1. The overall systematic trends in the kinematics of massive star forming regions Observations of HC 3 N* in hot cores Víctor M. Rivilla 41st Young European Astronomers Conference University of Manchester/Jodrell Bank Observatory 18-20 July 2011

2. Hot cores: the cradle of massive stars ■ Understanding the formation of massive stars requires knowledge of the physical conditions of the places where they are born. ■ Hot cores (HC) are deeply embedded, dense (n > 10 7 cm -3 ), hot (T > 200 K), and chemically rich condensations, considered to be the earliest stages of massive star formation. ■ Contain hot dust very bright mid-IR (10-50 μm) emitters. ■ HC are hidden behind large extinction (>25 mag) even in the mid-IR, preventing their direct observation at these wavelengths.

3. Why HC 3 N? ■ Indirect observations of the kinematics and the physical properties of the inner parts of the hot cores are possible by measuring the rotational lines of molecules in vibrationally excited levels. ■ Rotational lines are emitted at radio wavelengths, unaffected by the dust extinction. ■ The excitation of these lines is due to mid-IR radiation. ■ Cyanoacetilene (HC 3 N) is a very well suited molecule to study the hot cores : abundance enhanced due to the evaporation of the grain mantles. trace dense gas. vibrational levels are excited by IR radiation in the 15-50 μm range. ■ Rotational transitions from the vibrationally excited lines of HC 3 N (HC 3 N* hereafter) probe the high density hot gas and dust regions surrounding the very young massive stars. Wyrowski et al. (1999)

4. Previous observations and results ■ de Vicente et al. (2000) found that the HC 3 N* lines (1v5, 1v6 and 1v7) show in Sgr B2N and Sgr B2M massive HCs: Linewidth-E upp trend: a systematic trend in their linewidths to decrease with increasing energy of the upper energy level (E upp ) involved in the transition Jímenez-Serra et al. (2009) S ize-E upp trend: differences in the morphology of their emission, with the lines with lower E upp being more spatially extended than those with higher E upp. 1v6 line (higher excitation) 1v7 line (lower excitation) HW2 Cep A

5. New observations: our sample of hot cores ■ NRAO Arizona Radio Observatory (ARO) 12m (Kitt Peak) ■ Angular resolution: ~ 38" ■ J=18-17 rotational transition (2mm) of HC 3 N* from 2 different vibrational levels (1v7 and 1v6) Rivilla et al. (in preparation) ■ In order to confirm whether linewidth-E upp and E upp -size trends represent a general behavior of the HC 3 N* emission toward high-mass star forming regions, we have extend out study to a more complete sample of hot cores.

6. HC 3 N* spectra toward the sample of hot cores Rivilla et al. (in preparation) HC 3 N 1v7,1f ν=164.39 GHz E up =396K HC 3 N 1v6,1e ν=164.02 GHz E up =793K lower excitation higher excitation

7. LTE analysis of spectral lines: χ 2 method results ■ We have used our data along with data from the literature to characterize the T ex, N and size of the emitting region. Orion Hot Core SgrB2 MSgrB2 NG10.47+0.03

8. ■ We have redone the LTE analysis distinguishing between low excitation (E up 400-500K) lines. ■ The result confirm that low excitation lines arise from a more extended and colder component, and higher excitation lines from a more compact and hotter region. Low excitation (lower T ex and more extended) High excitation (higher T ex and more concentrated) 1v6 line (higher excitation) 1v7 line (lower excitation) Low excitationHigh excitation HW2 Cep A Jímenez-Serra et al. (2009) Rivilla et al. (in preparation) 1) Size – E upp trend

9. ■ These morphology differences could be explained as an excitation effect produced by the radiative pumping of the levels of HC 3 N by the dust-processed IR radiation coming from the massive star(s) within the core. ■ The levels with higher E upp are only excited in the inner parts around massive stars. ■ The levels with lower E upp can be pumped at larger distances. Low excitation (lower T ex and more extended) High excitation (higher T ex and more concentrated) 1) Size – E upp trend

