1. Loredana Spezzi INAF-Catania Astrophysical Observatory Loredana Spezzi INAF-Catania Astrophysical Observatory 4-8 Maggio 2008 INAF-CATANIA A. Frasca E. Marilli INAF-NAPOLI J. M. Alcalá E. Covino F. Comerón c2d Spitzer Legacy Team D. Gandolfi

2. (Evans et al. 2003, PASP 115, 965) Scientific aim: ……..to study the process of star and planet formation from the earliest stages of molecular cores to the epoch of planet-forming disks……… Observations (IRAC, MIPS, IRS@Spitzer): five nearby molecular clouds: Perseus, Ophiuchus, Serpens, Lupus, Chamaeleon II 150 compact molecular cores 300 stars in a wide range of evolutionary states disk frequency/characteristics accretion rates clustering properties kinematics binary statistics planetary companions sub-stellar IMF Different predictions on BD properties Problem: in the standard cloud fragmentation model self-gravitating objects with mass of only 1 M J continue to accrete matter from their surrounding cores, usually to the point of reaching stellar masses (Bate et al. 2003, Mon. Not. R.Astron. Soc. 339, 577) Possible explanations: 1) The simulations lack an important piece of physics, e.g. turbulence (Padoan & Nordlund 2004, ApJ 617, 599) 2) BDs are born when cloud fragmentation is modified by an additional process that prematurely halts accretion, i.e. dynamical ejection or photoevaporation by ionizing radiation from massive stars (Reipurth & Clarck 2001, ApJ 122, 432) http://astro.berkeley.edu/~stars/bdwarfs

3. MIPS WFI IRAC R, I, z, H 7, H 12, 856 nm, 914 nm WFI @ ESO 2.2m tel. (Spezzi et al. 2007, A&A 470, 218) 3.6, 4.5, 5.8 and 8 m IRAC@Spitzer (Young et al. 2005, ApJ 628, 283) 24, 70 and 160 m MIPS@Spitzer (Porras et al. 2007, ApJ 656, 493) Alcalà, Spezzi, et al. 2008, ApJ 676, 427 Cha II properties……… T association Age = 1-10 Myr Distance 180-200 pc Area 2 deg 2 Modest star formation activity ( 60 members) K. Luhman: Chamaeleon ASP Conf. Ser., B. Reipurth ed., in press (Spezzi et al., astro-ph 0802.4351 ; Alcalà, Spezzi et al. 2008, ApJ 676, 427)

4. Adapted from Cambrèsy 1999 Goals Same as in Cha II, but in a different star-forming environment! Lupus properties……… Complex of T associations Age < 2 Myr Distance 100-250 pc Area 20 deg 2 High star formation activity ( 250 members) Location: Scorpius-Centaurus F. Comeròn: The Lupus clouds ASP Conf. Ser., B. Reipurth ed., in press (Merìn, Jørgensen, Spezzi et al., astro-ph 0803.1504)

5. (Spezzi et al. 2007, A&A 470, 281; Alcalà, Spezzi et al. 2008, ApJ 676, 427; Spezzi et al., astro-ph 0802.4351) Meyer 1997 Selection of young objects with and without IR excess Instruments: FORS2@ESO-VLT (R>18 mag): 6000-11000 Å, R~2500 FLAMES@ESO-VLT (R 18 mag): MEDUSA: 6400-7200Å, R~9000 UVES: 5800-6800Å, R~47000 EMMI@NTT (R 18 mag) 4000-10000 Å, R~8000 Diagnostics of the PMS nature: LiI 6708Å absorption line (youth indicator) H emission line (accretion activity indicator) Spectral Type, Teff, Av: Spectral classification: standard templates (Gandolfi et al., ApJ, submitted) T eff - Spectral Type tabulation (Kenyon & Hartmann 1995, ApJ 101, 117; Luhman et al. 2003, AJ 593, 1093) Av = 4.605 E(R-I) (Weingartner & Draine 2001, ApJ 548, 296) Contaminant

6. (Spezzi et al., astro-ph 0802.4351 ; Alcalà, Spezzi et al. 2008, ApJ 676, 427) L STAR,R STAR L DISK / ENVELOPE NextGen & STARDUSTY Models for stellar atmospheres L*, R* Passive Disk Models by Dullemond et al. 2001 (AJ 560, 957) Accreting Disk Models by DAlessio et al. 2005 (R.M. A. Y A. 41, 61) Accreting Disk Models by Robitaille et al. 2006 (ApJS 167, 256) R hole, R disk, M disk,M accr, Grain size, incl. angle, etc…

7. M/M (Alcalà, Spezzi et al. 2008, ApJ 676, 427; Spezzi et al., astro-ph 0802.4351; Merìn, Jørgensen, Spezzi et al., astro-ph 0803.1504) Star Formation Rate Mean Age IMF slope (0.1M/M 2) Total Mass Mean Mass 0.52 ± 0.11 M 20 – 33 M 0.4 – 1 6-12% ? (OB associations 26%) 1- 4 % 4 ± 2 Myr ~ 8 M /Myr 0.1 1.0 Mass (M ) dN/dM M - bin=0.2 M Environmental conditions affect the BD formation mechanism Star Formation Rate Age IMF slope (0.1M/M Θ 2) Total Mass Mean Mass 0.5 M 8-62 M 0.9 ? ? 1- 7 % 2 Myr 4 - 31 M /Myr

8. (Alcalà, Spezzi et al. 2006, A&A 453, L1-L4) (Merìn,….Comeròn, Frasca, Alcalà et al. 2007, ApJ 661, 361) Spectral type: M7 T eff = 2880±80 K Av = 5.0±0.5 mag L* = 0.010±0.001 L L bol = 0.028±0.006 L R* = 0.38±0.05 R M = 0.05±0.01 M Age = 5±3 Myr T wall 1500 K R wall 0.02 AU R disk 0.4 AU Mdisk 10 -4 M IR class = II STARDUSTY STARDUSTY + BB FitCGplus fit FORS2@VLT Iso-ChaII-13 SST-Lup3-1 crystalline silicate features BDs Very-low mass stars & More massive stars Common formation process? (see also Alcalά et al. 2004; Barrado Y Navascués et al. 2004; Luhman 2005; Preibish et al. 2005)

9. (Alcalà, Spezzi et al. 2008, ApJ 676, 427; Merìn, Jørgensen, Spezzi et al., astro-ph 0803.1504) Thin disk fraction declines with mass Thick disk fraction peaks ~1 solar mass Do planets preferentially form around solar-mass like stars ? See also IC348 (Lada et al. 2006, AJ 131, 1574)

10. 1. The Spitzer c2d Survey in Cha II and Lupus 2. Star formation history - Mass spectrum: stellar and sub-stellar IMF - Ages - SFE and SF rate 3. Properties of circumstellar disks - Disks around sub-stellar objects - IR classification and disk fraction Future developments with: II generation VLT intruments (XSHOOTER, SPHERE) and HST Extend these investigations to low-metallicity Enviromments (Magellanic Clouds) Goulds Belt mapping with Herschel BD and planet formation: constrain the disk parameters

11. turn-off R in Log ( ) excess (Alcalà, Spezzi et al. 2008, ApJ 676, 427; Merìn, Jørgensen, Spezzi et al., astro-ph 0803.1504) R in 70 AU