud
Gray scale and contours:
SWIRE catalog with same cuts
in magnitude as our catalog.
Points: Chamaeleon On-cloud
MIPS Observations
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Observed on April 6, 2004
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Over 1.5 sq. degrees mapped
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MIPS Fast-scan Mapping
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2 epochs
-77 d
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- 78 d
13 h 20 m
12 h 40 m
Total integration time at:
- 24 microns = 30 sec
- 70 microns = 15 sec
- 160 microns = 0 - 3 sec
Separating the Vermin IV
Based on 24 micron detections.
Many “star+disk” (green)
Rising spectrum (magenta)
And mixed spectra (orange)
Likely to be galaxies
But stronger ones are not.
[5.8]–[8.0]
Source Identification:
K vs. K-24
Bandmerged 2MASS and
24 micron source list: 535
matches: most are stars or
galaxies
 Red: also has 70 micron detection
 2 clumps: Stars (K-24 = 0 mag)
and Galaxies (K > 13 mag)
 42 YSO candidates
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40 previously known,
1 background star,
& 2MASS 125605
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K. Young et al. In prep.
Cumulative Source Counts
Use color bin that removes
stars.
Stronger sources are dominated
by non-galaxies.
Contamination is
<50% for [24]<8
<10% for [24]<7
K. Young et al. In prep
Spectral Index Distribution
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III
Class II
alpha= log(λSλ(24)/λSλ(K))
log(24/K)
(Lada 1987)
Class I
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Most sources (90%) have
α < -2.5 (star ~ -2.8)
43 sources with α > -2.5
- All but 2 are previously
identified YSOs or candidates
Some T Tauri stars in
off-cloud region
K. Young et al. In prep
Complementary Millimeter & Spitzer
IRAC/MIPS Observations: B1 in Perseus
Bolocam 1mm
MIPS 24 m
Poster #25 by Enoch et al.
Dark blue: 24; light blue 70 microns
Small Cores
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Most observed, but data being processed
First observed (validation) was L1014
Tyler Bourke will report on others
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Based on preliminary analysis
Tracy Huard discussed extinction law studies
L1014: A Typical Starless Core
L1014 distance ~ 200 pc, but
somewhat uncertain.
R-band image from DSS
A Surprise from Spitzer
Three Color Composite:
Blue = 3.6 microns
Green = 8.0 microns
Red = 24 microns
R-band image from DSS at
Lower left.
We see many stars through
the cloud not seen in R.
The central source is NOT
a background star.
L1014 is not “source-less”.
Larger size in red is PSF.
C. Young et al. ApJS, 154, 396
JHK Image
J, H, K Image of L1014
KPNO 4-m + Flamingos
J (19.7) H(20.9) K(19.4)
Huard et al. In prep.
Preliminary reduction
Faint conical nebula to north
with apex on IRAC source.
BIMA peak to south likely
obscures southern lobe.
Not a background source.
Source Peaks on mm Emission
Both long-wave
maps are 3-sigma
contours.
C. Young et al.
ApJS, 154, 396
Left: 8 micron on 1.2 mm MAMBO dust continuum emission (Kauffmann & Bertoldi)
Right: 24 micron on 850 micron SCUBA data (Visser et al. 2002)
Models
Model of SED for d = 200 pc.
Central object has very low
luminosity: 0.09 Lsun.
Requires BB plus disk
(red line) in an envelope.
M(envelope) about 2 Msun.
Cannot be a stellar-mass
object with significant
accretion. Probably substellar at this point.
Alternative model: more
distant (2.6 kpc) object lined
up by chance with peak of a
foreground core (dashed line)
C. Young et al. ApJS, 154, 396
And an IRS spectrum
HH46/47
L1014
Compared to Photometry and
models…
Lessons from L1014
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“Starless” cores may not be
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Very low luminosity sources may exist
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Must be low mass and low accretion
Peculiar, non-thermal radio source (Y. Shirley, poster #39)
Early, small disks are easily detected
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Or may have substellar objects
Md ~ 4 x 10–4 Msun (Rd/50AU)0.5
Easily detected (SNR = 50–100)
Rd ~ 50 AU
Are there others?
 Tyler Bourke will report on these
Finding disks with MIPS
Model has 0.1 Mmoon of
30 m size dust grains
in a disk from 30–60 AU
Bars are 3 s
Model based on disks
around A stars
A New Disk in Cha II
One source not previously
identified as a YSO on
K vs. K-24 plot
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Factor of 3 excess in 24
micron flux over stellar
model indicating the
presence of a disk
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Evidence for large inner rims in cTTs
cgplus model (Dullemond et al. 2001)
 ~ 3.5
RrimA~ 0.04 AU
RrimA~ 0.07 AU
The solid blue line (Total SED
A) corresponds to the total
SED when the inner rim is
irradiated only by the
photosphere of the central
star (rim A). The solid red line
(Total SED B) corresponds to
the total SED when the
emission from the inner rim is
scaled by a factor  .
. ranges from ~ 1 to ~7.
The inner rim is powered by
more than the stellar
photosphere
ArimB
 
ArimA
Missing source of energy?
Arim Rrim  H rim RrimB  RrimA  2 / 5
3/ 2
H rim Rrim
5/ 2
Arim  Rrim
UV radiation from the
accretion shock
See Poster#7 by Lucas Cieza
Other Talks on c2d Results
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Paul Harvey on Serpens cloud
Debbie Padgett on wTTs
Lori Allen on Ophiuchus cloud
Ewine van Dishoeck on IRS program
Tyler Bourke on cores
Adwin Boogert on IRS spectra of ices
Klaus Pontoppidan on mapping ice distribution
Posters on c2d Results
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Tim Brooke (#6) on MIPS processing
Lucas Cieza (#7) on disk structure
Jackie Kessler-Silacci (#11) on disk mineralogy
Claudia Knez (#13) on MAMBO maps of cores
Lori Allen (#21) on Ophiuchus
Melissa Enoch (#25) on Bolocam map of Perseus
Fred Lahuis (#32) on gas-phase spectral features
Shih-Ping Lai (#33) on Ophiuchus emission
Lee Mundy (#34) on Lupus results
Debbie Padgett (#36) on wTTs
Yancy Shirley (#39) on L1014