Star Formation and Protostars at High Angular Resolution with the SMA

1. Star Formation and Protostars at High Angular Resolution with the SMA Jes Jørgensen (CfA)Tyler Bourke, Philip Myers, David Wilner (CfA), Fredrik Schöier (Stockholm), Ewine van Dishoeck (Leiden), ... and the PROSAC team. Submillimeter Astronomy in the era of the SMA, Cambridge, June 14, 2005 ACP

2. t ~ 105– 106 yrs T-Tauri star, disk, outflow t ~ 106– 107 yrs Pre-main sequence star, remnant disk t > 107 yrs Main-sequence star, planetary system Dark Cloud Cores t = 0Gravitational collapse t ~ 104– 105 yrs Protostar embedded in ~10,000 AU envelope Figure based on Shu (1987); from “NASA Origins”

3. Low-mass protostars ~ 20,000 AU (100”) ~ 200 AU (1”) • Densities ranging from 104 cm-3 to 107-108 cm-3 (H2) • Temperatures ranging from ~10 K to a few hundred K.

4. PROSAC: Protostellar Submillimeter Array Campaign PROSAC PROtostellar Submillimeter Array Campaign • Line + continuum survey (230/345 GHz) of deeply embedded (class 0) protostars • 8 protostellar sources from Ph.D. thesis of J. Jørgensen (Leiden Univ. 2004; Jørgensen et al. 2002, 2004, 2005)... • Single-dish survey at JCMT and Onsala 20m telescopes. • Follow-up 1, 3 mm interferometric measurements OVRO and BIMA. • All tied together by detailed line and continuum rad. transfer models. • 3 spectral setups per source: CO, CS, SO, HCO+, H2CO, CH3OH, SiO, ... transitions (and isotopes) Jørgensen (PI)Bourke, Di Francesco, Lee, Myers, Ohashi,Schöier, Takakuwa, van Dishoeck, Wilner, Zhang

5. In this talk... • What is the structure of protostellar envelopes on a few 100 AU scales? • What is the physical structure of circumstellar disks - and their molecular content? • Do low-mass protostars have hot cores, i.e., inner regions with temperatures higher than 100 K and where complex organic molecules might be present?

6. 2C 2A 2B NGC1333-IRAS2 SCUBA 850 µm • Tbol ~ 50 K, Lbol ~ 16 L • d ~ 220 pc (Cernis, 1990) • Three pre/protostellar objects (Looney et al. 2000, Sandell & Knee 2001, Jørgensen et al. 2004)

7. NGC1333-IRAS2A dust continuum at 850 µm. SMA 850 µm SCUBA 850 µm

8. Envelope (constrained through SCUBA observations; Jørgensen et al. (2002)) Disk (resolved) NGC1333-IRAS2A dust continuum at 850 µm. …the SMA resolves the warm dust in the inner envelope and the circumstellar disk SMA 850 µm

9. NGC1333-IRAS2A dust continuum at 850 µm. • The dust continuum emission follows a power-law F   2.2 from cm through submillimeter wavelengths. • Likely optically thick thermal dust emission from a circumstellar disk with a size of 300 AU and mass of a few  0.01-0.1 M • It is not evident from high-resolution data that the envelope extends all the way to the smallest scales. • The disk material will be dominating a hot core in the protostellar envelope. cm through mm measurements from Rodríguez et al. (1999), Reipurth et al. (2002), Jørgensen et al. (2004)

10. Envelope and disk chemistry • Low-mass hot cores: Presence of complex organic species on small scales (i.p., IRAS16293: Cazaux et al. (2003), Kuan et al. (2004), Bottinelli et al. (2004)).

11. Detections of high excitation transitions of CO, HCN (and H13CN), SO, SO2, CH3OH (and CH3OD), CH3OCH3 and CH3OCHO (tentative) in submm window toward NGC1333-IRAS2A.

12. 500 AU Organic molecules toward IRAS2A ...line emission compact (largely unresolved)

13. Envelope and disk chemistry • Complex organic species detected on small scales in IRAS2A. • ...but in the 2” SMA beam: the disk column density is dominating compared to the hot core. • Sulfur species are expected to be enhanced in typical hot cores (Charnley 1997, Wakelam et al. 2004) • Low-mass hot cores: Presence of complex organic species on small scales (i.p., IRAS16293: Cazaux et al. (2003), Kuan et al. (2004), Bottinelli et al. (2004)).

14. With SO abundance enhancements in hot core Envelope and disk chemistry Constant abund. envelope The SO abundance is almost constant throughout the envelope (consistent with single-dish obs. of S-species). An abundance enhancement in the innermost envelope is clearly ruled out.

15. Envelope and disk chemistry • The presence of the high excitation lines of in particular CH3OH suggests that the temperature is high ~ 150 K. Heated layer of circumstellar disk (e.g., Elias 29; Ceccarelli et al. 2002)? • Low-mass hot cores: Presence of complex organic species on small scales (i.p., IRAS16293: Cazaux et al. (2003), Kuan et al. (2004), Bottinelli et al. (2004)). • Complex organic species detected on small scales in IRAS2A. • ...but in the 2” SMA beam: the disk column density is dominating compared to the hot core. • Sulfur species are expected to be enhanced in typical hot cores (Charnley 1997, Wakelam et al. 2004) Jørgensen et al., ApJ, submitted

16. PROSAC: Protostellar Submillimeter Array Campaign ...much more to come!

17. Conclusions • High-angular resolution interferometric and single-dish continuum observations of NGC 1333-IRAS2A can be fitted by an extended envelope and a 300 AU (resolved) disk with a mass a few  0.01-0.1 M. • The large size of the disk suggests a rapid build-up of disks in the deeply embedded stages of protostellar evolution. • The molecular content of the disk is non-negligible compared to a candidate hot core. It is not evident from the dust observations/models that warm (T > 100 K) material is present in the envelope around NGC1333-IRAS2A. • No evidence is seen for sulfur enhancements on small-scales. Other species such as CH3OH may have their origin in the circumstellar disk... (don’t forget the outflows, though)