The Cores to Disks Spitzer Legacy Science Project PI: Neal J. Evans II and the c2d Team Maryland Team: Mundy, Lai, Chapman and several UG students

c2d Observational Goals  Complete database of stellar content for a representative sample of nearby (< 350 pc) regions  with sensitivity to see low mass star and substar formation  with coverage to modest Av (3-5 mags)  Follow evolution: starless cores to planet-forming disks  complete coverage from 0 to 10 Myr or more  large sample of sources to see rare stages.  Cover range of environmental variables  cloud mass, rotation, turbulence, environment, …  enough sample to separate these from evolution.

c2d Observations  (275 hr) Images of clouds, cores  IRAC 3.6, 4.5, 5.6, 8.0 micron; MIPS 24, 70, 160  5 large clouds (~20 sq. deg.) Perseus, Ophuchius, Lupus, Chamleon, and Serpens  88 smaller cores  (50 hr) Weak-line T Tauri stars  ~190 stars IRAC and MIPS Photometry  (75 hr) Spectroscopy (IRS)  >170 targets, embedded objects and stars with disks  Ancillary/complementary data from optical to mm  Collecting a very large data base  Will be publicly available eventually

What we can learn  The full population of young objects (YSOs)  Sensitive surveys  Where stars form in clouds  Comparison of stellar and dust/gas distributions  The initial conditions for collapse  Comparison of stellar, pre-stellar, and core distributions  Timescales for various stages  More complete, less biased surveys  How low in mass do independent YSOs extend?  Use Spitzer MIR sensitivity to detect low-mass disks  Timescales for disk evolution  Study large sample of stars (excess vs. age)

Perseus as seen by IRAC 3.6, 4.5, 8.0 NGC1333

Perseus as seen by MIPS 24, 70, 160

Dust Emission Map Enoch et al Largest map at 1 mm so far (~10 sq deg) Bolocam on CSO Most of cloud “empty” Over 100 dense cores Mostly along filaments

Dense cores in filaments of high extinction Enoch et al Extinction from NIR colors of background stars in contours

Perseus MIPS (24+70) Stapelfeldt et al. in prep.

Perseus Zoom 3.6, 5.8, 24

IC , 8.0, , 4.5, , 3.6, 8.0

Many potential YSOs, but … IRAC color-color diagram for Perseus, off-cloud region and SWIRE (exgal survey). Many galaxies in “YSO” regions. Joergensen et al., submitted sq deg0.05 sq degTrimmed to match Perseus Class II Class I Expect no YSOs

Separating YSOs from galaxies Black Dot (stars), Red Cross (YSO candidate), Blue Dot (“Other”) Most galaxies are faint, below a line of [8] = 14 – ([4.5] – [8]). Part of classification scheme. Joergensen et al., submitted Expect no YSOs

Low Luminosity objects Harvey et al Compare On and Off cloud counts (for Serpens) No excess for “stars”, but excess for “non-stars” down to lowest luminosities Off-cloud On SWIRE Off-cloud On SWIRE On-Off

Very Low-mass Objects with Disks Five found with M < 12 M jup (Allers et al. submitted) see also Luhman et al. (2005) NIR fits model atmosphere of 3 Myr old brown dwarf, T eff = 2100 K, M~10 M jup black line Has MIR excess: Fits model of disk With M d = 0.03 M BD R d = 5 AU, i = 40 deg green line

Really how low? A 2 M jup BD could be seen in NIR at 1 Myr and d = 125 pc. But we need a deeper Spitzer survey to show that it has a disk. Allers et al. submitted photosphereflat flared c2d limits near-IR limits

A Typical Starless Core L1014 distance ~ 200 pc, but somewhat uncertain. R-band image;dust blocks stars behind and our view of what goes on inside.

Or so we thought… 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 forming a star (or substar) C. Young et al. ApJS, 154, 396

Source Peaks on mm Emission 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) Both long-wave maps are 3-sigma contours. C. Young et al. ApJS, 154, 396

Models C. Young et al. ApJS, 154, 396 Model of SED for d = 200 pc. Central object has very low luminosity: 0.09 L sun. Requires BB plus disk (red line) in an envelope. M(envelope) about 2 M sun. Cannot be a stellar-mass object with significant accretion. Probably sub- stellar at this point. Alternative model: more distant (2.6 kpc) object lined up by chance with peak of a foreground core (dashed line)

Now other, similar sources L1521F L~0.04 L Sun Myers et al. in preparation CB130 L~ 0.03 L Sun L673-7 L ~ 0.01 L Sun DSS R

An Emerging Class of sources?  About 15 similar objects found in cores  Too faint to be seen by IRAS  Need to rule out background source  3 to 5 have L < 0.1 L Sun and embedded  Very Low Luminosity Objects (VeLLOs)  Standard accretion on M ~ 0.1 M Sun gives ~ 1 L sun  Product of M and accretion rate is very low  MAY be forming Brown Dwarfs

Formation Mechanisms  Increasing evidence for very low masses  In surveys of clouds  In more detailed studies with NIR data  Some spectroscopic follow-up  How do such things form?  Ejection from multiple systems  Formation “like stars”

Finding disks with MIPS Model has 0.1 M moon of 30  m size dust grains in a disk from 30–60 AU Bars are 3  Model based on disks around A stars

Classical T Tauri Stars Strong evidence for puffed up inner rim. Bigger than expected Requires extra flux; likely due to accretion shock Cieza et al in press

Weak-line T Tauri Stars Cieza et al. 2005b, in prep.

With inner holes Cieza et al. 2005b, in prep. Some wTTs have inner holes. May be cleared by planet formation But small fraction Disk clearing is fast Planet formation is “fast or not at all”

Evolving dust properties Background stars… And there are lots of them…. Give us information on dust extinction properties At low Av’s dust is Intermediate between WD R=3.1 and 5.5

Evolving dust properties At higher extinctions the extinction becomes marginally flatter than WD models

Evolving dust properties At very high Av’s, the extinction is nearly flat from 3.1 to 24 microns (not considering the silicate feature). The high opacity at 24 microns is not consistent with the WD models.

Evolving dust properties Interpretation of dust extinction is not simple because this is a plot of relative extinction…. How much is due to changes in optical to near-IR properties? How much is due to mid-IR changes?

New dust models Example of a new dust model with fewer small grains. No ice on the small grains. Ice mantles on the larger grains

C2d Data Products Public releases of mosaic images and catalogs Mosaic images of nearly all clouds and cores now available from SSC Legacy Data Product webpage Band merged catalogs of IRAC and MIPS 24 data are also there. The catalog is very useful: source identifications: star, star+disk, YSO candidate, Red, etc Av’s derived for all “star” sources lots of flags to allow user to select different quality samples.

Summary  c2d project nearly done. Final delivery of processed images and catalogs will be in late fall  Images and source catalogs are available to everyone – excellent database for follow-up  Science:  YSO candidates are being identified  Candidate forming Brown Dwarfs are being found  Variations in dust extinction properties are being found  Work is ongoing on clustering, correlations between dust gas and stars, and identifying YSOs  Lots more to do with data….