1 SIMBA survey of southern high-mass star forming regions Santiago Faúndez (U. de Chile) Leonardo Bronfman(U. de Chile) Guido Garay (U. de Chile) Rolf Chini (AIRUB) Lars-Ake Nyman(SEST,ESO-La Silla)

2 Introduction We present the results of a survey of 1.2 mm continuum emission toward 146 IRAS sources, selected from the CS(2-1) survey of Bronfman et al. (1996), which are thought to harbour high- mass star forming regions. Main objectives : (i) determine the physical characteristics of the dust content toward these regions; and (ii) identify candidates of massive starless cores.

3 Sources have at least one of the following characteristics: Bright CS sources (Ta > 2.0 K) Wings in CS spectrum No radio continuum in Walsh et al. (1998) survey CHARACTERISTICS OF THE SURVEY

4 Galactic distribution Kinematics distances using velocities reported by BNM96. Ambiguity solved by Bronfman (private communication) and searching in literature. Range of distances: 0.2 – 13 kpc Galactic coverage : 95% in inner Galaxy 5% in III Quadrant

5 Kinematic distances and galactic distribution

6 The observations SIMBA bolometer array installed at the 15m telescope SEST Three runs between June 2001 and July ¨ x 600¨ maps Resolution: 24¨, typical RMS : 40 mJy / beam

7 Results Outline Emission was detected in all maps In about 50% of the regions 2 or more sources were detected Determination of physical parameters of IRAS sources Identification of massive starless cores Study of filamentary structure

8 Number of sources per map

9 Distribution of sizes

10 The dust temperatures are derived by fitting the SED, using a modified blackbody model: Dust temperatures Two components are needed to obtain a good fit  is assumed a power law of

11 Temperature distribution

12 Since the emission is optically thin, dust masses are calculated using the expression: Mass distribution and Assuming:

13 Bolometric fluxes are calculated by integrating the SEDs Luminosity distribution

14 Density distribution

15 MORPHOLOGY 8 % of the sources show filamentary structure. 36% show irregular shapes

16 Regular shapes are found in 56 % of the sources

17 We are looking for cold, massive and dense cores lacking all signature of massive star formation. Need for large mm-submm maps in the neighborhood of massive star forming regions. Massive starless cores

18 The search of massive starless cores We searched for massive starless cores among the newly detected 1.2 mm objects by looking at the IRAS and MSX images of the mapped regions. Selection criteria: 1.2 mm object undetected by MSX undetected by IRAS We identified 5 candidates of massive starless cores

19 Williams et al. (2004)

20 IRAS 

21 IRAS 

22 IRAS 

23 IRAS 

24 Filaments in our sample Selection of the 11 most conspicuos (a/b > 3.5) filaments in our survey. Characteristics:

25 Conclusions Physical characteristics of MSFRs associated with the IRAS sources are: By comparing SIMBA, MSX and IRAS maps we have identified 5 candidates of massive starless cores. Three of them have been confirmed through molecular observations.