10. 2) Confirmation of the Δv – E upp trend ■ Our results show that the linewidth-E upp trend observed towards SgrB2 N and SgrB2 M by de Vicente (2002) are also found in our more complete sample of hot cores. Rivilla et al. (in preparation) Low excitation (lower T ex and more extended) High excitation (higher T ex and more concentrated) + +

11. COLLAPSE KEPLERIAN ROTATION Kinematics: ruling out… ■ Our result seems to rule out gravitational collapse or keplerian rotation (expected to decrease the linewidth with increasing size) as the major kinematic ingredients in these regions.

12. Broadening by outflows Molecular outflows? ■ The presence of molecular outflows is very common in star formation regions. The higher vibrational levels would be sensitive only to the inner and hotter gas close to the newly born stars, less affected by outflows. The broader lines from the lower vibrational levels of HC 3 N* (with more extended size emission) could probe shocked gas associated with massive molecular outflows, as that reported toward the Orion hot core (de Vicente et al. 2002).

13. The lines more extended have a higher v rigid, and hence, show a wider line. Broadening by rigid rotation Rigid rotation? Suggested for SgrB 2 N based on proper motions of H 2 O masers (Reid et al., 1988) v rigid =ω R

14. 3) Δv – luminosity trend Rivilla et al. (in preparation) ■ New trend between the HC 3 N* linewidths and the IR luminosity of the massive star forming region ■ Distance-bias? The linewidth may increase with distance since the beam of the observation correspond to larger physical sizes. ■ However, there is no correlation between the HC 3 N* linewidth and the distance to the different sources. ■ So this correlation is a real feature of the cores. This trend, along with the one presented by Kurtz et al. (2000) between the luminosity and the total mass, links the overall gas kinematics with the global physical parameters of these regions such as luminosity and mass.

15. ■ This correlation may be explained by the presence of a cluster of hot cores embedded in the region, which have been formed from molecular gas with a velocity gradient. ■ Each one of these individual hot cores would contribute to the total emission with a different central velocity, broadening the lines. Δv – luminosity trend Cluster of less luminous hot cores ?

16. Future work ■ We need HC 3 N* interferometric observations to: confirm directly the size-E upp correlation. reveal the presence of disk structures or outflows. study with high angular resolution the kinematics of the gas, the temperature and the density distributions. resolve the morphology of the cores cluster of cores? physical explanation for the linewidth-luminosity trend? ■ We have new VLA observations (B configuration, ̴ 0.2” ) of SrgB2N & M, G10.47+0.03 and Orion Hot Core. ■ SMA observations available for scheduling (extended configuration, ̴ 1” ) of W51e1e2, G31.41+0.31, G34.26+0.15, G19.61-0.23, G5.89-0.39.

17. Thanks! Víctor M. Rivilla

18. The overall systematic trends in the kinematics of massive star forming regions Observations of HC 3 N* in hot cores Víctor M. Rivilla 41st Young European Astronomers Conference University of Manchester/Jodrell Bank Observatory 18-20 July 2011

19. The overall systematic trends in the kinematics of massive star forming regions Observations of HC 3 N* in hot cores Víctor M. Rivilla 41st Young European Astronomers Conference University of Manchester/Jodrell Bank Observatory 18-20 July 2011

20. Massive stars ■ M>8M ⊙ ■ Several thousands of L ⊙ ■ Spectral types earlier B3. ■ Short lifetimes: 10 7 years. ■ Fast evolution ■ Main mechanical energy injection in the ISM (circumstellar disks, ionized regions, hot gas, outflows, supernovas, etc)‏. (Panagia, 1973)

21. LTE analysis of spectral lines: χ 2 method ■ LTE is a good aproximation for HCs. ■ Free parameters: size, T ex, N ■ RESULT: set of parameters (size, T ex, N) that minimize χ 2. II´ n d is the number of points (ie., spectral lines) n p is the number of free parameters=3 beam size