HUNTING CORESHINE WITH SPITZER: FROM GRAIN GROWTH TO PLANET FORMATION

Transcription

1 HUNTING CORESHINE WITH SPITZER: FROM GRAIN GROWTH TO PLANET FORMATION Roberta Paladini & The Hunting Coreshine Team 1

2 Outline of the Talk CORESHINE EFFECT: brief recap SPITZER CYCLE 8/9 SURVEY (PI. ): rationale & observations PRELIMINARY RESULTS FROM CYCLE 8 /9: à Andersen et al. 13 à Lefevre et al. 14 à Steinacker et al. 15 2

3 The Team Roberta Paladini (P.-I.) IPAC/Caltech (USA) Laurent Pagani Observatoire de Paris (France) Jurgen Steinacker IPAG/Grenoble (France) Sean Carey IPAC/Caltech (USA) Mika Juvela University of Helsinki (Finland) Charlene Lefevre* Observatoire de Paris (France) Morten Andersen* IPAG/Grenoble (France) Veli-Matti Pelkonen FINCA (Finland) Alberto Noriega-Crespo IPAC/Caltech (USA) Aurore Bacmann IPAG/Grenoble (France) Isabelle Ristorcelli IRAP/Toulouse (France) Ludovic Montier IRAP/Toulouse (France) Doug Marshall CEA (France) * Cycle 9 only 3

4 Coreshine Effect: what is it? Coreshine (Pagani et al. 2010, Steinacker et al. 2010): scattering of MIR light by micron-size (> 0.25 µm) dust grains Cloudshine (Lehtinen & Mattila 1996; Foster & Goodman 2006): scattering of NIR light by micron-size (> 0.25 µm) dust grains 3.6 µm 4.5 µm 8 µm L 183 d ~ 110 pc M ~ 80 M sol Pagani et al. 2004, Steinacker et al

5 Coreshine Effect: why do we care? ISM PROTOPLANETARY SYSTEMS e.g. MRN 1977: n(a) ~ a -3/5 For silicates: a max ~ 0.25 µm likely not by collision probably from secking (if enough turbulent velocity is provided) a ~ from a few µm to ~1 mm: µm silicate feature β from sub-mm/mm observations 5

6 No dust reprocessing after cloud collapse Ricci et al

7 Spitzer Cycle 8 Survey u The survey consists in hr of observing time with Warm IRAC (3.6 µm, 4.5 µm) u It is the largest Galactic program of Cycle 8 u Observations were executed between August 11 and May 12 u The survey reaches a sensitivity of MJy/sr in both ch1 and ch2, with a substantial improvement with respect to archival data (e.g. 3 X c2d and Gould Belt Survey, 10 X WISE w1 and w2) 7

8 Cycle 8 Survey: Rationale Ø Is grain growth universal in cold, dense environments? Ø What are the observational biases? Ø What are the dust models that are able to reconcile the observations? 8

9 Cycle 8 Survey: Observations Sample of 90 sources from Planck Early Release Cold Clumps Catalog (ECC) Planck ECC: 915 cold clumps T D < 14 K S/N > 15 distance for ~50% sources (mostly < 1 kpc) Planck CollaboraEon (2011r) Monte Carlo source selection: longitude latitude mass 9

10 Cycle 8 Detections Coreshine is detected in ~ 50% of the sources (50/90) Very high # of new detections (86%) 3.6 µm 4.5 µm 4.5 µm 8 µm 4.5 µm 8 µm ecc469 ecc µm 3.6 µm 8 µm 4.5 µm 8 µm 3.6 µm ecc806 ecc µm 4.5 µm 8 µm ecc815 R. Paladini ExEP Science Briefing May 23rd

11 Spitzer Cycle 9 Survey u The survey consists in 42.5 hr of observing time with Warm IRAC (3.6 µm, 4.5 µm) u Observations were executed between January and June 13 u The survey reaches a sensitivity of MJy/sr in both ch1 and ch2 11

12 Cycle 9 Survey: Rationale d ~ 150 pc M ~ 1 M sol Model by J. Steinecker 12

13 Cycle 9 Survey: Observations 10 sources selected from all known coreshine cases showing no or weak coreshine emission at 4.5 µm all the selected sources had been already observed during either the Spitzer cryogenic (e.g c2d, etc.) or the warm mission L 1512 d ~ 140 pc M ~ 2.4 M sol 3.6 µm 4.5 µm 8 µm 13

14 Cycle 9 Detections > 70% detections L 1512 d ~ 140 pc M ~ 2.4 M sol 3.6 µm 4.5 µm 8 µm 14

15 Radiative Transfer Modeling (Lefevre et al. 2014, Steinacker et al. 2015) Ø ConEnuum RadiaEve Transfer (CRT) model (Juvela & Padoan 2003; Juvela 2005): Ø Incident ISRF: DIRBE J, K, 3.5 µm, 4.9 µm, 12 µm rescaled to Spitzer IRAC bands Ø Molecular Clump model: inclined 3D ellipsoid + Plummer- like profile: α = 2.5 Ø several dust models (see next slide..) 15

16 Dust Models Ø Is coagulaeon (hence suppression of the smallest grains) required to explain coreshine? Ø Is there a size limit for the size distribueon? Ø Can the size distribueon be different from standard MRN distribueon? Ø What is the role of ice mantles? Ø What is the role of fluffly grains? 16

17 Coreshine Universality and Relation with Environment Ø Some GalacEc regions seem to be favored: Taurus, Perseus, Aquila, Cepheus, Chameleon. Perhaps large grains already exist in the diffuse medium before cloud formaeon, or coagulaeon happens fast aler cloud formaeon and before turbulence dissipaeon Ø Coreshine is a constrast problem: scatered light > background field. Cannot be seen towards GalacEc Plane and GalacEc Center Ø Coreshine increases in the presence of protostars, due to increase of local radiaeon field Cryo + Warm: ~ 200 sources Lefevre et al

18 Grain Growth & Constraints on Dust Models Ø grains larger than 0.25 µm are mandatory Ø Classical compact/bare diffuse medium grains (e.g., WD01) are not able to reproduce coreshine observaeons Ø small grains have no influence in the modelling of coreshine Ø Porosity has no impact on coreshine modelling, while a fractal structure is favored Ø We know grains have ice mantles at A V > 3 mag. However, current models of grains with ice mantles do not explain the observed coreshine 18

19 Future Challenge Ø treating simultaneously: emission, extinction and scattering through 3D RT 19